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1: Tube DIY Asylum, RE: Thanks for Suggestions - Problem Solved (0.00)
Posted by Michael Koster on 2012-08-12, 08:27:34 (71.141.246.234)
Maybe a little late but you really can't do much better than standard balanced audio cable at about 15-20 pF per foot. The digital cables and starquad tend to run closer to 15 pF per foot. ::: TOPIC: .......
2: Tube DIY Asylum, RE: so, the DC restorer helps to set a low and stable bias level for the tube (0.00)
Posted by Michael Koster on 2012-07-28, 13:55:01 (166.250.36.161)
"If low quiescent current, idle current, is better, then isn't Class B (no quiescent current) the "best". I kind of like to bias my amps heavily into Class A, not B. But class B amps can use smaller p .......
3: Tube DIY Asylum, RE: "a clamp " like a Zener? (nt) (0.00)
Posted by Michael Koster on 2012-07-28, 09:37:37 (166.250.39.21)
The DC restorer works the same way the old TV video DC restorer circuit works. The video signal is DC referenced and asymmetric. In a vacuum tube TV (B&W for example) the video signal is processed by .......
4: Tube DIY Asylum, RE: Using toroid AC mains tranny for output transformer question??? (0.00)
Posted by Michael Koster on 2012-07-02, 08:40:43 (71.141.227.202)
Al, Have you measured any matching transformers, or done an A/B comparison with a toroid of the same turns ratio? I think wer're, obviously, talking parafeed here... .......
5: Tube DIY Asylum, RE: How do you think the sonic charater when SS HVT regulator is used (0.00)
Posted by Michael Koster on 2012-07-02, 08:31:17 (71.141.227.202)
"IME, regulation of the entire amp does limit the dynamics and makes it sound "flat". However I believe the input and driver stages do benefit from regulation as it keeps the operating points where th .......
6: General Asylum, RE: you only get stuff YOU are connecting to. Obviously I am not getting hot babes ads... (0.00)
Posted by Michael Koster on 2012-05-29, 07:28:15 (71.141.233.224)
No. I don't do anything online even remotely like that. I should be getting vacuum tube and audio stuff based on my online habits. But I did just remove all my cookies and switch to the chrome browser .......
7: General Asylum, I'm not into it... (0.00)
Posted by Michael Koster on 2012-05-28, 22:30:52 (71.141.233.224)
the ridiculous infolinks are bad enough defacing my posts, but I'm just not into the "dating" scene on the audio forum :-( I don't think I'll be checking in very often any more .......
8: Tube DIY Asylum, RE: The Free Energy Motor, Laws of Physics & Vanity (0.00)
Posted by Michael Koster on 2012-04-24, 22:55:42 (67.142.174.27)
Here's the NASA technical report on asymmetric capacitors. They conclude that ionization and ion collisions are responsible for the observed thrust, and that only spurious mechanisms could cause thrus .......
9: Tube DIY Asylum, RE: The Free Energy Motor, Laws of Physics & Vanity (0.00)
Posted by Michael Koster on 2012-04-23, 17:57:57 (67.142.174.24)
The Naudin style thruster I built (rotary style) produced great thrust but produced zero thrust when a simple triangular blocking plate made of thin polycarbonate was added about 1 inch behind each th .......
10: Tube DIY Asylum, RE: The Free Energy Motor, Laws of Physics & Vanity (0.00)
Posted by Michael Koster on 2012-04-21, 23:13:13 (67.142.174.26)
I have also built and analyzed the lifter. Actually the thruster but it's the same principle. The operating mechanism is based on one electrode having a sharp radius (the wire) and another electrode h .......
11: Tube DIY Asylum, RE: A few conservative design hints (0.00)
Posted by Michael Koster on 2012-04-12, 07:15:38 (67.142.174.25)
'mornin, Henry... .......
12: Tube DIY Asylum, RE: Sakuma belongs to Warner? (0.00)
Posted by Michael Koster on 2012-03-30, 08:38:49 (67.142.174.24)
Actually they don't alert the copyright holder. They warn the "violator" .......
13: Tube DIY Asylum, RE: Sakuma belongs to Warner? (0.00)
Posted by Michael Koster on 2012-03-28, 22:42:31 (67.142.174.24)
Sakuma's amplifiers are demonstrated on youtube using copyrighted material :-( The Sakuma video constitutes online piracy because it contains a "public performance" of music legally owned by Warner Me .......
14: Tube DIY Asylum, RE: Resistor ratings question (0.00)
Posted by Michael Koster on 2012-03-28, 21:59:31 (67.142.174.24)
The data sheet has a dielectric strength spec of 1500VACrms, which is the voltage from the terminals to the mounting surface. The 300V is the breakdown voltage across the resistive element. Resisto .......
15: Tube DIY Asylum, RE: Tell me, Deathtube (0.00)
Posted by Michael Koster on 2012-03-24, 07:16:42 (184.53.24.115)
I have demonstrated by analysis, simulation, and direct measurement that the first stage of a "flywheel" filter has a special property that significantly improves the DC regulation of the supply while .......
16: Tube DIY Asylum, RE: Way to GO Michael !!! (0.00)
Posted by Michael Koster on 2012-03-21, 17:02:35 (67.142.174.27)
Events per instant is a poor definition really, because there is no quantitative definition for an instant, nor for what constitutes a musical event. Certainly the surfaces of these musical instrumen .......
17: Tube DIY Asylum, RE: All sounds, from the screech of nails on a blackboard to a symphony orchestra, are made up of sine waves. (0.00)
Posted by Michael Koster on 2012-03-21, 08:30:47 (67.142.174.27)
Also, what's the point? Are you making the claim that any amplifier that can correctly reproduce continuous sine waves over the human hearing range will sound the same as any other amp that also has t .......
18: Tube DIY Asylum, RE: All sounds, from the screech of nails on a blackboard to a symphony orchestra, are made up of sine waves. (0.00)
Posted by Michael Koster on 2012-03-21, 08:21:03 (67.142.174.27)
Now I know you be messin wid us! A sine wave is a rotating vector. It has no starting point or end point. Then you say that all sounds have a zero starting point... How can a thing have no starting po .......
19: Tube DIY Asylum, RE: Not really... (0.00)
Posted by Michael Koster on 2012-03-21, 08:03:52 (67.142.174.27)
Posts: 139 Joined: October 29, 2010 That is just a profoundly useful abstraction. +1 Sine waves are all about continuous Music is all about discontinuous ;-) .......
20: Tube DIY Asylum, RE: PP Class A OPT Loading (0.00)
Posted by Michael Koster on 2012-03-21, 07:52:21 (67.142.174.27)
I guess by negative current you mean that a tube can only sink, not source current. True, but sometimes OPT leakage inductance can fool feedback circuits into behaving as if the cutting-off tube is su .......
21: Tube DIY Asylum, RE: PP Class A OPT Loading (0.00)
Posted by Michael Koster on 2012-03-20, 11:54:00 (67.142.174.27)
When I first studied the treatment of push-pull tubes in the standard texts, including the Radiotron book, I found the following to be easier to understand. (Ignoring inductance and other reactive con .......
22: Tube DIY Asylum, RE: Are direct coupled amps more prone to hummm.....? (0.00)
Posted by Michael Koster on 2012-03-20, 11:38:58 (67.142.174.27)
That's an interesting question. I have built many directly coupled amps. Some with stacked supplies, some with single supplies. Some SE, some push-pull. Some old school tube circuits, some with solid .......
23: Tube DIY Asylum, RE: Diodes in a Greatz Hybrid (0.00)
Posted by Michael Koster on 2012-03-15, 08:04:58 (67.142.174.27)
snubbers should help with the noise? always This 1200V doubler uses UF4007 in series with the HV ceramic cap across each diode to help with switch-off and equalize the reverse voltage. .......
24: Tube DIY Asylum, RE: Diodes in a Greatz Hybrid (0.00)
Posted by Michael Koster on 2012-03-15, 07:03:21 (67.142.174.27)
Hi Jeff, More likely the diodes are failing from overvoltage than current in my own experience. Higher current rated diodes may be noisier on switching due to more capacitance. Peak curernt in a FWB w .......
25: Tube DIY Asylum, RE: Screen Drive (0.00)
Posted by Michael Koster on 2012-01-26, 10:55:17 (67.142.174.26)
Triode mu or g1/g2 mu is simply the ratio or g1 sensitivity to g2 sensitivity (gm): gm(g2) = gm(g1)/mu so for a given gm relative to g1, the higher the triode mu, the lower the g2 transconductance and .......
26: Tube DIY Asylum, RE: What happened to Electra-Print Custom Power Txs and Chokes? (0.00)
Posted by Michael Koster on 2012-01-12, 07:15:43 (67.142.174.26)
They no longer offer power components. The last time I heard about this it was mostly frustration around about requests for a particular DC winding resistance. It's disturbing how many people think th .......
27: Tube DIY Asylum, RE: Series differential vs. differential cascode vs. CCS differential (0.00)
Posted by Michael Koster on 2011-12-21, 09:51:45 (70.41.212.137)
"For series differential there is a major difference: if you need extended frequency response (I mean above 30-50 KHz), grid resistors must be of no more than 10 KOhm, so that input impedance can only .......
28: Tube DIY Asylum, RE: What Dykes, and Gneedle Gnose, are a pleasure to use? (0.00)
Posted by Michael Koster on 2011-12-04, 14:36:49 (70.41.212.137)
if you're truly serious .......
29: Tube DIY Asylum, RE: screen current regulation in low power SE class A... (0.00)
Posted by Michael Koster on 2011-11-30, 07:23:49 (70.41.212.137)
It would be nice if you could show a schematic diagram of your circuit. It sounds like you have built a shunt voltage regulator by feeding constant current through a gas regulator connected between .......
30: Tube DIY Asylum, RE: Peeling track on printed circuit board (0.00)
Posted by Michael Koster on 2011-08-22, 14:21:54 (70.41.243.208)
Super glue (cyanoacrylate)works pretty well and doesn't burn as easily as Epoxy. There is a line of cyanoacrylate adhesives especially for PC board rework if you want to get fancy... .......
31: Tube DIY Asylum, RE: Plate Choke VS. Cascode current source (0.00)
Posted by Michael Koster on 2011-08-09, 09:45:35 (70.41.243.208)
"Which one is the finest choice for my linestage? Since I'm duplicate my friend's DIY piece, he has plate choke in there. However, some of DIYers from my neighborhood claimed CCS supposed to be bet .......
32: Tube DIY Asylum, RE: Show me the kink, or I will deconstruct it (0.00)
Posted by Michael Koster on 2011-07-06, 14:13:20 (70.41.243.208)
"The slope of the Red lines I added to your pic represent the perm of the various loops and if you can imagine a few smaller loops around the shorter lines it becomes clear what is going on. Low level .......
33: Tube DIY Asylum, RE: Show me the kink, or I will deconstruct it (0.00)
Posted by Michael Koster on 2011-07-06, 10:14:33 (70.41.243.208)
""" Hey, That curve even if exaggerated is exactly what you get when measuring a steel core sample. The lower slope to the line around the axis simply means the material has a low initial perm. dave " .......
34: Tube DIY Asylum, RE: Show me the kink, or I will deconstruct it (0.00)
Posted by Michael Koster on 2011-07-06, 00:15:14 (70.41.243.208)
Finally, the most recent depiction of the kink does away with all the loops and calls this the exaggerated B-H curve for iron, again without citing a source for the data. The kinked curve doesn't .......
35: Tube DIY Asylum, RE: Show me the kink, or I will deconstruct it (0.00)
Posted by Michael Koster on 2011-07-06, 00:10:05 (70.41.243.208)
Another author a few years later reproduces this figure to illustrate the same point, only this one has had the smaller loops removed and shows just the dotted line inside as the "Ideal hysteresis- .......
36: Tube DIY Asylum, RE: Show me the kink, or I will deconstruct it (0.00)
Posted by Michael Koster on 2011-07-06, 00:06:13 (70.41.243.208)
Here's a scan of the oldest hand-drawn inferred curve. This dates to about 1994 and shows the behavior of the B-H loop as signal level is decreased, portrayed by the smaller and smaller loops. Doe .......
37: Tube DIY Asylum, RE: Show me the kink, or I will deconstruct it (0.00)
Posted by Michael Koster on 2011-07-04, 12:10:46 (70.41.243.208)
Thanks for being perfectly honest. To be perfectly honest, I'm already in the process of deconstructing what I believe to be an audio myth. Your description of how you inferred the kink from the state .......
38: Tube DIY Asylum, Show me the kink, or I will deconstruct it (0.00)
Posted by Michael Koster on 2011-07-04, 10:01:31 (70.41.243.208)
"Ferrous cored transformers have a little kink in their B-H curves as they switch magnetic polarity. Perhaps any audible effect this may have on the signal is less noticeable as the amplitude of the s .......
39: Tube DIY Asylum, RE: Has anyone ever used a diode going into a tube rectifier? (0.00)
Posted by Michael Koster on 2011-06-28, 08:35:59 (70.41.243.208)
Here's a full wave hybrid bridge. Sounds similar. Can't imagine how load on the rectifier is reduced by this though, or how "sonics" would be improved over a full wave CT with one tube (all else be .......
40: Tube DIY Asylum, RE: Use a FET follower and be done with. (nt) (0.00)
Posted by Michael Koster on 2011-06-23, 08:19:41 (70.41.243.208)
"The two sides of that sine wave do not look the same." Correct. That's because it's a 417A swinging 300V peak to peak and approaching cutoff in it's nonlinear region. The actual IR drop across the M .......
41: Tube DIY Asylum, RE: Use a FET follower and be done with. (nt) (0.00)
Posted by Michael Koster on 2011-06-22, 07:23:08 (70.41.243.208)
"Even followers do wacky things whe the load changes that drastically." My experience is that a MOSFET follower is very well behaved on abrupt transitions into grid current as shown above, where a .......
42: Tube DIY Asylum, RE: What's your preferred de-soldering device? (0.00)
Posted by Michael Koster on 2011-05-17, 22:48:41 (70.41.213.241)
Hakko 808 For through hole and point to point. Beefy enough to clean up old transformer terminals. .......
43: Tube DIY Asylum, RE: UTC Transformer Question (0.00)
Posted by Michael Koster on 2011-05-13, 08:20:38 (70.41.213.241)
Th LS-141 is a balanced hybrid repeat coil. It has two separate cores inside to isolate the circuits. Another use of this coil is to combine left and right channel signals to mono, or use them to enco .......
44: Tube DIY Asylum, RE: Be Careful with Ebay (0.00)
Posted by Michael Koster on 2011-05-13, 08:05:08 (70.41.213.241)
------------------------------------------- "I have seen on many occasions an auction on Ebay where something went for some sick money. Supposedly! I then saw it up again from the same seller a couple .......
45: Tube DIY Asylum, RE: face plate and chassis (0.00)
Posted by Michael Koster on 2011-05-07, 09:36:39 (70.41.229.152)
FPE will sand the edges if you request, which works pretty well if your enclosure is the natural anodized color. Some very nice things can be done with FPE. Going the custom machine shop route req .......
46: Tube DIY Asylum, RE: Clean Sinewave HF heating? (0.00)
Posted by Michael Koster on 2011-05-03, 06:19:48 (70.41.229.152)
It would be at most 66% efficient, thus worse than a good DC supply but not by much. I would consider driving a high Q circuit with a switch to generate the sine signal since you need a tuned circuit .......
47: Tube DIY Asylum, RE: Do yourselves a favor. (0.00)
Posted by Michael Koster on 2011-04-28, 08:25:26 (70.41.229.152)
The brown caps that I use are the KMH series from UCC and they are easily my first choice. They come with "snap-in" pins for PCB mounting but are easy to mount and solder in a discrete wired system .......
48: Tube DIY Asylum, Miss Piggy says "pardonez-moi" (0.00)
Posted by Michael Koster on 2011-04-12, 08:51:16 (70.41.229.152)
Allen Wright promoted his own design of augmented cathode follower that fixes the asymmetry problem. He called it the "Super Linear Cathode Follower". It bears more than passing similarity to some of .......
49: Tube DIY Asylum, RE: Just A reminder about lead solder. Dont use it! (0.00)
Posted by Michael Koster on 2011-03-27, 09:05:05 (70.41.229.152)
A doctor can prescribe a chelation regimen that will remove heavy metals from the body. It's a slow and rigorous process but it is possible. It's also a fairly simple test to determine the quantities .......
50: Tube DIY Asylum, RE: All pentode el84se no GFB: also for the lower output impedance (0.00)
Posted by Michael Koster on 2011-03-24, 13:09:23 (70.41.242.107)
I tried something much like this a couple of years ago and found it to have a nice harmonic structure and sounded great! The solid low end was refreshing to hear in a SET. It sounds so good, .......
51: Tube DIY Asylum, RE: Frying ECC99īs (0.00)
Posted by Michael Koster on 2011-01-26, 08:40:58 (70.41.214.88)
Based on your plate voltage readings everything is as expected and you're not overheating the plates of these tubes. The currents are all between 4.8mA and 6.3mA giving about one watt per plate. In my .......
52: Tube DIY Asylum, RE: Frying ECC99īs (0.00)
Posted by Michael Koster on 2011-01-24, 13:11:44 (70.41.214.88)
"Im frying my ECC99īs" I like to use olive oil and a little shallot... "Between pinīs 3 and 8 of the ECC99 I have 107V, this should be 130V." Do you mean between the junction of pins 3&8 and ground? M .......
53: Tube DIY Asylum, RE: Pinging Triode Kingdom (0.00)
Posted by Michael Koster on 2011-01-23, 09:44:49 (70.41.214.88)
...what would be wrong with using it with the contour active all the time if it sounded better? I think this illustrates one problem with "ears only" evaluation. Often when something in the sound is h .......
54: Tube DIY Asylum, RE: When you lack the technical understanding but still know what you hear... (0.00)
Posted by Michael Koster on 2010-12-23, 09:22:55 (70.41.214.88)
"If a drawn schematic of a circuit is copyrighted, that drawing is protected, not the circuit itself. I could be wrong about this." Yes, you could. Perhaps you should do some research before submittin .......
55: Tube DIY Asylum, RE: industrial control transfomer (0.00)
Posted by Michael Koster on 2010-12-19, 18:44:28 (70.41.214.88)
It's 2 diodes in series for each half of the doubler, to handle the >1000V reverse voltage. Electrolytics will work fine. I haven't had a problem with buzzing or vibration with any of 2-3 different IC .......
56: Tube DIY Asylum, RE: industrial control transfomer (0.00)
Posted by Michael Koster on 2010-12-18, 14:18:20 (70.41.214.88)
OK, the rectifier is 2x UF4007 each side, 4 total, with .01uF, 3KV Z5U ceramic caps across them to balance the inverse voltage. The doubler caps are 50uF 440V ASC film caps, then an LC filter using .......
57: Tube DIY Asylum, RE: Enhanced triode operation. anyone interested in this? (0.00)
Posted by Michael Koster on 2010-12-17, 15:10:09 (75.52.142.169)
Sorry, wrong forum ;-) .......
58: Tube DIY Asylum, RE: industrial control transfomer (0.00)
Posted by Michael Koster on 2010-12-17, 11:53:21 (75.52.142.169)
I probably used UF4007 diodes in series with ceramic caps across them and ~80uF, 440VAC motor run caps for the doubler. I follow the doubler with a 2.5H Hammond choke and a Dearborn high voltage film .......
59: Tube DIY Asylum, RE: industrial control transfomer (0.00)
Posted by Michael Koster on 2010-12-16, 22:43:02 (75.52.142.169)
The actual secondary AC voltage will be around 455-460 unloaded for PSUD modeling, because it's wound to compensate for losses in the forward direction, which gives it a little less step-up in the rev .......
60: Tube DIY Asylum, RE: Do a search for Screen drive pentode (0.00)
Posted by Michael Koster on 2010-12-16, 22:23:30 (75.52.142.169)
I can verify that crossover distortion is reduced at very low standing current levels using this kind of drive method. I have an experimental amplifier that drives both g1 and g2 at a particular ra .......
61: Asylum Feedback/Support, RE: Are those infolinks ads (everywhere) annoying or what! (0.00)
Posted by Michael Koster on 2010-12-02, 10:57:55 (70.41.242.148)
OK, I contacted the web admin about infolinks when they first showed up, and was told that they would get more relevant over time. Well, they're just as stupid and inane as ever. I recommend they be d .......
62: Tube DIY Asylum, RE: Belden 88641 is fantastic (0.00)
Posted by Michael Koster on 2010-11-13, 09:28:55 (70.41.242.148)
The 88641 jacketed shielded twisted pair sounds excellent. I'm currently using 9451 for balanced wiring with shield (to the XLRs in the image), but it's polypropylene and tends to melt back a bit o .......
63: Tube DIY Asylum, RE: What type of signal cable/wire do you use in your builds? (0.00)
Posted by Michael Koster on 2010-11-13, 09:06:08 (70.41.242.148)
My favorite hookup wire is the Belden 19 strand with teflon insulation, in 20,22,24,26 gauge, e.g. Belden 83027. High voltage rated, high temperature, easy to solder with no melt-back of the insulatio .......
64: Tube DIY Asylum, RE: Voltages for regulated filament supply (0.00)
Posted by Michael Koster on 2010-11-04, 07:56:36 (70.41.215.1)
I'd be looking for some diodes with lower Vf at high current. The voltage drop across your diodes will be for the peak charging current, 5 to 7 amps in your case depending on DCR of the rectifier c .......
65: Tube DIY Asylum, RE: Must have for the serious designer (0.00)
Posted by Michael Koster on 2010-10-27, 15:01:09 (70.41.215.1)
For serious designers of high end audio gear there's only one place to go: http://ap.com/products/2700 .......
66: Tube DIY Asylum, RE: Treating Paper Cone speakers (0.00)
Posted by Michael Koster on 2010-10-22, 09:38:59 (70.41.215.1)
I remember one time (as a kid) using a really old 6x9 that had a very fragile cone. I ended up coating the entire cone with rubber cement; did the trick. .......
67: Tube DIY Asylum, RE: Teflon sockets (0.00)
Posted by Michael Koster on 2010-10-18, 09:23:19 (70.41.215.1)
LOL I've pulled the contacts out of these and used them as flying tube leads on a breadboard and for a custom socket by mounting them in a 3/8" nylon plate with drilled holes. Teflon may creep, i.e. d .......
68: Tube DIY Asylum, RE: Getting rid of parasitic (0.00)
Posted by Michael Koster on 2010-10-18, 09:16:11 (70.41.215.1)
By parasitic I assume you mean ringing on a square wave. If so, what's the frequency of the ringing? Reason I ask is, I tried this setup except with pentode drivers and plate feedback instead of E-lin .......
69: Tube DIY Asylum, RE: The audio benevolent society (0.00)
Posted by Michael Koster on 2010-10-12, 09:11:25 (70.41.215.1)
"but with Andre "The Dork from Cork" Jute" Beetlejuice! BEETLEJUICE!!! ... Be careful what you ask for, Henry. The bad old days of RAT... When was that, 15 years ago? 20? .......
70: Tube DIY Asylum, RE: Scope image explanation (0.00)
Posted by Michael Koster on 2010-10-04, 09:56:06 (70.41.215.1)
PSUD does indeed simulate using the transformer DCR. V(T1) includes the effect of DCR. The tops of the sinewaves in the PSUD output are rounded off, but not as sharply squared off as in the scope shot .......
71: Tube DIY Asylum, RE: Explanation (0.00)
Posted by Michael Koster on 2010-09-30, 10:19:57 (70.41.215.1)
Henry, you nailed it! The inductor delivers a second charging pulse just as the capacitor voltage begins to decay, approximating a "longer, flatter" charging pulse. This improves regulation quite a bi .......
72: Tube DIY Asylum, RE: Siemens or Telefunken ECC88 Equivalents for Less $$$ ? (0.00)
Posted by Michael Koster on 2010-09-28, 09:07:06 (70.41.215.1)
Yes. Post this question on the "tubes" forum instead of the DIY forum. They talk all about how some type of getter sounds too edgy etc... Here we generally discuss circuits and construction... Cheers, .......
73: Tube DIY Asylum, Nothing to do with dropout voltage... (0.00)
Posted by Michael Koster on 2010-09-27, 14:15:44 (70.41.215.1)
Dropout voltage on the 1084 is only 1.5V at worst. Too high dropout voltage does not cause a regulator to turn off, it just operates at a lower unregulated output voltage. Without a whole schematic .......
74: Tube DIY Asylum, RE: Michael, (0.00)
Posted by Michael Koster on 2010-09-24, 23:22:25 (70.41.215.1)
Some may be more linear than others at low current. This one from a depletion mode MOSFET (DN2540) looks like almost constant ~80 mA/V in the region from 0 to 60 mA. The IXYS IXTP01N100D is anothe .......
75: Tube DIY Asylum, RE: Not quite the same as the triode version (0.00)
Posted by Michael Koster on 2010-09-24, 10:37:12 (70.41.215.1)
Hi Kurt, I think you may have made some assumptions about the circuit I was describing. This is a class A buffer for a high voltage microphone (DPA4003, etc). My circuit doesn't fight itself and ho .......
76: Tube DIY Asylum, RE: Cathode/source follower drivers (0.00)
Posted by Michael Koster on 2010-09-24, 09:22:19 (70.41.215.1)
Hi Henry, Here are some more things to think about regarding a MOSFET source follower. In a follower application, the only capacitive load seen on the gate pin is the reverse transfer capacitance C .......
77: Tube DIY Asylum, RE: Singing resistors? (0.00)
Posted by Michael Koster on 2010-09-22, 11:30:10 (70.41.215.1)
That is a bit surprising. The only thing I ever hear singing is the output transformer. Are you sure you're not hearing the OPT? .......
78: Tube DIY Asylum, RE: ST-70 clone / Delving into PushPull (0.00)
Posted by Michael Koster on 2010-09-21, 14:00:23 (70.41.215.1)
If you were trying to get 70 watts PER CHANNEL out of EL34s then the 1650R with 5K ohms Zpri would be about right. For pentode outputs the optimum Zpri depends on B+, screen voltage, and desired outp .......
79: Tube DIY Asylum, RE: Sim says it doesn't do much (0.00)
Posted by Michael Koster on 2010-09-18, 08:40:01 (70.41.215.1)
Ah, so you expect the filter to ring out but the gas tube will stay lit. That's cool. I suppose the filter will ring on load changes also. What advantage does the LC filter provide (besides the ringin .......
80: Tube DIY Asylum, RE: I can't see why that wouldn't work. (0.00)
Posted by Michael Koster on 2010-09-17, 11:48:25 (70.41.215.1)
I think it might be the DC model with hysteresis that gets you into trouble... .......
81: Tube DIY Asylum, RE: Screen supply for pentode operation (0.00)
Posted by Michael Koster on 2010-09-14, 11:27:39 (70.41.215.1)
I don't think you have a general rule about the ratio of stopper value to supply DCR, rather you have discovered a minimum g2 circuit resistance for your line stage circuit. What was the effect of goi .......
82: Tube DIY Asylum, RE: Do the math and find out. (0.00)
Posted by Michael Koster on 2010-09-14, 10:54:38 (70.41.215.1)
"The DC resistance is part of the load and really doesn't matter. If you look at the Lundahl LL1667/15mA it has 270H and a DCR of 2.4K ohms. So at 20Hz your load becomes ((2*Pi*20Hz*200H)+ 2400 ohms) .......
83: Tube DIY Asylum, This is the fallacy (0.00)
Posted by Michael Koster on 2010-09-11, 08:14:05 (70.41.215.1)
"400 Ohms source, to drive 800 Ohms load, how does that sound to you ?? Not too good at all." Here is the specific fallacy: The Rp of the output tube is not the load of an amplifier. It's a controllin .......
84: Tube DIY Asylum, RE: Hammond organ coupling transformers? (0.00)
Posted by Michael Koster on 2010-09-08, 11:29:40 (70.41.215.1)
I haven't tested them, preferring to leave them in-circuit ;-) But, the B3 output transformer might make a decent line out transformer. The two key busbar matching transformers (tapped for the drawbar .......
85: Tube DIY Asylum, RE: Recovery time (0.00)
Posted by Michael Koster on 2010-09-05, 08:38:46 (70.41.215.1)
Hi John, Thanks for again explaining the power supply recovery time issue. Can you explain a little further the mechanism by which audio signals impose varying DC current demands on the B+ of a class .......
86: Tube DIY Asylum, RE: rough numbers (0.00)
Posted by Michael Koster on 2010-09-04, 11:11:57 (70.41.215.1)
Hi Dave, That's interesting and tends to contradict "popular wisdom" that only the last filter cap is "in the signal path". But it's hardly surprising given the finite unwanted AC impedances involved .......
87: Tube DIY Asylum, RE: rough numbers (0.00)
Posted by Michael Koster on 2010-09-04, 08:33:04 (70.41.215.1)
"Spice can easily show me a measurable difference between a 33u and a 47u cap in the last position yet my ears don't tell me there is a difference. On the other hand switching from a 47u solen to an 4 .......
88: Tube DIY Asylum, RE: No tubes are matched well enough... (0.00)
Posted by Michael Koster on 2010-08-24, 07:52:01 (70.41.215.1)
" What strikes me as possibly an ideal solution would be somehow to rig the cathode bias circuit using the equivalent of CCS bias in some form of Blumlein Garter arrangement, which should be able to .......
89: Tube DIY Asylum, RE: V2 is Long Tailed Pair Inverter (0.00)
Posted by Michael Koster on 2010-08-18, 00:23:53 (70.41.215.1)
I should have this amp finished in a day, a nice way to add reverb to my little Hammond.-- Curious why you didn't go for the much simpler AO-44 amp as used in the later spinets. I have both an M3 and .......
90: Tube DIY Asylum, RE: Bob Carver says hi (0.00)
Posted by Michael Koster on 2010-08-17, 09:05:59 (70.41.215.1)
Hi Bob, It took me a long time to figure out the DC restorer because it's a somewhat counterintuitive approach, but I had already been thinking about a class B driver for a class B output stage i.e. d .......
91: Tube DIY Asylum, isolated current loop design concept (0.00)
Posted by Michael Koster on 2010-08-11, 19:02:06 (70.41.215.1)
Here's the thread over at DIYAudio where someone brought up this design concept in response to a mu-follower circuit. I asked how the design concept is relevant to the circuit presented in a multi-par .......
92: Tube DIY Asylum, RE: miller capacitance / PS isolation (0.00)
Posted by Michael Koster on 2010-08-10, 10:51:18 (70.41.215.1)
#1 agrees with the way I see it. #2 is one of a number of things. The low impedance output is good for driving Cmiller, or a phono EQ network, or a plate feedback network, or grid current large and sm .......
93: Tube DIY Asylum, RE: CCS plate load on a grounded cathode preamp (0.00)
Posted by Michael Koster on 2010-08-09, 20:40:31 (70.41.215.1)
Hi Tre, I totally agree. I would shunt regulate a micpre or phono pre B+ regardless of the topology. Whether using CCS or mu or anti-triode outputs. But for e.g. a driver stage it won't make a useful .......
94: Tube DIY Asylum, RE: CCS plate load on a grounded cathode preamp (0.00)
Posted by Michael Koster on 2010-08-09, 19:48:37 (70.41.215.1)
Hi Mach1, I guess you're talking about these 2 statements about mu-followers on Gary Pimm's page: "The drawback to this arrangement is the current to drive the next stage comes from the power supply, .......
95: Tube DIY Asylum, RE: CCS plate load on a grounded cathode preamp (0.00)
Posted by Michael Koster on 2010-08-09, 17:14:10 (70.41.215.1)
"P.S. The only thing using the "mu" output will give you is lower output impedance at the cost of re-introducing the power supply final cap into the signal path. (one benefit of using a CCS as a plate .......
96: Tube DIY Asylum, RE: Mains Transformers as OPTs (0.00)
Posted by Michael Koster on 2010-08-02, 08:14:42 (70.41.215.1)
"Ferrite comes in many different compositions and permeabilities. I don't think it likely that a mains core from one manufacturer will have the same characteristics as a core selected for audio use by .......
97: Tube DIY Asylum, RE: Driver requirements of DHT's (0.00)
Posted by Michael Koster on 2010-07-27, 09:47:23 (70.41.215.1)
"One could of course use a high inductance grid-choke or interstage transformer coupling to overcome or materially reduce the problem. Either approach makes for a very low DC resistance from the grid .......
98: Tube DIY Asylum, RE: Don't believe everything you read. (0.00)
Posted by Michael Koster on 2010-07-27, 09:06:10 (70.41.215.1)
"Miller capacitance is the actual grid to anode capacitance, as measured on a cold tube, multiplied by the mU of the tube." If we get really nit-picky we'll find that the Cgp (grid-to-plate capacitanc .......
99: Tube DIY Asylum, RE: A simple guitar booster with 807 tubes (0.00)
Posted by Michael Koster on 2010-07-23, 08:46:26 (70.41.215.1)
That's an interresting circuit. How did you arrive at 22K for R1 and R2? have you thought about using a 5:1 or so voltage divider from g2 to g1 instead? Have you tried changing the cathode feedback .......
100: Tube DIY Asylum, RE: output stage bias and power output question (0.00)
Posted by Michael Koster on 2010-07-19, 12:14:03 (70.41.215.1)
I was thinking it would be instructive to lovetube and others if you shared the assumptions and method so they could learn... And work it out for themselves when needed Cheers, Michael .......
101: Tube DIY Asylum, RE: output stage bias and power output question (0.00)
Posted by Michael Koster on 2010-07-19, 08:00:19 (70.41.215.1)
"You actually lose .5 watt in A1 because you are lowering the bias voltage. Now in AB you gain about 2.5 watts." Interesting result, Dan. How did you arrive at that? Cheers, Michael .......
102: Tube DIY Asylum, RE: Answer! (0.00)
Posted by Michael Koster on 2010-07-16, 08:14:32 (70.41.215.1)
If you want to know the "wattage" dissipated by the regulator, multiply the current by the voltage *across the regulator*, from it's input to it's output, not the voltage to the circuit it's supplying .......
103: Tube DIY Asylum, RE: Perhaps consider changing the SRPP to a basic grounded cathode? (nt) (0.00)
Posted by Michael Koster on 2010-07-03, 21:16:06 (70.41.215.1)
hi Michael I done it and ready to fire . do you means tie all the grid/anode/cathode of the unused section grounded ? Cheers LT Yes, cathode, anode, and grid of the unused section all to groun .......
104: Tube DIY Asylum, RE: Perhaps consider changing the SRPP to a basic grounded cathode? (nt) (0.00)
Posted by Michael Koster on 2010-07-02, 23:18:53 (70.41.215.1)
Yes, I meant you might be surprised at how good it sounds even though it may not look linear on the graph. For the unused sections just ground them Cheers, Michael .......
105: Tube DIY Asylum, RE: Perhaps consider changing the SRPP to a basic grounded cathode? (nt) (0.00)
Posted by Michael Koster on 2010-07-02, 20:19:57 (70.41.215.1)
A 12AY7 would be a lot more linear. The dotted line shows the parallel load of the inverter's 220K grid resistor. Assuming 1.2K cathode resistor, 100K plate resistor. Try it, you'll like it... You .......
106: Tube DIY Asylum, RE: Perhaps consider changing the SRPP to a basic grounded cathode? (nt) (0.00)
Posted by Michael Koster on 2010-07-02, 19:46:46 (70.41.215.1)
what would be good op point for the 12at7 with around 300v B+ available ? I would just use the 1 section of the 12AT7 with a 100K plate resistor for now. I think with your current 1.8K cathode resi .......
107: Tube DIY Asylum, RE: Perhaps consider changing the SRPP to a basic grounded cathode? (nt) (0.00)
Posted by Michael Koster on 2010-07-02, 12:27:26 (70.41.215.1)
It's not an SRPP or push-pull of any kind. With this connection you get a fairly low impedance CCS where dynamic impedance is on the order of Rk multiplied by mu, in this case 1.8K * 50 or about 90K o .......
108: Tube DIY Asylum, RE: I think I found the problem . (0.00)
Posted by Michael Koster on 2010-07-02, 08:34:39 (70.41.215.1)
"I think i might try grid-stopper on the 5687 , it might oscillating at the moment ." Probably wouldn't hurt to add a grid stopper to the 12AT7 while you're at it ;-) Both grids that is. Cheers! Micha .......
109: Tube DIY Asylum, RE: I think I found the problem . (0.00)
Posted by Michael Koster on 2010-07-01, 23:35:43 (70.41.215.1)
I guess you could make sure the grid of the bottom section is at zero volts. It's not clear from your schematic how the input is wired, but maybe your source has DC or some other thing e.g. oscillatio .......
110: Tube DIY Asylum, RE: I think I found the problem . (0.00)
Posted by Michael Koster on 2010-07-01, 10:21:50 (70.41.215.1)
Your 12AT7 voltages are still strange. With equal cathode resistors, the voltage should be exactly split, i.e. ~141V at the lower anode. Also with 1K8 in the cathodes you should be seeing ~ -2.2V grid .......
111: Tube DIY Asylum, RE: I think I found the problem . (0.00)
Posted by Michael Koster on 2010-07-01, 09:54:30 (70.41.215.1)
"the 12AT7 that I used have some problem" Good job! I thought about a low emission tube + a bad voltage reading as one possibility late last night... Good thing you didn't rip up the splitter circuit, .......
112: Tube DIY Asylum, RE: That will increase the 5687 feedback loop. (0.00)
Posted by Michael Koster on 2010-07-01, 09:47:40 (70.41.215.1)
Thanks, Douglas... The PI is at about the optimum bias for best swing, and it's enough to drive the output fully as long as the CFB is 4:1 or less. There is no need to mess with the PI. IOW, it would .......
113: Tube DIY Asylum, RE: What bias voltage on the El34's??? (0.00)
Posted by Michael Koster on 2010-07-01, 01:04:59 (70.41.215.1)
"the bias voltages on the EL34s is 26v" You should then need about 26 volts peak signal from grid-cathode (52V Pk-Pk). Assuming the load line above, you would have 200V peak plate swing on the EL34 .......
114: Tube DIY Asylum, RE: please give me some comments on this EL34 PP amp circuit (0.00)
Posted by Michael Koster on 2010-07-01, 00:17:45 (70.41.215.1)
I think your 5687 splitter is actually about as good as it gets with 360V. You can get about 150V peak-peak per side of drive voltage, which is about 3X what the EL34 needs in triode mode, which .......
115: Tube DIY Asylum, RE: EL84 SE homebuilt ps grounding weirdness! Help! (0.00)
Posted by Michael Koster on 2010-06-30, 09:02:17 (70.41.215.1)
"I still can't wrap my mind around the fact that (-) is so elevated from the outlet ground... (100V across 10k resistor-star to outlet ground)" This should not be the case. There is something major wr .......
116: Tube DIY Asylum, RE: You haven't answered my question. (0.00)
Posted by Michael Koster on 2010-06-30, 08:54:49 (70.41.215.1)
"A 50VA mains toroid can tolerate 4mA of offset " Al, don't stop there... Under what conditions and with what as the limiting factor? How much AC signal voltage at what frequency at what distortion li .......
117: Tube DIY Asylum, RE: EL84 SE homebuilt ps grounding weirdness!!!!!!!!!! Help!!!!!! (0.00)
Posted by Michael Koster on 2010-06-29, 07:52:36 (70.41.215.1)
Hi!!! For safety reasons, your amp should not have either hot or neutral connected to the chassis!!!! I recommend installing a 3 wire power cord, and connecting the ground wire to the chassis. Make su .......
118: Tube DIY Asylum, RE: You haven't answered my question. (0.00)
Posted by Michael Koster on 2010-06-27, 09:22:31 (70.41.215.1)
A DC servo is a little tricky outside class A operation. Also a servo has a time constant which may induce infrasonic artifacts if not very well designed. I like the idea of a small gap myself. Carve .......
119: Tube DIY Asylum, RE: Requirements are only 20-25mA per CCS (0.00)
Posted by Michael Koster on 2010-06-25, 08:08:31 (70.41.215.1)
One huge advantage of tubes is they don't need a heatsink! For 100mA you would need a TV sweep tube, but if all you need is 20-25mA then the 6CL6 sounds like an *excellent* choice. You could even run .......
120: Tube DIY Asylum, RE: Pentode CCS with -80V/100mA supply avail ? (0.00)
Posted by Michael Koster on 2010-06-24, 19:02:06 (70.41.215.1)
On second thought, even if the plate can take the 8W the screen dissipation is likely to be a problem at a constant 80Vpk and 100mA for a lot of smaller pentodes. I can't think of any 9 pins right off .......
121: Tube DIY Asylum, RE: Ah yes - a toroid interstage! (0.00)
Posted by Michael Koster on 2010-06-24, 17:31:41 (70.41.215.1)
"But I'd need 1:1, so 120-120 into 120-120. For some reason this useful toroid is quite hard to find!" I'm not exactly recommending a toroid for this, just an example of sometimes you can't guess at t .......
122: Tube DIY Asylum, RE: Any interstage can work in push pull; and even work well... (0.00)
Posted by Michael Koster on 2010-06-24, 09:10:26 (70.41.215.1)
Give it a try, folks...with good old trannies, it sounds nice... Try it also with a Hammond 126 as the OP asked about... I can't claim it won't work because I haven't tried it. I *have* tried it with .......
123: Tube DIY Asylum, RE: How to terminate a SE interstage into push pull? (0.00)
Posted by Michael Koster on 2010-06-23, 10:19:49 (70.41.215.1)
Conventional wisdom is that you need a phase splitting transformer to drive SE to PP. The Hammond 126 are bifilar wound; as such they like the voltage swing on each end of the secondary to be the sam .......
124: Tube DIY Asylum, RE: "Transmitter tubes are for transmitters"...Am I a tube racist? (0.00)
Posted by Michael Koster on 2010-06-22, 07:31:33 (70.41.215.1)
Would you like the 5 minute argument, or the full half hour? .......
125: Tube DIY Asylum, RE: Cleantimestream, check out this schematic. (0.00)
Posted by Michael Koster on 2010-06-20, 09:45:02 (70.41.215.1)
"Notice, I never said NEW designs cannot be created." So to summarize, there are only 4 circuits out there and everything else is a variation of these 4: 1. Mullard 2. Williamson 3. Berning screen dri .......
126: Tube DIY Asylum, RE: You know, you could put the snubbers on the primary and get the same effect. (0.00)
Posted by Michael Koster on 2010-06-20, 09:33:18 (70.41.215.1)
"I've been thinking about this while out walking my dog. I think what's really going on is that I am snubbing the transformer itself. During the AC cycle there is a dead zone where the rect has discon .......
127: Tube DIY Asylum, RE: What about a transformer? (0.00)
Posted by Michael Koster on 2010-06-18, 09:41:01 (70.41.215.1)
Yes! Edcor makes a purpose-built module. The price is almost unbelievable for a hi-fi unit but it wouldn't be much risk to try it. .......
128: SET Asylum, Serious question (0.00)
Posted by Michael Koster on 2010-06-18, 09:33:49 (70.41.215.1)
Dennis, I'd like to hear more of your thoughts on chassis finishing. Your amps are made on what looks like about 10 or 12 ga steel with a commercial power coat. What if for example one were to hot-gal .......
129: Tube DIY Asylum, Special audio definitions for common engineering terms (0.00)
Posted by Michael Koster on 2010-06-18, 09:12:55 (70.41.215.1)
We should create a special audio dictionary with special narrow definitions: It might be technically an amplifier but it's not an *AMP* unless it drives a speaker It's not class A unless it has symmet .......
130: Tube DIY Asylum, RE: Stereo to Mono Combiner - Resistor Values (0.00)
Posted by Michael Koster on 2010-06-18, 08:59:48 (70.41.215.1)
The above circuit is for balanced lines. It won't work properly with single ended (RCA jack) signals because the common ground will short circuit the bottom 600 ohm resistor. .......
131: Tube DIY Asylum, RE: What about a transformer? (0.00)
Posted by Michael Koster on 2010-06-18, 08:57:03 (70.41.215.1)
You need a "hybrid repeat coil" which has 2 cores, or 2 separate transformers. The secondaries connect in series. Otherwise any difference between left and right signals will be destructively cancelle .......
132: Tube DIY Asylum, RE: schottky diodes for filament supply (0.00)
Posted by Michael Koster on 2010-06-15, 10:21:19 (70.41.215.1)
you probably want to consider the unloaded voltage of your secondary with the highest expected line voltage. If you power up with a tube out or if a filament opens, you will see 1.414x the unloaded vo .......
133: Tube DIY Asylum, RE: schottky diodes for filament supply (0.00)
Posted by Michael Koster on 2010-06-15, 07:43:01 (70.41.215.1)
These are the parts I was looking for a couple of weeks ago; low voltage high current schottky diodes in TO-220. I think 15V reverse breakdown should be fine in a C-input circuit supplying 5 or 6 v .......
134: Tube DIY Asylum, RE: schottky diodes for filament supply (0.00)
Posted by Michael Koster on 2010-06-14, 21:33:22 (70.41.215.1)
To make a bridge you would need a common anode part and a common cathodde part. I was having a hard time finding super-low Vf at 20 amps, which is the peak current expected at my 4A DC output, in TO-2 .......
135: Tube DIY Asylum, RE: mouser (nt) (0.00)
Posted by Michael Koster on 2010-06-14, 09:01:10 (70.41.215.1)
It's not that easy. I'm looking myself and the high current diodes are all going into SMT packaging. There are still some good ones in DIY-friendly packages. The best ones I have found so far seem to .......
136: Tube DIY Asylum, RE: ping PakProtector (0.00)
Posted by Michael Koster on 2010-06-09, 07:36:25 (70.41.215.1)
"IXYS chips which should be even better than the TO-220 DN2540 for the top" I've been using the IXTP01N100D, which is rated for 1000Vds with very low capacitance (6pF Crss). It's nice for a top dev .......
137: Tube DIY Asylum, RE: "but I'm weary of smoking this thing" (0.00)
Posted by Michael Koster on 2010-06-08, 12:21:11 (70.41.215.1)
There are explicit warnings about applying too much DC to low level transformers, which may permanently magnetize the core. There is probably enough DCR to prevent burning out the coil with a couple o .......
138: Tube DIY Asylum, RE: D-oh (0.00)
Posted by Michael Koster on 2010-06-05, 07:59:58 (70.41.215.1)
Nice points Chris, but I don't think this is about logic... This is an *argument*. If you don't take a side you aren't part of the discussion. After all, they can't *both* be right... can they? :: .......
139: Tube DIY Asylum, RE: hybrid (0.00)
Posted by Michael Koster on 2010-06-01, 22:40:48 (70.41.215.1)
I built the circuit with a few minor tweaks and tested it. The result is a very simple amp with a nice low distortion (~1% up to about 8W) with f2 dominating at low power and f3 increasing to ab .......
140: Tube DIY Asylum, RE: pins connectors for eimac tubes (0.00)
Posted by Michael Koster on 2010-05-25, 11:44:09 (70.41.215.1)
The Eimac 4-65A for one has a plate cap sleeve that mounts onto the pin with a setscrew and has a 5/16 OD that would accept a ceramic cap. I think it may be unreasonable to derate the anode dissipatio .......
141: Tube DIY Asylum, RE: Nah, a real V8 has the banks... (0.00)
Posted by Michael Koster on 2010-05-25, 10:55:04 (70.41.215.1)
There are plenty of 60 degree V8 engines out there. I guess they go ka-lump, ka-lump... some early V8s were 45 degrees with an 8-throw crank, and there's a new design diesel from GM with 72 degree ban .......
142: Tube DIY Asylum, RE: pins connectors for eimac tubes (0.00)
Posted by Michael Koster on 2010-05-24, 19:13:03 (70.41.215.1)
Not safe for the tube, I'm afraid. The cooling fins on the heat dissipating connectors provide an important function in keeping the glass-to-metal seals at a safe operating temperature. I don't know h .......
143: Tube DIY Asylum, RE: Why a Transformer? (0.00)
Posted by Michael Koster on 2010-05-24, 09:06:09 (70.41.215.1)
"It will be safe (in the US anyway if wired correctly AND a three prong grounded power cord is used. The larger of the plug and the green ground wire must be connected to the chassis. That's how I wir .......
144: Tube DIY Asylum, RE: hybrid (0.00)
Posted by Michael Koster on 2010-05-23, 10:54:59 (70.41.215.1)
OK, after some more thought, a simple amp design occurred to me. The basic concept is to emulate a triode spud amp using "Schade" style plate-to-grid feedback. I would use a depletion mode MOSFET, .......
145: Tube DIY Asylum, RE: choke ratings question (0.00)
Posted by Michael Koster on 2010-05-19, 07:40:58 (70.41.215.1)
They should work fine if your filament supply runs on 1000 Hz and the ripple voltage is less than 2 volts.. If they're rated for 2 volts AC at 1000 Hz, they will saturate at a much lower AC voltage at .......
146: Tube DIY Asylum, RE: Apparently, Jack at Electra-Print. (0.00)
Posted by Michael Koster on 2010-05-14, 13:12:35 (63.81.26.200)
That circuit is meant to swing a 300B or super 2A3 grid 200V pk-pk into positive grid current through a step-up transformer. In this case power grid drive is the goal. IMO it's hardly an ideal choice .......
147: Tube DIY Asylum, RE: What is wrong with carbon compositiosn resistors at Plate/cathode loads? (0.00)
Posted by Michael Koster on 2010-05-12, 09:21:48 (72.173.132.129)
Noise - I guess so, but this alone might not be a problem for a plate load if the signal voltage is a few volts or more. Drift - Has anyone here experienced a properly applied CC resistor change value .......
148: Tube DIY Asylum, RE: Hook-up wire prefernce (0.00)
Posted by Michael Koster on 2010-05-09, 16:38:53 (72.173.132.129)
Ever heard of "groundside electrons" ? .......
149: Tube DIY Asylum, RE: Vao Rating (0.00)
Posted by Michael Koster on 2010-05-08, 09:34:53 (72.173.132.129)
I can't think of any reason cutoff bias would be any different from the cold filament condition (no electrons is no electrons) so I suppose you could use the spec that way also. The datasheets I have .......
150: Tube DIY Asylum, RE: Funny you should mention the 813 ... (0.00)
Posted by Michael Koster on 2010-05-07, 13:32:37 (72.173.132.129)
Right on... I wonder if small signal performance would be better dropping the D3A screen to around 108 and kicking the grid bias to about -1.25V (still 16mA).. just one of the D3A OPs I have yet to tr .......
151: Tube DIY Asylum, RE: Funny you should mention the 813 ... (0.00)
Posted by Michael Koster on 2010-05-07, 11:23:12 (63.81.26.200)
I agree with your assessment of the D3a; it's hard to beat in a number of respects. The 813 looks like a big brother of the Eimac 4-65A I have been playing with. Due to the low gm of these DH tran .......
152: Tube DIY Asylum, RE: Funny you should mention the 813 ... (0.00)
Posted by Michael Koster on 2010-05-07, 08:10:10 (72.173.132.129)
The Vao spec is for cold filament, only important during warmup. Signal excursions shouild be no problem if static Va max is observed. Michael .......
153: Tube DIY Asylum, RE: Vao Rating (0.00)
Posted by Michael Koster on 2010-05-07, 08:00:30 (72.173.132.129)
The correct interpretation of Vao and Vg2o is maximum voltage with a cold filament. Cheers, Michael .......
154: Tube DIY Asylum, RE: I just got a stormer of an idea (0.00)
Posted by Michael Koster on 2010-05-07, 07:15:56 (72.173.132.129)
How many dual .1uF capacitors is anyone going to sell at $250? "We offer access to Electronic Parts at prices typically reserved for wholesale customers. " I guess that's why motor runs are marked up .......
155: Tube DIY Asylum, RE: Driving a type 50 triode (0.00)
Posted by Michael Koster on 2010-04-27, 09:58:51 (63.81.26.200)
Actually, Dan, I never said the circuit wouldn't work with Rg=48K or that any type 50 you plug in would run away. The circuit works because the spec for grid resistance is conservative and/or the part .......
156: Tube DIY Asylum, RE: Driving a type 50 triode (0.00)
Posted by Michael Koster on 2010-04-26, 08:25:08 (72.173.132.129)
"Your explanation sounds good BUT ... It must be wrong or the 50 tube that needs under 10K has 48K on it and is fine. So the CF MUST have the grid biased stong or Sound Practices would not publish it. .......
157: Tube DIY Asylum, I think you missed JRB's point (0.00)
Posted by Michael Koster on 2010-04-26, 08:14:55 (72.173.132.129)
I read JRB's article, with my thinking cap on, and I take away an entirely different conclusion. The one thing I see in the linked article that resembles the DanL circuit is what he calls an "Aikido-S .......
158: Tube DIY Asylum, RE: I really hate forked contacts (0.00)
Posted by Michael Koster on 2010-04-25, 09:12:25 (72.173.132.129)
The expensive teflon ones from DIYhifisupply have very nice split barrel contacts. They grip tight and seem to hold "forever". What could be better? http://www.diyhifisupply.com/node/285 .......
159: Tube DIY Asylum, RE: Maybe Not the Unit You Need (0.00)
Posted by Michael Koster on 2010-04-25, 09:06:36 (72.173.132.129)
"I have seen some units that do have variable crossover slopes - Behringer maybe? " Behringer DCX2496 to be precise... http://www.diyaudio.com/forums/multi-way/63433-behringer-dcx-2496-prototype-activ .......
160: Tube DIY Asylum, RE: Driving a type 50 triode (0.00)
Posted by Michael Koster on 2010-04-22, 10:51:25 (72.173.132.129)
Since I joined this thread anyway, I'll try to think through an answer to your original question. As I point out elsewhere, a follower has low impedance when calculated by 1/gfs or whatever but can on .......
161: Tube DIY Asylum, RE: Driving a type 50 triode (0.00)
Posted by Michael Koster on 2010-04-22, 10:34:19 (72.173.132.129)
Yes,it's -ve grid current I'm talking about also. Your quoted explanation is basically the same mechanism of runaway; whether by ionization or by grid emission or both, what's needed is a low DC resis .......
162: Tube DIY Asylum, RE: New DIY 300B creation (0.00)
Posted by Michael Koster on 2010-04-22, 08:48:19 (72.173.132.129)
The virtual choke will work very well fed by a a CLC using relatively small inductance and capacitance (20uF, 1H, 40uF C2 for example) values. The choke will recover some 30-40 volts DC ripple from C1 .......
163: Tube DIY Asylum, RE: Driving a type 50 triode (0.00)
Posted by Michael Koster on 2010-04-22, 08:37:57 (72.173.132.129)
"Directly coupled to a cathode follower will ensure that the grid bias is locked firmly." I'm not so sure. When a tube goes into runaway due to grid current, the grid heats up and starts emitting "ele .......
164: Tube DIY Asylum, RE: Custom Linestage & Phonostage by Paul Birkeland (0.00)
Posted by Michael Koster on 2010-04-21, 18:41:03 (72.173.132.129)
"Those are actually giant 1.0uf teflon V-caps. They are big enough that it made some sense to let them poke out a little bit. " Sure, and at $270 each they should print pictures of heads of state on t .......
165: Tube DIY Asylum, RE: Pentode Loading Question (0.00)
Posted by Michael Koster on 2010-04-21, 08:23:09 (72.173.132.129)
Interesting indeed, can I have a look at your ASC? .......
166: Tube DIY Asylum, RE: Custom Linestage & Phonostage by Paul Birkeland (0.00)
Posted by Michael Koster on 2010-04-21, 08:04:28 (72.173.132.129)
Wow! Looks like some way serious Frontpanel Express work. What are the 2 displays in the lower right with the red pointers and the word (cap?) on the face? Michael .......
167: Tube DIY Asylum, RE: Pentode Loading Question (0.00)
Posted by Michael Koster on 2010-04-21, 07:58:53 (72.173.132.129)
"Whats the problem wasting some watts in a preamp if it works better. Noone objects when burning up substantial power in a 300B amp or other triode-amp ;-)." I suppose that's for the builder to decide .......
168: Tube DIY Asylum, RE: Pentode Loading Question (0.00)
Posted by Michael Koster on 2010-04-20, 09:18:10 (72.173.132.129)
Since I already have this graphic, I'll use it as an example. for a pentode: gain ~= gm * (Zload || Rp) Assuming the D3a gm = 42mA/V and Rp is about 100K, I think 51K load on a D3a at 20mA/150V wi .......
169: Tube DIY Asylum, RE: Dirty earth (0.00)
Posted by Michael Koster on 2010-04-19, 09:21:12 (72.173.132.129)
"You will notice that in the following paragraphs, I will not once mention how my interconnects sound." But there on the front page in huge type "KICK ASS SOUND"... LOL To learn about "ground noise" .......
170: Tube DIY Asylum, RE: PS design issues & fidelity (0.00)
Posted by Michael Koster on 2010-04-17, 13:48:08 (72.173.132.129)
"Without getting into the settings..." ? What's the problem with enabling me to try to repeat your results by telling me your horizontal time base and vertical sensitivity? Michael .......
171: Tube DIY Asylum, RE: PS design issues & fidelity (0.00)
Posted by Michael Koster on 2010-04-16, 21:27:18 (72.173.132.129)
Hi Tre, Interesting observation. On your SET amp playing the "200Hz and above" part of the music at the volume level you test with your speakers, using your measurement technique, you see "nothing". .......
172: Tube DIY Asylum, RE: PS design issues & fidelity (0.00)
Posted by Michael Koster on 2010-04-16, 08:50:14 (72.173.132.129)
Very interesting comments! I am in partial agreement. I have been studying this phenomenon for some time and have come to many of the same conclusions. I agree with your definition of musical attack t .......
173: Tube DIY Asylum, RE: Check ou the LT1963A.... (0.00)
Posted by Michael Koster on 2010-04-15, 10:21:21 (72.173.132.129)
I didn't see the adjustable option. That looks like a keeper! The low dropout voltage will enable using a regular 6.3V AC filament winding to feed the rectifier and a cheap filter. Awesome. Thanks, Mi .......
174: Tube DIY Asylum, RE: Check ou the LT1963A.... (0.00)
Posted by Michael Koster on 2010-04-15, 08:51:42 (72.173.132.129)
From the LT1963 datasheet: "Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 3.3V" How do you use this as a heater regulator? .......
175: Tube DIY Asylum, RE: Dan, I don't seem to get through to you. (0.00)
Posted by Michael Koster on 2010-04-14, 11:52:04 (72.173.132.129)
I think I see what's going on: "I just add a cathode bypass to the table so the ultrapath cap can be much smaller as it doesn't have to do the cathode bypass duty." So what I think will actually happe .......
176: Tube DIY Asylum, RE: RCA jacks (0.00)
Posted by Michael Koster on 2010-04-14, 11:00:07 (72.173.132.129)
"Supposed to be gold over copper, no nickel." What's the advantage in omitting the hard nickel under the gold? Seems to me it would result in a less durable connector overall. Big ground? Is this a s .......
177: Tube DIY Asylum, RE: RCA jacks (0.00)
Posted by Michael Koster on 2010-04-14, 10:39:22 (72.173.132.129)
Real studios don't use RCAs much. Balanced, XLR all the way baby... Some mastering people (Paul S comes to mind) do use RCAs because they believe simgle ended has less junk in the signal path. I'm not .......
178: Tube DIY Asylum, RE: "rated for 2000 insertions" (-- that's what she said! (0.00)
Posted by Michael Koster on 2010-04-14, 10:30:50 (72.173.132.129)
2000 mating cycles is pretty good for this type connector, but I have an old rooster that's been good for more than that ;-) Seriously a mating cycle is one insertion and one removal. .......
179: Tube DIY Asylum, RE: impedence of CCS mu output (0.00)
Posted by Michael Koster on 2010-04-14, 10:14:57 (72.173.132.129)
"I have built several phono stages and this approach (low Zout active stages and low R RIAA) gives me the best results. " Hi Mike C, It's your post from a few years ago that induced me to try this app .......
180: Tube DIY Asylum, RE: Series AC (0.00)
Posted by Michael Koster on 2010-04-13, 09:55:54 (72.173.132.129)
As long as they're in phase the voltage will add. As long as ohms law (and Kirchoff's etc) is used and voltage and power limits are observed it is safe. Michael Ps For example, if you want higher seco .......
181: Tube DIY Asylum, RE: Dont' forget a cap where you raise the 6GK5 heater to 50 volts. (0.00)
Posted by Michael Koster on 2010-04-13, 09:33:07 (72.173.132.129)
I read total current thru the 15K resistor as 40mA: 10mA channel A driver 10mA channel B driver 20mA idle in VR tube The problem with this is while the driver heaters are cold, the VR tube will have t .......
182: Tube DIY Asylum, RE: impedence of CCS mu output (0.00)
Posted by Michael Koster on 2010-04-12, 23:50:46 (72.173.132.129)
"My circuit uses a MOSFET as a follower, as such all the gain is in the LM431, which is regulating the gate voltage all it can to a steady fixed number..." I would think about it a little differently: .......
183: Tube DIY Asylum, RE: impedence of CCS mu output (0.00)
Posted by Michael Koster on 2010-04-10, 08:24:29 (72.173.132.129)
Very interesting. That's what I started with, using the D3A load resistor as the "R1" of the equalizer, but missed the trick of taking the output at the low-Z "follower" connection. I of all people sh .......
184: Tube DIY Asylum, RE: impedence of CCS mu output (0.00)
Posted by Michael Koster on 2010-04-09, 08:02:47 (72.173.132.129)
I see what you mean. The AC current loop includes C5 and creates a voltage divider of R10+R11 and R14. This would reduce the effective gfs by the voltage divider ratio R14/(R10+R11+R14). Otherwise I t .......
185: Tube DIY Asylum, RE: impedence of CCS mu output (0.00)
Posted by Michael Koster on 2010-04-08, 12:57:26 (72.173.132.129)
I'm not sure about the Pimm CCS equivalent resistance, but you are using the same formula I did. I am thinking the load resistance also needs to be accounted for in the impedance but it's bootstrapped .......
186: Tube DIY Asylum, RE: impedence of CCS mu output (0.00)
Posted by Michael Koster on 2010-04-08, 10:06:33 (72.173.132.129)
" nice design! I'd recommend to use the D3A as input tube because of his higher mu & gm. The low output impedance is perfect for an LCR-RIAA as well." Thanks, but it's really based on Gary Pimm's cir .......
187: Tube DIY Asylum, RE: What is a linear tube? (0.00)
Posted by Michael Koster on 2010-04-08, 08:30:58 (72.173.132.129)
"It is interesting to note that for a given tube, when keeping output power constant, moving from a 5K to a 10K output transformer actually increases distortion yet many people still insist on the opp .......
188: Tube DIY Asylum, RE: Michael, to split hairs... (0.00)
Posted by Michael Koster on 2010-04-08, 08:11:19 (72.173.132.129)
"A classic mU output is per Alan Kimmel, and needs a extra cap to allow a large resistor between the lower anode and the upper cathode." I like splitting hairs though. Here's what Broskie says abou .......
189: Tube DIY Asylum, RE: impedence of CCS mu output (0.00)
Posted by Michael Koster on 2010-04-07, 22:56:52 (72.173.132.129)
This is a circuit I'm working on which I think is representative of your case. The Zout of the mu-output is a function of the gfs of the MOSFET you are using, the value of the MOSFET source resisto .......
190: Tube DIY Asylum, RE: 6AM4 max grid resistance ? (0.00)
Posted by Michael Koster on 2010-04-05, 09:43:56 (72.173.132.129)
Hmm I wonder what safe Rg values are with a CCS supplying the plate? It seems like the CCS on the plate, particularly at low plate current, is a natural for grid-leak bias or for using Rg values great .......
191: Tube DIY Asylum, RE: Tetrode pinout questions (0.00)
Posted by Michael Koster on 2010-04-02, 21:57:58 (72.173.132.129)
You don't need to use a center tap in your application. Just use an isolated switcher like a Xantrex/EMS lab industrial supply (1Kw in 1 rack space for $100 surplus) and make the cathode connection to .......
192: Tube DIY Asylum, RE: Who orders Pizza in a Burger Joint? (0.00)
Posted by Michael Koster on 2010-03-25, 21:24:17 (72.173.132.129)
I think you're right, it must be some effect with L-input and coupling in the transformer or winding capacitance. That's interesting. .......
193: Tube DIY Asylum, RE: Hamburger, Fries and a shake. (0.00)
Posted by Michael Koster on 2010-03-25, 19:10:38 (72.173.132.129)
OK, supersize that? ;-) My experiment was with a voltage doubler and it didn't seem to matter. Can you explain your result? .......
194: Tube DIY Asylum, RE: I question the accuracy of Dave's statement (0.00)
Posted by Michael Koster on 2010-03-25, 16:43:31 (72.173.132.129)
That thread is full of misinformation. To the first order there is no diffence. It is a current loop. To the second order there is no difference; stray capacitance to ground is the same to AC regardle .......
195: Tube DIY Asylum, RE: Maximum power output for class A2: about 45% (0.00)
Posted by Michael Koster on 2010-03-22, 09:16:56 (72.173.132.129)
Hmmm... The 211 anode swings down to 100V in A2! How about a pentode driver with a MOSFET follower to drive the grid, local V=>I feedback from the 211 plate to the driver plate ahead of the MOSFET. .......
196: Tube DIY Asylum, RE: one ideal feature is ability to swing the anode to very low Vak (0.00)
Posted by Michael Koster on 2010-03-21, 17:51:43 (72.173.132.129)
I believe the confusion between the 25% and 50% efficiency rating lies in the load. If you resistively load a device in a class-A circuit, the max AC output efficiency is 25%, whereas with transform .......
197: Tube DIY Asylum, RE: one ideal feature is ability to swing the anode to very low Vak (0.00)
Posted by Michael Koster on 2010-03-21, 17:42:38 (72.173.132.129)
Power bandwidth is not exactly "old lore". Look into Transient Intermodulation Distortion (TIM) caused by slew-limiting of signals within the audio bandwidth. Of course this happens in the upper frequ .......
198: Tube DIY Asylum, RE: one ideal feature is ability to swing the anode to very low Vak (0.00)
Posted by Michael Koster on 2010-03-21, 17:20:46 (72.173.132.129)
LOL ... are we done swingin' our anodes around? My goal was an appropriate power level for driving JBL 4312s, which I connect to an amp I build and play at reasonable levels for what I do -- room moni .......
199: Tube DIY Asylum, RE: one ideal feature is ability to swing the anode to very low Vak (0.00)
Posted by Michael Koster on 2010-03-21, 15:19:31 (72.173.132.129)
It was but a contrived example to demonstrate a mathematical limit. The desireability of trying to actually get that behavior with a triode is questionable, I agree. There is, however, an easy way to .......
200: Tube DIY Asylum, RE: one ideal feature is ability to swing the anode to very low Vak (0.00)
Posted by Michael Koster on 2010-03-21, 10:16:12 (72.173.132.129)
"Try it in real lifer, not a &^%$#@! simulation with "ideal" triodes." The model using ideal triodes is simply to show that the THEORETICAL MAXIMUM anode efficiency of a class A amplifier is 50% ra .......
201: Tube DIY Asylum, RE: Measured output power - or just calculated? (nt) (0.00)
Posted by Michael Koster on 2010-03-21, 10:08:22 (72.173.132.129)
The measured output of the Solstice amp is ~16 watts after OPT losses. It is about 18W power output at the anodes. The anode dissipation is actually currently running 24W per tube (39% efficiency at t .......
202: Tube DIY Asylum, 39% anode efficiency (0.00)
Posted by Michael Koster on 2010-03-20, 16:21:38 (72.173.132.129)
It's the same 40% power ratio whether SE or PP-- So I just checked my notes again and I think the WE chart has an error. I think the 400V B+, 4000 ohm, 9.4 watt OP needs 60mA idle. This is actually .......
203: Tube DIY Asylum, Maximum power output for class A (0.00)
Posted by Michael Koster on 2010-03-20, 14:27:15 (72.173.132.129)
I thought I would start a new thread to discuss this subject. I have seen numerous references to a power output limit for class A amplifiers of 25% of quiescent anode dissipation. In my own experie .......
204: Tube DIY Asylum, RE: Not 20W... (0.00)
Posted by Michael Koster on 2010-03-20, 11:12:07 (72.173.132.129)
"that's not the same as a single tube," I'm using the 9.4W output op point on each tube, which yields about 16 watts after transformer losses. It's the same 40% power ratio whether SE or PP. I have do .......
205: Tube DIY Asylum, RE: Not 20W... (0.00)
Posted by Michael Koster on 2010-03-20, 10:44:20 (72.173.132.129)
"Trying to get more than 10 watts out of a single 300B is OK if you can afford it or have lots of spares." That may be true but it's not what Allen claimed. Maybe this belongs in another topic, but .......
206: Tube DIY Asylum, RE: Not 20W... (0.00)
Posted by Michael Koster on 2010-03-20, 10:03:44 (72.173.132.129)
"...as a pure Class A1 amp is only 25% efficient." Hi Allen, I think it all depends on how you define class A. Maybe the operative word is "pure", but there's not a universal definition... I hav .......
207: Tube DIY Asylum, RE: Snubber across on/off switch (0.00)
Posted by Michael Koster on 2010-03-20, 09:41:33 (72.173.132.129)
It has nothing to do with sequencing; there's no time for anyting to sequence before the pop occurs. Probably inductive "kick" from leakage inductance of the power transformer primary. Try putting the .......
208: Tube DIY Asylum, RE: But they are NOT... (0.00)
Posted by Michael Koster on 2010-03-18, 13:14:35 (72.173.132.129)
I built a spud amp for 5842 or 6C45P using a MOSFET active load and parafeed output to a cheap toroid. It puts out up to 2 watts (1.5W with the 5842) and has excellent frequency response. I hadn't .......
209: Tube DIY Asylum, RE: Old PA-amp converted into a clean , guitaramp (0.00)
Posted by Michael Koster on 2010-03-16, 11:43:12 (75.105.174.115)
I don't know how far along you are but the original EL34 circuit with a new OPT would probably be an excellent basis for a clean guitar amp, tweaking some R and C values here and there for gain and fr .......
210: Tube DIY Asylum, RE: The Class A1.5 Amplifier (0.00)
Posted by Michael Koster on 2010-03-14, 16:37:02 (75.105.174.115)
"I don't see any examples or discussion of Class A circuits that are purposely biased where the symmetry would be less than could be obtained for the chosen tube." Hi Tre' This is the very popular .......
211: Tube DIY Asylum, RE: The Class A1.5 Amplifier (0.00)
Posted by Michael Koster on 2010-03-14, 13:34:38 (75.105.174.115)
LOL look at the description of class AB2 on the same page ... He shows hard clipping where the grid current should be. If this is your bible no wonder you don't believe in A2 ;-) he also incorrectly s .......
212: Tube DIY Asylum, RE: Bench On A2 (0.00)
Posted by Michael Koster on 2010-03-13, 10:00:14 (75.105.174.115)
I still don't think there's a bright line where the designer intends/doesn't intend for positive grid swing to result in more power. What's the minimum duty cycle of a peak?" What subclass is this? .......
213: Tube DIY Asylum, RE: Bench On A2 (0.00)
Posted by Michael Koster on 2010-03-13, 09:45:41 (75.105.174.115)
Ooh now that I've had my coffee... I like Dave's suggestion. There's no redefinition of what exists, but a new clarification. But what if a class A2 biased amp loses grid conduction on the peaks? ; .......
214: Tube DIY Asylum, RE: The Class A1.5 Amplifier (0.00)
Posted by Michael Koster on 2010-03-13, 08:10:08 (75.105.174.115)
New definitions are not needed, nor IMO particularly helpful. It's just more stuff for people to argue about... There is a perfectly fine existing definition of class AB2 vs class AB1. If the grid go .......
215: Tube DIY Asylum, RE: New design (0.00)
Posted by Michael Koster on 2010-03-08, 11:37:12 (75.105.174.115)
OK, I think I understand. I'm quoting "RMS watts" and you're quoting "Peak Watts", but it's at the same actual signal voltage. Thanks, Michael PS. If Peak-to-Peak voltage is 2X Peak voltage (which is .......
216: Tube DIY Asylum, RE: New design (0.00)
Posted by Michael Koster on 2010-03-08, 10:34:05 (75.105.174.115)
Hi Dan, I'm wondering about the power estimate. For the voltages you show, I get about 8.6W in class A1 for the EML 320B. Giving the benefit of the doubt to the ability of a plate choke to drive A2 (n .......
217: Tube DIY Asylum, RE: Does size matter (for chokes)? (0.00)
Posted by Michael Koster on 2010-03-07, 18:08:25 (75.105.174.115)
Hmmm is the total flux not the sum of AC and DC? Are you saying that the AC voltage capability doesn't depend on the DC current at all? Or that the effect is small? In practice I have had good results .......
218: Tube DIY Asylum, RE: Should chokes have continuity? (0.00)
Posted by Michael Koster on 2010-03-07, 08:05:16 (75.105.174.115)
Sometimes a DMM will just not read a coil. I have some that just flash random numbers when reading high inductance coils. Also helps to short the coils on the same core you're not reading. This is a g .......
219: Tube DIY Asylum, RE: Does size matter (for chokes)? (0.00)
Posted by Michael Koster on 2010-03-07, 07:57:46 (75.105.174.115)
For power filtering, particularly for a critical-L filter input choke, it seems to be a good thing to spec a choke with a higher current rating than needed (maybe even by 2X-3X), but that's primarily .......
220: Tube DIY Asylum, RE: question of power supply capacitor value (0.00)
Posted by Michael Koster on 2010-03-06, 10:40:26 (75.105.174.115)
I would rather have the energy come from the final PS cap, with a well defined impedance characteristic. Who knows what the impedance versus frequency characteristics of a 5 or 25 KW transformer loc .......
221: Tube DIY Asylum, RE: question of power supply capacitor value (0.00)
Posted by Michael Koster on 2010-03-06, 10:04:23 (75.105.174.115)
"looking carefully at O'scope traces while playing music..." If more people would do *this* we might end up on a single discussion. Set the trace on relatively slow and look at changes in the B+ while .......
222: Tube DIY Asylum, Buddy can you spare a cation? (0.00)
Posted by Michael Koster on 2010-03-06, 09:17:08 (75.105.174.115)
A ferrous wheel... .......
223: Tube DIY Asylum, RE: You certainly can't... (0.00)
Posted by Michael Koster on 2010-02-28, 09:16:59 (75.105.174.115)
pouring gasoline on a fire to cool it down. (!) Sure it could cause oscillation if the MC galvanometer had enough inductance. I thought one would get away with it doing a DC test. By all means keep th .......
224: Tube DIY Asylum, RE: Thanks all, and a further comparison: (0.00)
Posted by Michael Koster on 2010-02-28, 07:40:37 (75.105.174.115)
Sorry, there may be a misunderstanding. I am recommending using a separate transformer for the front end. A full wave bridge rectifier with your existing 230V transformer to power the 6C33s, and a se .......
225: Tube DIY Asylum, RE: I think that's it... (0.00)
Posted by Michael Koster on 2010-02-27, 23:36:48 (75.105.174.115)
I found this in my junk box. It's about the right range for testing leakage current, zero to 0.5 mA (500 uA). It has a shunt resistance of 1100 ohms. You connect the meter in series in the circuit, .......
226: Tube DIY Asylum, RE: Testing for Grid Current (0.00)
Posted by Michael Koster on 2010-02-26, 13:01:40 (75.105.174.115)
Oh, right. Just connect a micro-ammeter in series in the grid circuit, or measure voltage drop across a series resistor in the grid circuit, i.e. open the connection and insert the meter or resistor i .......
227: Tube DIY Asylum, RE: Testing for Grid Current (0.00)
Posted by Michael Koster on 2010-02-26, 08:39:12 (75.105.174.115)
"Should I just monitor the voltage across the series grid resistor in the bias circuit (100k)?" The resistor in the bias circuit will always have signal voltage across it regardless of grid current. .......
228: Tube DIY Asylum, RE: That is because with the DC setup you should (0.00)
Posted by Michael Koster on 2010-02-26, 08:26:53 (75.105.174.115)
Connect the 3k resistor and 47uF cap from the Cathode to ground. Either via your hum pot CT or with 2 resistors as Tre showed. Or even just to either side of the filament. With DC it doesn't need to b .......
229: Tube DIY Asylum, RE: Voltage doubler and half-wave supplies from same tap? (0.00)
Posted by Michael Koster on 2010-02-25, 22:48:54 (75.105.174.115)
That's theoretically possible but you would have what amounts to a 1/2 wave rectifier supplying B+ to 6C33s.. Not the best topology for high current, plus it introduces DC offset in the power transfor .......
230: Tube DIY Asylum, RE: Voltage doubler and half-wave supplies from same tap? (0.00)
Posted by Michael Koster on 2010-02-25, 22:42:05 (75.105.174.115)
That looks like a bridge rectifier with the center tap of the transformer supplying 1/2 voltage. I wonder why the negative legs of the bridge are series diodes but the positive legs are single diodes? .......
231: Tube DIY Asylum, RE: Just like this (0.00)
Posted by Michael Koster on 2010-02-25, 21:41:21 (75.105.174.115)
en if it would work you wouldn't want the music going through the parts (caps, choke, etc...) of the power supply filter. It's worse than that. Making the cathode connection to the CT of the rectifier .......
232: Tube DIY Asylum, RE: Swinging chokes (0.00)
Posted by Michael Koster on 2010-02-25, 12:41:56 (75.105.174.115)
Swinging chokes are designed to decrease inductance at higher DC current, so as to maintain critical inductance over a wide load range. A swinging choke is the *only* way of doing the L-input thing if .......
233: Tube DIY Asylum, RE: Would a choke made especially for choke input PS provide less hum than a "regular" choke used for choke i (0.00)
Posted by Michael Koster on 2010-02-25, 12:35:26 (75.105.174.115)
Thanks for the thorough explanation, John. I too wish the coilwinders would spec max AC voltage@frequency with a given DC current, *like Lundahl does*. I used a 500mA 193P Hammond choke as the input L .......
234: Tube DIY Asylum, RE: Bias and a SMPS (0.00)
Posted by Michael Koster on 2010-02-24, 10:03:49 (75.105.174.115)
Hi Jeff, Most SMPS modules I have used are isolated from input to output to something like 2KV. Line isolation is needed in most applications for safety reasons. You really don't have any choice abou .......
235: Tube DIY Asylum, 1:1 Bifilar Push-Pull Interstage Transformer? (0.00)
Posted by Michael Koster on 2010-02-22, 19:34:21 (75.105.174.115)
I'm considering a circuit which would use a 1:1 bifilar Push-Pull IT. I'm looking for ~300H Lpri and the ability to handle 1-2 mA of DC offset. AC voltage will only be ~70VRMS down to 20 Hz. It seems .......
236: Tube DIY Asylum, Also here (0.00)
Posted by Michael Koster on 2010-02-22, 17:15:48 (75.105.174.115)
http://don-audio.com/Frequency-Spare-Knobs-for-EQP-1A-Equalizer http://don-audio.com/Dakaware-Knobs-Collins-Knob-Radio-Knob-EQP-1A-Knobs-black-knob-black-knobs-plastic-knob-plastic-knobs http://don-a .......
237: Tube DIY Asylum, RE: pultecs controls (0.00)
Posted by Michael Koster on 2010-02-22, 17:06:09 (75.105.174.115)
Do you need to duplicate the Pultec knobs exactly? If not, there are some very similar knobs I am using for some pro audio gear that are available through Allied, made by Davies Molding and EHC. Davie .......
238: Tube DIY Asylum, RE: Tube noise (from socket connections I think) (0.00)
Posted by Michael Koster on 2010-02-12, 09:46:46 (70.41.228.160)
Like he says... The fact that messing about around the socket clears the noise for a while but it comes back right away is a clue that the problem is *near* the pin-socket connection. I would resolder .......
239: Tube DIY Asylum, RE: Anyone Have This Capacitor Insulator (0.00)
Posted by Michael Koster on 2010-02-09, 17:51:30 (70.41.228.160)
I think Radio Shack sells the light bakelite material in sheets. A few minutes with a drill press and jewler's saw and you could make one. Michael .......
240: Tube DIY Asylum, RE: sockets (0.00)
Posted by Michael Koster on 2010-01-27, 23:26:13 (66.124.82.241)
Here is a novar socket with molded mounting ears instead of a metal flange. Is this what you mean? Maybe this vendor has octal and 9-pin miniature also http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&it .......
241: Tube DIY Asylum, RE: voltage divider (0.00)
Posted by Michael Koster on 2010-01-19, 08:39:32 (70.41.228.160)
"Be always more than cautious and if possible do not even touch the probes and the amp when testing. Leave the probes there where you are supposed to take measurements and turn on the amp, read the va .......
242: Tube DIY Asylum, RE: I think he's talking about A1 bias and A2 on peaks (0.00)
Posted by Michael Koster on 2010-01-15, 12:05:11 (70.41.228.160)
Output power at the anode is equal to the voltage swing at the anode (RMS) squared, divided by the load impedance seen at the anode (3K ohms in your case, plus the DCR contribution etc.) In the dotte .......
243: Tube DIY Asylum, RE: Cathode Bias (0.00)
Posted by Michael Koster on 2010-01-15, 11:32:59 (70.41.228.160)
"However, my decision to use it was based on sonics, i.e. which method produced best sound, rather than a belief that one method is inherently a better performer from a technical perspective." Why do .......
244: Tube DIY Asylum, RE: How to drive the 300B into A2?? (0.00)
Posted by Michael Koster on 2010-01-15, 11:16:11 (70.41.228.160)
Here are a couple more things to think about. If you use cathode bias on the 300B, the grid current could be shifting the bias and reducing the anode swing. Also, what's the output impedance of the .......
245: Tube DIY Asylum, RE: Cathode Bias (0.00)
Posted by Michael Koster on 2010-01-15, 10:42:25 (70.41.228.160)
"I don't use cathode bias in my SETs, but why would A2 be any different than AB1 push-pull in this respect? AB1 also causes abrupt increases in tube conduction (cathode current). Isn't this resolved i .......
246: Tube DIY Asylum, RE: I think he's talking about A1 bias and A2 on peaks(nt) (0.00)
Posted by Michael Koster on 2010-01-15, 08:28:17 (70.41.228.160)
How does A2 work with cathode bias? Grid current returning through the cathode would shift the cathode voltage upward on peaks. The upper trace is grid drive voltage to a DHT and the lower trace is .......
247: Tube DIY Asylum, RE: I think he's talking about A1 bias and A2 on peaks(nt) (0.00)
Posted by Michael Koster on 2010-01-14, 22:19:46 (70.41.228.160)
Indeed. The loadline needs to be raised up to get 15W in A2. Dissipation is a little high though; I would use a JJ 40 watt tube or equivalent. (I personally like 4K load and 400V/80mA for occasiona .......
248: Tube DIY Asylum, RE: Ads By Google. (0.00)
Posted by Michael Koster on 2009-12-01, 18:26:35 (70.41.215.56)
Doh! Now look what you've done by calling attention to it! .......
249: Tube DIY Asylum, RE: CCS as plate load on direct coupled input/diver... (0.00)
Posted by Michael Koster on 2009-11-30, 12:08:26 (63.81.26.200)
Here's another option that doesn't depend on the anode voltage of the driver being constant with current. It uses fixed DC bias but for AC signal it behaves like the CCS/mu-follower and can happily .......
250: Tube DIY Asylum, RE: Missed the point (0.00)
Posted by Michael Koster on 2009-11-18, 08:50:15 (70.41.214.37)
There is the engineering definition (RC-30 uses the word "approximately" to define class B by the way) which is what it is. Technically, class A means no cutoff. But where exactly is "cutoff" in a vac .......
251: Tube DIY Asylum, Definitions (0.00)
Posted by Michael Koster on 2009-11-17, 12:49:46 (63.81.26.200)
Hey Chris O, Sorry to be pedantic but I don't agree with your definition of class A. Here are the definitions I'm used to. Curious why you believe class A means that the current can't change. Class A .......
252: Tube DIY Asylum, RE: Would rather choose parallel (0.00)
Posted by Michael Koster on 2009-11-17, 11:42:32 (63.81.26.200)
Hey Beq, Parallel is spelled correctly but: The power handling is 3X that of a single part whether you connect 3 resistors of equal value in series or in parallel. The voltage handling is 3X if they'r .......
253: Tube DIY Asylum, RE: Hemp cone speakers (0.00)
Posted by Michael Koster on 2009-11-15, 08:38:33 (70.41.214.37)
Thanks, that will get me started. I'm hoping to use a 12" in a regular open baffle with the champ style circuit (beam tube/no feedback) so will be looking for a speaker that has good bass control. Al .......
254: Tube DIY Asylum, RE: The parts may not make it, but they can help (0.00)
Posted by Michael Koster on 2009-11-14, 12:35:34 (70.41.214.37)
I think he's talking about the "brown drops"... Actually they looked like CDE DME metalized polyethylene to me, but now that you mention it, the CDEs have black printing. .......
255: Tube DIY Asylum, RE: Vishay PR03 Resistors (0.00)
Posted by Michael Koster on 2009-11-14, 09:24:39 (70.41.214.37)
The PR0x line is one of my personal favorites. They are compact and rugged, but the distinguishing feature for me is the voltage rating. The 1W, 2W, and 3W are rated at 350V, 500V, and 750V respective .......
256: Tube DIY Asylum, RE: from my experience unless you are gigging with a full band... (0.00)
Posted by Michael Koster on 2009-11-14, 08:43:04 (70.41.214.37)
"prolly more songs had Deluxes and Champs in the studio than ppl believe" Amen amen amen. It's all about the difference between "big" and "loud". My latest bug is a Champ style amp using an 807. Just .......
257: Tube DIY Asylum, RE: Using a regular OPTX in an UL schematic (0.00)
Posted by Michael Koster on 2009-11-12, 19:59:25 (70.41.214.37)
How to determine screen voltage? I like to draw the load line. Let's assume your OPT is about 5K ohms anode-anode Zpri. That gives 1250 ohms load on each anode in class AB. Also assuming 550V B+ an .......
258: Tube DIY Asylum, RE: Edcor WSM 600/600 wiring question, project schematic shown (0.00)
Posted by Michael Koster on 2009-11-10, 10:51:50 (63.81.26.200)
Flipping phase of the IT doesn't change the output power (7w) or bandwidth but it does change the distortion. The driver distortion in both cases is .94% and the distortion at the output as drawn is 2 .......
259: Tube DIY Asylum, RE: Edcor WSM 600/600 wiring question, project schematic shown (0.00)
Posted by Michael Koster on 2009-11-09, 14:22:04 (75.105.173.110)
Hey Lars and JANDG, I'm not sure a bifilar is the best choice, because there are no 2 ends with equal AC swing. The outer end of the primary is at fixed potential, while both ends of the secondary hav .......
260: Tube DIY Asylum, RE: Help for a novice! (0.00)
Posted by Michael Koster on 2009-11-02, 10:01:08 (70.41.243.170)
How have you handled elevating the filament voltage for V3 so as not to exceed the +/- 90 volts 5687 max filament to cathode voltage? I would think one would want a separate filament transformer and h .......
261: Tube DIY Asylum, RE: "a Williamson-style 6SN7 voltage amp and concertina splitter" (0.00)
Posted by Michael Koster on 2009-11-02, 08:22:28 (70.41.243.170)
Hey Lars, You can use the graphical method to dial in the nonlinearity also. If you want to predict the distortion cancellation accurately you would need to use spice, right? I would go with g2=150 .......
262: Tube DIY Asylum, RE: Yeah, that little tube sucks a lot of current... (0.00)
Posted by Michael Koster on 2009-11-01, 09:37:10 (70.41.243.170)
20ma continuous is too much for a 150-200 mAH NiCd or NiMH 9V battery, The 6SL7 would be OK at a couple of mA but not 5687 at 20mA. I use a rule of thumb of C/100 (Capacity/100) for charging rate and .......
263: Tube DIY Asylum, RE: ANY 100W Monoblock Schematics??? (0.00)
Posted by Michael Koster on 2009-11-01, 09:24:20 (70.41.243.170)
The best match I can come up with is parallel 807s, 600V in class AB1 with 5K plate-plate will give you a little over 100W. I guess KT88 or GU50, etc. will work as well (TT21...) anything with a 600V .......
264: Tube DIY Asylum, RE: "a Williamson-style 6SN7 voltage amp and concertina splitter" (0.00)
Posted by Michael Koster on 2009-11-01, 08:50:07 (70.41.243.170)
Hey Ray and Lars, Now I think the load line diagram I posted up at the top of this thread might be helpful. I think you need to get the quiescent current of the driver up where it can accomodate th .......
265: Tube DIY Asylum, RE: Has anyone had success with "Partial Feedback" recently (0.00)
Posted by Michael Koster on 2009-10-28, 09:20:51 (70.41.243.170)
Hi Ray, This is how I determine the OP for the driver with plate feedback. Here is an example load line for the pentode loaded by the output plate feedback current. Taking the voltage between the o .......
266: Tube DIY Asylum, RE: DIY .... (long and graphic intensive).not for dial up! (0.00)
Posted by Michael Koster on 2009-10-26, 08:56:03 (70.41.243.170)
Yeah, but did you ever try to jiggle a conducting strip? Yes, all the time. You take the same wooden chopstick and push and tap the connections on the PCB to find cold or microphonic solder joints. Wo .......
267: Tube DIY Asylum, RE: So, you DO like NFB! (0.00)
Posted by Michael Koster on 2009-10-24, 19:00:07 (70.41.243.170)
The way I see it, the input signal to, let's say a triode, is the grid-cathode voltage. The output signal is the plate-cathode voltage. If, for example, there is a resistive load on the plate, then th .......
268: Tube DIY Asylum, RE: No scope, but you better have at least a voltmeter (0.00)
Posted by Michael Koster on 2009-10-20, 09:14:02 (70.41.243.170)
I taught myself graphical load line analysis out of the RCA receiving tube manual in 1968, when I was 10 years old. I got my first scope in 1980, when I was 22 years old. Between 1968 and 1980 I desig .......
269: Tube DIY Asylum, RE: PSUD and AB1 operation (0.00)
Posted by Michael Koster on 2009-10-18, 18:03:51 (70.41.243.170)
If you want a critical-L input filter, you may need a swinging choke and maybe "bleeder" loads to deal with the current swing. The bleeder resistors increase the minimum load and the swinging choke in .......
270: Tube DIY Asylum, RE: Series fed and CCS? (0.00)
Posted by Michael Koster on 2009-10-12, 16:59:14 (70.41.243.170)
The simple answer is that there would be no return path for the (changing) signal current in the plate circuit. There would be no output. Nice flat load line in other words ;-) If you were to return t .......
271: Tube DIY Asylum, RE: dooooood!!!!! (0.00)
Posted by Michael Koster on 2009-10-12, 08:26:27 (70.41.243.170)
"It isn't just Rdyn...the numbers just don't tell the whole thing IME. Cascode either of them, preferably a suitable IXYS 10Mxx( depedant on voltage ), over a DN3545N3 Supertex chip. This unique co .......
272: Tube DIY Asylum, Now THIS is a Power Transformer... (0.00)
Posted by Michael Koster on 2009-10-07, 12:09:57 (63.81.26.200)
"Hi Michael, Nice maybe for bass, but keep in mind, the larger the output transformer, in SE particularly, the worse will be the high end, and potting an output is not the best sonically. Now for .......
273: Tube DIY Asylum, RE: You seem to have some takers... (0.00)
Posted by Michael Koster on 2009-10-05, 10:56:32 (63.81.26.200)
"But with only 4 tubes, how long do you expect it to keep working?" Now there's an excellent point. TT100s don't exactly grow on bushes. It would be good to have a second choice valve that is close or .......
274: Tube DIY Asylum, RE: Valve amp DIY (0.00)
Posted by Michael Koster on 2009-10-04, 11:31:42 (70.41.243.170)
"I will do it for $12,000" I will do it for $25,000 US ;-) .......
275: Tube DIY Asylum, RE: Valve amp DIY (0.00)
Posted by Michael Koster on 2009-10-04, 11:29:19 (70.41.243.170)
"Also I have some TT100 valves..on Duncan's amps page there is a schematic of these tubes and they seem to be very powerful...I got 4 of these...anyone can actually design an amp for these valves to b .......
276: Tube DIY Asylum, Now THIS is an OPT... (0.00)
Posted by Michael Koster on 2009-10-04, 10:51:36 (70.41.243.170)
for a 300W per channel tube amp. These weigh 25lbs each but won't work with KT88s. They are 8K primary impedance and more suitable for transmitting tubes and high voltage B+ ;-) Michael ::: TOPIC:: .......
277: Tube DIY Asylum, RE: Are any really able to hear audible differences? (0.00)
Posted by Michael Koster on 2009-09-30, 16:12:41 (70.41.243.170)
"Yeah, folks tell me it's compression and other magic done in the studio. I don't think that many studio recordings have the intention of ever faithfully reproducing live music. I'm not a recording en .......
278: Tube DIY Asylum, RE: What's the advantage? (0.00)
Posted by Michael Koster on 2009-09-29, 14:55:19 (63.81.26.200)
"Last but not least, you can use economic AC mains transformers (the same as for linear power supply) instead of expensive audio transformers (because of the perfect balance of the bias current)." You .......
279: Tube DIY Asylum, RE: OPT misuse and abuse (0.00)
Posted by Michael Koster on 2009-09-25, 09:21:55 (70.41.243.170)
Transcendar also wind a 3K:8 OPT on the same core. .......
280: Tube DIY Asylum, RE: All-pentode diff PP amp (0.00)
Posted by Michael Koster on 2009-09-25, 09:17:29 (70.41.243.170)
The problem with the schematic is that the AA server limits the display size to less than 640x480. Jpeg would be OK if it allowed a larger image dimension. I know I've seen larger ones posted in the p .......
281: Tube DIY Asylum, RE: Stonehenge Schematic (0.00)
Posted by Michael Koster on 2009-09-22, 13:21:38 (63.81.26.200)
Gain stage=> concertina => diffamp driver => series push-pull output stage. Broskie showed a similar outstage topology some years ago on tubecad journal. Nice way to use a mains toroid at higher powe .......
282: Tube DIY Asylum, Tesla Coil! (0.00)
Posted by Michael Koster on 2009-09-19, 07:19:29 (70.41.243.170)
Bzzzzzzzzzzzzzzzzzzzt! .......
283: Tube DIY Asylum, RE: Nice catch (0.00)
Posted by Michael Koster on 2009-09-18, 15:54:31 (63.81.26.200)
The comment about scope transformers is they seem to be low voltage high current and suitable for doubler service. Parallel windings was for the sake of comparing the doubler to cap input, apples to a .......
284: Tube DIY Asylum, RE: Nice catch (0.00)
Posted by Michael Koster on 2009-09-18, 14:27:12 (63.81.26.200)
Why use doublers? so you can use old scope transformers to power tube amps of course! "Of course there are two kinds of doublers as I think you know: full wave and half wave. Full wave doublers .......
285: Tube DIY Asylum, RE: how do I build low DCR power supply? (0.00)
Posted by Michael Koster on 2009-09-06, 11:59:53 (70.41.214.171)
"My latest incarnations are actually CLCLC designs, starting with a very small first cap (usually between .1uf and .47uf) followed by a choke (usually less than 1H and less than 1 ohm) followed by .......
286: Tube DIY Asylum, RE: how do I build low DCR power supply? (0.00)
Posted by Michael Koster on 2009-09-06, 11:46:41 (70.41.214.171)
I'll second the voltage doubler approach as well. I just breadboarded an amp with a low impedance voltage doubler + LC filter and I found it has the same characteristic of fast settling, reasonably go .......
287: Tube DIY Asylum, RE: how do I build low DCR power supply? (0.00)
Posted by Michael Koster on 2009-09-06, 09:48:16 (70.41.214.171)
John, Thanks for being an example to us all of how not to lower ourselves to the least common denominator of this discussion. I have not kept to the high ground wery well, but I am learning and trying .......
288: Tube DIY Asylum, RE: Yes and no. (0.00)
Posted by Michael Koster on 2009-09-06, 09:20:45 (70.41.214.171)
You're right, Ray. RDH4 gives the definition of bleeder resistor as the minimum load resistor and says nothing about discharging capacitors, so it must have been common usage back then. Funny, I also .......
289: Tube DIY Asylum, RE: Yes and no. (0.00)
Posted by Michael Koster on 2009-09-05, 09:38:49 (70.41.228.113)
Hey Ray, I always thought the term "bleeder" referred to the slow discharging of the filter capacitors, i.e. to "bleed off" the charge. The one used to keep the choke at critical inductance would also .......
290: Tube DIY Asylum, RE: Too much time on their hands? (0.00)
Posted by Michael Koster on 2009-08-31, 07:26:24 (70.41.228.113)
"I must say, out of all the forums posted, audioasylum is the absolute worst. It's a pathetic combination of audiophile dick waving competitions, brand elitism, and (dopeyface)." He has a point... I t .......
291: SET Asylum, RE: What you have and heard........ (0.00)
Posted by Michael Koster on 2009-08-30, 10:16:05 (75.105.173.26)
Jeff, I'd take this up with you privately but I don't want to risk being threatened with a lawsuit (I thought it was just a hobby!) so will keep it all in the public domain. Please don't send me any m .......
292: Tube DIY Asylum, RE: You need quite a bit more inductance that 640 Henries. (0.00)
Posted by Michael Koster on 2009-08-24, 16:07:07 (70.41.242.160)
Maybe he switched direction a few times ;-) .......
293: Tube DIY Asylum, RE: High voltage Low current current source? (0.00)
Posted by Michael Koster on 2009-08-24, 10:55:48 (70.41.242.160)
Cascode pair of LND150? http://www.supertex.com/pdf/datasheets/LND150.pdf .......
294: Tube DIY Asylum, RE: .asc file (0.00)
Posted by Michael Koster on 2009-08-24, 08:43:07 (70.41.242.160)
Dave, Thanks for the files. Now we can play along... The sine wave in this case has dv/dt high enough (higher frequency than the LC resonance) to excite the LC in the way a step function would through .......
295: Tube DIY Asylum, RE: Latest build up-date (0.00)
Posted by Michael Koster on 2009-08-23, 11:25:52 (70.41.242.160)
Get up in the range of 70-200 KHz and no rectifier is needed (if not wanted). HF heating could use a single converter with a tiny transformer at each tube socket to produce the correct voltage for tha .......
296: Tube DIY Asylum, RE: Latest build up-date (0.00)
Posted by Michael Koster on 2009-08-23, 10:16:40 (70.41.242.160)
Your photo seems to show monoplates. But it was twin plate tubes that had less filament hum? Interesting... .......
297: Tube DIY Asylum, RE: grid choke vs. grid resistor (0.00)
Posted by Michael Koster on 2009-08-23, 09:22:24 (70.41.242.160)
Hi Dave, Isn't this to be expected when the grid draws current and partialy rectifies the signal? The fact that the LF ringing starts out on a (-) excursion suggests to me that the grid current is dis .......
298: Tube DIY Asylum, RE: Did you know? (0.00)
Posted by Michael Koster on 2009-08-21, 13:09:28 (70.41.242.160)
That sounds like fun! Could you still call it a spud? .......
299: Tube DIY Asylum, RE: My Name Is Death (0.00)
Posted by Michael Koster on 2009-08-21, 08:43:09 (70.41.242.160)
The UTC A-12 only has a 500V Hipot test; not sufficient for line isolation :-( .......
300: Tube DIY Asylum, RE: NO! (0.00)
Posted by Michael Koster on 2009-08-20, 09:26:28 (70.41.242.160)
Do watch out for kickback. Use sufficient blade extension and don't let the workpiece climb up the back of the blade, as it did here! Freud recommends a squirt of WD40 every few cuts. I do every cu .......
301: Tube DIY Asylum, RE: Cutting 1/4" aluminum plate (0.00)
Posted by Michael Koster on 2009-08-19, 18:52:46 (70.41.242.160)
This is the table saw blade I use. Lots of safety equpment & precautions needed, and the sliding table or boat is safer in addition to cleaner. The blade will cut sideways almost as easily as straight .......
302: Tube DIY Asylum, RE: Ideas/suggestions and stuff to read up on when building a high voltage psu (0.00)
Posted by Michael Koster on 2009-08-19, 10:43:47 (70.41.242.160)
I have been playing with KV B+ supplies lately and I like voltage doublers. I think for low current ues, a pair of damper diodes might work well. Edit: You do need 2 filament transformers so as not .......
303: Tube DIY Asylum, RE: two words...damper diodes (0.00)
Posted by Michael Koster on 2009-08-18, 17:26:33 (70.41.242.160)
Solves a lot of problems... Nice choice; octal base, no top caps .......
304: Tube DIY Asylum, RE: 0D3 glow tubes flickering - why??? (0.00)
Posted by Michael Koster on 2009-08-18, 16:48:50 (70.41.242.160)
The oscillation is acting like either you have more R or C than you think or there is some other load such that the VR tubes have less than the 5mA minimum current to keep them lit. They will strike, .......
305: Tube DIY Asylum, RE: failure in the B+ supply... (0.00)
Posted by Michael Koster on 2009-08-17, 12:39:58 (70.41.242.160)
"Why do you think that cap blew in the first place? Faulty cap, only?" Just a guess, not knowing maldar's B+ and exact PS topology, but it could be overvoltage on the cap. The reverse biased diode wil .......
306: Tube DIY Asylum, RE: trying to learn about transformers - dumb questions (0.00)
Posted by Michael Koster on 2009-08-14, 12:29:09 (70.41.242.160)
There are no dumb questions... Try 5K with the 6V6 As for the significance, you need to look at the loadline for the operating voltage and current, but most likely the 6V6 was set up for 5K or a littl .......
307: Tube DIY Asylum, RE: Is it possible to run 809 in Class A cathode follower (0.00)
Posted by Michael Koster on 2009-08-12, 15:33:11 (63.81.26.195)
I think a 5K load would be OK for these also. Think 807 load line to the first order. Pentode + mosfet follower gives you gain and drive current. The pentode is especially suited to the plate feedback .......
308: Tube DIY Asylum, RE: Is it possible to run 809 in Class A cathode follower (0.00)
Posted by Michael Koster on 2009-08-11, 19:52:29 (63.81.26.195)
Yes, it's possible to run this as a CF but there is a way to use it in common cathode mode with 2 stages and no global negative feedback. I would treat this tube as a power grid pentode without the .......
309: Tube DIY Asylum, RE: But what is dynamic coupling? (0.00)
Posted by Michael Koster on 2009-08-11, 18:10:15 (63.81.26.195)
In dynamic coupling the load on the driver anode is the grid current of the output tube. The output tube is run in continuous grid current mode. Michael .......
310: Tube DIY Asylum, RE: WTFI Tube wash really...? (0.00)
Posted by Michael Koster on 2009-08-11, 18:06:16 (63.81.26.195)
I guess it's another part of the "tube sound" ;-) .......
311: Tube DIY Asylum, RE: Deoxit 5 Pump Spray WARNING!! (0.00)
Posted by Michael Koster on 2009-08-09, 17:07:15 (70.41.242.160)
What the MSDS says is "sorry, you don't get to know what the active ingredient is because it's a trade secret. And it's not been evaluated for all of the potential health hazards." I'd use a respirato .......
312: Tube DIY Asylum, RE: WTFI Tube wash really...? (0.00)
Posted by Michael Koster on 2009-08-08, 08:29:09 (70.41.242.160)
"Tube wash or hiss as it sounds like, is a term used when you turn up a tube preamp or amp to a point where you hear the tube(s) hissing almost like a pink noise." Paul, I can't find this in common us .......
313: Tube DIY Asylum, RE: CCS noise (0.00)
Posted by Michael Koster on 2009-08-07, 21:16:05 (70.41.242.160)
A CCS should not hiss, but RF oscillation sounds like hiss. You should be able to see it with a 100+ MHz scope. PS where can I find out more about "Tube Wash"? Is this something audio gear reviewers t .......
314: Tube DIY Asylum, RE: no sweat (0.00)
Posted by Michael Koster on 2009-08-05, 11:11:39 (63.81.26.195)
Is that PT 325-0-325 on the secondary like the later Champ? Also I take it that's a 6500 ohm Triad OPT... But it looks like the PT Thanks, Michael .......
315: Tube DIY Asylum, RE: What do you think of Tube Wrangler's construction suggestions? (0.00)
Posted by Michael Koster on 2009-08-04, 13:49:10 (63.81.26.195)
What are the wine bottle corks doing? It looks like one of the high-transfer-efficiency wire bundles goes through the cork. Thanks, Michael .......
316: Tube DIY Asylum, RE: Yes, it is! (0.00)
Posted by Michael Koster on 2009-08-04, 12:24:50 (63.81.26.195)
"...After the SS diode fully turns on, there's only 0.7 volts across the tube rectifier so conduction is minimal. The main advantage to adding the tube is the avoidance of the sudden "bump" at .6 - .......
317: Tube DIY Asylum, RE: The load line will look like thissss (0.00)
Posted by Michael Koster on 2009-08-01, 10:20:03 (70.41.214.73)
Dave, Why is the 20Hz load line a spiral? Is there some "DC shift" happening? Is the 20Hz before or after the cannon fire? Thanks Michael .......
318: Tube DIY Asylum, RE: Some more weird supply simulation - opinions needed (0.00)
Posted by Michael Koster on 2009-08-01, 09:51:45 (70.41.214.73)
Joe and Dave, What is typically meant by "common mode choke" and "common mode rejection"? In the schematic shown the coils are wired effectively in series re the AC ripple voltage, even though they ha .......
319: Tube DIY Asylum, RE: The load line will look like thissss (0.00)
Posted by Michael Koster on 2009-08-01, 08:32:43 (70.41.214.73)
"The loadline you showed would be that of a tube loaded with a 24K resistor driving a 190hy inductance" Oh, of course! There will only be a high value grid resistor if anything besides the AVC/TVC. .......
320: Tube DIY Asylum, RE: Do I have to have the best or is it even the best? (0.00)
Posted by Michael Koster on 2009-08-01, 08:14:42 (70.41.214.73)
"Best is for salesmen" Yeah, best is at best highly subjective. You need a salesman to help you believe in one particular best. When I was in school they taught "New Math". I think it was the same old .......
321: Tube DIY Asylum, The load line will look like thissss (0.00)
Posted by Michael Koster on 2009-07-30, 23:15:43 (66.134.65.220)
The 20 Hz load line will be an ellipse because the load is reactive. This is magnified so you can see it... The 7119 has about the same Rp but higher gm and mu. Doesn't look so bad really. ::: TOPI .......
322: Tube DIY Asylum, RE: If it doesnt draw grid current, it's not worth building! (0.00)
Posted by Michael Koster on 2009-07-28, 23:41:06 (66.134.65.220)
Being able to light AND heat a room with the filaments is a bonus .......
323: Tube DIY Asylum, RE: cool! (0.00)
Posted by Michael Koster on 2009-07-27, 17:40:43 (70.41.228.156)
If it is critical inductance, then B+ should be about 250V (assuming 300mA total load). Ripple a little over 300mV RMS. .......
324: Tube DIY Asylum, RE: PINGING MIKE KOSTER... (0.00)
Posted by Michael Koster on 2009-07-19, 08:10:01 (70.41.228.156)
The IT already provides a high AC impedance plate load to the driver. Adding a CCS in series would not change the plate load but would prevent any signal current from flowing in the IT, i.e. it would .......
325: Tube DIY Asylum, RE: PSUD II screen shots (0.00)
Posted by Michael Koster on 2009-07-17, 21:21:50 (70.41.228.156)
I first set up the screen I want to capture at 640x480 or smaller, so no zooming is needed, if possible. Then I use the windows snipping tool to cut out the area and save it as a jpeg. Jpeg usually .......
326: Tube DIY Asylum, RE: PINGING MIKE KOSTER... (0.00)
Posted by Michael Koster on 2009-07-17, 15:46:35 (70.41.228.156)
"I find that using a band-aid to fix a transformer problem close to the audio band is simply a recipe for bad / unpredictable sound." So you understand my lack of enthusiasm for proceeding in that dir .......
327: Tube DIY Asylum, RE: PINGING MIKE KOSTER... (0.00)
Posted by Michael Koster on 2009-07-17, 14:40:41 (70.41.228.156)
Hi Dave, I did consider a current mirror but there were 2 problems. There would need to be a high voltage offset from cathode to the bias supply, and the bypass cap would introduce a time constant tha .......
328: Tube DIY Asylum, RE: PINGING MIKE KOSTER... (0.00)
Posted by Michael Koster on 2009-07-16, 23:45:46 (70.41.228.156)
That was one of those "try it and see", simple ideas. What I learned is that is a high gm triode with diode bias and fixed B+ doesn't hold very constant current. Not constant enough for the perfect DC .......
329: Tube DIY Asylum, RE: Twisting AC heater line (0.00)
Posted by Michael Koster on 2009-07-15, 08:43:30 (70.41.228.156)
It doesn't matter as long as the pitch of the twists is an exact sub-multiple of the wavelength of the AC frequency. Either acoustic or electrical wavelength is OK to use as long as it's mathematicall .......
330: Tube DIY Asylum, RE: Here is why the loadline becomes elliptic.. (0.00)
Posted by Michael Koster on 2009-07-14, 23:33:24 (70.41.228.156)
With inductive reactance, the current in the load "lags" the voltage across the load as you show. (You show anode voltage, which is the inverse of load voltage.) Here is a sine wave at 48 Hz with t .......
331: Tube DIY Asylum, RE: Power Supplies & LTspice (0.00)
Posted by Michael Koster on 2009-07-14, 13:53:20 (70.41.228.156)
I have just started doing this to evaluate the same parameter you have above. I use a frequency-swept AC current source. Here is a plot of output impedance (V/I expression) and phase in the interes .......
332: Tube DIY Asylum, RE: Mr Wright,....can you please expound on the.... (0.00)
Posted by Michael Koster on 2009-07-13, 09:07:34 (70.41.228.156)
Building an audio amp using DHT transmitting tubes can be fun and rewarding - depending on your goals. High power super clean DC filament supplies are certainly one drawback. And to extend Allen's sta .......
333: Tube DIY Asylum, RE: Running them gently is what causes the problems. (0.00)
Posted by Michael Koster on 2009-07-13, 08:42:28 (70.41.228.156)
"These tubes use a zirconium getter ring on the plate. That getter is not effective at scavenging gas unless it is very hot - so you need to run the tubes hard, near 40W plate dissipation or so. If yo .......
334: Tube DIY Asylum, RE: "Loopy loadlines"... (0.00)
Posted by Michael Koster on 2009-07-13, 08:33:35 (70.41.228.156)
Driving JBL 4312 3-way box speakers, Zout ~= 2 ohms, Zload 8 ohms nominal Michael .......
335: Tube DIY Asylum, Sorry... I had the SV572-10 (0.00)
Posted by Michael Koster on 2009-07-13, 08:10:34 (70.41.228.156)
Different tube... need to back off on the load line a bit and maybe go with 10K Zpri for this one. The plate curves look very similar between the 572-10 and 811-10. I would still go with A1/A2 as a .......
336: Tube DIY Asylum, This is your loadline on music (0.00)
Posted by Michael Koster on 2009-07-13, 01:12:49 (70.41.228.156)
AC plate voltage on X, cathode current on Y PS It takes a reactive load to get a loopy load line. In the spice examples above, there must be more than just resistance in the load? .......
337: Tube DIY Asylum, RE: Good OP point and driver for SV811-10? (0.00)
Posted by Michael Koster on 2009-07-12, 21:24:21 (70.41.228.156)
Funny, I was just looking at the SV811-10 data sheet thinking it would make a nice amp. Edit -- I was actually looking at the SV572-10 datasheet, but a lot of this appplies to both tubes... I would .......
338: Tube DIY Asylum, RE: Questions Re: Battery Bias Problem (0.00)
Posted by Michael Koster on 2009-07-08, 12:01:41 (70.41.228.156)
I only have a couple of data points: I have operated a 2000mAH NiMH AA at 30mA continuously with no heating or overcharging, so C/66 is definitely OK in this case. I have operated a 9V 8 cell batter .......
339: Tube DIY Asylum, RE: Questions Re: Battery Bias Problem (0.00)
Posted by Michael Koster on 2009-07-07, 15:08:30 (64.105.170.146)
Bulging NiMH == Overcharge. NimH voltage is up to 1.5V per cell on charge, down to 1.1V on discharge. "9V" NiMH have 6, 7, or 8 cells (nom 7.6V, 8.4v, 9.6V) sounds like you have a 7-cell version, so i .......
340: Tube DIY Asylum, RE: Anode caps (0.00)
Posted by Michael Koster on 2009-07-06, 21:59:05 (208.74.180.50)
These are the ebay ones that fit 1/4" caps. They have a stamped contact made of some kind of soft spring bronze that can be shaped and soldered. They make a tight contact but I don't know how well .......
341: Tube DIY Asylum, RE: Is an unresponded posting a sign of victory or something? (0.00)
Posted by Michael Koster on 2009-07-06, 09:33:04 (70.41.228.156)
If you posted facts in a flame thread it would be a distraction from the central flame and could get ignored. It's happened to me. Especially if what you post has a moderating or de-polarizing influen .......
342: Tube DIY Asylum, RE: What do you guys use for HV chokes? (0.00)
Posted by Michael Koster on 2009-07-03, 12:44:46 (70.41.228.156)
This isn't very helpful but I don't know... I'm looking for a pair 3H/500mA/25DCR/1500V but don't need much ripple capability (50V p-p). I found a Freed choke on ebay 2.6H/700mA/26DCR/2000V which wou .......
343: Tube DIY Asylum, RE: The PSUD step function (0.00)
Posted by Michael Koster on 2009-07-03, 08:11:03 (70.41.228.156)
The stepped load can be programmed to change (increase or decrease) after a desired delay in seconds. I usually set up PSUD to run for 2 or 3 seconds of simulated time, allowing plenty of time for the .......
344: Tube DIY Asylum, RE: Itâs not about averages, it about instantaneous. (nt) (0.00)
Posted by Michael Koster on 2009-07-02, 12:50:01 (208.74.180.50)
I think I get it. Your current step from idle to peak represents the PS response to the leading edge of a musical event, for example the attack of a drum note (or a piano note for that matter). I thin .......
345: Tube DIY Asylum, RE: Diode Biasing using other than LEDs (0.00)
Posted by Michael Koster on 2009-07-02, 09:49:06 (70.41.228.156)
I would definitely give the SiC diodes a try. The impact of any differences in noise will depend on the circuit and application. I was only familiar with the low voltage drop (0.2V) Si Schottky diode .......
346: Tube DIY Asylum, RE: Dynamic impedance explained (0.00)
Posted by Michael Koster on 2009-07-02, 08:54:13 (70.41.228.156)
-- On page three it is easy to see that at full power the tube swings from 118mA down to 12.5mA. That is a change of 105.5mA with the quiescent current of 60mA. That is a current change of 176%. The a .......
347: Tube DIY Asylum, RE: Diode Biasing using other than LEDs (0.00)
Posted by Michael Koster on 2009-07-02, 07:56:58 (70.41.228.156)
"Seems as if you could achieve a -2.4V (two 1.2V cells in series) bias with an internal resistance of less than 14 milliohms." Maybe... That 7 milli-ohm figure is a marketing number for electric vehic .......
348: Tube DIY Asylum, RE: Diode Biasing using other than LEDs (0.00)
Posted by Michael Koster on 2009-07-01, 15:58:26 (64.105.170.146)
Here's something to try if you want about 2.5 volts - a small MOSFET, like this 2N7000, with gate connected to drain. Dynamic resistance is around 10 ohms (similar to an LED)and voltage drop is Vth .......
349: Tube DIY Asylum, RE: How big does a filament choke have to be? (0.00)
Posted by Michael Koster on 2009-06-21, 09:32:30 (70.41.228.156)
-- Hey Michael... I'm with you on the topic and agree but I think this needs some discussion. Thanks Dave, I didn't think about the use of a common mode choke wired the "usual" way (for example, with .......
350: Tube DIY Asylum, RE: How big does a filament choke have to be? (0.00)
Posted by Michael Koster on 2009-06-20, 09:41:30 (70.41.228.156)
A choke will not do anything for DC regulation. At DC it's just a piece of wire. It will be constant voltage drop with current due to it's DCR. There are at least 2 different purposes for multiple fil .......
351: Tube DIY Asylum, RE: "eliminate Global Feedback loop" (0.00)
Posted by Michael Koster on 2009-06-18, 08:05:04 (70.41.228.166)
"Why did McIntosh decide to make an OPT with a separate secondary wind, just for the GFB? Thanks! " Looking at note 1 on the schematic, it's to provide for floating output (maybe for bridging 2 amps t .......
352: Tube DIY Asylum, RE: it's not that simple (0.00)
Posted by Michael Koster on 2009-06-16, 12:40:24 (70.41.228.166)
"Yes indeedy, as the pot is cranked "down" in resistance the power dissipation capacity decreases likewise. If you don't take this into account, you burn up pots. I found this out at about age 10 ;-)" .......
353: Tube DIY Asylum, RE: you still miss my point (0.00)
Posted by Michael Koster on 2009-06-16, 12:33:08 (70.41.228.166)
"The pot can handle a certain amount of current no matter what the setting. If you design your circuit so you won't exceed that current then it will be fine. " I totally agree! Michael .......
354: Tube DIY Asylum, RE: it's not that simple (0.00)
Posted by Michael Koster on 2009-06-13, 00:02:49 (70.41.228.11)
Good point. In terms of current and P= I^2 * R, the lower resistance, the lower the power (assuming constant current). A 3/4 watt pot at 1/2 travel should be good for 3/8 watt minus the usual additio .......
355: Tube DIY Asylum, RE: pretty simple (0.00)
Posted by Michael Koster on 2009-06-12, 09:09:30 (70.41.228.11)
"It is possible with this arrangement to wind it down to a point where the current could burn it out." Yes indeedy, as the pot is cranked "down" in resistance the power dissipation capacity decreases .......
356: Tube DIY Asylum, RE: New 100TH on eBay (0.00)
Posted by Michael Koster on 2009-06-08, 00:49:17 (70.41.228.11)
Interesting SET I've been looking at these for sale and trying to think about ways to use them like a 100TL in a class A or A2 SET amplifier. The 100TH would be difficult to use in a couple of w .......
357: Tube DIY Asylum, Sunday Paper (0.00)
Posted by Michael Koster on 2009-06-07, 08:22:30 (70.41.228.11)
Someone who is on vacation at the moment commented on another forum that reading AA was like reading a newspaper. Well here's your Sunday scramble! Cheers, Michael .......
358: Tube DIY Asylum, RE: custom chokes with 4 separate windings (0.00)
Posted by Michael Koster on 2009-06-01, 07:49:35 (12.213.224.58)
Any suggestions for further measurements ? Saturation voltage at 20Hz - With only the choke as anode load, increase sine wave voltage until saturation, for the design current, all coils in series. DC .......
359: Tube DIY Asylum, RE: How do I drop the 600 ohm output to a load presentable to an 8 ohm speaker? (0.00)
Posted by Michael Koster on 2009-05-31, 09:04:40 (12.213.224.56)
How do they sound? .......
360: Tube DIY Asylum, RE: Testing Altec 438 Tube compressor limiters??? (0.00)
Posted by Michael Koster on 2009-05-30, 10:44:55 (12.213.224.38)
The 600 ohm output is a pro audio line level; this unit doesn't have enough output power to drive speakers. What are your plans for using these? Whare are they going in your audio chain? You can test .......
361: Tube DIY Asylum, RE: Big honkin CCS. (0.00)
Posted by Michael Koster on 2009-05-27, 11:43:38 (12.213.224.38)
Here's a suggeastion for a loadline that's just as linear, will give you 18 watts Po at the anode in class A1 (though you should see where grid current really starts on a 3CX300), and will reduce t .......
362: Tube DIY Asylum, RE: Big honkin CCS. (0.00)
Posted by Michael Koster on 2009-05-27, 11:29:46 (12.213.224.58)
"I'm not very experienced with a CCS, perhaps someone will check my math. I have a tube that I want to run @300ma, it has a mu of 8, and a -40 bias. Bias voltage 40 x mu 8 = 320VP X .707 = 226VRMS .......
363: Tube DIY Asylum, RE: Mono Combiner - What would you do? (0.00)
Posted by Michael Koster on 2009-05-25, 14:43:42 (12.213.224.58)
Thanks Dave, I was thinking of the Fairchild 670 with it's built-in M+S encoders where L+R are combined in a single transformer. I'm not sure if the coupling in this transformer is special, like 2 sep .......
364: Tube DIY Asylum, RE: Class A2 Direct MOSFET coupled SE (0.00)
Posted by Michael Koster on 2009-05-25, 01:39:15 (12.213.224.58)
Here's the voltage and current at Q1 source (grid of the 4-65A). Maximum output power occurs at about 260V P-P; here I'm driving 300V P-P. The bottom trace is grid current, beginning to increase as .......
365: Tube DIY Asylum, RE: ...plates mounted vertically... (0.00)
Posted by Michael Koster on 2009-05-24, 22:47:49 (12.213.224.58)
Is that so that the heat from one section doesn't rise directly into the other? I don't think convection happens in a vacuum. The radiated heat from each section would affect the other equally regardl .......
366: Tube DIY Asylum, RE: Class A2 Direct MOSFET coupled SE (0.00)
Posted by Michael Koster on 2009-05-24, 11:17:22 (12.213.224.56)
Hi Al, I think the 5K units might be the better deal after all, based on a more correct analysis. It looks like the thing to be gained is lower -3db power point at the expense of a slightly worse d .......
367: Tube DIY Asylum, RE: Mono Combiner - What would you do? (0.00)
Posted by Michael Koster on 2009-05-24, 11:02:05 (12.213.224.58)
A repeat coil (1:1 line transformer with split coils) wired with one channel to each input coil and output coils in parallel (lose 6db of the repeat coil but with an LS-30 you still get +18dbu). Like .......
368: Tube DIY Asylum, RE: Since this is controlled at the source fix it there (0.00)
Posted by Michael Koster on 2009-05-24, 10:52:18 (12.213.224.56)
"One can quickly assume that with multi track recordings there are likely mics connected both ways." I would not make that assumption; having been around more than a few recording and mastering studio .......
369: Tube DIY Asylum, RE: Class A2 Direct MOSFET coupled SE (0.00)
Posted by Michael Koster on 2009-05-23, 18:29:05 (12.213.224.38)
The 1N60 is doing more than CCS, I'm getting 300V P-P from the 5842 whilst driving the 4-65A grid +50V. I don't think a Valab choke will do that... Looking at the grid voltage waveform, there is th .......
370: Tube DIY Asylum, RE: Is reversing the polarity audible? (0.00)
Posted by Michael Koster on 2009-05-23, 12:21:16 (12.213.224.38)
I see what you mean about the amp-speaker interface. One possibility is that one amp-speaker polarity is additive and the other is subtractive wrt the first order nonlinearity, and that effect is more .......
371: Tube DIY Asylum, Is reversing the polarity audible? (0.00)
Posted by Michael Koster on 2009-05-23, 09:30:41 (12.213.224.36)
In discussions I've been in at AES meetings etc, the word "polarity" was used rather than "absolute phase". I don't quite follow what is meant by benign. Do you mean to not color the sound with the p .......
372: Tube DIY Asylum, RE: Class A2 Direct MOSFET coupled SE (0.00)
Posted by Michael Koster on 2009-05-22, 09:13:56 (12.213.224.56)
Hi Al, Here's what I have on the breadboard now. The coupling circuit gets a fixed votage reference from Q2/R3 and holds the driver anode and power tube grid at that fixed bias voltage. I put a tri .......
373: Tube DIY Asylum, RE: What are YOU working on? (0.00)
Posted by Michael Koster on 2009-05-21, 13:05:54 (12.213.224.36)
"I discarded the D3a" Don't do that, send them to me; I'll pay the postage! ;-) Your amp looks like a beast! how much does it weigh? Did you coat the top with anything or are you going to let it "age" .......
374: Tube DIY Asylum, RE: Cooling fans with tube amps... (0.00)
Posted by Michael Koster on 2009-05-21, 10:18:10 (12.213.224.58)
"You actually need VERY LITTLE cooling air to make a huge difference, you really just need to give the air a "nudge" to get airflow happening. A good solution is to rectify the heater supply to get .......
375: Tube DIY Asylum, Class A2 Direct MOSFET coupled SE (0.00)
Posted by Michael Koster on 2009-05-19, 21:42:46 (12.213.224.38)
Here's a work in progress.. glacial progress, but progress. Breadboard for the "Meteor" amp, little brother to Thor. This is for learning about driving transmitting tubes in class A2 and trying som .......
376: Tube DIY Asylum, RE: What are YOU working on? (0.00)
Posted by Michael Koster on 2009-05-16, 19:40:35 (12.213.224.36)
The motor runs have extra tabs; you can just solder the bleeders on permanently .......
377: Tube DIY Asylum, Faraday's Law of induction (0.00)
Posted by Michael Koster on 2009-05-16, 08:15:58 (12.213.224.38)
E is EMF or voltage, "dee Phi bee" is change in magnetic flux, and "dee tee" is that which we all fear ;-) (changing time) The dt part of this equation says that the voltage is smaller for either " .......
378: Tube DIY Asylum, RE: There seems to be. (0.00)
Posted by Michael Koster on 2009-05-12, 08:36:39 (12.213.224.58)
AA is either a place for the exchange of information about the DIY theory, design, construction, and operation of vacuum tube audio, or a clever social experiment. I often wonder about the choices to .......
379: Tube DIY Asylum, RE: Ohm's law (0.00)
Posted by Michael Koster on 2009-05-07, 23:04:35 (12.213.224.36)
"If a speaker needs that much power, the user would likely be better off with a good Boulder solid state amplifier. It won't have Eimac "catchet", just pure performance." I would estimate the power .......
380: Tube DIY Asylum, 500 Watts of filament power for 4 tubes! (0.00)
Posted by Michael Koster on 2009-05-07, 18:28:31 (12.213.224.58)
Plus another 420 watts anode power. Can it be powered from a single 120 volt circuit once all the losses are added in? Michael PS And I thought I was ambitious! .......
381: Tube DIY Asylum, RE: what is this circuit? (0.00)
Posted by Michael Koster on 2009-05-03, 20:39:10 (66.53.122.158)
Footswitch circuits are some of the most bizarre circuits but clever nonetheless. Notice that this circuit is driven by 28V AC. The LEDs light up when the switches are opened. They show the switches i .......
382: Tube DIY Asylum, RE: Are the fancy teflon sockets worth the extra money..... (0.00)
Posted by Michael Koster on 2009-04-26, 10:50:15 (12.213.224.56)
Bakelite has been the material of choice for tube sockets for about 100 years. A lot of it's properties depend on the filler material the phenolic resin is mixed with in the manufacturing. I don't wor .......
383: Tube DIY Asylum, RE: Are the fancy teflon sockets worth the extra money..... (0.00)
Posted by Michael Koster on 2009-04-25, 14:30:42 (12.213.224.56)
"I had heard that most people who had tried teflon found out that teflon as a material doesn't have enough structural rigidity to be suitable as a tube socket. I'd stick with the tried and true sol .......
384: Tube DIY Asylum, RE: Tektronix 502a scope; help please (0.00)
Posted by Michael Koster on 2009-04-20, 17:21:20 (64.105.170.146)
200 uV/division differential input is what I remember from my old 502A. I had to sell it when I moved from Alaska in 1985 :-( It's one of the best scopes for audio if you have room for it. I would spe .......
385: Tube DIY Asylum, RE: Temp controlled fans (0.00)
Posted by Michael Koster on 2009-04-15, 08:14:24 (12.213.224.36)
DC fans generate electrical noise through internal commutation, but it should be OK if the fan is some distance from the input circuits. I would simplify and use a large (5" or so) diameter fan (or 2) .......
386: Tube DIY Asylum, How do electron beams supress secondary emission? (0.00)
Posted by Michael Koster on 2009-04-12, 09:04:48 (67.46.77.226)
Glad you asked! L.L. Williams explains it in the very next paragraph. Continuing: "Focussing the electrons into flat beams has three important effects. Very few primary electrons are captured by th .......
387: Tube DIY Asylum, From "The Beam Tetrode" - L.L. Williams (0.00)
Posted by Michael Koster on 2009-04-11, 20:31:00 (67.46.77.226)
"The beams, which give the beam tetrode its name are flat sheets of electrons which pass betweeen the grid and screen wires on their way to the anode. They are not formed by the so-called beam form .......
388: Tube DIY Asylum, RE: There have been good and not-so-good versions (0.00)
Posted by Michael Koster on 2009-04-11, 20:23:08 (67.46.77.226)
Quote: """The article you linked seems to go against many other articles I've read and my general understanding about how beam tubes work. It suggests that the beam forming action is produced by the a .......
389: Tube DIY Asylum, RE: Rectifiers w/ choke input (0.00)
Posted by Michael Koster on 2009-04-03, 19:35:54 (67.46.77.226)
I see, you're thinking about start-up. As pointed out, the turn-on current surge comes from charging the 1st cap, so it can bee too big as to cause too much surge current at start-up. With the 100-200 .......
390: Tube DIY Asylum, RE: Rectifiers w/ choke input (0.00)
Posted by Michael Koster on 2009-04-03, 10:27:03 (67.46.77.226)
The maximum input C spec has no bearing when you're using a critical L input filter. There is no input cap with a (true) L input filter. You can use any value C after a critical L with no ill effects .......
391: Tube DIY Asylum, RE: Before buying... (0.00)
Posted by Michael Koster on 2009-03-31, 11:54:28 (67.46.77.226)
What's the shelf life of a MPP or MKP capacitor? .......
392: Tube DIY Asylum, RE: Is you ready eddy? (0.00)
Posted by Michael Koster on 2009-03-31, 09:43:30 (67.46.77.226)
Doh! These are superior caps in all respects. They're polypropylene foil with low DF and non-conductive packaging, and compact to boot. They make super PS filters and also sound good a parafeed output .......
393: Tube DIY Asylum, RE: Grounding schemes: Bus vs Star or is there really any "difference"? (0.00)
Posted by Michael Koster on 2009-03-23, 10:51:19 (67.46.77.226)
I've never had a noise problem with a star ground that a buss would alleviate. I don't thing it matters much where it is located if it's a true star ground. Perhaps a better term would be star retu .......
394: SET Asylum, RE: 3C24 A2 class SE amplifier prototype (0.00)
Posted by Michael Koster on 2009-03-14, 08:54:55 (67.46.77.226)
I've got a 3C24 A2 in the early breadboard stages myself and would like to compare notes. How are you driving the 3C24 grid? Schematic would be cool. I'm wondering about your op point; how much anode .......
395: Tube DIY Asylum, RE: Building a battery charger (0.00)
Posted by Michael Koster on 2009-03-13, 17:53:02 (67.46.77.226)
There are a few ways to deal with unequal charging of series strings. The 12V battery is a series string itself, of 6 2V cells, so even 12V batteries potentially have this problem. 1. Keep them all .......
396: Tube DIY Asylum, RE: Battery question.... (0.00)
Posted by Michael Koster on 2009-03-13, 12:52:43 (64.105.170.146)
Put them in series and make a *real* B+. It would be a great way to power a parallel 6080 amp, for example. You can discharge a SLA battery like these down by about 25%-50% regularly. Deeper discharge .......
397: Tube DIY Asylum, RE: I decided to let my brother in law do it on an industrial drill press. (0.00)
Posted by Michael Koster on 2009-03-07, 08:22:19 (67.46.77.226)
Nobody intentionally strips threads, but there may have been a thread adhesive used that can be softened by adding a little heat. Or it may just be very tight. If you haven't stripped the socket yet, .......
398: Tube DIY Asylum, RE: OOPs - That's Lacquer Thinner. Get from Home Depot/Lowes /NT (0.00)
Posted by Michael Koster on 2009-03-06, 13:47:29 (67.46.77.226)
Last time I tried Lacquer thinner with a toothbrush it dissolved the bristles. And the brush. And almost every other piece of plastic it came in contact with. Not to mention being a major health hazar .......
399: Tube DIY Asylum, RE: Flux removers? (0.00)
Posted by Michael Koster on 2009-03-06, 13:45:17 (67.46.77.226)
If your solder joints aren't shiny after cleaning with alcohol (I use ethanol "shellac thinner") then I believe you are seeing flux residue. Sometimes you need to wash the joint 4 or 5 times with clea .......
400: Tube DIY Asylum, RE: Aluminum Types: (0.00)
Posted by Michael Koster on 2009-02-27, 16:54:11 (67.46.77.226)
"There are several different types of aluminum sheet. Like T5055." I'm familiar with a few different alloys but not that one. In sheet I usually get 5052, which is pretty strong but good for brake .......
401: Tube DIY Asylum, RE: Chassis construction question (0.00)
Posted by Michael Koster on 2009-02-26, 14:35:09 (67.46.77.226)
I do a lot of aluminum work with a table saw. It can yield excellent results but requires some care. No one has yet pointed out that there is a special type table saw blade for non-ferrous metals. The .......
402: Tube DIY Asylum, RE: no (nt) (0.00)
Posted by Michael Koster on 2009-02-18, 18:14:28 (67.46.77.226)
"One could pass a constant DC current that is equal to the zero signal plate current of the SE output tube" I think you would want to allow the full opposite voltage swing on the "free" end of the pri .......
403: Tube DIY Asylum, RE: Help with a schematic... (0.00)
Posted by Michael Koster on 2009-02-15, 08:45:12 (67.46.77.226)
The old WE datasheet is available at Pete Millett's site: http://www.pmillett.com/tubedata/we300a_b.pdf It taught me that using a characteristic curve chart or doing what others have done for op point .......
404: Tube DIY Asylum, RE: Help with a schematic... (0.00)
Posted by Michael Koster on 2009-02-14, 17:49:29 (67.46.77.226)
If you like 2.5V filaments use the JJ 2A3-40 and run it as a 300B. You can literally use 300B op points up to 40W dissipation. You can use the circuit above with the 2A3-40 at any of these op point .......
405: Tube DIY Asylum, RE: big SF Fenders (0.00)
Posted by Michael Koster on 2009-02-14, 09:56:25 (67.46.77.226)
I remember that 3 position switch. I think my old twin had it. Sometimes you could reduce hum by flipping it one way or the other. This only occurs when there is a bad or multiple AC ground path in th .......
406: Tube DIY Asylum, RE: wholesale component upgrade vs "letting sleeping dogs lie" (0.00)
Posted by Michael Koster on 2009-02-13, 19:33:48 (67.46.77.226)
"the only non-polar I non-polar cap I always change is any hanging off the power switch opr off the standby switch." Does this mean you're using the two-wire power cord? The first upgrade I would do i .......
407: Tube DIY Asylum, RE: What is the fidelity of this transformer? (0.00)
Posted by Michael Koster on 2009-02-08, 09:27:32 (67.46.77.226)
Good point Tim, My probes on this meter will read 000.0 if I bolt the connection together. There is a little drift to 000.1 and back but I watch the meter for a while. If I was building filament suppl .......
408: Tube DIY Asylum, The best microphones are colored... (0.00)
Posted by Michael Koster on 2009-02-06, 09:08:11 (67.46.77.226)
No one I know would describe the Neumann U47 an accurate microphone. I agree that accuracy has meaning in the recording world, but in my experience it's not necessarily a goal of the recording proc .......
409: Tube DIY Asylum, Anode Bake (0.00)
Posted by Michael Koster on 2009-02-05, 01:15:58 (67.46.77.226)
First try, no blue glow, no sparks, just a nice orange anode and the correct DC characteristics. Grid at 0V. A metal base Eimac 3C24 570V * 30mA = 17W 665V * 37mA = 25W 755V * 45mA = 34W I gu .......
410: Tube DIY Asylum, RE: Yes, Folks, This Is Definitely The Audio ASYLUM... (0.00)
Posted by Michael Koster on 2009-02-04, 22:07:08 (67.46.77.226)
Mr Hernia above is an ACME transformer and no one's going to be chasing road runners carrying that mass. I found it on ebay. the seller thought it was a 3 phase transformer but it's kind of obvious fr .......
411: Tube DIY Asylum, RE: Yes, Folks, This Is Definitely The Audio ASYLUM... (0.00)
Posted by Michael Koster on 2009-02-03, 15:59:25 (67.46.77.226)
;-) .......
412: Tube DIY Asylum, What is the fidelity of this transformer? (0.00)
Posted by Michael Koster on 2009-02-03, 14:03:45 (67.46.77.226)
40 to 80 ohms.....low fidelity 20 to 40 ohms..... mid fidelity 20 to 10 ohms..... high fidelity 10 ohms and below ..... ultra high fidelity ~ 1 ohm .... angel voices faithfully rendered, micro-dyna .......
413: Tube DIY Asylum, RE: Any credence to this? (0.00)
Posted by Michael Koster on 2009-02-02, 15:05:48 (67.46.77.226)
"for whatever it's worth ... Morgan Jones' book rejects phenolic sockets for RF ... apparently something to do with insulation and stray capacitance. " Right, phenolic is "not advised for use above 10 .......
414: Tube DIY Asylum, RE: EDIT: My values are different (0.00)
Posted by Michael Koster on 2009-02-01, 12:22:37 (67.46.77.226)
Paul, I think you're right if I follow what you're saying. I too would use one pair of caps for the doubler and the second pair in series as a filter. There will still be a few volts P-P ripple unl .......
415: Tube DIY Asylum, RE: EIMAC saga (continues) (0.00)
Posted by Michael Koster on 2009-02-01, 11:42:21 (67.46.77.226)
Hi Jeff, I did peruse the Jac music site, but the blue glow article there seems to be about barium-getter tubes that have become gassy and how to restore them through trying to reactivate the getter. .......
416: Tube DIY Asylum, RE: Any credence to this? (0.00)
Posted by Michael Koster on 2009-02-01, 11:21:59 (67.46.77.226)
I agree with Chris O. A bad connection on a grid pin can cause an output tube to overheat due to positive bias and potential runaway. There is nothing inherently wrong with the phenolic material itsel .......
417: Tube DIY Asylum, RE: EIMAC saga (continues) (0.00)
Posted by Michael Koster on 2009-02-01, 08:49:11 (67.46.77.226)
More voltage? With a good vacuum you would need ~750V at 0V on the grid to get 75 watts Pd (according to the constant current chart on the datasheet) I'm following this closely as I am starting throug .......
418: Tube DIY Asylum, RE: Finished...testing this weekend,,WARNING..DOWNLOAD INTENSIVE (0.00)
Posted by Michael Koster on 2009-01-31, 18:19:07 (67.46.77.226)
"On an aside, I also built a PP monkey a number of years ago, on a gutted ST-70 chassis. Same circuit you drew right down to the negative supply in the cathode and input transformer for splitting." So .......
419: Tube DIY Asylum, RE: Is this O'scope worth spending on? (0.00)
Posted by Michael Koster on 2009-01-31, 14:59:18 (67.46.77.226)
I used a scope very similar to this one, if not the same exact model, for audio troubleshooting when I started my first audio repair shop in 1978 or so. As I recall the bandwidth was less than 1MHz, .......
420: Tube DIY Asylum, RE: Finished...testing this weekend,,WARNING..DOWNLOAD INTENSIVE (0.00)
Posted by Michael Koster on 2009-01-31, 14:48:18 (67.46.77.226)
Hi Dave, It was my impression that "DRD" stands for "Direct Reactance Drive" and as such could be implemented with stacked supplies. Maybe DRD also requires that the driver current go through the c .......
421: Tube DIY Asylum, RE: Do you think it helps? (0.00)
Posted by Michael Koster on 2009-01-31, 13:11:11 (67.46.77.226)
I don't know; I think the ID thread is very revealing indeed. Many who advocate notions of intellectual isomorphism and "common wisdom" also speak of the creator as a discrete entity... The creator en .......
422: Tube DIY Asylum, RE: Does an R-C-R filter network supply adequate channel separation like in the Morrison Micro? (0.00)
Posted by Michael Koster on 2009-01-31, 10:45:51 (67.46.77.226)
One thing I've wondered about this and other LW-ish designs is how a significant change in driver Rp affects the DC stability of the amp. It seems to me that the driver Rp is effectively the low side .......
423: Tube DIY Asylum, RE: The test you describe was single blind... (0.00)
Posted by Michael Koster on 2009-01-31, 10:22:10 (67.46.77.226)
"snatching your rattling last breaths with deep sea diver sounds" ,and the flowers bloom like madness in the spring... Thanks ever so much Henry! The rest of the threads on this board have been much m .......
424: Tube DIY Asylum, RE: 2A3 Parallel vs P-P (0.00)
Posted by Michael Koster on 2009-01-28, 09:26:34 (66.134.65.220)
"When you parallel two 2A3s in SE, you get twice the power, (which is only 3 dB louder), but, you gain FOUR times the PEAK current. Its JUST what the speaker's voice coil wants to "see"!!" Too much ar .......
425: Tube DIY Asylum, RE: vitamin Q caps different body styles (0.00)
Posted by Michael Koster on 2009-01-25, 10:48:17 (67.46.77.226)
I believe VitaminQ is/was a registered trademark of Sprague, so it was probably licensed to other manufacturers to be used for a particular type of construction and materials. Here's a different bo .......
426: Tube DIY Asylum, RE: Minor Surgery (0.00)
Posted by Michael Koster on 2009-01-19, 13:51:22 (67.46.77.226)
Kinda reminds me of my vasectomy, which I got to watch ;-) .......
427: Tube DIY Asylum, RE: Difference between a standard SET and a Parafeed (0.00)
Posted by Michael Koster on 2009-01-17, 10:13:39 (67.46.77.226)
Hi Paul, Some people have heard about how OPTs have "magnetic crossover distortion" and how the DC bias and gap in a conventional SE OPT "linearizes" the output and enables more low level detail. Conv .......
428: Tube DIY Asylum, RE: 3C24 Project Complete "Thorium" (0.00)
Posted by Michael Koster on 2009-01-14, 15:30:17 (67.46.77.226)
OK, I'm doing my next amp panels with Frontpanel Express. There must be some shape libraries people are sharing... Speaking of sharing, I acquired a pair of NOS Johnson 122-105-100 sockets which are n .......
429: Tube DIY Asylum, RE: It was so cold here I cryoed my tubes outside! (0.00)
Posted by Michael Koster on 2009-01-14, 08:29:18 (67.46.77.226)
Right now it seems they're just cryo'in on our shoulder, eh? PS Prudhoe Bay Alaska, January 1985, -92F, windchill -116, your eyelids freeze instantly... .......
430: Tube DIY Asylum, RE: Just finished JE Labs 2A3... (0.00)
Posted by Michael Koster on 2009-01-13, 14:55:56 (67.46.77.226)
There is a supplier in the SF Bay area called Sequoia Brass and Copper (or close to that) I have used in the past that will let you go in and pick through offcuts of plate and tubing. They're in Union .......
431: Tube DIY Asylum, RE: Just finished JE Labs 2A3... (0.00)
Posted by Michael Koster on 2009-01-12, 09:32:31 (67.46.77.226)
That's an inspiration! Copper and wood are so beautiful in concert. Cheers, Michael PS The patina on the copper is sublime. Is it just the handling you did building the amp or is it a treatment? ::: T .......
432: Tube DIY Asylum, RE: OTL or SET (0.00)
Posted by Michael Koster on 2009-01-11, 16:46:52 (67.46.77.226)
Those 2 amps would have almost no parts in common. Build them both. Would you be more comfortable designing an electric chair or a forklift? ;-) Cheers, Michael .......
433: Tube DIY Asylum, RE: something that you CAN NOT get ANY other way (0.00)
Posted by Michael Koster on 2009-01-11, 12:16:18 (67.46.77.226)
I agree, all of the music is affected by the response of the power supply. The oscillation and ringing etc problems often happen at low frequency i.e. it might "ring" at 5 Hz, so I refer to it as LF r .......
434: Tube DIY Asylum, RE: something that you CAN NOT get ANY other way (0.00)
Posted by Michael Koster on 2009-01-11, 10:47:52 (67.46.77.226)
Whell it was really a rhetorical question. I have no hard and fast rules myself, but I do know it makes a difference in the LF response and I suppose there is such a thing as too low. Without any resi .......
435: Tube DIY Asylum, RE: something that you CAN NOT get ANY other way (0.00)
Posted by Michael Koster on 2009-01-11, 08:19:21 (67.46.77.226)
Hey, I have family in the twin cities. Does Dr. Low Ohms build tube amps? What is the DCR of the power tranny I would need for a 200 watt tube amp? Push-pull of course ;-) Certainly less than one ohm. .......
436: Tube DIY Asylum, RE: something that you CAN NOT get ANY other way (0.00)
Posted by Michael Koster on 2009-01-10, 12:16:55 (67.46.77.226)
The amp is on, but there's no tone Your mind is on your ohms Doc says "goodness sakes, twenty or less is what it takes" You can't sleep, no-oo, you can't eat There's no doubt you're in deep It's so mi .......
437: Tube DIY Asylum, RE: 3C24 Project Complete "Thorium" (0.00)
Posted by Michael Koster on 2009-01-08, 10:31:35 (67.46.77.226)
Yes! This is very interesting and a cool build. I can't wait to see your schematic. I'll be running 3C24s in class A and I wonder what your Pd is to get that nice red-orange color. The working name f .......
438: Tube DIY Asylum, RE: Tubeshunter - Ebay seller in China (0.00)
Posted by Michael Koster on 2009-01-05, 11:12:47 (67.46.77.226)
Hi, I don't want to be negative, but I had a mixed experience with this seller. If you buy anything heavy from him, give him detailed packing instructions. He ships using an extremely slow method t .......
439: Tube DIY Asylum, RE: Oil not Oyle (0.00)
Posted by Michael Koster on 2009-01-03, 08:54:23 (67.46.77.226)
My grandmother always had some Castor (bean) oil around for ... ahem.. digestive difficulties. For cutting lubricant, almost anything that makes a film will work. My comment about low speed is that: h .......
440: Tube DIY Asylum, RE: 813 driving 813? (0.00)
Posted by Michael Koster on 2009-01-02, 20:14:13 (208.74.180.50)
Thanks Dave! On further thought, the Rp of the triode 4-65A is more like 1600-1800 ohms, so 6K or more would be a much better load to work into. I haven't used spice yet but do have LTspice instal .......
441: Tube DIY Asylum, RE: Greenlee punches and 12 gauge steel ??? (0.00)
Posted by Michael Koster on 2009-01-02, 15:43:13 (208.74.180.50)
If it's formed and welded it will be low carbon and fairly workable. The Greenlee hydraulic ram is the thing to use for this thickness if you must use a punch. It will be hard to turn the threads and .......
442: Tube DIY Asylum, RE: 813 driving 813? (0.00)
Posted by Michael Koster on 2008-12-30, 20:56:32 (67.46.77.226)
Thanks Dave, This looks interesting as a medium power SET with a reasonable OPT of 4K. I could drive it with a 3C24 parafeed + MOSFET. Maybe I'm just recreating Al's amp here.. Michael OOPS It's pr .......
443: Tube DIY Asylum, RE: Tie Both Grids Together (0.00)
Posted by Michael Koster on 2008-12-30, 19:14:54 (208.74.180.50)
Hello, That's a version of the long-necked pair. Unity gain inverter? What are the advantages of this circuit over a cathode follower? Cheers, Michael .......
444: Tube DIY Asylum, RE: Your link forces the user to register to its site. (0.00)
Posted by Michael Koster on 2008-12-30, 00:07:39 (67.46.77.226)
No wonder you have to register; it's a porn site! I can't quite make out the working voltages on the CR oil caps. Is that four zeros? Now you got me to sign up... Michael .......
445: Tube DIY Asylum, RE: Your link forces the user to register to its site. (0.00)
Posted by Michael Koster on 2008-12-29, 15:42:10 (67.46.77.226)
Nope, you also need webaccess to citationsound. Looks like a private group. If the web interface isn't pretty, neither is the data in most cases ;-) .......
446: Tube DIY Asylum, RE: Pentode for 10Y amp (0.00)
Posted by Michael Koster on 2008-12-29, 14:11:43 (67.46.77.226)
The issue I'm currently concerned about is a good OPT for the 10Y. The 10Y Rp is somewhere in the 4K-5K range, which to me would require an output transformer with a lot of inductance for good bass re .......
447: Tube DIY Asylum, RE: 813 driving 813? (0.00)
Posted by Michael Koster on 2008-12-28, 21:43:50 (67.46.77.226)
--- I'll have to put in that I would *NOT* wait with the cathode hot before applying anode voltage. The Tantalum anode valves I've managed to save from on-the-shelf gas is immediately getting the anod .......
448: Tube DIY Asylum, RE: Pentode for 10Y amp (0.00)
Posted by Michael Koster on 2008-12-28, 13:58:08 (67.46.77.226)
Hi, Is the pentode driving the 801A (class A1 or A2?) or is the 801A driving the pentode? Could work either way. Cheers, Michael .......
449: Tube DIY Asylum, RE: neat... (0.00)
Posted by Michael Koster on 2008-12-28, 13:51:47 (67.46.77.226)
--- What the heck is that? Beam tetrode is one beastie, supressor grid pentode for another. No three-grid plus a beam former though...at least so far...:) cheers, Douglas Hi Douglas, I thought beam ac .......
450: Tube DIY Asylum, RE: 813 driving 813? (0.00)
Posted by Michael Koster on 2008-12-28, 12:20:56 (67.46.77.226)
sorry for the off-topic but Hey Al, When you triode connect the 4-65A do you connect g2 to the anode and run at low voltage or do you connect g2 to g1 and run in A2? (I have a clutch of 3C24s and 4-65 .......
451: High Efficiency Speaker Asylum, RE: Pics of my new LascalaVott (0.00)
Posted by Michael Koster on 2008-12-24, 12:11:05 (67.46.77.226)
I know exactly what LaScalaVott means. I'm building a DJK ported LaScala bottom with an Altec 299/MR594 top. It's great to hear about success stories using this approach. I like the slot mod! I have s .......
452: Tube DIY Asylum, RE: Parallel Cascode DN2540 CCS (0.00)
Posted by Michael Koster on 2008-12-24, 09:58:29 (67.46.77.226)
Hmm. You might try just paralleling the bottom one. If you're getting over 100mA now it could work. Not sure about the stability but you can judge that. I hope you're in the mood for some experimen .......
453: Tube DIY Asylum, RE: Help needed for Cascode DN2540 CCS (0.00)
Posted by Michael Koster on 2008-12-23, 23:11:04 (67.46.77.226)
The spec of Idss is the minimum saturated current. i.e. the device is guaranteed to sink at least 150mA when saturated(but not necessarily more). You can obviously get more according to the curves, bu .......
454: SET Asylum, RE: The actual benefit of SET (0.00)
Posted by Michael Koster on 2008-12-22, 16:14:06 (67.46.77.226)
Does the Compact have the harmonic signature of a SE or a PP? I.e. does even harmonic distortion cancel in the self-splitting output stage of the Leibowitz Compact? Michael .......
455: Tube DIY Asylum, RE: Is it possible to build an amp without plastic? (0.00)
Posted by Michael Koster on 2008-12-13, 15:43:50 (67.46.77.226)
Insulators are pretty important to electronics... some really good insulators are made from plastics. Also degradation of plastics and adhesives are responsible for much of the product life limitation .......
456: Tube DIY Asylum, RE: How to "seat" a motor-run cap upside down, and make it fast, for someone without much knowledge (0.00)
Posted by Michael Koster on 2008-12-13, 14:42:50 (67.46.77.226)
I measure 260-280 pF from either tab to case on the 2" diameter 4.5" long motor run caps in 330 and 440 volt ratings, so if it's used as a coupling cap I would definitely recommend to isolate the case .......
457: General Asylum, Continuous improvement theory for audio? (0.00)
Posted by Michael Koster on 2008-12-12, 09:52:58 (67.46.77.226)
I've become aware of a particular way of thinking in audio that proposes that audio quality or sound quality can continuously improve (forever). At first blush, it sounds to me like those economic the .......
458: Tube DIY Asylum, Mother Of Tone == Laugh Of The Day (0.00)
Posted by Michael Koster on 2008-12-12, 09:24:49 (67.46.77.226)
"Okay, soundcheck: The guitar now looks different, and sounds great . It has to sound great, since all the features that made it sound bad before have been removed." sounds logical to me... NOT I like .......
459: Tube DIY Asylum, RE: Try this ... (0.00)
Posted by Michael Koster on 2008-12-09, 14:40:31 (67.46.77.226)
Yes, old transformers can degrade in ways that cause them to draw more current and act as if they're saturated all the time, getting hot and buzzing and radiating more EMI. The copper electrostatic sh .......
460: Tube DIY Asylum, RE: Mercedes Benz (0.00)
Posted by Michael Koster on 2008-12-09, 11:44:46 (67.46.77.226)
I hear you I have 2 Toyotas with a total of about 350K miles on them. 3 days ago I hit a deer with one of them at 45 MPH and just drove on. They have never broken down other than a dead battery. I had .......
461: Tube DIY Asylum, RE: A good summary ... (0.00)
Posted by Michael Koster on 2008-12-09, 09:28:33 (67.46.77.226)
Here's an example of what I was suggesting with a separate power supply, which can be really tiny (40V/100mA) but needs to be isolated. This will allow the CCS, gyrator, mufollower, or whatever to .......
462: Tube DIY Asylum, RE: You really like Mosfets ... (0.00)
Posted by Michael Koster on 2008-12-08, 21:53:05 (67.46.77.226)
"Hey Michael, Geee I thought I was pretty lazy..." You ain't seen nothin' yet... Stage 2 is what I call active parafeed. What is in the signal path? The way I look at it, the MOSFETS are being used as .......
463: Tube DIY Asylum, RE: A good summary ... (0.00)
Posted by Michael Koster on 2008-12-07, 23:20:03 (67.46.77.226)
Here's a schematic for the breadboard I'm building. This is to keep it simple. I also prefer stacked supplies but on the breadboard I'm using shunt regulators. I also might rather stack another LV .......
464: Tube DIY Asylum, RE: It's even simpler than that ... (0.00)
Posted by Michael Koster on 2008-12-07, 17:35:16 (67.46.77.226)
Hi Naz, I think the 5mA refers just to the current going through the 30K cathode resistor. Another 15mA goes through the CCS for a total of 20mA going through the 12B4. Of course for the 6C41 in the o .......
465: Tube DIY Asylum, RE: Yes, I guess this is how you ment Naz (0.00)
Posted by Michael Koster on 2008-12-07, 14:35:23 (67.46.77.226)
You could connect a *well-isolated* 12V (or more) DC supply (-) to the 12B4 cathode and (+) to the CCS (+). You only need enough voltage to get to 0V on the grid relative to the cathode, plus some ope .......
466: Tube DIY Asylum, RE: Power supply building (0.00)
Posted by Michael Koster on 2008-12-06, 09:02:50 (67.46.77.226)
Sure, a choke provides much better filtering of 60Hz and lower fundamentals. I wouldn't depend on 60Hz chokes to filter "RF hash" and higher frequency junk from the line. They don't really do a good j .......
467: Tube DIY Asylum, RE: Recovery time (0.00)
Posted by Michael Koster on 2008-12-06, 08:38:27 (67.46.77.226)
Hi John, Interesting application of linear supplies. Do you find you need a spread spectrum clock as well, or does most of the EMI come from the switchers? Is there also a balance between compute powe .......
468: Tube DIY Asylum, Dolly explains magnetic fields to Billy (0.00)
Posted by Michael Koster on 2008-12-04, 12:44:21 (67.46.77.226)
In her inimitable way! Actually, though, could there not be an AC electrostatic field developed if there is an exposed winding at high potential? Copper around a transformer or choke winding is use .......
469: High Efficiency Speaker Asylum, RE: ok , are these new marketing terms? (0.00)
Posted by Michael Koster on 2008-11-28, 11:59:06 (67.46.77.226)
Google sez: Whizzy lets you pee standing up! Just thought I'd share... According to the urban dictionary, "whizzy" is a really, really lame way of saying something's good. Zinck'y means of or pertain .......
470: High Efficiency Speaker Asylum, mantaray vs. 511 for small PA cabs (0.00)
Posted by Michael Koster on 2008-11-28, 11:38:58 (67.46.77.226)
Hi, I'm planning some small PA cabinets using a 2 way horn design. The overall system is going to be a tube-powered hi-fi PA system for small festivals and medium size venues. The tube amps will be in .......
471: Cable Asylum, RE: What is wrong with a Banana Plug?? (0.00)
Posted by Michael Koster on 2008-11-27, 08:39:31 (67.46.77.226)
I believe the expression was "Horse Puckey" Horse hockey sounds like a lot of fun though... .......
472: Cable Asylum, RE: I am still using mine DC-200KHz, made in Japan ! (0.00)
Posted by Michael Koster on 2008-11-27, 08:37:50 (67.46.77.226)
Sansui .......
473: Tube DIY Asylum, RE: Big (tube) amps AND high-eff speakers! (0.00)
Posted by Michael Koster on 2008-11-24, 09:51:30 (67.46.77.226)
Thanks! I took a risk in going with this as I haven't heard it. My biggest unknown is whether the 414s can really cover 100Hz to 1KHz in a reasonably sized baffle. Sounds encouraging! Cheers, Michael .......
474: Tube DIY Asylum, RE: I tried the branching "Y" PS schematic... (0.00)
Posted by Michael Koster on 2008-11-22, 23:21:02 (67.46.77.226)
The amp I did a scaled-up 'LSES' with used an Eimac 4-65A for the final. I'm getting interested in this tube. Did you use it as a tetrode or triode mode? Triode would be with both grids together I ima .......
475: Tube DIY Asylum, Big (tube) amps AND high-eff speakers! (0.00)
Posted by Michael Koster on 2008-11-21, 20:45:40 (67.46.77.226)
What happened with the AMT? I have a pair and I think only dipole mids make sense. Of course it's a slippery slope to dipole woofers... I'd like to hear what people have used for crossover frequencies .......
476: Tube DIY Asylum, RE: And .... (0.00)
Posted by Michael Koster on 2008-11-21, 11:34:28 (67.46.77.226)
I'm not sure the sums always add up. At some point, each db of power into a speaker does not return a db of loudness. Maybe lower efficiency speakers get into this nonlinear region at lower acoustic o .......
477: Tube DIY Asylum, RE: DHT preamplifiers- Do they all lack density?(long) (0.00)
Posted by Michael Koster on 2008-11-21, 10:32:34 (67.46.77.226)
Andy, Thanks for the impressions on DHTs. You and Elektron have steered me to a 01A => 71A => 801A choke and IT coupled design I'm just starting to lay out. The 01A and 71A have easy filament supplies .......
478: Tube DIY Asylum, RE: DHT preamplifiers- Do they all lack density?(long) (0.00)
Posted by Michael Koster on 2008-11-21, 09:44:08 (67.46.77.226)
"Mah!? I use a 211 in my pre and I am 95% satisfied with. I just need to revisit the filament supply." I'm thinking the Eimac 4-65A would make a nice preamp ;-) Starve the plate at about 600V... ::: T .......
479: Tube DIY Asylum, RE: Interesting (0.00)
Posted by Michael Koster on 2008-11-20, 19:51:09 (67.46.77.226)
The sound levels quoted in industrial exposure charts (music is an industry too) are much higher than any listening level. They are worst-case numbers of the "guaranteed not to exceed" type. The other .......
480: Tube DIY Asylum, RE: Mounting oil caps (0.00)
Posted by Michael Koster on 2008-11-17, 19:50:14 (67.46.77.226)
Maybe aluminum is OK but they should be cut to the golden mean proportions. Maybe gold anodized and call them Golden Meanies. I would use 3. Michael PS Very very nice build. Is the top plate 1/8"? Wha .......
481: Tube DIY Asylum, RE: How is subCritL like a weak rectifier? (0.00)
Posted by Michael Koster on 2008-11-17, 16:52:33 (67.46.77.226)
So gusser, you seem to be explaining the similarity between a power supply with small chokes and a bad 5U4 through a direct personal experience involving a console TV set at age 11. Where is the power .......
482: Tube DIY Asylum, How is subCritL like a weak rectifier? (0.00)
Posted by Michael Koster on 2008-11-16, 14:09:53 (67.46.77.226)
>>[GUSSER] That's right, I never directly heard Jeff's implementation. But I do know first hand what a weak 5U4 sounds like. Isn't that similar, that is a amp starved for current. But as a token of re .......
483: Tube DIY Asylum, RE: Come on, (0.00)
Posted by Michael Koster on 2008-11-16, 13:43:51 (67.46.77.226)
No, to save further embarrassment, my question was a loose analogy to the original post which was like, OK, who's built it and says it sounds bad (well actually there were a couple but that must have .......
484: Tube DIY Asylum, Even tuning dots on ICs? (0.00)
Posted by Michael Koster on 2008-11-16, 11:22:35 (67.46.77.226)
has anyone ever put tuning dots on their digital ICs and had it sound bad? ;-) .......
485: Tube DIY Asylum, RE: Come now, that's hardly fair, is it? (0.00)
Posted by Michael Koster on 2008-11-16, 10:55:12 (67.46.77.226)
Gusser, It seems we're still unclear about what the debate really is. I wrote a post earlier where I basically dismissed the fraction of an ohm stuff et. al. and you seem to want to make that the iss .......
486: Tube DIY Asylum, RE: Come now, that's hardly fair, is it? (0.00)
Posted by Michael Koster on 2008-11-16, 09:19:44 (67.46.77.226)
This all seems so personal, but really it hardly is. We don't really know each other well enough. My conclusion is that it's mostly not personal, and it's still in the domain of ideas and perceptions. .......
487: Tube DIY Asylum, RE: The drlowmu Related Debate (0.00)
Posted by Michael Koster on 2008-11-15, 13:33:30 (67.46.77.226)
"I respectively submit that there may be more to an amp's "jump factor" than what you have experienced yet or are aware of." Well,I won't argue with that, and it wasn't to dismiss your suggestion, jus .......
488: Tube DIY Asylum, RE: The drlowmu Related Debate (0.00)
Posted by Michael Koster on 2008-11-15, 10:40:14 (67.46.77.226)
I forgot one of the debates. This one is a little more delicate but here goes. It's the one-size-fits-all debate: http://www.audioasylum.com/cgi/vt.mpl?f=tubediy&m=154338 In the example thread, Joe Gi .......
489: Tube DIY Asylum, RE: Sunrise (0.00)
Posted by Michael Koster on 2008-11-15, 10:00:56 (67.46.77.226)
I've been on the other side also, engineer co-workers telling me I'm silly for liking tube amps and SS *has* to sound better because of lower distortion and near-infinite damping factor. The ideal amp .......
490: Tube DIY Asylum, RE: Sunrise (0.00)
Posted by Michael Koster on 2008-11-15, 09:32:34 (67.46.77.226)
that's OK just send him some TUBES. Some of those 250s would be cool! .......
491: Tube DIY Asylum, RE: Sunrise (0.00)
Posted by Michael Koster on 2008-11-15, 09:26:18 (67.46.77.226)
First, thanks Henry for bringing the Sun up this morning. Just a few weeks ago some friends got together and turned the wheel of the year another notch, so you can be thankful to us for winter. I mis .......
492: Tube DIY Asylum, RE: The drlowmu Related Debate (0.00)
Posted by Michael Koster on 2008-11-15, 09:05:09 (67.46.77.226)
(apologies to Jeff, who must be thoroughly enjoying all this attention) To which drlowmu debate are you referring? Is it the debate about hearing audible difference in some fraction of an ohm audible .......
493: Tube DIY Asylum, RE: That's a good question ... (0.00)
Posted by Michael Koster on 2008-11-15, 07:35:55 (67.46.77.226)
"""Personally, I've heard it and cannot explain it. I think I even know some of the design principles behind why it happens but that isn't the answer either. I've even heard it in phono stages where a .......
494: Tube DIY Asylum, RE: A2 and pentodes (0.00)
Posted by Michael Koster on 2008-11-14, 17:54:49 (67.46.77.226)
Right, Rp is not a function of emission. It's u/gm... Is it simply that the characteristic of relatively high Rp leads to an extended +Vg operating range in A2? Perhaps ironically, on p56 of the Reich .......
495: Tube DIY Asylum, RE: Brook (0.00)
Posted by Michael Koster on 2008-11-14, 17:28:35 (67.46.77.226)
Very interesting! Why was I not reading the tubecad blog while working on my own servo-bias controller? I need to read Broskie more often. There are even more bias control articles on tubecad; seems t .......
496: Tube DIY Asylum, RE: A2 and pentodes (0.00)
Posted by Michael Koster on 2008-11-14, 07:48:47 (67.46.77.226)
-- and just like the pentode, there is a knee on the left side. Quite pentodely. But is it the Rp that matters, and can we use pentodely techniques to build a better high-Rp transmitter tube amp? Sin .......
497: Tube DIY Asylum, RE: A2 and pentodes (0.00)
Posted by Michael Koster on 2008-11-13, 18:29:23 (67.46.77.226)
There was the cascode == pentode, which is pretty much a textbook case. I think you're referring to the A2 triode == pentode, which was more controversial as I recall. Sorry to mis-characterize it. Ma .......
498: Tube DIY Asylum, RE: I'm sure it's just a typo... (0.00)
Posted by Michael Koster on 2008-11-13, 18:18:16 (67.46.77.226)
Maybe more to the point, the Rp is in the 12K-14K range. I would say it looks like the higher Rp (which means higher mu given similar gm) tubes driven into A2 do behave a lot like pentodes. It also se .......
499: Tube DIY Asylum, RE: A2 and pentodes (0.00)
Posted by Michael Koster on 2008-11-13, 14:35:19 (67.46.77.226)
Interesting and confusing. Someone had a big argument with Darius who was saying essentially the same thing. For the 801A example above, it looks like the +Vg is simply a continuation of the same .......
500: Tube DIY Asylum, RE: Michael a question for you..... (0.00)
Posted by Michael Koster on 2008-11-13, 13:26:15 (67.46.77.226)
"If the DC is smooth and without ringing, then the degredation of the tubes over time will be more of an issue than the DC circuit itself....am I right about this?" Basically, that is what it comes do .......
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