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1: Speaker Asylum, Help replacing JBL L60T Speakers (0.00)
Posted by mikeyb on 2020-10-09, 15:10:05 (47.4.217.244)
I love my JBL L60T speakers, but one tweeter no longer works, the cabinets are shot, and the woofers never sounded as good after they were re-conned. I'm looking for suggestions for new speakers that .......
2: Tube DIY Asylum, RE: "Singing" Power Transformer (0.00)
Posted by mikeyb on 2019-10-14, 18:55:21 (97.94.49.170)
Thanks for the analysis. I was curious, so attached a 11:1 external resistor divider from cathode to ground. Then measured the voltage with an oscilloscope. It confirms your analysis. The peak positiv .......
3: Tube DIY Asylum, RE: "Singing" Power Transformer (0.00)
Posted by mikeyb on 2019-10-14, 09:57:46 (97.94.49.170)
The heater-cathode voltage limit of the 6CA4 is 500 volts. T1 secondary is 350-0-350 VAC, so the cathode voltage is around 300 VDC with the LCLC filter. Why do you say that the heater-cathode voltage .......
4: Tube DIY Asylum, RE: "Singing" Power Transformer (0.00)
Posted by mikeyb on 2019-10-13, 11:37:10 (97.94.49.170)
The same filament transformer is used for the amp (4*EL84, 4*6SN7), because there isn't room for two filament transformers. Grounding the center tap of the filament transformer to the audio tubes is a .......
5: Tube DIY Asylum, RE: Tube Amp for Planar HeadAmp (0.00)
Posted by mikeyb on 2019-10-12, 07:49:15 (97.94.49.170)
Funny you should mention this ... the EL84 amp I just built is intended to be used with Sennheizer headphones as well as speakers. They have a 55 Ohm impedance and are VERY sensitive. In order to obta .......
6: Tube DIY Asylum, RE: "Holding the transformer's hosing stops the noise.Holding the transformer's hosing stops the noise." Bingo! (0.00)
Posted by mikeyb on 2019-10-12, 07:36:53 (97.94.49.170)
Rubber washers will be problematic to implement, because the unit is fully built and the transformer mounting bolts are underneath the 50 uFd capacitors. Worth a try though - the block of wood is tack .......
7: Tube DIY Asylum, RE: Can you feel the vibrations on the laminations... (0.00)
Posted by mikeyb on 2019-10-11, 20:02:44 (97.94.49.170)
No singing in the audio from the amp. Amp is clean. It's coming from the case of the power transformer. Holding the transformer's hosing stops the noise. The amp electronics are in a separate enclosur .......
8: Tube DIY Asylum, RE: "Singing" Power Transformer (0.00)
Posted by mikeyb on 2019-10-11, 17:31:47 (97.94.49.170)
No, with no load (other than the bleeder resistors), the noise is essentially inaudible. I placed a tight fitting block of wood between the power and filament transformers, and that reduced the noise .......
9: Tube DIY Asylum, RE: did it always sing? (0.00)
Posted by mikeyb on 2019-10-11, 16:45:16 (97.94.49.170)
Schematic below. Very "classic" design. The Hammond components (power transformer, chokes, filament) are new; L1 and L3 are vintage Military Grade potted units. .......
10: Tube DIY Asylum, "Singing" Power Transformer (0.00)
Posted by mikeyb on 2019-10-11, 07:35:48 (97.94.49.170)
I recently built a EL84 based push-pull stereo amp, using a Hammond 710 power transformer (375-0-375 VAC, 345 ma). It "sings", emitting a high frequency tone that is NOT present in the DC output. The .......
11: Tube DIY Asylum, RE: You guys have to look at this... (0.00)
Posted by mikeyb on 2019-04-21, 16:46:15 (131.93.15.26)
A quick glance suggests that it is the Svetlana "Six Pack" Power Amplifier, designed by David Wolze and appeared in the Svetlana Technical Bulletin #50 in May 1999. I have a copy. It is a push-pull am .......
12: Tube DIY Asylum, RE: Use a 6SN7 and everything becomes a lot easier. (0.00)
Posted by mikeyb on 2019-04-20, 16:37:39 (131.93.15.26)
I agree, but the loss through the Baxandal tone stack (21 dB) requires more gain than a 6NS7 provides. The output tubes will be either 6BQ5s or 6V6GTs. I am leaning toward a 6N1P (mu of 33) as the dif .......
13: Tube DIY Asylum, RE: Miller Effect in Differential Amplifier Stage (0.00)
Posted by mikeyb on 2019-04-18, 14:38:57 (131.93.15.26)
I agree, that formula applies to the common cathode configuration, where the cathode to ground impedance is low. In this case, the cathode of one triode is directly tied to the cathode of another, and .......
14: Tube DIY Asylum, Miller Effect in Differential Amplifier Stage (0.00)
Posted by mikeyb on 2019-04-18, 13:17:30 (131.93.15.26)
I will be using a differential amplifier (6SL7) as a phase splitter in a push pull design. It will be fed from a Baxandahl tone stack (no comments please - my hearing is going and I need high frequenc .......
15: Tube DIY Asylum, RE: 12SN7GTA versus 6BQ5 (EL84) in low power amp (0.00)
Posted by mikeyb on 2019-03-29, 19:52:16 (131.93.15.26)
The issue is inductance, which determines impedance. PP transformers generally have much higher inductance than SE transformers of the same physical size because they do not need as large an air gap ( .......
16: Tube DIY Asylum, RE: 12SN7GTA versus 6BQ5 (EL84) in low power amp (0.00)
Posted by mikeyb on 2019-03-29, 15:44:50 (131.93.15.26)
Oops! I meant 12V6GT, not 12SN7GTA. Sorry!! .......
17: Tube DIY Asylum, 12SN7GTA versus 6BQ5 (EL84) in low power amp (0.00)
Posted by mikeyb on 2019-03-29, 11:22:39 (131.93.15.26)
I am in the process of building a low power (5 - 10 watts) stereo audio amp, primarily for headphone use, with the option of driving small bookshelf speakers. It will be push-pull "ultra linear" desig .......
18: Tube DIY Asylum, RE: That's a polystyrene cap. (nt) (0.00)
Posted by mikeyb on 2015-08-13, 06:53:50 (24.179.130.178)
I haven't used those in years, but I recall that they melt and deform rather easily if too much heat is applied to the leads while soldering. .......
19: Tube DIY Asylum, RE: PSU design II result (0.00)
Posted by mikeyb on 2015-08-09, 10:27:28 (24.179.130.178)
Remove R1 and C3. With the large valued chokes and caps that you are using, filtering should be adequate without R1/C3. With an LCLC filter, a critical current must be drawn at all times in order to m .......
20: Tube DIY Asylum, RE: loftin white : voltages (0.00)
Posted by mikeyb on 2015-08-06, 10:07:19 (24.179.130.178)
Just one man's opinion. And what exactly is wrong with a "hand me down", anyway? .......
21: Tube DIY Asylum, RE: PSU design II result (0.00)
Posted by mikeyb on 2015-08-06, 10:03:44 (24.179.130.178)
What is the application? I strongly suggest that you get rid of R1 and C3. Unless the connected circuit is a true differential (constant current draw) design, changing current draw in response to an A .......
22: Tube DIY Asylum, RE: PSU design II result (0.00)
Posted by mikeyb on 2015-08-05, 13:41:06 (24.179.130.178)
That picture simply shows the start up response with an unknown load, not the transient response to a step change in current draw. The later would be far more informative. .......
23: Tube DIY Asylum, RE: transformer puzzle (0.00)
Posted by mikeyb on 2015-07-28, 08:54:33 (24.179.130.178)
A resistance of 2 Ohms between terminals 1 - 2 and 3 - 4 is about right for a dual winding transformer. It's too high to be a low voltage filament winding. A resistance of 127 ohms between 5 and 7 is .......
24: Tube DIY Asylum, RE: Pleasantly surprised by 6N1P tubes (0.00)
Posted by mikeyb on 2015-07-22, 09:54:59 (24.179.130.178)
I have been using Svetlana 6N1Ps for years, and they sound fine to me. They have a higher mu and lower Rp than a 12AU7 or 6SN7, which better suits my amps. .......
25: Tube DIY Asylum, RE: Ok, so how about best use of 27 tubes ???? (0.00)
Posted by mikeyb on 2015-07-02, 11:05:13 (24.179.130.178)
Ah yes, I remember the grid stopper "debate", none to fondly.. Curious schematic. Why did you leave the cathode resistor of the 2A3s un-bypassed? Are you aware that that can cause distortion if the mu .......
26: Tube DIY Asylum, RE: It's a False Premise (0.00)
Posted by mikeyb on 2015-06-19, 06:46:30 (24.179.130.178)
You are correct. I haven't visited audioasylum in six months or so, and it's disappointing to see that things haven't changed much. Same old topics, same old point of view (or is it an imperative?) fr .......
27: Tube DIY Asylum, RE: Happy April Fools Day !! (0.00)
Posted by mikeyb on 2015-04-03, 17:48:56 (24.179.130.178)
Report him to the Bored? Why? Are you that paranoid? .......
28: Tube DIY Asylum, RE: round plate 46 tube? (0.00)
Posted by mikeyb on 2015-01-22, 15:55:33 (24.179.130.178)
It's rare bit apparently not unique http://www.ebay.com.au/itm/1-NOS-4-PILLAR-GLOBE-RAYTHEON-ER-46-RADIO-TUBE-TYPE-46-TESTED-110-50-ON-TV-7-/310656601248 .......
29: Tube DIY Asylum, RE: Interesting discussion of amplifier power and listening, Steve Deckert (0.00)
Posted by mikeyb on 2014-09-03, 14:04:54 (69.244.223.163)
Lots of claims with no credible explanations. The reason no manufacturer specifies "useable power" is that it's not measurable. How do you quantify "sounds good" or "sounds best"? It's a highly subjec .......
30: Tube DIY Asylum, RE: Are big capacitors required after a B+ regulator? (0.00)
Posted by mikeyb on 2014-08-20, 11:30:02 (66.188.193.13)
What kind of regulator? What voltage? Some regulators - e.g., gas tube regulators - should not be loaded with more than 1 ufd of capacitance. From your question, you must be referring to a solid state .......
31: Tube DIY Asylum, RE: Not really looking to deal with (0.00)
Posted by mikeyb on 2014-08-16, 07:55:48 (66.188.193.13)
O.K. Getting back to your original question, I usually separate the power supply from the amp using separate chassis, and interconnect them with a cable of less then 3 feet in length. Unless you can f .......
32: Tube DIY Asylum, RE: Looking to build a 6V6 amp! Thoughts? (0.00)
Posted by mikeyb on 2014-08-15, 12:18:18 (66.188.193.13)
If you use pentode mode, the 6V6 has rather high distortion - 8% to 12%, according to the RCA specs. That pretty much means that feed back is a must. I haven't found any specs on distortion in triode .......
33: Video Asylum, Thanks! (0.00)
Posted by mikeyb on 2014-07-18, 06:15:56 (66.188.193.13)
Thanks for the information. It confirms what I had guessed. I'll probably go back to using my old Toshiba BlyRay player, at least until I determine and decide on a better approach. .......
34: Video Asylum, New Blu Ray DVD player has no analog outputs (0.00)
Posted by mikeyb on 2014-07-10, 17:22:26 (97.88.229.112)
I understand that the industry assumes that everybody is willing to update their home theater system every few years, but really ... Why did they decide to discontinue analog outputs on new Blu Ray DV .......
35: Tube DIY Asylum, RE: Can I use these "Output Autoformers" Triad S-46A (0.00)
Posted by mikeyb on 2014-06-27, 13:05:56 (97.88.229.112)
I'm confused - you called it a "70 Volt line autoformer". If you mean "autotransformer", it has only a single winding (i.e., no secondary. Unless you use a "parafeed" approach (including a blocking ca .......
36: Tube DIY Asylum, All right - I'll bite ... (0.00)
Posted by mikeyb on 2014-01-09, 09:45:19 (66.191.132.64)
What IS the significance of the number 57? This discussion is reminiscent of Stephen King's "The Dark Tower" series, where much mystery is linked to the number 19. .......
37: Tube DIY Asylum, RE: Experimenting with Output Transformers (0.00)
Posted by mikeyb on 2013-10-30, 12:48:35 (66.191.132.65)
You really are crazy, you know that? Just for "fun" and the sake of "science", try appling B+ to the primary's center tap, one "end" to the output tube's plate, and the other "end" to a constant curre .......
38: Tube DIY Asylum, RE: Start-up with small capacitor...then switch in large capacitor using ground leg as the one switched... (0.00)
Posted by mikeyb on 2013-10-23, 13:31:07 (66.191.132.67)
Need more details. How big is C1? The 5R4 is sort of a lousy rectifier. If you have the filament current available, the 5V3 can handle a LOT more peak plate current. I'm using two 5V3s with a cap inpu .......
39: Tube DIY Asylum, Doesn't the "buzzing" tell you something? (0.00)
Posted by mikeyb on 2013-10-10, 09:07:50 (66.191.132.66)
Like maybe you are abusing them (exceeding the design values)? Is this the first choke in a "LES" supply? What value is the following cap? .......
40: Tube DIY Asylum, RE: Inductance of James JS-6112HS transformer (0.00)
Posted by mikeyb on 2013-10-04, 06:27:22 (66.191.132.69)
Thanks, you all. Looks like the James transformer is out of the question. 13.7 Hys is an impedance of only 1721 Ohms at 20 Hz, nearly equal the plate resistance of a 45 (1650 Ohms) and lower than that .......
41: Tube DIY Asylum, Inductance of James JS-6112HS transformer (0.00)
Posted by mikeyb on 2013-10-03, 14:01:27 (66.191.132.70)
For a headphone amplifier application using a 45 or 46 in SE, I am looking for an output transformer. James makes a 10W transformer, the JS-6112HS, but does not specify the inductance. Does anyone kno .......
42: Tube DIY Asylum, RE: ormon delay switch on noise (0.00)
Posted by mikeyb on 2013-08-22, 08:03:20 (66.191.132.66)
Are the relay contacts connected the primary of the power transformer or to the secondary? Most small relays are rated for switching no more than 24 VAC. There are big ones designed for 110 or even 22 .......
43: Tube DIY Asylum, RE: ormon delay switch on noise (0.00)
Posted by mikeyb on 2013-08-21, 09:50:27 (66.191.132.64)
What do you mean by "noise"? Where in the circuit is the relay placed? Is it switching AC or DC? .......
44: Tube DIY Asylum, RE: Kind of ironic (0.00)
Posted by mikeyb on 2013-08-14, 19:05:13 (24.179.242.80)
That's a special, rather unusual, case. .......
45: Tube DIY Asylum, A common missconception ... (0.00)
Posted by mikeyb on 2013-08-14, 09:48:22 (66.191.132.63)
"because of the class A current being inherently constant" Not necessarily! It MAY be more or less constant in a properly designed and implemented push pull class A amp, but certainly not in a SE amp, .......
46: Tube DIY Asylum, RE: Learning from an inadequate design (0.00)
Posted by mikeyb on 2013-07-25, 12:52:07 (24.179.242.80)
"Jeff Medwin, DIY equipment safety expert .... EE approved." EE approved. Oh really? That may be debatable ... Why do you feel that you need to add that? It's rather surprising, given the general disd .......
47: Tube DIY Asylum, RE: What are "the rules" of replacing electrolytic with film caps? (0.00)
Posted by mikeyb on 2013-07-16, 10:41:11 (66.191.132.60)
The primary reason for replacing electrolytic caps with film caps is that (in general) film capacitors have a much more "ideal" frequency response than do electrolytics. Other considerations include t .......
48: Tube DIY Asylum, RE: Unprecedented, Heavy Handed . (0.00)
Posted by mikeyb on 2013-07-11, 05:57:04 (66.191.132.66)
Unless I'm missing something, here it is ... http://www.audioasylum.com/forums/amp/messages/18/187342.html .......
49: Amp/Preamp Asylum, RE: Serious Stereo 2A3 amps (0.00)
Posted by mikeyb on 2013-07-10, 14:53:40 (66.191.132.66)
I guess what bothers me (aside from the price) is the "just trust me" attitude. No technical information or specifications are available, no pictures of the underside have ever been seen, etc. Would y .......
50: Amp/Preamp Asylum, RE: It is high margin ... but ... (0.00)
Posted by mikeyb on 2013-07-10, 14:05:56 (66.191.132.66)
If they are buying one off the shelf (and are you absolutely sure they are?) here is a link to my "source": http://www.audioasylum.com/forums/set/messages/6/61794.html .......
51: Amp/Preamp Asylum, RE: Serious Stereo 2A3 amps (0.00)
Posted by mikeyb on 2013-07-10, 12:46:19 (66.191.132.61)
Hmm, if you know what's inside, why can't you tell us? Clearly the 2A3 is an EML - you can see that in the pictures. A little WEB reasearch says that they cost $550, and a little further reaserch wil .......
52: Amp/Preamp Asylum, Serious Stereo 2A3 amps (0.00)
Posted by mikeyb on 2013-07-10, 07:32:16 (66.191.132.63)
$15,000 apiece or for a pair? Either way they are seriously overpriced. The output tranie (Magnaquest) sells for $200. The EML 2A3 for $550. The chokes and power supply capacitors are small and relati .......
53: Tube DIY Asylum, RE: Commercial product safety (0.00)
Posted by mikeyb on 2013-06-24, 08:19:57 (66.191.132.63)
Frankly, I don't know. You probably should contact a lawyer. There should be some disclaimer that you could include as part of the sale that limits your liability. Maybe a waning label "caution high v .......
54: Tube DIY Asylum, RE: Can't wait to mod this - teflon caps, paper in oil PSU caps, OPT (0.00)
Posted by mikeyb on 2013-06-19, 12:50:29 (66.191.132.61)
Sorry. I'm an EE and not big on irony. These days, you can't be sure what is and what isn't, particularly on this forum. .......
55: Tube DIY Asylum, RE: Can't wait to mod this - teflon caps, paper in oil PSU caps, OPT (0.00)
Posted by mikeyb on 2013-06-19, 10:06:00 (66.191.132.61)
Tango output transformer??? This is a single tube preamplifier, rated at 20mW output. Why would you connect it to an output transformer, particularly one that probably costs 3 times as much as the pre .......
56: Tube DIY Asylum, RE: Congratulations....I can't believe you (0.00)
Posted by mikeyb on 2013-06-13, 10:21:30 (66.191.132.61)
Bear in mind that most likely the chokes are under 1 Hy and therefore physically rather small. .......
57: Tube DIY Asylum, RE: Skin Resistance! (0.00)
Posted by mikeyb on 2013-05-21, 13:02:36 (66.191.132.61)
"But raise that to 240v or higher, the odds of death decrease." Don't you mean increase? Meaning that you are much more likely to die from touching a 1200 volts source than a 120 volt source? Of cour .......
58: Tube DIY Asylum, RE: Maxim GM70 (0.00)
Posted by mikeyb on 2013-05-21, 09:58:48 (66.191.132.63)
You will have lot's of trouble finding an output transfomer with an adequate breakdown voltage rating. At 1200 VDC plate voltage and allowing for a 600 Vpp swing (it may be more than that if pushed), .......
59: Tube DIY Asylum, RE: Help ordering Resistor (0.00)
Posted by mikeyb on 2013-05-02, 07:36:58 (24.179.242.80)
I haven't used a phono cartridge in 20 some years (CDs are just fine, thanks), but my recollection is that you must match the cartridge manufactures recommended load impedance and capacitance for opti .......
60: Tweakers' Asylum, RE: New Philips Mod (0.00)
Posted by mikeyb on 2013-04-03, 05:40:36 (66.191.132.70)
You really are crazy, Jeff. Short out the fuse? Three parallel TCSS wires to feed a (well, two actually) power transformers from an 18 guage power cord? And now you can't put the top of the cabinet ba .......
61: Tube DIY Asylum, RE: Output Z, Rp, Load Z etc. (0.00)
Posted by mikeyb on 2013-04-01, 09:57:49 (66.191.132.62)
Let's think this through a bit. A cathode follower "idles" (no signal) at a current largely determined by the voltage across its cathode resistor divided by its resistance or the current supplied by a .......
62: Tube DIY Asylum, RE: Trade : TO 330 for a pair of 16458 ?? (0.00)
Posted by mikeyb on 2013-02-28, 09:45:51 (66.191.132.66)
Ah, I'm afraid that you are going to have to explain what a TO 330 and 16458 are/is. Of course if I don't know what they are, I don't have them. Just curious. .......
63: Tube DIY Asylum, RE: The peak current, instantaneous peak, in my 60 mA. amp (total draw), is easily in AMPERES DUDE. (0.00)
Posted by mikeyb on 2013-02-28, 09:42:48 (66.191.132.66)
So, if I understand you correctly, what your are saying is that you hear a difference, therefore, the instaneous peak curret must be 2 amps or more. And that there is no way to measure such a peak. No .......
64: Tube DIY Asylum, The peak current, instantaneous peak, in my 60 mA. amp (total draw), is easily in AMPERES DUDE. (0.00)
Posted by mikeyb on 2013-02-27, 10:05:17 (66.191.132.65)
"The peak current, instantaneous peak, in my 60 mA. amp (total draw), is easily in AMPERES DUDE." Upon what do you base that statement? Show me proof or at least some rational explanation. I see that .......
65: Tube DIY Asylum, RE: OT - well, not entirely :-) [Apologies to another fforum where I got the original] (0.00)
Posted by mikeyb on 2013-02-23, 20:11:56 (24.179.242.80)
Jeff, life IS about more than low DCR power supplies, ans so should this forum. .......
66: Tube DIY Asylum, RE: PP VR questions (0.00)
Posted by mikeyb on 2013-02-22, 11:44:12 (66.191.132.61)
In my opinion, this is a very risky design. If you drive the tubes into class B, the gas regulator might briefly extinguish. There is no cathode bypass resistor, other than "C" which is limited in va .......
67: Tube DIY Asylum, RE: Anyone use the Hammond chassis covers? (0.00)
Posted by mikeyb on 2013-02-21, 10:59:47 (66.191.132.62)
They seem pretty nice to me, but maybe I'm easy to please. Remind me of the old Heathkit tube amps (WM5). If you have a deep chassis, you could mount the tube sockets below the chassis top surface (us .......
68: Tube DIY Asylum, RE: 6N1P is a great little triode! (0.00)
Posted by mikeyb on 2013-02-16, 06:59:28 (24.179.242.80)
Thanks for the info! I never caught that. .......
69: Tube DIY Asylum, RE: 6N1P is a great little triode! (0.00)
Posted by mikeyb on 2013-02-15, 07:19:30 (66.191.132.67)
I agree. The 6N1P is a great little triode, and cheap! With a reltively high mu of 33 and a reltively low Rp of 4400 Ohms, it makes an ideal driver tube in a simple two stage application. I'm using it .......
70: Tube DIY Asylum, RE: Has anybody ever tried 6360? (0.00)
Posted by mikeyb on 2013-02-04, 06:05:14 (66.191.132.63)
It's just a matter of opinion, but with new 6V6s going for as little as $10, I wouldn't waste my time with a transmitter tube that costs nearly as much and was clearly not optimized for use as an audi .......
71: Tube DIY Asylum, RE: Has anybody ever tried 6360? (0.00)
Posted by mikeyb on 2013-02-01, 07:50:39 (66.191.132.64)
It was designed for use in a transmitter at "high" frequencies (up to 200 MHz). I used it in a ham radio transmitter at 144 MHz about 45 years ago (still have the tube). I don't think it will work wel .......
72: Tube DIY Asylum, Old adage applies here (0.00)
Posted by mikeyb on 2013-01-31, 07:54:02 (66.191.132.62)
If it works, don't mess with it. You will only do more harm then good. The copper wires wrapped around the core MUST be insulated from each other. Why do the windings need to be polished? By the way, .......
73: Tube DIY Asylum, RE: Add a little picture (0.00)
Posted by mikeyb on 2013-01-30, 13:38:01 (66.191.132.62)
So what should I conclude from this? That if I place, say a peice of plastic coated wire inbetween to charged plates, that the plastic will deform? That as in place a charge across a capacitor's leads .......
74: Tube DIY Asylum, RE: Ping Tre'! (0.00)
Posted by mikeyb on 2013-01-22, 10:49:24 (66.191.132.61)
I'm not Tre either, but I can tell you that 1) No, you cannot parallel VR tubes. If you want one per channel (and that's a good idea, to maintain the best isolation between channels), you will need an .......
75: Tube DIY Asylum, RE: Pros and cons of shared vs single bias resistor (0.00)
Posted by mikeyb on 2013-01-21, 07:31:37 (66.191.132.64)
I assume that the shared bias resistor is NOT bypassed in the amp to which you are referring. In theory, if the two outputs tubes had identical characteristics, in class A push pull, the current throu .......
76: Tube DIY Asylum, difference of opinion (0.00)
Posted by mikeyb on 2013-01-15, 13:47:07 (66.191.132.67)
I used one of the 3U (5.25") full width rack mount units and was rather impressed. It's a preamp and the power supply is external, so it's not heavy. The tubes (four 46s) are internal and mounted hori .......
77: Tube DIY Asylum, RE: Heresy ... (0.00)
Posted by mikeyb on 2012-12-21, 13:27:11 (66.191.132.64)
I'll tell you what popular receiver of 1970s vintage DOESN't sound good ... Marantz Model 2225 .......
78: Tube DIY Asylum, RE: Dennis Miller (0.00)
Posted by mikeyb on 2012-12-21, 12:24:14 (66.191.132.64)
"grid admittance efficiency" I've never heard of the term. Can you explain? Admittance is the inverse of impedance, but the term "efficiency" doesn't apply to either. You also make the asuumption that .......
79: Tube DIY Asylum, Heresy ... (0.00)
Posted by mikeyb on 2012-12-21, 10:49:38 (66.191.132.64)
I realize that this heresey, but .. I have a PP KT88 amp with global negative feedback that measures about 50 watts RMS into 8 Ohms just prior to clipping. I also have PP 300B amp (no feedback) that m .......
80: Tube DIY Asylum, The golden rule ... (0.00)
Posted by mikeyb on 2012-12-13, 13:17:38 (66.191.132.62)
Rules of SE Amplifier Design: 1) There is only one acceptable approach 2) To pursue any other approach will result in a mediocre (or worse) sounding amplifier and is, therefore, a waste of time 3) Any .......
81: Tube DIY Asylum, RE: just finished a pair of mono block KT120 pp .but having a little problem I need to solve (0.00)
Posted by mikeyb on 2012-12-13, 09:35:28 (66.191.132.62)
"problem I have is my fixed bias supply take 20 or so seconds to fully operating at the current set but B+ is almost instantly full on" That IS a problem that must be fixed! I have solved this problem .......
82: Tube DIY Asylum, RE: Need schematic and advice / tips on these organ PPP 6L6 amps I picked up (0.00)
Posted by mikeyb on 2012-12-06, 09:16:31 (66.191.132.63)
make em PP rather than PPP That's a problem. If the output transformer is optimized for PPP, it's going to have half of the impedance required for optimum performance in PP. That will increase distort .......
83: Tube DIY Asylum, RE: Also, isn't the definition of "Class A" constant current draw? (0.00)
Posted by mikeyb on 2012-12-04, 07:53:41 (66.191.132.63)
Why do you think that a Class A amplifier has a constant current draw? On average, the current draw is "constant" (the no signal value), but the current drawn by the tube has to vary with the signal, .......
84: Tube DIY Asylum, "Flywhhel Effect" (0.00)
Posted by mikeyb on 2012-11-23, 11:02:57 (24.179.242.80)
Correct me if I am wrong, but the latest and greatest LSES is NOT an implimentation of Henry's "Flywheel" effect supply. From what I remember, in order to get a "flywheel" effect, you need a L1 of som .......
85: Tube DIY Asylum, RE: O.K. (0.00)
Posted by mikeyb on 2012-11-21, 12:49:58 (66.191.132.64)
"There is a dropping resistor prior to the 56 uF cap, so, the power supply cap for that stage is located at the point-of-use." I get it, you put the cap at the point of use to minimize the lead lengt .......
86: Tube DIY Asylum, O.K. (0.00)
Posted by mikeyb on 2012-11-21, 11:04:49 (66.191.132.64)
That's what I figured. O.K. so let's look at what function this filter will perform. Since you haven't specified the value of the RF inductor, it is not possible to predict what effect it will have. F .......
87: Tube DIY Asylum, RE: LSES is not a mystery! (0.00)
Posted by mikeyb on 2012-11-21, 08:37:45 (66.191.132.61)
"Nothing is as bad as someone who THINKS he knows, but he doesn't comprehend at all" There is an old expression (idiom) that applies here ... "the pot calling the kettle black" In case you have never .......
88: Tube DIY Asylum, RE: Gosh....... Really.................... ???? (0.00)
Posted by mikeyb on 2012-11-21, 07:55:56 (66.191.132.61)
I'm still confused. Starting from the tubes plate, you have 1) Plate resistor, RF inductor, 56 uFd electrolytic to ground in parallel with two film caps OR 2) Plate resistor, two film caps to ground. .......
89: Tube DIY Asylum, RE: Can I use these in place of UF 4007? (0.00)
Posted by mikeyb on 2012-11-20, 10:04:25 (66.191.132.67)
Probably not. The 1N4007 has a PIV (peak inverse voltage) rating of 1000 volts, versus only 600 for the one you are considering. .......
90: Tube DIY Asylum, RE: Gosh....... Really.................... ???? (0.00)
Posted by mikeyb on 2012-11-20, 05:30:58 (66.191.132.69)
Excuse me, but what style of cap is shown in the picture??? So I guess you have a CLC filter, with the first cap a large electrolytic and the second a film (somewhere between .01 uF and 4 uF in value) .......
91: Tube DIY Asylum, RE: Gosh....... Really.................... ???? (0.00)
Posted by mikeyb on 2012-11-19, 10:12:18 (66.191.132.61)
The choke that you picture most likely has an inductance value in the nh (.00000000x hHy) to uH (.00000x Hy) range. So what impedance does it have at say 1 kHz? Somewhere between .00628 and .00000628 .......
92: Tube DIY Asylum, RE: Who cares? I mean, really... (0.00)
Posted by mikeyb on 2012-11-19, 06:52:22 (66.191.132.61)
What bothers me is exemplified in 6AS7_6SN7’s post “DIY Documentation” of a few days ago. The guy comes up with a suggestion, and gets blasted for “poor construction techniques”. Wires too long, too t .......
93: Tube DIY Asylum, RE: A higher standard ....... (0.00)
Posted by mikeyb on 2012-11-15, 13:49:38 (66.191.132.62)
"Do you think there would be ANY difference between that span being solid bell wire, one run of TCSS, two paralleled runs of TCSS, or one run of Siltech 13 AWG wire?? Most would say, "yes, there would .......
94: Tube DIY Asylum, RE: Sonic benefits to switching from 5R4( traditional rectifers) to damper diodes. (0.00)
Posted by mikeyb on 2012-11-15, 12:19:21 (66.191.132.62)
So, in reality, what you just stated is precisely what "we" have been saying all along - that the low L low C supply "responds" very quickly to a change in current demand. The question is - HOW does i .......
95: Tube DIY Asylum, RE: Sonic benefits to switching from 5R4( traditional rectifers) to damper diodes. (0.00)
Posted by mikeyb on 2012-11-14, 07:00:20 (66.191.132.62)
Assuming that you are correct and the "results" are better, how can you jump to the conclusion that "Directly-heated diodes will outperform the T.V. Dampers because they do not have a separate coated .......
96: Tube DIY Asylum, RE: Check out "CABLE ASYLUM's" mission statement.... (0.00)
Posted by mikeyb on 2012-11-09, 11:51:42 (66.191.132.61)
It just bugs me one someone states as "fact" what is merely a conjecture .......
97: Tube DIY Asylum, RE: Sonic benefits to switching from 5R4( traditional rectifers) to damper diodes. (0.00)
Posted by mikeyb on 2012-11-08, 17:28:00 (24.179.242.80)
Directly-heated diodes will outperform the T.V. Dampers because they do not have a separate coated cathode sleeve-- which has many operating anomalies. On what basis do you make that claim? If one cho .......
98: Tube DIY Asylum, Well, I tried (0.00)
Posted by mikeyb on 2012-11-01, 05:47:11 (66.191.132.65)
I can't make it any clearer. You are right; you haven't "followed my logic". I give up. Believe what you want. But please stop touting the same idea over and over and over again. .......
99: Tube DIY Asylum, RE: What a Difference Chokes and Caps Make !! (0.00)
Posted by mikeyb on 2012-10-31, 12:28:16 (66.191.132.65)
I'll try one more time ... Let's take the case of a SE amp with a no signal current draw by the output tube of 40 ma. Now introduce a 20 Hz square wave signal of an amplitude such that the output tube .......
100: Tube DIY Asylum, RE: Single ended el84 amp rebuild (0.00)
Posted by mikeyb on 2012-10-31, 10:22:58 (66.191.132.65)
The fact that the cap has a value of only 100 pF leads me to believe that the feedback is there to prevent HF oscillation ... It won't have much effect in the audio frequency range. .......
101: Tube DIY Asylum, RE: You're VEL-come !! (0.00)
Posted by mikeyb on 2012-10-26, 12:43:09 (66.191.132.68)
You stated in a prevoius posting that "About the only change in the audio section was for me to direct couple the input tube to the driver tube (got rid of any series coupling cap) and make the input .......
102: Tube DIY Asylum, RE: Having fun listening to tubes...... (0.00)
Posted by mikeyb on 2012-10-25, 12:47:14 (66.191.132.65)
Glad to hear that you are enjoying your new amp. Good job! I do have an isssue with the statement that the "power supply deserves the credit". How do you know that? How many other things have you chan .......
103: Tube DIY Asylum, Say what? (0.00)
Posted by mikeyb on 2012-10-19, 13:55:17 (66.191.132.63)
Why would you use only half of a 6CG7 in a long tailed pair> A long tailed pair is, by defintion, a differential amplifier and requires two triodes. I must be missing something ... .......
104: Tube DIY Asylum, Mostly correct (0.00)
Posted by mikeyb on 2012-10-18, 09:45:44 (66.191.132.63)
I agree with your comments for the most part. That said, let me point out that (ignoring Miller capacitance), as long as a grid is not driven positive, grid current is negligble. So, if run in class A .......
105: Tube DIY Asylum, Far easier to drive (0.00)
Posted by mikeyb on 2012-10-16, 09:20:33 (66.191.132.63)
"If this is too big a mess for you, use a pair of EIMAC 35T. This tube is even better, and has an amp-factor of 35, which is FAR easier to drive." Why would a tube with an amplification factor of 35 b .......
106: Tube DIY Asylum, Ahh, what IS it?) (0.00)
Posted by mikeyb on 2012-10-13, 13:59:25 (24.179.242.80)
It sort of looks like a crockpot with oversized walls or some cryogenic freezer for body parts. A head maybe? .......
107: Tube DIY Asylum, RE: testing by ear (0.00)
Posted by mikeyb on 2012-10-12, 07:49:21 (66.191.132.63)
"If we discount the notion that our ear can hear differences reliably, what on earth are we doing here in the first place?" That's a question that only the individual can answer. There are no "correct .......
108: Tube DIY Asylum, testing by ear (0.00)
Posted by mikeyb on 2012-10-11, 09:51:55 (66.191.132.63)
Some observations related to “testing by ear” alone. I suggest that there is a “repetitive listening” effect. Have you noticed that the more you hear a song, the more you pick up? I frequently listen .......
109: Tube DIY Asylum, Let me clarify (0.00)
Posted by mikeyb on 2012-10-06, 13:53:51 (24.179.242.80)
I'm not trying to belabor the point, but some clarification is in order. I wrote the above post in a hurry, and it shows. You have to recognize that how you would build any amplifier is dependent upon .......
110: Tube DIY Asylum, At first glance ... (0.00)
Posted by mikeyb on 2012-10-05, 10:16:54 (66.191.132.63)
No, I would not build an amp using printed circuit boards, place transformers close together, use ICs in the regulator circuit and cheap electrolytic capacitors. But I wouldn't attempt to build a home .......
111: Tube DIY Asylum, RE: Why would you want to do such a thing? (0.00)
Posted by mikeyb on 2012-10-04, 13:23:53 (66.191.132.66)
A shocking difference? Maybe in the insulation is frayed ... .......
112: Tube DIY Asylum, Why would you want to do such a thing? (0.00)
Posted by mikeyb on 2012-10-04, 06:57:17 (66.191.132.63)
A power transformer high voltage secondary is would with probably 100's of feet of copper "magnet" wire. What possible difference could changing the last few inches to another wire style make? Leave t .......
113: Tube DIY Asylum, RE: Today a few steps closer...... (0.00)
Posted by mikeyb on 2012-10-03, 06:07:33 (66.191.132.63)
Those are the interstage transformers??? Wow! They are big enough to be output transformers! I'm anxious to see the output transformers. Can I ask one more time - what are those things with the plunge .......
114: Tube DIY Asylum, RE: adding tilt type tone controls? (0.00)
Posted by mikeyb on 2012-10-02, 13:52:16 (66.191.132.64)
Here is a web site describing one version of "tilt" controls: http://kenrockwell.com/audio/quad/34-preamplifier.htm#spex .......
115: Tube DIY Asylum, Cute, really Cute! (0.00)
Posted by mikeyb on 2012-10-02, 12:23:00 (66.191.132.64)
Made my day ... .......
116: Tube DIY Asylum, RE: Making progress...... and more (0.00)
Posted by mikeyb on 2012-10-02, 07:52:45 (66.191.132.63)
What are the weird looking white thingies in the back row with the plungers? Looks like some medical devive designed to inflict torture. .......
117: Tube DIY Asylum, RE: DIY pre amp BASIC (0.00)
Posted by mikeyb on 2012-10-01, 05:45:03 (66.191.132.64)
To me, the critical question is wether or not the preamp should include tone controls. This has a major impact on the design, becuse a typical Baxandall passive tone control circuit adds a loss of bet .......
118: Tube DIY Asylum, Stereo DHT amp (0.00)
Posted by mikeyb on 2012-09-28, 10:19:17 (66.191.132.64)
Three stages, DHT outputs. Judgeing by the large holes, the output tubes will be something like 813s or 811s. You will be using 8 pin octal tubes in the front end stages. I see holes for two rather la .......
119: Tube DIY Asylum, RE: Resistor dissipation Question (0.00)
Posted by mikeyb on 2012-09-26, 10:24:38 (66.191.132.64)
Add a diode? You would need more that one to drop 45 volts. 45/.7 = 64 diodes! Sort of impractical. .......
120: Tube DIY Asylum, RE: Carbon composition resistors (0.00)
Posted by mikeyb on 2012-09-21, 15:17:57 (24.179.242.80)
I understand what you are saying, but it conflicts with the practice that was fairly coomon in the days of discrete transistor usage, where ferrite beads were placed on the lead to the base of the tra .......
121: Tube DIY Asylum, RE: Carbon composition resistors (0.00)
Posted by mikeyb on 2012-09-21, 12:40:27 (66.191.132.65)
For use as a "grid stopper", a little inductance may be a good thing. Carbon composition resistors are known to be comparatively noisy, but in your application, the current through the resistor should .......
122: Tube DIY Asylum, RE: The cheapest and probably best answer for" timp" (0.00)
Posted by mikeyb on 2012-09-21, 10:09:55 (66.191.132.69)
Your idea of using a filament transformer to lower the volatge on the power transformer's primary is a good one, but let me suggest an alternative that I consider to be even better. As I mentioned in .......
123: Tube DIY Asylum, RE: That's not so ugly! (0.00)
Posted by mikeyb on 2012-09-20, 09:10:24 (66.191.132.64)
What are the ouput tubes? 811As? I see a Lundahl interstage transformer. How do you like it? .......
124: Tube DIY Asylum, 6B6G (0.00)
Posted by mikeyb on 2012-09-20, 06:39:53 (66.191.132.63)
Hmm, looking at the spec sheet for the 6BG6G, I think that the 6BG6G is not a good choice. It's not really designed for use as a audio output tube and has a rather low plate dissipation rating (20 wat .......
125: Tube DIY Asylum, Oh come on .. (0.00)
Posted by mikeyb on 2012-09-19, 07:52:31 (66.191.132.63)
It's not that bad! Sometimes it gets rather amusing, and some times thought provoking. Such as the comment that bolting a power resistor to a chassis will cause a difference in sound due to the induce .......
126: Tube DIY Asylum, RE: Would you mind... (0.00)
Posted by mikeyb on 2012-09-18, 06:05:52 (66.191.132.66)
If you are dissipating 13 watts, wether you use a resistor rated for 25 watts or one rated for 50 watts you are going to create 13 watts of heat. The difference is in the area used to dissipate that h .......
127: Tube DIY Asylum, RE: Get your FACTS straight !!!!!!!!!!!!!!!!!! (0.00)
Posted by mikeyb on 2012-09-14, 13:49:01 (66.191.132.65)
"Also, I am also not sure if simulations are measuring relevant things and how they might sound in real life" If that's true, you really shoudn't be putting so much (apparant) trust in PSUD2. It's a s .......
128: Tube DIY Asylum, RE: Get your FACTS straight !!!!!!!!!!!!!!!!!! (0.00)
Posted by mikeyb on 2012-09-14, 11:43:34 (66.191.132.65)
Where do I begin. First, I don't believe that Dave intended to "try to use his simulation software to 'disprove' what PSUD2 shows me with a modern supply". In fact, all of his plots compare a filter w .......
129: Tube DIY Asylum, RE: Get your FACTS straight !!!!!!!!!!!!!!!!!! (0.00)
Posted by mikeyb on 2012-09-14, 06:10:59 (66.191.132.64)
If we are to get our "facts" straight, PLEASE stop talking about "dynamic Z". There is no such currently accepted term in electronics jargon - it's a term you created, I believe, to represent transien .......
130: Tube DIY Asylum, RE: I've Heard It Before (0.00)
Posted by mikeyb on 2012-09-13, 13:44:27 (66.191.132.66)
'I am sure cotton and silk would sound better simply because it has less mass then plastic and therefore more transparent to the hi frequency's traveling through it." Right, I am sure that those elect .......
131: Tube DIY Asylum, RE: So... (0.00)
Posted by mikeyb on 2012-09-12, 19:08:53 (24.179.242.80)
Thanks for running these simulations, Dave. They make perfect sense, although I have to admit that I was surprised by the last plot until I realized that you had switched colors. It shows beautifully .......
132: Tube DIY Asylum, RE: So... (0.00)
Posted by mikeyb on 2012-09-12, 10:12:40 (66.191.132.67)
What exactly makes it "the worst filter ever"? You are, I think, buying into the "fast transient response is essential" (Jeff Medwin) theory. Not everybody does! .......
133: Tube DIY Asylum, RE: Does TUBE rectifier have advantage over SS rectification (0.00)
Posted by mikeyb on 2012-09-11, 12:04:18 (66.191.132.63)
I'm just diametrically opposed to using SS diodes in a power supply of a TUBE amplifier, on general principles. If you want a tube amp, use tubes! Besides, there is nothing in electronics cuter than t .......
134: Tube DIY Asylum, Unreliable!!!! (0.00)
Posted by mikeyb on 2012-09-11, 05:18:44 (66.191.132.64)
The number that have failed for me goes beyond reasonable doubt. Besides, metal film look nicer ... .......
135: Tube DIY Asylum, RE: metal film or metal oxide film (0.00)
Posted by mikeyb on 2012-09-10, 10:13:17 (66.191.132.64)
Metal oxide resistors - just say NO!!! I have had sevearl 10 ohm 2 watt metal oxide power resistors "open" for no explainable reason. They were used as cathode resistors in a 6550 PP amp. In order to .......
136: Tube DIY Asylum, Be careful! (0.00)
Posted by mikeyb on 2012-09-10, 05:43:33 (66.191.132.64)
You must find out for which configuration the "340 mA DC" applies- capacitor input or choke input. There is a huge difference. If you use a capacitor input filter, you will get 1.1 to 1.4 times the tr .......
137: Tube DIY Asylum, RE: what is TIM? (nt) (0.00)
Posted by mikeyb on 2012-09-05, 13:05:46 (66.191.132.66)
Transient Inter-Modulation distortion. It relates to how an amplifier reacts to tranisents, changes in input signals that are non sinusoidal. Usually, IMD (Inter Modulation Distortion) is measured usi .......
138: Tube DIY Asylum, RE: Another beauty from China.... (0.00)
Posted by mikeyb on 2012-09-04, 14:04:40 (66.191.132.60)
Well, the filaments are hand wired ... Reminds me of a NAD 5.1 receiver that I repaired. A cheap cap in the power supply had shorted, and I had a container filled with about 40 screws by the time I co .......
139: Tube DIY Asylum, RE: I wonder if this 845 amp is any good? (0.00)
Posted by mikeyb on 2012-09-04, 06:00:25 (66.191.132.63)
I find it a bit odd that they make a big deal of the amp being "hand wired", claiming that this leads to the best sound, yet they very clealy show a picture of a rather cheap circuit board. While it's .......
140: Tube DIY Asylum, RE: Misinformation !! Answer this then ...... (0.00)
Posted by mikeyb on 2012-09-04, 05:52:05 (66.191.132.63)
There is ALWAYS a danger in believing anything you read on the WEB, but, frankly, this article made technical sense. The theory seems reasonable, but I'm a bit skeptical that the impedance of a typica .......
141: Tube DIY Asylum, RE: Interesting (0.00)
Posted by mikeyb on 2012-08-29, 10:38:14 (66.191.132.63)
A recording engineer! Still working in that field? Asa listener, I can say that there are very discernable differences in the way "modern" music is recorded that "old". Which is not to say that everyt .......
142: Tube DIY Asylum, RE: Japanese Zero at 12 o'clock...... (0.00)
Posted by mikeyb on 2012-08-29, 07:06:50 (66.191.132.64)
I'm not sure what that means ... The preamp that I worked on for over 5 years was - frankly - a disappointment. No, it has nothing to do with the power supply, but everything to do with the choice o .......
143: Tube DIY Asylum, RE: What sounds 'god sent'............ (0.00)
Posted by mikeyb on 2012-08-28, 20:05:12 (24.179.242.80)
What I had ten years ago IS what I have now ... .......
144: Tube DIY Asylum, Yes, it does! (0.00)
Posted by mikeyb on 2012-08-27, 10:46:26 (66.191.132.68)
See my note above. .......
145: Tube DIY Asylum, RE: Answer number TWO of two, 2010 (0.00)
Posted by mikeyb on 2012-08-27, 10:45:19 (66.191.132.68)
Jeff - Again,you are confusing "DC" (frequency of 0 Hz) resistance with impedance. The imedance of a cap is a function of the driving (source voltage) frequency, given by the equation Z = 1/jWC, where .......
146: Tube DIY Asylum, RE: Consider PSUD 2 and mikeyb's supply (0.00)
Posted by mikeyb on 2012-08-26, 12:12:14 (24.179.242.80)
I'm not sure what makes this "my supply", but whatever. Jeff, as you often say, "you just don't get it". Transiant response is NOT the most important consideration in this application, and there is no .......
147: Tube DIY Asylum, RE: Where does the current come from? (0.00)
Posted by mikeyb on 2012-08-26, 12:03:22 (24.179.242.80)
Thanks for doing the sims, Dave. They make sense. 1) More current comes from C1 (the cap closest to the 2A3) than from C3, especialy if a higher inductance (10 Hy) is used. This is more so at higher .......
148: Tube DIY Asylum, Thanks! (0.00)
Posted by mikeyb on 2012-08-24, 13:40:58 (66.191.132.64)
Nice job. However, I am confused about the plots of current in the first inductor. I would have expected the current to drop to zero during a portion of the 60 Hz cycle for the 1 Hy inductor, because .......
149: Tube DIY Asylum, Hardly ... (0.00)
Posted by mikeyb on 2012-08-24, 05:45:51 (66.191.132.64)
I intend to use a Pspice simulator to monitor current going into/out off the final cap in the filter. I recall doing this before - I may have posted it to the Asylum - but it won't hurt to do it again .......
150: Tube DIY Asylum, Thanks! (0.00)
Posted by mikeyb on 2012-08-23, 10:14:36 (66.191.132.65)
I'll give it a try. I'd like a plot of the current in to /out of the last filter cap with a stepped load, to debunk the theory that "the filter cap hogs all of the current" .......
151: Tube DIY Asylum, Good job! (0.00)
Posted by mikeyb on 2012-08-23, 09:50:31 (66.191.132.65)
Nice job of explaining this. How did you get the graphs embeded into the post? .......
152: Tube DIY Asylum, RE: 24 caps? (0.00)
Posted by mikeyb on 2012-08-23, 05:51:03 (66.191.132.65)
$1200/24 = $50 per cap (on average). That's insane. I'd love to measure the impedance over frequency of the result of placing six non-identical (I assume) caps in parallel. .......
153: Tube DIY Asylum, 24 caps? (0.00)
Posted by mikeyb on 2012-08-22, 11:49:07 (66.191.132.69)
Are you serious? 24 caps in parallel to bypass Rk of the output tube? How do all those caps fit in the chassis? .......
154: Tube DIY Asylum, RE: Here we are ! (0.00)
Posted by mikeyb on 2012-08-22, 10:23:08 (66.191.132.69)
or even better yet - perhaps the BEST : "incapable", "incompetent" So called "conventional' power supplies have served us well for nearly a century. Surely describing them as "incable" is inaccurate. .......
155: Tube DIY Asylum, RE: Generally speaking ......... (0.00)
Posted by mikeyb on 2012-08-20, 07:42:44 (66.191.132.65)
1) Many EEs (like me) are not willing to spend a lot of time and money on an unsubstantiated idea that flies in the face of established theory. 2) Most of the populous are either unable or unwilling t .......
156: Tube DIY Asylum, RE: 1983, 1992 (0.00)
Posted by mikeyb on 2012-08-16, 09:55:47 (66.191.132.65)
O.K. - it's another one of those "take it on faith" issues that steel sounds better than aluminum. Personally, I don't like steel because it can rust or corrode and look like crap. I suppsoe a good pa .......
157: Tube DIY Asylum, Too long ... (0.00)
Posted by mikeyb on 2012-08-16, 09:10:10 (66.191.132.65)
Over 6 years, I'm guessing. .......
158: Tube DIY Asylum, Why steel? (0.00)
Posted by mikeyb on 2012-08-15, 14:48:13 (66.191.132.67)
Steel is magnetic. Doesn't that have the potential to disrupt the magnetic fields in the transformers? .......
159: Tube DIY Asylum, RE: 4 pole caps in a voltage doubler circuit (0.00)
Posted by mikeyb on 2012-07-30, 11:01:15 (66.191.132.63)
What's a "4 pole cap?" One with 3 caps with a common ground? The term is could be confused with 4 terminal "feedthrough caps" (the inner and outer foils have leads attached at both ends of the cap) wh .......
160: Tube DIY Asylum, RE: " Insert a "hash" filter" (0.00)
Posted by mikeyb on 2012-07-30, 10:52:37 (66.191.132.63)
A choke and cap in parallel form a tuned circuit, which, if reasonably high in Q and in series with the rectified B+, will only be effective (as a filter) around the resonant frequency. I blieve what .......
161: Tube DIY Asylum, "No single technology in audio is perfect" (0.00)
Posted by mikeyb on 2012-07-24, 09:59:07 (66.191.132.63)
You must not be following Audio Asylum for the last few years. Dennis's Serious Stereo amp is perfect - just ask him (and Jeff). .......
162: Tube DIY Asylum, I can't hold back any longer!!! (0.00)
Posted by mikeyb on 2012-07-19, 12:41:22 (66.191.132.64)
While the article may (arguably) be useful as a description as to how to use PSUD, it is horribly flawed in its conclusions. For once, I actually agree with Dr Low Mu. The author spent a lot of time a .......
163: Tube DIY Asylum, RE: Seeking for opinion on Zener regulation (0.00)
Posted by mikeyb on 2012-07-16, 05:30:48 (66.191.132.63)
Gas regulator tubes do NOT have a filament. Forget zeners - why add "sand" to a tube amp? A 450 volt regulator would require a 600 volt (or greater) supply voltage to reliably "fire" the tubes (at st .......
164: Tube DIY Asylum, RE: FOR ITS INTENDED PURPOSE... (0.00)
Posted by mikeyb on 2012-07-13, 08:47:38 (66.191.132.66)
Another decided advantage of PP versus SE is that the current drawn by the output tubes is relativey constant, which results in far less transient current demand on the power supply. Some amp designs .......
165: Tube DIY Asylum, RE: Question: how does low current affects the plate curve and power supply noise of a hugh mu driver? (0.00)
Posted by mikeyb on 2012-07-12, 18:44:23 (24.179.242.80)
The bug wasn't THAT bad, even though it was probably not designed for american roads. I had a diesel VW rabbit that acellerated rather well and could sustain 75 MPH with a 17 foot canoe on the top. Ye .......
166: Tube DIY Asylum, RE: Question: how does low current affects the plate curve and power supply noise of a hugh mu driver? (0.00)
Posted by mikeyb on 2012-07-12, 10:18:31 (66.191.132.64)
The design philosophy that you are "suggesting' (ramming down our throats, actually) is sort of like designing a car for a maximum speed of 65 mph on a level road, because that's the maximum speed at .......
167: Tube DIY Asylum, RE: 300B SE vs 2A3 PP (0.00)
Posted by mikeyb on 2012-07-11, 20:08:06 (24.179.242.80)
Thanks for the info - very interesting. 300Bs have become less popular, at least judging by availability. I'm using a PP 300B amp, by the way, but with a 6SN7 diver coupled to 12BH7 cathode followers. .......
168: Tube DIY Asylum, RE: 300B SE vs 2A3 PP (0.00)
Posted by mikeyb on 2012-07-11, 05:33:51 (66.191.132.63)
But where can you get decent 2A3s these days? EH? JJ? Sovtek? Do the 40 watt 2A3s sound as good as the 15 watt? How do they compare to 300Bs? A 40 watt 2A3 looks (from the specs) to be pretty much the .......
169: Tube DIY Asylum, Nope! (0.00)
Posted by mikeyb on 2012-07-06, 13:10:17 (66.191.132.70)
You could add a series regulator or simply replace the power transformer with a different one. Steve Bench describes an excellent, simple, series regulator that does not employ an error amplifier and .......
170: Tube DIY Asylum, Oofta! (0.00)
Posted by mikeyb on 2012-07-06, 11:47:50 (66.191.132.70)
You do NOT want to do that (place resistors in series with the plates of the rectifier). It will cause MAJOR regulation issues. Jeff would have a hissy fit. A better idea would be to reduce the voltag .......
171: Tube DIY Asylum, Interesting ... (0.00)
Posted by mikeyb on 2012-07-04, 15:01:47 (24.179.242.80)
So what you are claiming is that it is not possible that anyone can build a better sounding amp than your design. How discouraging to the rest of us. We might as well quit. .......
172: Tube DIY Asylum, RE: Single PSU or dual mono best in amps?? (0.00)
Posted by mikeyb on 2012-06-18, 13:46:25 (66.191.132.65)
Is this a SE or PP design? The demands on the power supply are much greater in a SE design. My PP 300B amp is fully differential, including (the two) input stages. A nice design, lifted from Kevin Ken .......
173: Tube DIY Asylum, RE: Tired of all those spools cluttering? *pic* (0.00)
Posted by mikeyb on 2012-06-11, 13:31:24 (66.191.132.68)
"Calling an illegal alien an 'undocumented immigrant' is like calling a drug dealer an 'unlicensed pharmacist'" Hmm, I'll bet you listen to Rush and watch Fox news ... Please refrain from such politca .......
174: Tube DIY Asylum, RE: vs. ClarityCap TC (0.00)
Posted by mikeyb on 2012-05-30, 06:03:36 (66.191.132.64)
Thanks for the info! These caps look great. Who is the U.S distributor? .......
175: Tube DIY Asylum, RE: Cornell Dubilier 944U series polypropylene (0.00)
Posted by mikeyb on 2012-05-29, 19:54:30 (24.179.242.80)
Unfortunately, I can't find a spec for ESR on the motor run caps that I use. Nor can I give an answer regarding sound quality. I have one amp that uses computer grade electollytics in the power supply .......
176: Tube DIY Asylum, you CAN"t be serious ... (0.00)
Posted by mikeyb on 2012-05-29, 10:00:25 (66.191.132.69)
Take a "cleansing breath", re-read your post, and see if your argument still makes sense to you. .......
177: Tube DIY Asylum, RE: Cornell Dubilier 944U series polypropylene (0.00)
Posted by mikeyb on 2012-05-24, 06:21:53 (66.191.132.66)
These caps have fantastic specs! The 100 ufD has an ESR of 0.004 ohms at 120 Hz. I'd love to use these, but they are quite expensive when compared to motor run caps. a good choice, if you can afford t .......
178: Tube DIY Asylum, RE: Will direct coupling shorting tube life?? (0.00)
Posted by mikeyb on 2012-05-21, 07:47:49 (66.191.132.61)
I suspect that the damper diode is used as a time delay element (to delay B+ tirn on) and not for surge protection. Damper diodes such as the 6DE4 take a long long time to warm up - something greater .......
179: Tube DIY Asylum, For those of us unfamiliar with Bokonon ... (0.00)
Posted by mikeyb on 2012-05-08, 08:15:14 (66.191.132.64)
From the First Book of "The Books of Bokonon": Warning from title page: Don't be a fool! Close this book at once! It is nothing but foma! Verse 1: All of the true things that I am about to tell you a .......
180: Tube DIY Asylum, RE: in your own words... (0.00)
Posted by mikeyb on 2012-05-07, 10:03:12 (66.191.132.65)
Just out of curiosity, what is your business? .......
181: Tube DIY Asylum, What have you been drinking? (0.00)
Posted by mikeyb on 2012-05-04, 14:13:20 (66.191.132.64)
I need some of that on a Friday ... .......
182: Tube DIY Asylum, RE: A primer on Modern Physics as it relates to tube amp design (0.00)
Posted by mikeyb on 2012-05-04, 12:44:59 (66.191.132.63)
To be honest, Henry, I'm having a hard time buying all of this. "Thin wires (or foil) have low mass and therefore exert less gravitational force on the electrons moving through them. This reduces "gra .......
183: Tube DIY Asylum, RE: 1629 magic eye level indicator (0.00)
Posted by mikeyb on 2012-05-02, 14:38:10 (66.191.132.67)
"Dennis Fraker and Jeff Medwin are the experts in regards to all modern tube amp design elements. I will defer to them on the subject of what type of hookup wire is best in a magic eye circuit." O.K. .......
184: Tube DIY Asylum, RE: 1629 magic eye level indicator (0.00)
Posted by mikeyb on 2012-05-02, 11:49:44 (66.191.132.63)
Yes, I am all too familiar with the many Medwin/Fraker "rules". I don't buy into the concept that a black wire can sound different than any other color when used in an audio path, but blind adherence .......
185: Tube DIY Asylum, RE: WRONG! (0.00)
Posted by mikeyb on 2012-05-01, 05:51:58 (66.191.132.64)
Yes, you are correct - RG59 is 75 Ohms and has been around for nearly as long as I have. Actually, the cable that works well is some 40 plus year old RG59/U. It's the new cheap crap from China that (a .......
186: Tube DIY Asylum, RE: 1629 magic eye level indicator (0.00)
Posted by mikeyb on 2012-05-01, 05:44:53 (66.191.132.64)
Nice job - "I've always wanted" to use a couple of 1629 "magic eye" tubes as level indicators on my preamp. "black insulation on clip leads and ground wires is for working out the basic circuit only. .......
187: Tube DIY Asylum, Who knows ... (0.00)
Posted by mikeyb on 2012-04-30, 11:43:17 (66.191.132.65)
To be honest, I have no idea what style of cable the mysterious white coaxial cable is. It's some cheap brand form Menards (the poor mans version of Home Depot and Lowes). It's intended for TV, so I a .......
188: Tube DIY Asylum, Components (0.00)
Posted by mikeyb on 2012-04-26, 07:44:44 (66.191.132.68)
Looking at this picture, it appears that you are using some very old components. Those wax caps and resistors are pre 1960, I'm guessing. Be very careful! If they are used, be sure to measure the resi .......
189: Tube DIY Asylum, Example (0.00)
Posted by mikeyb on 2012-04-24, 10:27:00 (66.191.132.67)
I have a crapie Coby TV in my kitchen. It's connected to the cable splitter via a WHITE coaxial cable. The picture is terrible - "snowy", like in the "good old days" of TV antennas when the station wa .......
190: Tube DIY Asylum, Fraker amp (0.00)
Posted by mikeyb on 2012-04-17, 17:47:58 (24.179.242.80)
Nor will I ever hear a "Serious Stereo" amp. For two reasons: 1) I'm not about to pay the - what is it - $10,000 for an amp with a parts value of no more than $1000 and 2) I'm not about to buy an amp .......
191: Tube DIY Asylum, Cowboy logic ... (0.00)
Posted by mikeyb on 2012-04-16, 17:59:00 (24.179.242.80)
That explains a lot. Bigger = better, etc. .......
192: Tube DIY Asylum, I suspect (0.00)
Posted by mikeyb on 2012-04-12, 14:06:29 (66.191.132.63)
I suspect that the brass washers provide some ventilation. Brass and steel are dissimilar metals - doesn't that create a small voltage at the junction? Maybe that effects the sound ... "Dissimilar met .......
193: Tube DIY Asylum, RE: A few conservative design hints (0.00)
Posted by mikeyb on 2012-04-12, 12:22:00 (66.191.132.63)
"I have been (in that) particular pair amps, in Livingston MT, with Dennis working, me looking." Blessed be you. No one else has been allowed to peer into an open Serious Stereo amp and lived to tell .......
194: Tube DIY Asylum, RE: What attenuator do Y'all recommend? (0.00)
Posted by mikeyb on 2012-04-10, 10:22:18 (66.191.132.63)
Why on earth would you use an expensive inductive device (a tapped transformer) with limited bandwidth and non-ideal behavior (transformers saturate), the impedance of which is a function of frequency .......
195: Tube DIY Asylum, And then ... (0.00)
Posted by mikeyb on 2012-04-09, 13:11:50 (66.191.132.63)
Connect the amp to a MP3 player for the ultimate in sound ... I'm glad I'm not burdened with such sensitive ears (or foolishness) that I feel that it's necessary to tear apart an expensive Russian Tef .......
196: Tube DIY Asylum, RE: SE Power Supply (0.00)
Posted by mikeyb on 2012-04-07, 13:36:14 (24.179.242.80)
I like the 6DE4. Very rugged, very inexpensive, and very cute with the 'piggy tail' (curly) filament. I'll refrain from comment on the rest of the supply, for fear of the rath of the "power supply god .......
197: Tube DIY Asylum, RE: I see your question is about current from the driver to drive Miller (0.00)
Posted by mikeyb on 2012-02-10, 05:39:19 (97.86.249.211)
And since the required slew rate = 2*PI*BW*Vin, increaing the bandwidth by 10 times would require a multipler of 10X, which is (more or less) in line with Rankin's 5X 'fudge factor'. .......
198: Tube DIY Asylum, RE: Does high plate resistance hi gain tubes explain superior tone. And why tubes like 6c41c sound aggressive? (0.00)
Posted by mikeyb on 2012-02-02, 09:56:26 (97.86.249.211)
Hmm ... sounds a bit like marketing hype to me. As they said, the higher the plate resistance the more difficult it is to find a "good' output transformer (with sufficent inductance yet low capacitanc .......
199: Tube DIY Asylum, RE: size of those 50uF motor runs? (0.00)
Posted by mikeyb on 2012-01-27, 05:34:49 (97.86.249.211)
2" diameter by 3.75" tall. CSC 325P506H37N336A4XTE. Probably bigger than your 39 uFd Solens. .......
200: Tube DIY Asylum, RE: This is going to be a bit on the lengthy side but any (0.00)
Posted by mikeyb on 2012-01-26, 18:14:40 (97.86.249.211)
You must not be married. That would explain a lot, actually. .......
201: Tube DIY Asylum, RE: You can do that but why not just use motorrun caps (0.00)
Posted by mikeyb on 2012-01-26, 18:09:28 (97.86.249.211)
Personally, I wouldn't push any cap beyond 1.414 times the AC rating; 523 VDC for a cap rated at 370 VAC and 622 VDC for a cap rated at 440 VAC. Why push your luck? I just got ten new 50 uFd 370 VAC m .......
202: Tube DIY Asylum, NO!!!! (0.00)
Posted by mikeyb on 2012-01-17, 10:55:29 (68.115.91.207)
Thet are good for paper weights, and that's about it. A transformer designed for 400 HZ will not have enough inductance for use with a 60 Hz source. I know, I tried it once (in high school) - it quite .......
203: Tube DIY Asylum, RE: Any ideas about a very low gain linestage (0.00)
Posted by mikeyb on 2012-01-08, 16:38:14 (68.115.91.207)
"Triode Connected" 46 with simple 12K resistor load. Gain of about 5, Zout of about 2K. A little micrphonic, but liveable. Very low distortion. .......
204: Tube DIY Asylum, RE: AC relays (0.00)
Posted by mikeyb on 2011-12-22, 11:55:20 (68.115.91.207)
No, I'm sure they are not as accurate as a 555 timer with a regulated supply. But really, what does it matter if the period is 8 seconds or 12 seconds instead of 10? They certainly are much simpler to .......
205: Tube DIY Asylum, Frankly ... (0.00)
Posted by mikeyb on 2011-12-08, 13:19:55 (192.91.66.186)
I would build and test an actual circuit, and not trust simulation all that much. It's good for rough design work, but that's about it. This from an engineer who has worked with analog simulators for .......
206: Tube DIY Asylum, RE: ripple is way over-rated...... (0.00)
Posted by mikeyb on 2011-12-07, 10:11:00 (192.91.66.186)
"ripple is way over-rated" I can certainly agree that Ripple is lousy wine ... If there are any of you that remember it. As for AC on the filaments of a DHT, I again emphasize that it depends upon the .......
207: Tube DIY Asylum, RE: 211 and GM70 (0.00)
Posted by mikeyb on 2011-12-06, 12:28:04 (192.94.92.11)
"Now, think about this, instead of using a C input filter (that puts spikes on the line), you can use some intelligent version of Henry Pasternak's "Flywheel" L1 / C1 combination filter." The presence .......
208: Tube DIY Asylum, RE: What hook-up wire are you using? (0.00)
Posted by mikeyb on 2011-12-02, 14:22:41 (192.91.66.186)
Some 20 gauge pre-tined wire that I got form Axman surplus for $11 for 1000'. Silver plated copper. "Pre tined" means that it's been run through solder, which gives it some stiffness (please, no jokes .......
209: Tube DIY Asylum, Watt Meters (0.00)
Posted by mikeyb on 2011-11-30, 13:42:04 (192.91.66.186)
A true watt meter measures both voltage and current, using two differnt coils. It responds to the product of voltage and current. They were fairky common 50 years ago, and were used to measure the pow .......
210: Tube DIY Asylum, I wouldn't do that! (0.00)
Posted by mikeyb on 2011-11-28, 06:23:11 (192.91.66.186)
Screen current is expected to vary with plate voltage - that is perfectly normal. I suspect that you are affecting the tube's transfer characteristics by using current regulation at the screen grid. I .......
211: Tube DIY Asylum, RE: 500 mVAC for a 2A3 supply (0.00)
Posted by mikeyb on 2011-11-23, 12:07:05 (192.94.92.11)
"Ripple, we have ably demonstrated, isn't important" Maybe not for a 2A3 amp driving a speaker, but it IS a problem for a preamp or headphone amplifier. Simply stated, a LES design may not be appropri .......
212: Tube DIY Asylum, RE: Who WERE the best contributors to this forum? (0.00)
Posted by mikeyb on 2011-11-22, 10:18:53 (192.91.66.189)
Ahh, Jeff (alias drlowmu) isn't gone. .......
213: Tube DIY Asylum, RE: Is anyone building anything? (0.00)
Posted by mikeyb on 2011-11-22, 10:16:38 (192.91.66.189)
Just finished a 46 (DHT) based line level preamp, with tone controls. Sounds terrific! Am currently working on a replacement for my all tube headphone amp. The current design uses cathode follower out .......
214: Tube DIY Asylum, RE: Who WERE the best contributors to this forum? (0.00)
Posted by mikeyb on 2011-11-22, 08:25:42 (192.94.92.11)
Henry, whose last known alias was op48no1. .......
215: Tube DIY Asylum, RE: one rectifier tube vs 2 or more in power supply... (0.00)
Posted by mikeyb on 2011-11-21, 12:52:59 (192.91.66.189)
"5U4Gs also are DIRECTLY heated rectifiers, instantaneous response, unburdened by a cathode...DIRECT." It what way does the presence of a cathode "burden" the rectifier? Instantaneous response to what .......
216: Tube DIY Asylum, RE: Real EE question: super low noise fixed bias supply w/ Zeners (0.00)
Posted by mikeyb on 2011-11-08, 10:39:12 (192.91.66.186)
First of all, as has been already pointed out, noise is additive so putting a low noise zener is series with a high noise zener isn't going to help. Well not exactly additive - I think the noise at th .......
217: Tube DIY Asylum, RE: Orientation of Dynamicaps (0.00)
Posted by mikeyb on 2011-11-01, 08:46:28 (192.91.66.189)
Think of it this way. Generally, the driving source has a much lower impedance than the input it's driving. Therefore, you want to connect the outer foil of the capacitor to the lower impedance (the s .......
218: Tube DIY Asylum, 'tubey' euphonious quality (0.00)
Posted by mikeyb on 2011-10-31, 12:28:21 (192.91.66.186)
I really have no idea as to what "'tubey' euphonious quality" sounds like, much less how to achieve it. John Broskie wrote an excellent article on our perception as to what sounds good - see http://w .......
219: Tube DIY Asylum, RE: You are, as usual, all wet, and you missed the boat (0.00)
Posted by mikeyb on 2011-10-27, 06:05:34 (192.94.92.11)
"I say your analysis is irrelevant since the amp runs between 1/10th to 3/4s of a Watt 98 percent of the time, when using efficient speakers." 1) I don't have efficent speakers, nor do I intend to rep .......
220: Tube DIY Asylum, RE: one stage versus 2 stage driver (0.00)
Posted by mikeyb on 2011-10-26, 11:41:37 (192.91.66.189)
Thanks for the advice. The 6N1P (mu = 35, Rp = 4400) might also be a good choice for a single stage driver. It was sort of a theoretical question, to be honest. I mentioned the 5687 because I am curr .......
221: Tube DIY Asylum, RE: You are, as usual, all wet, and you missed the boat (0.00)
Posted by mikeyb on 2011-10-26, 05:59:08 (192.91.66.189)
So what you are saying is that a two stage, low mu design is "WAY too conventional an analysis and WAY too conventional and outmoded an approach". Let me point out that the Loftin-White design was pat .......
222: Tube DIY Asylum, RE: Shucks........ (0.00)
Posted by mikeyb on 2011-10-25, 19:55:30 (68.115.91.207)
L60T. I also have a pair of Decade 16's that are even older. Unfortunately, when I had them reconed, I went cheap and had non JBL cones put in. I wish I hadn't. They never sounded as good after reconi .......
223: Tube DIY Asylum, RE: Shucks........ (0.00)
Posted by mikeyb on 2011-10-25, 14:34:49 (192.91.66.186)
I am using 30 year old JBL speakers that are very inefficient, and I want my amp to be able to displace the cones a few inches on low notes and rattle the windows. I can't do that with a sub 1 watt am .......
224: Tube DIY Asylum, RE: one stage versus 2 stage driver (0.00)
Posted by mikeyb on 2011-10-25, 05:20:57 (192.91.66.186)
Very interesting article - thanks! .......
225: Tube DIY Asylum, No math involved! (0.00)
Posted by mikeyb on 2011-10-24, 17:13:20 (68.115.91.207)
To be honest, I was simply quoting tables in the 12AX7 and 5687 data sheets. I'm not saying this is the best design point, but, in the case of the 12AX7, close to what drlowmu is advocating so vehemen .......
226: Tube DIY Asylum, RE: Jeff, I know you're latest 2A3...... (0.00)
Posted by mikeyb on 2011-10-24, 15:00:26 (68.115.91.207)
The question arises as to how the superiority of a one stage design versus a two stage design is determined. Superior in what sense? "We have existing proofs of this, all over the place". Your opinion .......
227: Tube DIY Asylum, one stage versus 2 stage driver (0.00)
Posted by mikeyb on 2011-10-24, 14:26:26 (192.91.66.186)
If you look at the "Resistance Coupled A.F. Amplifier" tables for the EC83\12AX7, you will see that with a Plate supply voltage of 200 volts, a plate resistor of 100 K Ohms, the plate current will whe .......
228: Tube DIY Asylum, RE: Cowboy Music (0.00)
Posted by mikeyb on 2011-10-21, 12:45:15 (192.94.92.11)
No disagreements from me! The quality of the recording also enters into the equation. Among the best recordings that I have are "Potter's Wheel" (from "Midnight at Cabell Hall" by Freyda & Acoustic At .......
229: Tube DIY Asylum, RE: RMAF 2011 (0.00)
Posted by mikeyb on 2011-10-21, 06:09:31 (192.91.66.186)
"Tons of cowboy" (and country) music? You’re not encouraging me to attend RMAF. Country music to me is like accordion music to a classically trained musician. How can you tell if "cowboy music" is "wa .......
230: Tube DIY Asylum, Engineers ... (0.00)
Posted by mikeyb on 2011-10-21, 06:03:59 (192.91.66.186)
"Engineers screw up. I've got a McIntosh MC-30, and calculated that one of the resistors is slightly underspecified for power. It's a one-watt unit that dissipates ~1.1 watts at idle." An equally prob .......
231: Tube DIY Asylum, RE: B+ from center tap of rectifier filament winding any good? (0.00)
Posted by mikeyb on 2011-10-19, 05:22:19 (192.94.92.11)
Yes, it's the best way if you are not using a 'hum pot' (a low valued pot connected across the filament pins with the 'wiper' connected to ground or to the 'cathode' bias resistor). If use use the tra .......
232: Tube DIY Asylum, RE: GZ34 / 5AR4 Full-Wave Rectifier (0.00)
Posted by mikeyb on 2011-10-12, 05:37:59 (192.91.66.186)
This is done to reduce the heater-to-cathode voltage difference to near zero. .......
233: Tube DIY Asylum, "are you just a troll or the village idiot?" (0.00)
Posted by mikeyb on 2011-10-07, 08:45:23 (192.91.66.189)
Neither. I live in a city with a population of over 100,000, so I can't technically be a "village idiot". As to a troll, I'm not sure what exactly a troll is. J R R Tolkein describes trolls in "The Ho .......
234: Tube DIY Asylum, RE: DC amps : " risky and destroy tubes" ???? (0.00)
Posted by mikeyb on 2011-10-07, 05:21:00 (192.91.66.186)
His statement is not unfounded. If you can site "experts", so can I. From "Tube CAD journal": "Recently resurrected, the darling of the SE set, the amplifier without a coupling capacitor, the Loftin-W .......
235: Tube DIY Asylum, RE: Rotary switch for attenuator (0.00)
Posted by mikeyb on 2011-10-04, 08:53:43 (192.91.66.189)
Actually, you can get a very good 2 or 4 pole 24 position make-before-break (necessary!!) rotary switch for less then $10. I'm using the 2 pole version, and am very pleased with it. The only drawback .......
236: Tube DIY Asylum, RE: Confess you're insane part's cost story! (0.00)
Posted by mikeyb on 2011-09-29, 10:23:03 (192.94.92.11)
My problem is not buying 'expensive' parts, but over designing. For example, I've been working for three years on a tube type 46 based line level preamp (with tone controls). The 46 is a DHT that requ .......
237: Tube DIY Asylum, Giant step (0.00)
Posted by mikeyb on 2011-09-27, 06:28:32 (192.94.92.11)
To go from LPs to a music server. Are the recordings MP3 encoded? .......
238: Tube DIY Asylum, RE: can't control bias (0.00)
Posted by mikeyb on 2011-09-22, 05:46:28 (192.91.66.186)
Measure the voltage on the GRID of the output tube, not at the negative supply. If it's -70 volts at the grids of the KT88's, they should be in cutoff, and drawing no current from the positive supply. .......
239: Tube DIY Asylum, RE: Are all the MI sockets made of amphenol? nt (0.00)
Posted by mikeyb on 2011-09-13, 20:20:14 (68.115.91.207)
Amphenol is a manufactuer, not a style, of tube sockets. Amphenol made some excellent quality sockets, and are a favorite of mine. As far as I know, they were not the only manufactuer of micalex socke .......
240: Tube DIY Asylum, RE: Do You Have Others... (0.00)
Posted by mikeyb on 2011-09-13, 09:31:28 (192.94.92.11)
I am using MIP (molded in place) 4 pin sockets. The pins are tight, and you cannot miss-orient the tube. The last set I got off of Ebay and were made in England. Great sockets! .......
241: Tube DIY Asylum, No! (0.00)
Posted by mikeyb on 2011-08-29, 13:31:55 (192.91.66.186)
You would be much better served by a relay whose contacts are rated for at least 277 VRMS, such as this one: http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&KeyWords=PB488 The con .......
242: Tube DIY Asylum, RE: Stop! (0.00)
Posted by mikeyb on 2011-08-25, 14:32:39 (192.94.92.11)
I guess it depends upon what is meant by "swapped out". Does that mean replaced, or swaped from one (stereo) side to the other? .......
243: Tube DIY Asylum, Stop! (0.00)
Posted by mikeyb on 2011-08-25, 13:56:52 (192.91.66.186)
Don't waste your time rewiring the 6CG7s. Motorboating is most fequently caused by feedback from the output to the input via the power supply. Check the filter caps in your power supply first. If they .......
244: Tube DIY Asylum, Much ado about nothing ... (0.00)
Posted by mikeyb on 2011-08-12, 06:03:56 (192.94.92.11)
First of all, it's the seconday winding of the bucking transformer that's in series with the amp, not the primary. A 12 volt transformer rated at 5 amps is unlikely to have a secondary with a DCR of . .......
245: Tube DIY Asylum, RE: Yowser....Its the "tough part" I solved ... (0.00)
Posted by mikeyb on 2011-08-11, 17:14:30 (192.94.92.11)
For what it's worth, I'm an electrical engineer with a MEE degree, not a technician. Six years of college education should buy me something! .......
246: Tube DIY Asylum, Your only 'solved' part of the problem ... (0.00)
Posted by mikeyb on 2011-08-11, 16:25:15 (192.91.66.186)
I suspect that the filament supply is about 7% high as well (125/117). The insertion of a choke in the HV supply ahead of the first C will not address that. .......
247: Tube DIY Asylum, RE: Silk SE Transformer (0.00)
Posted by mikeyb on 2011-08-10, 05:58:18 (192.94.92.11)
Perhaps (it's not specified), but not by a factor of 4! The inductance is a function of core gap, which is related to maximum DC (no signal) current, which is why PP transformers generally have much h .......
248: Tube DIY Asylum, RE: Silk SE Transformer (0.00)
Posted by mikeyb on 2011-08-09, 18:04:53 (68.115.91.207)
Hmm, the only Silk output transformer for which I could fine specs had an inductance of only 10 Hys, which is very low when compared to others (e.g., The Lundahl LL1623 has an inductance of 46 Hys). T .......
249: Tube DIY Asylum, RE: You don't worry about it! (0.00)
Posted by mikeyb on 2011-08-02, 12:43:36 (192.91.66.186)
No big deal. .......
250: Tube DIY Asylum, You don't worry about it! (0.00)
Posted by mikeyb on 2011-08-02, 10:49:26 (192.91.66.186)
105 volts is only 5% higher than 100 volts - why worry? Is it that critical to have exactly 105 volts? You could add a 5 v zener diode in series with the load, but it's really not worth the effort. :: .......
251: Tube DIY Asylum, RE: BORING! (0.00)
Posted by mikeyb on 2011-07-22, 12:06:14 (192.91.66.186)
I agree with you on the boring issue. Maybe we should restart the LES debate. Just kidding!!! Single ended or PP? I like Kevin Kennedy's PP 300B design, and am using a modified version with a Lundahl .......
252: Tube DIY Asylum, RE: Feedback when direct coupling (0.00)
Posted by mikeyb on 2011-07-08, 10:19:13 (192.91.66.186)
Why do you want to remove the cathode bypass cap? Doing so can dramatically effect both stage gain and output impedance. Assuming a common cathode triode amplifier, the output impedance is (approximat .......
253: Tube DIY Asylum, RE: Ken Gilbert - Gary Dahl interstage coupled 300b SET (0.00)
Posted by mikeyb on 2011-07-05, 07:07:28 (192.91.66.186)
I have heard that the 417 is touchy at best - very difficult to stabilize. It has multiple grid pins, each one of which is normaly connected to a seperate 'grid stopper' resistor. The 417A was "primar .......
254: Tube DIY Asylum, RE: Dumb question - output tube for a tube rectified SET amp (0.00)
Posted by mikeyb on 2011-07-02, 09:06:53 (68.115.91.207)
My favorite rectifier tube is the 6DE4. It's an IDHR, but the 'slow warmup" is, I think, and advantage. Plus the 6DE4 has that really cute "piggy tail" style filament. Very low voltage drop (for a tub .......
255: Tube DIY Asylum, RE: Dumb question - output tube for a tube rectified SET amp (0.00)
Posted by mikeyb on 2011-07-01, 14:47:55 (192.91.66.186)
I would use a 45, 46, 2A3, or 300B DHT for a SET application regardless of the style of rectification, and I would always choose tube rectification over SS. The two really aren't related. .......
256: Tube DIY Asylum, Not really ... (0.00)
Posted by mikeyb on 2011-06-17, 13:08:01 (192.91.66.189)
Why would a half way rectified power have a lower DCR than a full wave bridge rectified power supply using the same power transformer? In fact, the effective DCR of the half wave rectfied PS is over t .......
257: Tube DIY Asylum, RE: Using multiple rectifiers (0.00)
Posted by mikeyb on 2011-06-10, 06:34:21 (192.94.92.11)
O.K., I buy your argument, but how much difference does it make? What is the relationship between filament current and rectifier voltage drop? Assuming that the filaments of both rectifiers are connec .......
258: Tube DIY Asylum, RE: A CCS driving a gas regulator tube 0A2/0B2/0C3/0D3 (0.00)
Posted by mikeyb on 2011-04-29, 19:54:39 (68.115.91.207)
5 mA? That's a the bare minimum required to keep an 0B2 'struck', and doesn't allow for current in the bias adjustment pot. As I said before, using a regulated bias supply when B+ is unregulated is a .......
259: Tube DIY Asylum, RE: Recipe for a great bias supply..... (0.00)
Posted by mikeyb on 2011-04-29, 12:15:37 (192.91.66.186)
Here's the rub ... If you go LC, there will be too much ripple, even with a 100 uF C (values over 100 uFd are not practical if you want to use a film cap). So you are forced into LCLC. Critical induct .......
260: Tube DIY Asylum, RE: Recipe for a great bias supply..... (0.00)
Posted by mikeyb on 2011-04-29, 11:16:34 (192.94.92.11)
full wave rectification - yes, but be sure that the 'warm up' time of the bias supply is less then that of the B+ supply. Bias voltage MUST be present before B+. I use a 5AR4 for the bias supply and 6 .......
261: Tube DIY Asylum, Weeend project (0.00)
Posted by mikeyb on 2011-04-27, 12:47:54 (192.91.66.189)
If you can get something like that built in a week, you are doing a lot better than me. I have been working on a all DHT (46s) line level preamp for nearly 10 years! I just noticed that the original s .......
262: Tube DIY Asylum, RE: EF86 in triode (0.00)
Posted by mikeyb on 2011-04-21, 12:52:53 (192.94.92.11)
Try the Russian 6N1P. I have had good results with both the 6N1P and a triode wired EF86, altough the 6N1P may be a better choice because it has a lower plate resitance and can handle more current. :: .......
263: Tube DIY Asylum, RE: My amplifier hums LOUDLY when I disconnect my CD player....HELP!!!! (0.00)
Posted by mikeyb on 2011-04-19, 06:55:21 (192.91.66.186)
Assuming that there is a resistor from grid to ground of the first stage, wht is it's value? You might try placing a 47K ohm resistors across the input (RCA?) connector to see if tha kills the hum (wi .......
264: Tube DIY Asylum, RE: My amplifier hums LOUDLY when I disconnect my CD player....HELP!!!! (0.00)
Posted by mikeyb on 2011-04-18, 10:21:33 (192.94.92.14)
I have had the same problem with a high gain tube power amp with high input impedance. It's the result of using a physically large DC blocking cap at the input to the amp and a wood chassis (no shield .......
265: Tube DIY Asylum, RE: What's the formula for maximum system detail? (0.00)
Posted by mikeyb on 2011-04-13, 05:44:11 (192.91.66.186)
If you are of the belief that reducing the number of active stages is a requirement, than yes, I can see your logic. And yes, using a transformer or plate choke in the driver will allow for larger vol .......
266: Tube DIY Asylum, RE: What's the formula for maximum system detail? (0.00)
Posted by mikeyb on 2011-04-12, 13:16:49 (192.91.66.186)
"Transformer coupling to eliminate resistors and caps as much as possible" May I ask why you assume that transformer coupling is better than capacitor? Seems to me that good transformers are much more .......
267: Tube DIY Asylum, RE: SND Tubes- What a Jerk............ (0.00)
Posted by mikeyb on 2011-04-12, 06:01:28 (192.91.66.189)
Let's see ... the guy at SND is a jerk, Steve at Angela is a jerk, the guy at Triode Electonics is dissagreeable ... Whose left? .......
268: Tube DIY Asylum, I can't believe it works! (0.00)
Posted by mikeyb on 2011-04-08, 10:25:03 (192.94.94.105)
An SRPP with a supply voltage on only 48 volts? How can that work? .......
269: Tube DIY Asylum, zip cord for speaker interconnect (0.00)
Posted by mikeyb on 2011-04-08, 06:26:00 (192.91.66.189)
So what do you use for speaker interconnect wire? Solid wire seems pretty impractical. .......
270: Tube DIY Asylum, RE: Better how? What do you want to use it for? nt (0.00)
Posted by mikeyb on 2011-04-08, 06:23:45 (192.91.66.189)
48 volts for a plate supply? That's strange. The LM317 can't handle an input to ouput differential of more than 40 volts, so I am curious as to what your circuit looks like - can you provide a schemat .......
271: Tube DIY Asylum, RE: Running heaters on battery... (0.00)
Posted by mikeyb on 2011-04-07, 06:30:52 (192.91.66.189)
What is the total filamnet current draw? What filament transformer are you using (voltage, current)? I'd be happy to design a circuit for you. .......
272: Tube DIY Asylum, RE: Running heaters on battery... (0.00)
Posted by mikeyb on 2011-04-07, 05:32:45 (192.91.66.189)
It would be interesting, if not enlightening, to compare the voltage at the filaments 'both ways' (with batteries versus without). I'll bet that the difference in sound that you are hearing is because .......
273: Tube DIY Asylum, RE: what is a good diodes for 300b DC heater ? (0.00)
Posted by mikeyb on 2011-04-05, 10:24:13 (192.94.92.11)
I'm using the MUR1620CT dual diode (common cathode) with a center tapped transformer. It's readily available (e.g., DigiKey. If you need a full wave bridge (four diodes), use a MUR1620CTR (common anod .......
274: SET Asylum, Thanks! (0.00)
Posted by mikeyb on 2011-04-01, 14:10:27 (192.94.92.11)
Thanks for the replies\advice. .......
275: Tube DIY Asylum, RE: DIY (0.00)
Posted by mikeyb on 2011-04-01, 07:47:32 (192.91.66.186)
This isn't your April fools joke, is it Henry? .......
276: Tube DIY Asylum, You have to have a sense of humor (0.00)
Posted by mikeyb on 2011-03-30, 05:40:26 (192.94.92.14)
You have to have a sense of humor in order to handle all of this ... .......
277: Tube DIY Asylum, RE: Really??? (0.00)
Posted by mikeyb on 2011-03-29, 13:33:05 (192.91.66.186)
Yes, Jeff, I am well aware of the term "Transfer Function" as applied to electronics. I am an engineer, as you know, and have been dutifully contaminated by formal training. However, the term "optimal .......
278: SET Asylum, RE: New 45s (0.00)
Posted by mikeyb on 2011-03-29, 13:25:38 (192.91.66.186)
$445 a pair? Wow! That makes NOS RCAs look pretty cheap. Thanks for the reply. .......
279: Tube DIY Asylum, Please Please Please (0.00)
Posted by mikeyb on 2011-03-29, 10:49:43 (192.91.66.186)
Quit referring to "optimal internal transfer function". That is a totally undefined, totally meaningless phrase. .......
280: SET Asylum, New 45s (0.00)
Posted by mikeyb on 2011-03-29, 08:03:07 (192.94.92.11)
Are the Sophia/TJ the only new 45s available? .......
281: Tube DIY Asylum, RE: Death..... (0.00)
Posted by mikeyb on 2011-03-28, 13:44:19 (192.94.92.14)
Gee, thanks for the encouraging news. Right up there with Fox and CNN. I'm 63 - so I've only got a few years left. Oh well, if the lead doesn't get me, the radiation from Japan will. Or global climate .......
282: Tube DIY Asylum, Cell phones ... (0.00)
Posted by mikeyb on 2011-03-28, 07:13:32 (192.94.92.14)
It's not just woman. Ever try to communicate with upper level managers, whose Balckberries ring and beep every 2 minutes? Then there are those who talk while in the men's room ... Have you ever tried .......
283: Tube DIY Asylum, RE: PP 300b Bias (0.00)
Posted by mikeyb on 2011-03-25, 11:34:23 (192.94.92.11)
Use a 125-0-125 (250 VCT) transformer, such as these from Hammond, followed by a LCLC filter. You will wind up with about 100 VDC, if the first L meets crtical inductance. Primary 115 VAC, 60 Hz. Desi .......
284: Tube DIY Asylum, I'm curious ... (0.00)
Posted by mikeyb on 2011-03-25, 10:23:30 (192.94.92.11)
In the 'old days' when you used double regulation, what was the voltage in and voltage out of each? Did you maintain sufficent input to output voltage difference for the second regulator to work prope .......
285: Tube DIY Asylum, RE: Running a regulated HV into another regulator board!!! (0.00)
Posted by mikeyb on 2011-03-25, 06:42:24 (192.94.92.11)
My first question would be why? Why do you feel the 'need' to double regulate? Is the voltage required by the preamp lower than that supplied by the external (regulated) supply? All of the linear regu .......
286: K&K Audio / Lundahl Transformers, RE: LL1677 configured as SE to PP (grids) (0.00)
Posted by mikeyb on 2011-03-24, 12:21:08 (192.91.66.189)
Thanks, Kevin. My alternative (if I really HAVE to use 45s), is PP 45s with a LL1671 PP or LL1660 PP. Recomendations? .......
287: K&K Audio / Lundahl Transformers, LL1677 configured as SE to PP (grids) (0.00)
Posted by mikeyb on 2011-03-24, 07:36:10 (192.91.66.189)
Any problems with this configuration? If I back down the current in the primary to 40 mA, does the primary inductance increase much? I am thinking of using a 2A3, 45 or 46 to drive PP 300Bs in class A .......
288: Tube DIY Asylum, RE: Signal path wire!!!!!!!! (0.00)
Posted by mikeyb on 2011-03-22, 13:06:09 (192.91.66.186)
And why are you doing this (rewiring with silver wire)??? Yes, the quality of the 47K resistor at the input to the preamp is important. You want a low noise resistor. The commonly held wisdom is to us .......
289: Tube DIY Asylum, RE: FILTER REACTOR FOR AN EICO HF89? (0.00)
Posted by mikeyb on 2011-03-21, 13:53:33 (192.91.66.186)
So you are going from 300 ufd to 1800 uFd for the caps in the votage doubler? Slow down there ... That's going to cause quite a current surge when you turn on the amp, or at least a considerably longe .......
290: Tube DIY Asylum, RE: Damper tubes as PS rectifier (0.00)
Posted by mikeyb on 2011-03-14, 10:21:48 (192.91.66.189)
I agree with Lynn - damper diodes are great! They (generally) have a very low voltage drop and have a very desirable slow warm up time - sometimes over 30 seconds. As for sound ... I'm not a believer .......
291: Tube DIY Asylum, RE: All the EE books must be wrong then (0.00)
Posted by mikeyb on 2011-03-10, 08:46:03 (192.94.92.11)
I believe that the 'discussion' revolves around power supply step response (a change in the current drawn by the output tube), which CAN be easily simulated with PSUD2. More sophisticated simulators ( .......
292: Tube DIY Asylum, I believe .. (0.00)
Posted by mikeyb on 2011-03-10, 05:35:58 (192.94.92.14)
"usual bunch of Forum jokers" Hmm, I believe that you were the one who said "Quit 'yer silly flaming" .......
293: Tube DIY Asylum, RE: All the EE books must be wrong then (0.00)
Posted by mikeyb on 2011-03-10, 05:30:14 (192.94.92.14)
Of course not. You are just not applying the 'rules' correctly. The power supply filter is not just a capacitor; it's a nework of Ls and Cs and Rs. You have to look at the total circuit. Run a simulat .......
294: Tube DIY Asylum, RE: For what it is worth............ (0.00)
Posted by mikeyb on 2011-03-09, 20:10:51 (68.115.91.207)
"Sound" thinking! I totally agree (for whatever that's worth). .......
295: Tube DIY Asylum, RE: Settling Time (0.00)
Posted by mikeyb on 2011-03-09, 07:34:47 (192.94.92.11)
Nor does it exist if a more sophisticated simulator is used. .......
296: Tube DIY Asylum, RE: Not sure about that....... (0.00)
Posted by mikeyb on 2011-03-08, 14:45:39 (192.91.66.189)
What you stated is that 'the P-P amp gets "TWO pulls" on the power supply filter, from the Finals tubeS, for a waveform to complete.' On what do you base that statement? Lacking any kind of proof of .......
297: Tube DIY Asylum, RE: Not sure about that....... (0.00)
Posted by mikeyb on 2011-03-08, 13:25:18 (192.91.66.189)
Not so. PP stands for push-pull. In a class A push pull amp, the current drawn by one tube is the complment of that drawn by the other, so that the sum of the current drawn by the two tubes remains co .......
298: Tube DIY Asylum, RE: tube rectifier recommendation (0.00)
Posted by mikeyb on 2011-03-07, 14:34:12 (192.94.92.11)
The 5U4 and the 5AR4 are VERY different. The 5U4 is directly heated and draws 3 amps of filament current. The 5AR4 is indirectly heated and draws 1.9 amps of filament current. If the circuit was desig .......
299: Tube DIY Asylum, The only way ... (0.00)
Posted by mikeyb on 2011-03-07, 11:01:10 (192.91.66.189)
The only way we are going to make any progress on this issue is for you to provide more information. 1) When you say 'dips', do you mean a change in volume? 2) Put a volt meter on the B+ supply to the .......
300: Tube DIY Asylum, RE: 8 Ohm or 12 Ohm OPTs (0.00)
Posted by mikeyb on 2011-03-04, 14:58:48 (192.91.66.189)
By loading the 16 Ohm tap with a 12 Ohm speaker, your output tube will 'see' a lower impedance load than it wants. Don't do that - rewire the transformer for 8 Ohms and be happy. From what I read, Jam .......
301: Tube DIY Asylum, RE: Dilemma with AC coming out of my wall outlets(Maybe) (0.00)
Posted by mikeyb on 2011-03-04, 14:46:10 (192.94.92.11)
Hmm .. both preamps do the same thing? Are you sure it's not the amp? It doesn't do it using a CD player? .......
302: Tube DIY Asylum, RE: Dilemma with AC coming out of my wall outlets(Maybe) (0.00)
Posted by mikeyb on 2011-03-04, 11:38:56 (192.94.92.11)
Sounds like your phono preamp is hyper sensitive to changes in the B+ and /or filament supply voltages. Try coonecting an AC voltmeter at the outlet socket into which your preamp is plugged. How much .......
303: Tube DIY Asylum, RE: diy hifi tube amp (0.00)
Posted by mikeyb on 2011-03-03, 10:19:03 (192.91.66.189)
"About the choke, I was repeatedly told that it could be avoided ... I'd like to hear why you think it's a necessity - experience or theory? Theory. I'd never be crazy enough to design an audio amp wi .......
304: Tube DIY Asylum, RE: diy hifi tube amp (0.00)
Posted by mikeyb on 2011-03-02, 09:55:50 (192.91.66.189)
"I really liked the idea of LED cathode biasing for the preamp, and was told that feeding back in the input grid was fine. is there an issue with that? Please explain." The issue is that the way it is .......
305: Tube DIY Asylum, RE: diy hifi tube amp (0.00)
Posted by mikeyb on 2011-03-02, 06:20:16 (192.91.66.186)
Here are some potential improvements: 1) Why two volume controls? As shown, the amount of feedback is dependent upon the (second) volume control setting, because it connects to the wiper. Conventional .......
306: Tube DIY Asylum, RE: ARRRRG! (0.00)
Posted by mikeyb on 2011-02-28, 10:33:41 (192.94.92.14)
Thanks for the info. Adding the last LC was a good idea, if your goal was to reduce ripple to an acceptable level. With those 'huge' chokes, I'm not sure that this design would be considered a 'Modern .......
307: Tube DIY Asylum, ARRRRG! (0.00)
Posted by mikeyb on 2011-02-28, 07:31:15 (192.91.66.189)
Where did you add the choke? What is the final power supply design? When you added the choke, did the power supply voltage change? If so, by how much? Your comments are virtually meaningless without t .......
308: Tube DIY Asylum, Agreed (0.00)
Posted by mikeyb on 2011-02-25, 10:27:44 (192.91.66.189)
I'm tired of the name calling and criticism of any alternative approach anyway. .......
309: Tube DIY Asylum, RE: You can again... Redo the Redo (0.00)
Posted by mikeyb on 2011-02-24, 14:29:23 (192.94.92.11)
Does this help? Yes, you have come to the heart of the matter - is a settling time of over 100 msec acceptable or not. I have one opinion, you have another. I say who cares - the current demanded b .......
310: Tube DIY Asylum, Redo the Redo (0.00)
Posted by mikeyb on 2011-02-24, 10:54:40 (192.91.66.186)
Jeff was correct on two accounts: I didn't simulate the right thing in my previous post (which I can't delete) and the Wards Web 2A3 power supply is underdamped. Yes, with the second choke at 15 Hy .......
311: Tube DIY Asylum, You are correct - my apologies (0.00)
Posted by mikeyb on 2011-02-23, 19:32:29 (68.115.91.207)
Reviewing the schematic posted on Wards Web, you are correct - there are two inductors before the 2A3. My mistake. I'll run it again tomorrow and edit the original post. .......
312: Tube DIY Asylum, Redo, looking at the correct votage for the 2A3 (0.00)
Posted by mikeyb on 2011-02-23, 13:55:50 (192.91.66.189)
I redid the simulation, looking at V(C2) rather then V(C3). I1 is stepped from 42 to 48.3 mA, as in Jeffs later simulations. It's slow to respond, but it does appear to be criticaly damped (no boun .......
313: Tube DIY Asylum, RE: Fixing a Ringing 2A3 supply (long) 3 of 4 (0.00)
Posted by mikeyb on 2011-02-23, 12:35:14 (192.94.92.14)
"Wrong fruit, its sour-grapes as usual with you." Gosh, thanks. O.K. Your 14K resistor has an impedance and a DC resiatance of 14K Ohms. The 15 Hy choke used in the original design has an impedance of .......
314: Tube DIY Asylum, RE: Fixing a Ringing 2A3 supply (long) 3 of 4 (0.00)
Posted by mikeyb on 2011-02-23, 11:35:42 (192.94.92.14)
In page 1, you showed results for a 67.5 to 71.875 mA (9.375 mA) change in I2. On this page, you show results for a 42 to 48.3 mA change (6.3 mA)in I1. Is that a fair comparison? .......
315: Tube DIY Asylum, RE: Fixing a Ringing 2A3 supply (long) 3 of 4 (0.00)
Posted by mikeyb on 2011-02-23, 11:29:04 (192.91.66.186)
Me thinks that you are comparing apples to oranges ... Run your sim again with I2 jumping from 65 to 71.87 mA, as in your first example. Now tell me what the power supply output impedance is at C3. If .......
316: Tube DIY Asylum, RE: Again the question is asked! (0.00)
Posted by mikeyb on 2011-02-18, 07:05:44 (192.94.92.14)
Unless you have defined the laws of physics (Ohms law), there is something else wrong. What is the current drawn by the filaments? If it's a preamp, I guessing that you have a few 12AX7s that togethe .......
317: Tube DIY Asylum, RE: Common Sense (0.00)
Posted by mikeyb on 2011-02-17, 12:52:45 (192.94.92.11)
Unfortunately, neither 'simple logic' nor 'common sense' answer the question. I'll let it drop, it's not worth arguing about. .......
318: Tube DIY Asylum, On what do you base that assertion? (0.00)
Posted by mikeyb on 2011-02-17, 10:18:15 (192.94.92.11)
"Individual adjustmments to balance phase splitting would only be in static / idle terms, under music, it will not apply." On what do you base that assertion? Apply in what sense? Equal amplitudes ov .......
319: Tube DIY Asylum, RE: EDCOR Chokes (0.00)
Posted by mikeyb on 2011-02-17, 09:07:05 (192.91.66.189)
Very nice looking chokes, but not less expensive than Hammond for the compariable size. Edcor CXC100-5H-200ma 5 Hy 200 mA 58 Ohms enlosed - $39 Hammond 193H 5 Hy 200 mA 65 Ohms enclosed - $30 ::: TOPI .......
320: Tube DIY Asylum, RE: Filter Reactor Choke Connection (0.00)
Posted by mikeyb on 2011-02-13, 20:10:58 (68.115.91.207)
I have a very nice UTC 'Linear Standard' choke (LS-980) with a 'hum bucking' tap. The total inductance is 14 Hy, with a tap at about 1.5 Hy. On page 5 of the pdf (below), you will see how the 'hum bu .......
321: Tube DIY Asylum, Not so (0.00)
Posted by mikeyb on 2011-02-10, 06:10:21 (192.94.92.11)
The subject at the time, at least in my understanding, was wether or not the high frequency voltage spikes across L1 shown by PSUD II are real. The Cadence and TINA TI simulators say no, PSUD II is in .......
322: Tube DIY Asylum, Here's a TINA TI simulation of the same circuit (0.00)
Posted by mikeyb on 2011-02-09, 11:16:57 (192.94.92.11)
The two plots are of V(L1)(red) and V(L2) (pukey yellow). Note that V(L1) is scarry, but not nearly so much as what PSUD2 'shows'. The Y axis is in volts. .......
323: Tube DIY Asylum, PSUD II is somewhat missleading (0.00)
Posted by mikeyb on 2011-02-08, 05:49:12 (192.91.66.189)
Different simulators will give different results. I believe that PSUD II is missleading in this case. Cadence and Tina TI show voltage spikes across the inductors (as much as 200 Vpp), but not the 'ha .......
324: Tube DIY Asylum, RE: Very low gain active preamp build (0.00)
Posted by mikeyb on 2011-02-06, 14:19:02 (96.42.68.12)
Be forwarned that it's probably 'overdesigned' but I'll attach a schematic in a day or two ... .......
325: Tube DIY Asylum, RE: Very low gain active preamp build (0.00)
Posted by mikeyb on 2011-02-03, 14:34:17 (192.91.66.186)
PLEASE don't tell me that having the interconnect cables touch the ground is going to make a differance ... .......
326: Tube DIY Asylum, RE: Instead of the 6AS7/6080 maybe a 6c19pi (0.00)
Posted by mikeyb on 2011-02-03, 14:32:20 (192.91.66.186)
Interesting drawing - the tubes look like a sad\mad face ... .......
327: Tube DIY Asylum, RE: Very low gain active preamp build (0.00)
Posted by mikeyb on 2011-02-03, 14:27:24 (192.91.66.186)
Try a stepped attenuator followed by a 46 DHT amplifier stage. The mu and Rp of a 'Class A' connected 46 is similar to that of a 45, but the tube is (so far) much less expensive. Using DHTs is a pain, .......
328: Tube DIY Asylum, ya got me ... (0.00)
Posted by mikeyb on 2011-02-03, 10:43:11 (192.91.66.186)
How did you do that? .......
329: Tube DIY Asylum, I agree (0.00)
Posted by mikeyb on 2011-02-02, 10:25:18 (192.94.92.14)
"Don't put in a crappy 2 watt metal oxide" I've had 2 watt 10 Ohm metal oxide resistors 'open' for no apparent reason twice on a KT88 push pull amp. I can't see how they could have been oveloaded - it .......
330: Tube DIY Asylum, Question ... (0.00)
Posted by mikeyb on 2011-01-24, 20:08:40 (96.42.68.12)
"Inefficent bookshelves, FMI 80s with an analogue front end and very good solid state gear is what I use now" So why all the lectures on how to build tube amps? It appears that you don't even use one! .......
331: Tube DIY Asylum, Similar story (0.00)
Posted by mikeyb on 2011-01-22, 14:17:40 (69.246.164.161)
When I was a lad of 14, I was building tube amps as a hobby. Really - what a geek! Anyway, while listening to the amp, I accidentally shorted the cathode of a 12AX7 driver to ground and 'discovered' t .......
332: Tube DIY Asylum, RE: RCA Panel Connectors (0.00)
Posted by mikeyb on 2011-01-21, 05:58:28 (69.246.164.161)
I'm using the Neutrik version of these connectors, and they look great. Nice tight fit. I had to buy a special chassis punch (7/8 inch, if I remember correctly), but it was worth it. .......
333: Tube DIY Asylum, RE: Pay attention, now (0.00)
Posted by mikeyb on 2011-01-14, 08:12:15 (192.94.94.106)
You’re right - it's probably nearly impossible to simulate what's happening in an amplifier while playing 'real music'. We can't accurately ‘describe’ (simulate) the current waveform demanded of the p .......
334: Tube DIY Asylum, RE: If you married a tube, what kind of relationship would you have? (0.00)
Posted by mikeyb on 2011-01-14, 06:21:03 (192.94.94.106)
Speaking of which, consider the names of some of the products from "Bottlehead" (www.bottlehead.com): "foreplay", "seduction", and "quickie". .......
335: Tube DIY Asylum, RE: Acceptable DC through coupling cap (0.00)
Posted by mikeyb on 2011-01-13, 14:33:27 (192.91.75.30)
"I've been noticing larger woofer excursions on the left vs right speaker, so decided to investigate the amp to see if something might be amiss." But how does that correlate to a leaky coupling cap? A .......
336: Tube DIY Asylum, LSES ripple (0.00)
Posted by mikeyb on 2011-01-13, 14:22:17 (192.91.75.30)
Simulation will show you that LSES supplies have considerably more 120 Hz ripple at their output than does a convetionally designed LCLC or even a CLC supply, which may be an issue for a preamp. You m .......
337: Tube DIY Asylum, RE: Interesting thread at DIY Audio ... (0.00)
Posted by mikeyb on 2011-01-11, 10:20:46 (192.94.94.105)
"Noise cancelling power supply - two power transformers in parallel with one transformer out of phase - the minus ripple from one transformer will cancel out with the + ripple of the other transformer .......
338: Tube DIY Asylum, RE: Sound of Rectifiers and Regulators (0.00)
Posted by mikeyb on 2011-01-03, 16:42:05 (96.42.73.52)
I guess that I didn't state that very clearly. Yes, the statement "The power supply output impedance is dominated by the capacitance of the last cap in the filter" applies to the unregualted case. :: .......
339: Tube DIY Asylum, RE: zoomed a little (0.00)
Posted by mikeyb on 2011-01-03, 12:27:39 (192.94.94.105)
Well, kind of. The filament of V1 in series with the filament of V6 are the cathode resistor. A really half a** way of supplying filmant current to these tubes! It depends upon the cathode current of .......
340: Tube DIY Asylum, RE: Sound of Rectifiers and Regulators (0.00)
Posted by mikeyb on 2011-01-03, 10:14:59 (192.94.94.105)
Some opinions: "Does a regulator circuit after a tube rectifier change the sound of said rectifier tube?" Yes! For the better or the worse depends upon the type of regulator. A good regulator will sta .......
341: Whiner's Woad, RE: They are bums........stick around please.......nt (0.00)
Posted by mikeyb on 2010-12-23, 10:29:31 (192.91.75.29)
Oh for God's sake - why are 'we' placating a whiner? It seems to me that the 'bad behavior' went both ways. The guilt should be shared - it was not one sided. .......
342: Tube DIY Asylum, RE: On Breaking In... (0.00)
Posted by mikeyb on 2010-12-23, 10:21:00 (192.91.75.29)
Sounds like a good test plan. I'd be interested to see if there is any measureable difference after 'break in'. Personally, I doubt it. It seems more likely that it's the power of suggestion that prev .......
343: Tube DIY Asylum, RE: 300Bs (0.00)
Posted by mikeyb on 2010-12-08, 05:28:09 (192.94.94.105)
FYI. I'm currently using EH 'gold grid' 300Bs - have been for about 2 years now. Prior to that, I had JJ 300Bs installed in a PP amp, one of which developed a grid to heater short. As for sound qualit .......
344: Tube DIY Asylum, 300Bs (0.00)
Posted by mikeyb on 2010-12-07, 12:40:40 (192.94.94.105)
You think 300Bs are expensive, try 45s! The NOS version are at least $120 a pair, and new Sophia mesh plates run around $300 a pair! I wanted to use a pair of 45s as drivers for a PP 300B amp, but the .......
345: Tube DIY Asylum, RE: AC neutral return caused main fuse to jump (0.00)
Posted by mikeyb on 2010-12-06, 16:46:47 (96.42.73.52)
If your power source uses a GFI (ground fault interrupter), there may be an explaination. GFIs work by monitoring the difference in current between the 'hot' and 'neutral' wires. They should always be .......
346: Tube DIY Asylum, for what it's worth ... (0.00)
Posted by mikeyb on 2010-11-17, 11:54:28 (192.91.75.29)
The 'Miller' capacitance of a 2A3 is higher than that of a 300B - 93 pF versus 82 pF. That of a 45 is lower - 36 pF. So if I were to choose a 2A3 driver for a 300B, the 'predriver' would see a more c .......
347: Tube DIY Asylum, Mountain out of a mole hill (0.00)
Posted by mikeyb on 2010-11-08, 05:31:40 (192.94.94.105)
"I saw some tube amplifier has boost up effect on the bass due to improper design." Why do you think that your amplifier has an 'improper design'? Up .23 volts at 8 Hz relative to 120 Hz (out of 3.73) .......
348: Tube DIY Asylum, RE: Transformer hum (0.00)
Posted by mikeyb on 2010-11-05, 10:23:29 (192.91.75.30)
"Also have one side of the heater tied to ground." I believe that the preferred method is to use a 'hum pot', like you would for a DHT. That is, connect the two filament supply leads across the 'arms' .......
349: Tube DIY Asylum, Symphony perhaps ... (0.00)
Posted by mikeyb on 2010-10-28, 05:27:41 (192.91.75.29)
But don't expect good audio at a musical. I recently went to a performance of Wicked in Minneapolis. Horribly amplified and compressed. A great musical, but the audio quality was worse than what a MP3 .......
350: Tube DIY Asylum, RE: Must have for the serious designer (0.00)
Posted by mikeyb on 2010-10-27, 08:21:00 (192.94.94.105)
Great instrument, but, ya know, I'll bet you still can't see\measure the difference between using a single 20 gauge wire and 3 paralleled TSS wires for transformer leads. But, by gosh, you can hear it .......
351: Tube DIY Asylum, Some advice on over engineering ... (0.00)
Posted by mikeyb on 2010-10-19, 05:41:12 (192.94.94.105)
Been there, done that, never again. It's called over engineering. You want to improve something, feel that you have terrific ideas, and get this mind set that you have to have a tube in there some whe .......
352: Tube DIY Asylum, Yes! (0.00)
Posted by mikeyb on 2010-10-15, 10:57:27 (192.94.94.105)
"Is there a problem with running a 60Hz transformer on 50Hz?" Yes, it is likely to overheat, particularly if run near maximum capacity. You can use a transformer designed for 50 Hz at 60 Hz, but not t .......
353: Tube DIY Asylum, Good grief NO (0.00)
Posted by mikeyb on 2010-10-12, 11:57:10 (192.91.75.30)
The center tap of the 300Bs filament transformer must go to ground or to the cathode 'self bias' resistor, NOT to the plate! The filament transformer CT and the hum pot are redundant - use one or the .......
354: Tube DIY Asylum, RE: LOTS!!! (0.00)
Posted by mikeyb on 2010-10-12, 09:01:34 (192.91.75.30)
That would potentially help the 'loose tube' problem, but not the warm up issue. I really should replace all of the tube sockets, but it's a lot of work. .......
355: Tube DIY Asylum, Just another term for 'ground' (0.00)
Posted by mikeyb on 2010-10-12, 07:11:52 (192.94.94.106)
Or common or whatever is your preference. The negative lead of the plate supply or the positive lead of the bias supply. .......
356: Tube DIY Asylum, Sub Zero (0.00)
Posted by mikeyb on 2010-10-12, 05:58:59 (192.91.75.29)
"A good capacitor to go along with the Sub-Zero appliances and the Land Rover" My son used to work as an appliance repair man. His specialty was Sub Zero refrigerators - they were the best (and most e .......
357: Tube DIY Asylum, Good Idea! (0.00)
Posted by mikeyb on 2010-10-12, 05:42:16 (192.91.75.29)
I like it. Now if a reasonable way can be found to eliminate the cathode bypass cap ... Just one question - Why is an inductor (in the plate of the driver) considered to be preferable to a (DC blockin .......
358: Tube DIY Asylum, LOTS!!! (0.00)
Posted by mikeyb on 2010-10-11, 10:26:51 (192.91.75.29)
All that needs to happen is for the driver tube to become loose in it's socket, or age such that the mu changes. I have a 1920's vintage Sterling radio with a 'Loftin-White' directly coupled output (s .......
359: Tube DIY Asylum, RE: Opinion needed -- how much capacitance? (0.00)
Posted by mikeyb on 2010-10-11, 05:55:49 (192.94.94.105)
Without a great deal of analysis, I would go for 200 uFd (two 100 uFd 370 VAC motor run caps in parallel) as the last cap in the PS, in order to keep the output impedance reasonably low. From the spec .......
360: Tube DIY Asylum, No worky ... (0.00)
Posted by mikeyb on 2010-10-10, 19:35:48 (97.86.224.88)
There must be a lot more than a 5 volt differential between the output voltage of the power supply and the zener regulation point (in shunt mode). I would recommend 50 to 100 volts. You MUST have a re .......
361: Tube DIY Asylum, RE: PSUD 5R4 Anomaly (0.00)
Posted by mikeyb on 2010-10-08, 12:35:39 (192.94.94.105)
PSUD2 includes the transformer winding resistance, the data sheet does not. Try changing the DCR of the transformer windings in PSUD2 to sub 1 Ohms and see if that helps. .......
362: Tube DIY Asylum, But it's a 'small' one ... (0.00)
Posted by mikeyb on 2010-10-04, 12:13:33 (192.91.75.30)
Yes, the grid resistor bypass cap is in the signal path. But typically, I use a bias supply with a voltage output on at least 3 times the required grid bias voltage, so that I can use a rather high im .......
363: Tube DIY Asylum, RE: Fixed! (0.00)
Posted by mikeyb on 2010-10-01, 10:24:44 (192.94.94.106)
"Ever buit a self-bias amp/" No, not since high school, when I was uneducated in electronics and blindly followed others schematics. Many commercial amps use fixed bias, including Heathkit and Dynaco. .......
364: Tube DIY Asylum, Fixed! (0.00)
Posted by mikeyb on 2010-10-01, 05:45:14 (192.91.75.30)
I have built 3 amps using fixed bias exclusively and have never lost a tube due to that. I prefer fixed bias over cathode bias because fixed bias eleminates the need for a high valued (greater than 10 .......
365: Tube DIY Asylum, RE: Slow to warm up (0.00)
Posted by mikeyb on 2010-09-27, 10:54:17 (192.91.75.29)
I have a Russian made EF86 (Svetlana) and a Amperex Bugle Boy in a stereo headphone amplifier. The Bugle boy is working by the time the 5AR4 rectifier is working, but the Svetlana takes a few minutes. .......
366: Tube DIY Asylum, poor design for a line stage application (0.00)
Posted by mikeyb on 2010-09-27, 10:22:53 (192.94.94.105)
The plate resistance of an EF86 in triode mode is very high for a triode (16.5K), and it will be even higher if the cathode resistor is left unbiased. Why would you want a low to high impedance transf .......
367: Tube DIY Asylum, It's still being done ... (0.00)
Posted by mikeyb on 2010-09-24, 10:26:59 (192.94.94.106)
Take a look at what's inside a power entry 'RFI Filter' - there are caps from hot and neutral to ground. These filters are very common in modern equipment. Every (decent) desktop computer has one. ::: .......
368: Tube DIY Asylum, RE: Cathode/source follower drivers (0.00)
Posted by mikeyb on 2010-09-24, 10:16:36 (192.94.94.106)
Heathkit used a 12BH7 as a cathode follower, placed between the driver and the output tubes (6550), in its W6-M amp. See the link below. I am using a similar design, but with the 6N1P in place of the .......
369: Tube DIY Asylum, Not much (0.00)
Posted by mikeyb on 2010-09-21, 11:02:37 (192.94.94.105)
Depends upon the DC resistance and DC saturation current, but offhand I can't think of any application for them. The 1000 Hz makes me think that they were intended for military electronics application .......
370: Tube DIY Asylum, Thanks! (0.00)
Posted by mikeyb on 2010-09-20, 06:26:23 (192.94.94.105)
Thanks for all of the replies. I'll plan on using 2 Teflons and one 'oiler' (DC blocking cap on at the plate of the second stage) in each channel. .......
371: Tube DIY Asylum, RE: "one at the input?" (0.00)
Posted by mikeyb on 2010-09-17, 12:16:52 (192.94.94.105)
Both stages employ fixed bias. The heater (actually the center tap thereof) is at ground potential and the grid is biased at a negative voltage. Therefore, the coupling caps at the input to both stage .......
372: Tube DIY Asylum, 0.22 uF Teflon or 1.0 uF oil or both (0.00)
Posted by mikeyb on 2010-09-17, 11:35:48 (192.94.94.106)
I am building a 2 stage line level preamp with DHTs (Directly Heated Triodes) that requires 3 AC coupling caps - one at the input, one between stages, and one at the output. I have a sufficent number .......
373: Tube DIY Asylum, RE: Regulated Driver B+ (0.00)
Posted by mikeyb on 2010-09-16, 08:56:44 (192.94.94.105)
As several others have mentioned, you should not use a LC filter after the gas ergulator - it is unnecessary and will cause problems. If you are directly connecting the grid of the 300B to the plate o .......
374: Tube DIY Asylum, Generlizations ... (0.00)
Posted by mikeyb on 2010-09-10, 10:52:51 (192.91.75.30)
Oh come on, Jeff, you really shouldn't assume that all engineers only rant theory and never build amps. I have built 3 so far, two monoblocks that I use at home and one integrated (stereo) that I gave .......
375: Tube DIY Asylum, How do you know? (0.00)
Posted by mikeyb on 2010-09-09, 06:10:38 (192.94.94.106)
O.K. So you listen to a music passage. Then you take the amp apart and modify the leads to the caps. This takes - what - 1 to 3 hours? Then you put the amp back together and play (I'm guessing) the sa .......
376: Tube DIY Asylum, RE: Dynamic Impedance of your supply, using PSUD2 (0.00)
Posted by mikeyb on 2010-09-07, 05:55:34 (192.91.75.30)
Jeff, the simulation that you are presenting shows us that at a very low frequency, approaching DC (0 Hz), the power supply impedance is 2K Ohms. That's NOT the same as the impedance at some realistic .......
377: Tube DIY Asylum, RE: rough numbers (0.00)
Posted by mikeyb on 2010-09-03, 11:54:47 (192.94.94.106)
"Power supply regulation is only a concern when there will be long term current draw changes (like in a Class A/B amplifier circuit)." Good point, Tre. So in class A/B, the average current drawn by th .......
378: Tube DIY Asylum, RE: Lets focus on the OP original question please (0.00)
Posted by mikeyb on 2010-09-03, 08:43:22 (192.91.75.30)
O.K. - good point. I think Tre (above) has the right idea. What's important is the load, not the source. .......
379: Tube DIY Asylum, RE: Hypothetical and Unfounded (0.00)
Posted by mikeyb on 2010-09-03, 08:03:33 (192.91.75.29)
Hypothetical, perhaps. Unfounded, no. Logical, yes. O.K, O.K. I'll just shut up and let it be. Frankly, I use fully differential push pull amps (300B, KT88, EL34), wherein the current drawn from the p .......
380: Tube DIY Asylum, let's look at this another way (0.00)
Posted by mikeyb on 2010-09-02, 14:57:48 (192.94.94.106)
Let's look at what happens under the hypothetical 'worst case' situation where a SE amp is 'asked' to reproduce a 20 Hz sine wave. Furthermore, let's assume that 'no signal' current drawn by the outpu .......
381: Tube DIY Asylum, RE: Jeff's response, one time (0.00)
Posted by mikeyb on 2010-08-30, 05:43:38 (192.91.75.29)
"Wow. Pretty sophomoric - and boring." Gosh, thanks for the concise critique and encouragement. 1) The ideal power supply is one that is rock solid, that does not respond at all to changing current de .......
382: Tube DIY Asylum, RE: Conventiona\LES response to low frequency changes in current (0.00)
Posted by mikeyb on 2010-08-27, 13:36:59 (192.91.75.29)
No, not with this simulator (Tina TI). I can't add models. .......
383: Tube DIY Asylum, Conventiona\LES response to low frequency changes in current (0.00)
Posted by mikeyb on 2010-08-27, 10:26:50 (192.94.94.106)
Please go to the link below and look at the document showing the result of simulation of both a 'conventional' LCLC supply and a 'LES' style supply. The current draw by the simulated output tube is 60 .......
384: Tube DIY Asylum, RE: Traditional power supplies are not very good (0.00)
Posted by mikeyb on 2010-08-19, 05:46:47 (192.91.75.30)
Eloquently stated, but basically flawed thinking. A capacitor is an energy storage device, right? So when the amp (output tube) demands more current, where does in come from? Primarily the last cap in .......
385: Tube DIY Asylum, RE: Power Supply PSUD2 , #1 of 2 (0.00)
Posted by mikeyb on 2010-08-17, 10:36:26 (192.94.94.105)
Somehow I knew the subject would come up (again) ... You are entirely too 'hung up' on a 'fast' responding power supply. Granted, in the first sim, it takes 500 msec to reach a new (lower) steady stat .......
386: Tube DIY Asylum, RE: Hammond AO-35: where's the phaseinverter? (0.00)
Posted by mikeyb on 2010-08-16, 10:26:11 (192.94.94.105)
V2 is the phase inverter. The two triodes are cathode coupled. This is a very standard differential amnplifier configuration, where the cathodes are tied together and unbypassed. One grid is driven, t .......
387: Tube DIY Asylum, RE: DC supplies for DHT's (0.00)
Posted by mikeyb on 2010-08-11, 13:02:22 (192.91.75.30)
Then NO, you should not. The cathode resistors would be in parallel, causing the bias voltage to be the same for both tubes. In a perfect world, with perfectly matched output tubes an power supplies, .......
388: Tube DIY Asylum, RE: Anybody know who made this tube amp and power supply (0.00)
Posted by mikeyb on 2010-08-11, 05:57:56 (192.94.94.106)
I'm 99% certain that it's home built, not commercial, probably form the 60s. Notice the power plug - that's 50's and 60's - anything in the last 20 years would have an IEC plug. I haven't seen caps wi .......
389: Tube DIY Asylum, RE: Switchers for Filaments (0.00)
Posted by mikeyb on 2010-08-06, 10:26:01 (192.94.94.105)
I don't think that reliability is an issue, but I'd be concerned about the amount of 'hash' they put on the AC mains and the RFI that they generate. Personally, I'd use a conventional DC supply, maybe .......
390: Tube DIY Asylum, RE: JC (0.00)
Posted by mikeyb on 2010-08-04, 10:29:08 (192.91.75.29)
JC? I thought he died around 33 AD, came back, and started a church ... .......
391: Tube DIY Asylum, RE: A heretic question for peoples, who belive in simmulations (0.00)
Posted by mikeyb on 2010-08-04, 10:22:46 (192.91.75.29)
"Maybe everybody wants to go on their soapbox and preach the message they been wanting to preach." So, what's new? Have you been reading the power supply threads? I'm not sure what the point of the or .......
392: Tube DIY Asylum, RE: A heretic question for peoples, who belive in simmulations (0.00)
Posted by mikeyb on 2010-08-04, 06:03:44 (192.91.75.30)
Let me give you some specific examples as to where I have used simulation in the design of a tube based audio amplifier, and why. I like tone controls, specifically the Baxandall passive circuit. I wa .......
393: Tube DIY Asylum, RE: A heretic question for peoples, who belive in simmulations (0.00)
Posted by mikeyb on 2010-08-03, 13:08:05 (192.94.94.105)
I'll ignore the question and get to the meat of the argument. IMHO, you are being entirely too harsh on the usefullness of simulations. Agreed, the simulator is only a mathamatical tool, and the resul .......
394: Tube DIY Asylum, RE: What about the WE 421A? (0.00)
Posted by mikeyb on 2010-08-02, 12:26:40 (192.94.94.106)
The WE 421A is a different animal than the 6080, having much higher gain (about 6). Actually, that's higher than the 2A3's gain (4.2). It's linearity (judging by the plate curves) is still poor compar .......
395: Tube DIY Asylum, RE: SET 6080? (0.00)
Posted by mikeyb on 2010-08-02, 10:47:54 (192.91.75.30)
I suspect that you would be very dissapointed in a 6080 based SE amp. It's gain is very low (only 2, as compared to 4.2 for the 2A3), which means that you would need a lot of voltage (maybe 200 vPP) t .......
396: Tube DIY Asylum, just curious (0.00)
Posted by mikeyb on 2010-08-02, 07:12:28 (192.94.94.106)
Why on earth would you want to waste a 300B or 211 as a rectifier? If you have 300Bs to spare, sell them to me! .......
397: Tube DIY Asylum, RE: Too big transformer (0.00)
Posted by mikeyb on 2010-07-30, 13:26:09 (192.94.94.105)
The 400V rating on the choke (generally) refers to the winding to frame breakdown voltage. If your Vout is 525 volts, the winding is at that potential, and the choke's frame is grounded, you have exce .......
398: Tube DIY Asylum, RE: constant voltage transformer for PP DHT filaments (0.00)
Posted by mikeyb on 2010-07-29, 11:51:17 (192.94.94.105)
That's fine Jeff, but you are missing the point. The problem is that the operating point and sonics of a DHT are affected by the filament voltage, which is directly related to line (supply) voltage wh .......
399: Tube DIY Asylum, RE: Driver requirements of DHT's (0.00)
Posted by mikeyb on 2010-07-26, 14:03:55 (192.94.94.105)
Most likely, the statement derives from the fact that DHT tend to have low gain (mu), as compared to tetrodes\pentodes. For example, a 300B has a gain of only about 4, as compared to approximately 15 .......
400: Tube DIY Asylum, RE: My My MY, ... so many of my nice friends are posting this week !! (0.00)
Posted by mikeyb on 2010-07-22, 08:48:58 (192.94.94.105)
We can still be friends if we disagree, right? While I frequently disagree with you posts, they are always amusing. They sometimes make my day. Without them, the Asylum is boring. It's like listening .......
401: Tube DIY Asylum, Power cord (0.00)
Posted by mikeyb on 2010-07-21, 11:40:11 (192.91.75.30)
So is a black power cord acceptable, or do I need one of a different color? I've seen grey cords ... .......
402: Tube DIY Asylum, Questionable (0.00)
Posted by mikeyb on 2010-07-20, 08:41:10 (192.94.94.105)
Of course your designs are questionable. Most everything in life is questionable (except that we are all going to die eventually). PSUD2 results are questionable. What's the saying - the unreasoned li .......
403: Tube DIY Asylum, RE: B+ Supply and Filter to the Finals (0.00)
Posted by mikeyb on 2010-07-20, 05:58:19 (192.91.75.30)
Same old mantra - if the power supply doesn't conform to Jeffs questionable 'standards', the amp will be junk. .......
404: Tube DIY Asylum, RE: DIY SE Output transformer Lead Outs (0.00)
Posted by mikeyb on 2010-07-19, 09:06:24 (192.94.94.106)
By your logic, Jeff, you should be using a Lundahl output transformer (well, power and interstage as well, I guess). They have no leads. The 'terminals' are simply the windings brought out so that you .......
405: Tube DIY Asylum, RE: 46 is excellent, 807 pretty good (0.00)
Posted by mikeyb on 2010-07-13, 12:58:49 (192.94.94.106)
I'll take them off your hands ... My latest project (line level preamp with tone controls) uses 4 of them. .......
406: Tube DIY Asylum, Hammond 1650R (0.00)
Posted by mikeyb on 2010-06-10, 19:06:02 (96.42.88.236)
Actually, my 'other' amp (PP KT88s, UL with negative feedback - a very conventional design) uses a 1650R. BIG transformer. I don't like the high end of the PP KT88 amp as compared to the PP 300B amp w .......
407: Tube DIY Asylum, RE: Checked out Lundahl... (0.00)
Posted by mikeyb on 2010-06-10, 16:35:32 (96.42.88.236)
Hi Mike. On further thought, the idea that increasing load impedance will decrease distortion is probably more applicable to triodes with no negative feedback then to tetrodes\pentodes, especially whe .......
408: Tube DIY Asylum, RE: Checked out Lundahl... (0.00)
Posted by mikeyb on 2010-06-10, 13:45:29 (192.91.75.29)
1629? Can't find a spec for it. I wouldn't hesitate to increase the trasformer impednace from 4300 Ohms to 5600 or 6000 ohms. You may not get as much power, but distortion should be lower. ::: TOPIC:: .......
409: Tube DIY Asylum, RE: Output Transformer Upgrade (0.00)
Posted by mikeyb on 2010-06-10, 12:59:38 (192.91.75.30)
I'd question wether or not a Hammond would be much of an improvement. A better choice would be the Lundahl 1663PP (40W at 30 Hz, $145) or 1620PP (125W, $235). The LL1620PP doesn't have a UL tap, howev .......
410: Tube DIY Asylum, RE: DGC Hare? (0.00)
Posted by mikeyb on 2010-06-04, 06:18:56 (192.94.94.105)
I'd be hesitant to buy from a guy who claims that 6146's are 'Directly Heated Triodes'. They are neither triodes nor directly heated. The one transformer looks like a UTC unit to me. Can't tell if it .......
411: Tube DIY Asylum, Those Hammond Chassis are so flimsy, and the amp takes on that sound (0.00)
Posted by mikeyb on 2010-05-22, 11:09:10 (96.42.69.2)
Come again? What is the sound of a 'flimsy chassis'? Are you referring to mechanical vibration of the tube (2A3) elements (microphonics)? .......
412: Tube DIY Asylum, You are correct. (0.00)
Posted by mikeyb on 2010-05-21, 14:27:08 (192.91.75.29)
Most likely there are three .1uF caps with a common terminal (one side of each cap connects to the 'common' terminal). You could, of course, tie the 'uncommon' lead of all three caps together to form .......
413: Tube DIY Asylum, RE: choke ratings question (0.00)
Posted by mikeyb on 2010-05-19, 05:34:55 (192.94.94.106)
They are probably useless at 60 Hz line voltage - note the '.05 Hy at 1000 CPS' rating. This implies that they were designed for use in aircraft, where the supply voltage was 400 or 800 Hz. Are they p .......
414: Tube DIY Asylum, RE: OT, Luxury automaker Acura is using......tubes (0.00)
Posted by mikeyb on 2010-05-17, 06:46:46 (192.94.94.105)
I'm never buying an Accura now! Coudn't they at least have used somebody who knew what they were talking about? A nice nerdy engineer? .......
415: Tube DIY Asylum, RE: Right, picking a preamp and amp independently is a recipe for disaster. (0.00)
Posted by mikeyb on 2010-05-14, 05:40:18 (192.91.75.30)
"Nothing is as bad as attenuating your 2 volt source down to 0.1 volts so you can amplify it back up to 1 volt to feed the amp." When considering SNR (Signal to Noise Ratio), that's probably a true st .......
416: Tube DIY Asylum, RE: Russian 6SN7GT, can they bias up to 10ma like the NOS? (0.00)
Posted by mikeyb on 2010-05-06, 13:19:49 (192.91.75.30)
The russian 'equivalent' of a 6SN7GT is listed as the 6H8-C, and has a plate dissipation rating of 2.75 W. Vp = 250, Ik = 10 mA = 2.5 watts, kind of pushing it. The Sylvania 6SN7GT has a rated plate d .......
417: Tube DIY Asylum, You can't be serious (0.00)
Posted by mikeyb on 2010-05-03, 05:32:38 (192.94.94.105)
What possible difference could the ratio of the dimensions of the box make? What's next - CDs whose circumference to thickness ratio is 'golden'? Good grief, Charlie Brown. .......
418: Tube DIY Asylum, RCA jack update (0.00)
Posted by mikeyb on 2010-04-27, 08:38:13 (192.94.94.106)
I'm impressed with the Neutrik NF2D series of RCA jacks. They are well made, fit tight, and are (relatively) inexpensive at $3.79 apiece. The platting is 5 um gold over 5 um nickel, which is quite a b .......
419: Tube DIY Asylum, RE: You can't have both ways - Either caps are low impedance or they're not. (0.00)
Posted by mikeyb on 2010-04-20, 08:28:53 (192.94.94.106)
"Dated ideological model?" Give me a break! As far as I know, the properties of a capacitor have not changed. Unlike an ideal resistor, the impedance of a capacitor is a function of frequency. Z = 1/( .......
420: Tube DIY Asylum, RE: Nice work, but ... (0.00)
Posted by mikeyb on 2010-04-20, 05:43:45 (192.94.94.105)
What superstition? I'm not following you ... .......
421: Tube DIY Asylum, RE: Here we are, 2010 (0.00)
Posted by mikeyb on 2010-04-19, 17:05:27 (97.86.225.111)
Claiming Henry as blessing 'your' supply is a bit of a stretch. "I can assist on the PSUD work for you, or look it over for you." That makes about as much sense as me advising you how to do surgery o .......
422: Tube DIY Asylum, jeff - (0.00)
Posted by mikeyb on 2010-04-19, 08:54:06 (192.94.94.105)
I'm not saying I disagree with your (PSUDII) analysis, but I do say that you may be desiging to the wrong criteria. Tre and I (and others) are simply qusetioning the conclusion that you have reached t .......
423: Tube DIY Asylum, Nice work, but ... (0.00)
Posted by mikeyb on 2010-04-19, 06:14:40 (192.91.75.29)
What you have done, by reducing the inductance of L1, is to move more toward the characteristics of a CLC supply. That's why you needed to reduce the power transformer's secondary voltage from 650 to .......
424: Tube DIY Asylum, To be honest ... (0.00)
Posted by mikeyb on 2010-04-18, 12:36:36 (96.42.88.108)
I don't know for sure. That scenario is rather complex. What's the frequency of the drum note? Is the signal more or less a sine wave, with varying\decaying amplitude? I live in Minnesota and we tole .......
425: Tube DIY Asylum, Are you sure about that? (0.00)
Posted by mikeyb on 2010-04-17, 15:03:37 (96.42.88.108)
So, if Jeff's example, where does the extra 15 mA of current come from? In the PSDII plot above, the skinny red line is the current delivered to the load. The yellow line is the current drawn throu .......
426: Tube DIY Asylum, Say what? (0.00)
Posted by mikeyb on 2010-04-17, 14:26:47 (96.42.88.108)
"and you can use driver tubes that draw minimal plate current, and thus, respond far better to input signals on their grids." On what do you base that statement? .......
427: Tube DIY Asylum, Sigh ... (0.00)
Posted by mikeyb on 2010-04-15, 16:58:55 (96.42.90.49)
That 1300 Ohm impedance value that you stated applies at something like .2 Hz. Who cares? Is your amp going to respond to a .2 Hz signal? I hope not. It would never get through the output transformer. .......
428: Tube DIY Asylum, RE: What if the voltage to the finals was regulated? (0.00)
Posted by mikeyb on 2010-04-15, 10:10:40 (192.94.94.106)
"Think of a piano, multiple transients requiring quick recovery so as not to blurr or deface the playback.: Better yet is a power supply with very low output impedance, from which 'recovery' is not ne .......
429: Tube DIY Asylum, Found it! (0.00)
Posted by mikeyb on 2010-04-15, 08:40:46 (192.91.75.29)
Found the technical specs (thanks to Google): http://www.neutrik.com/fl/en/audio/210_724542351/NYS367-__detailtechnical.aspx?title=NYS367-* They are NOT the same as the more expensive NF2D series http .......
430: Tube DIY Asylum, RE: Markertek (0.00)
Posted by mikeyb on 2010-04-14, 13:58:35 (192.94.94.106)
Interesting. They are sold by Mouser as well (as a new product), but are not listed on the Nuetrik web site. Do you know where they are made? .......
431: Tube DIY Asylum, Thanks! (0.00)
Posted by mikeyb on 2010-04-14, 13:55:49 (192.94.94.106)
Thanks for the input. Of course I'm now more confused than before, but that's what I asked for ... .......
432: Tube DIY Asylum, The heart of the matter (0.00)
Posted by mikeyb on 2010-04-14, 13:53:37 (192.94.94.106)
Jeff - Nothing surprising. You changed the value of the second cap from 420 uF to 50 uFd, so, yes, the time constant will be reduced by a factor of 8. The real qustion is this - how likely is it that .......
433: Tube DIY Asylum, RE: "rated for 2000 insertions" (-- that's what she said! (0.00)
Posted by mikeyb on 2010-04-14, 05:45:49 (192.94.94.105)
I'm not sure 'mating cycles' is any better ... either way, my mind goes elsewhere. .......
434: Tube DIY Asylum, RE: Try these (0.00)
Posted by mikeyb on 2010-04-13, 14:07:01 (192.94.94.106)
Interesting - rated for 2000 insertions. I wonder if it's true ... Have you used these? .......
435: Tube DIY Asylum, RCA jacks (0.00)
Posted by mikeyb on 2010-04-13, 11:48:40 (192.91.75.30)
O.K, so apparantly no one is familiar with the Cardas RCA jacks (see message below). So what are you all using for chassis mounted RCA jacks (female)? My budget limit is no more than $10/pair. ::: TOP .......
436: Tube DIY Asylum, Cardas CTFA RCA Connectors (0.00)
Posted by mikeyb on 2010-04-12, 07:08:58 (192.94.94.105)
Have any of you used the Cardas CTFA RCA jacks? If so, where they undersized\a bit loose? I used RCA jacks from an unremembered source about 3 years ago that are problematic because cables connected t .......
437: Tube DIY Asylum, Sprauge 716P versus Multicap RTX capacitors (0.00)
Posted by mikeyb on 2010-04-08, 14:51:16 (192.94.94.105)
The application is a Baxandal syle tone control circuit, for which I need a .047 uFd cap. The Sprauge 716P series caps (foil and polystyrene) costs $1.18, whereas the Mutlticap RTX series caps (polyst .......
438: Tube DIY Asylum, RE: Um, what have I got here? (0.00)
Posted by mikeyb on 2010-04-08, 13:52:37 (192.94.94.106)
Can I still use it for a 1x probe even if it says 10x on the clip? Yes, but the probe bandwidth will be less. Usualy probes are rated for bandwidth as well as attenuation. Generally, the higher the at .......
439: Tube DIY Asylum, RE: Um, what have I got here? (0.00)
Posted by mikeyb on 2010-04-08, 12:55:35 (192.94.94.105)
The blue cylinder conains the attenuator, which consists of a 9 meg in parallel with a variable cap in series with the probe tip. The antenuator reduces the signal at the scope by a 10:1 ratio, assumi .......
440: Tube DIY Asylum, RE: What is a linear tube? (0.00)
Posted by mikeyb on 2010-04-06, 10:58:19 (192.91.75.30)
You are comparing apples to oranges in this case - the tube on the top is only useful for small signal applications (Ip max is about 8 mA) and the tube in the bottom plot has a maximum Ip of perhaps 6 .......
441: Tube DIY Asylum, RE: puzzled (0.00)
Posted by mikeyb on 2010-03-30, 09:03:48 (192.94.94.105)
So, did you breadboard a single channel or two? I'm concerned about the statement you made that the 10 Volt filament supply is shared between the two output tubes. This 'should' be O.K, but not really .......
442: Tube DIY Asylum, Thanks! (0.00)
Posted by mikeyb on 2010-03-29, 10:49:22 (192.91.75.30)
Thanks for all of the good advice. I just have to decide wether or not it's worth the hassel and bulk of and all DHT design. I 'need' tone controls, which adds complexity, particullarly to a all DHT d .......
443: Tube DIY Asylum, Good idea! (0.00)
Posted by mikeyb on 2010-03-26, 12:50:38 (192.94.94.105)
Hadn't thought of that. Thanks! .......
444: Tube DIY Asylum, Headphone 'output' transformer (0.00)
Posted by mikeyb on 2010-03-26, 12:24:29 (192.94.94.105)
Does anyone now of a source for an output transformer to match a small DHT (e.g., 46 or 2A3) to a 50 to 65 Ohm headset? Something like 5K Ohms to 60 Ohms at less than 1 Watt. My Senheizer headphones H .......
445: Tube DIY Asylum, RE: ceramic caps Z5U -Y5P? (0.00)
Posted by mikeyb on 2010-03-26, 08:34:19 (192.94.94.105)
Give it a try with the ceramic caps - the most that you can loose is a few bucks. .......
446: Tube DIY Asylum, RE: ceramic caps Z5U -Y5P? (0.00)
Posted by mikeyb on 2010-03-26, 07:50:39 (192.91.75.29)
Yes, Z5U and Y5P are commonly used dielectrics for ceramic capacitors, such as those shown in my original link. They are generally not used for non ceramic capacitors. 'Snubbers' are not commonly used .......
447: Tube DIY Asylum, RE: ceramic caps Z5U -Y5P? (0.00)
Posted by mikeyb on 2010-03-26, 05:57:14 (192.94.94.106)
My inclanation is to say 'none' (remove the caps). If you really fell that you need snubber caps, than disc ceramic is about your only practical choice. Why do you feel that you need snubbers? ::: TOP .......
448: Tube DIY Asylum, RE: ceramic caps Z5U -Y5P? (0.00)
Posted by mikeyb on 2010-03-25, 05:30:10 (192.91.75.29)
See data sheet at link below. The Z5U and Y5P dielectrics have very high dissipation factors and terrible tolerances. They are probably O.K. for use as snubbers, but don't use them for anything else i .......
449: Tube DIY Asylum, RE: optimum - bias voltage (0.00)
Posted by mikeyb on 2010-03-24, 08:11:18 (192.91.75.30)
One can't say what the 'optimum bias voltage' should be - it depends upon the transcoductance of the specfic tube, and can vary considerably from tube to tube (even of the same type). What's important .......
450: Tube DIY Asylum, RE: Is this how many of us got our start in DIY? (0.00)
Posted by mikeyb on 2010-03-22, 10:07:25 (192.94.94.105)
And some go to the other extreme (LES) for the same reason. Your point? .......
451: Tube DIY Asylum, RE: FE for 300b PP A1 (0.00)
Posted by mikeyb on 2010-03-19, 10:27:07 (192.94.94.105)
My speakers are old JBL L60Ts that are relatively inefficent by today's standards (89 dB?). Need power ... .......
452: Tube DIY Asylum, RE: FE for 300b PP A1 (0.00)
Posted by mikeyb on 2010-03-19, 07:53:32 (192.94.94.105)
The 6BL7 is not a particularly linear tube, and the mu is low (15). I suspect that unless your preamp has a very high output level, you won't have enough gain with a 6SN7\6BL7 combo. The differential .......
453: Tube DIY Asylum, RE: How many would live with hum from your amp if the sound is really good? (0.00)
Posted by mikeyb on 2010-03-18, 18:35:08 (96.42.76.86)
You may have a bigger problem ... When you went from CLC to LC, the output voltage of the power supply dropped considerably - perhaps by as much as 40%. Did you compenste for this? Your amp may now be .......
454: Tube DIY Asylum, RE: 300B SE power amp circuit please give me some comment (0.00)
Posted by mikeyb on 2010-03-16, 16:36:49 (96.42.76.86)
Why ruin a 300B by driving it with a 12AX7 and 12AU7? A 6SL7/6SN7 combo would be much better. Or a 6N1P in place of the 12AX7, with a reasonable current running through it (10 mA). .......
455: Tube DIY Asylum, RE: IDHT driver vs. DHT driver.. (0.00)
Posted by mikeyb on 2010-03-15, 20:31:42 (96.42.76.86)
Absolutely! Why ruin a perfectly good DHT output tube(s) with a IDHT driver that is less linear than a DHT driver? The problem is gain, of course - IDHT (in general) have higher gains than DHTs. ::: T .......
456: Tube DIY Asylum, RE: question of power supply capacitor value (0.00)
Posted by mikeyb on 2010-03-10, 05:47:45 (192.94.94.106)
Dennis - This note is to let you know I am not ignoring you, but simply don't have the time to run the simulations to prtoperly respond. There are, in my opinion, some falacies in your reasoning, but .......
457: Tube DIY Asylum, The implication being ... (0.00)
Posted by mikeyb on 2010-03-09, 16:31:34 (96.42.76.86)
The implication being that new is better? Not necessarily. True, every design was new once upon a time, but not all 'new' designs are better. I know that from experience (and logic). .......
458: Tube DIY Asylum, dead horse (0.00)
Posted by mikeyb on 2010-03-05, 10:30:31 (192.94.94.105)
My irritation comes from the use of the term 'slower'. In what sense? What exactly is a 'slow sound'? What is a 'fast' sound? Can you expalin and\or enlighten me? It's like saying big caps are goofie .......
459: Tube DIY Asylum, RE: question of power supply capacitor value (0.00)
Posted by mikeyb on 2010-03-05, 05:44:12 (192.91.75.29)
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 locat .......
460: Tube DIY Asylum, a little humor in life is a good thing! (0.00)
Posted by mikeyb on 2010-03-04, 06:38:38 (192.94.94.105)
I think the comment was with reference to sounding 'fast'. How does one define that? That's my problem. I know what lound and soft and perhaps bright mean (with reference to sound), but 'fast' is a me .......
461: Tube DIY Asylum, RE: question of power supply capacitor value (0.00)
Posted by mikeyb on 2010-03-03, 10:16:22 (192.94.94.105)
It's not a stupid question, but there is no black and white 'always true' answer. It depends upon which side of the LES (Low Energy Storage) debate you buy into. Personally, I like a reasonably large .......
462: Tube DIY Asylum, RE: MPS AO6 (0.00)
Posted by mikeyb on 2010-02-24, 10:29:42 (192.94.94.106)
The MPSA06 is a rather cheap low power NPN transistor. CBE stands for Collector, Base, Emitter. This must be a really old design. Most new designs use integrated circuits, not discrete transistors, f .......
463: Tube DIY Asylum, RE: Would a choke made especially for choke input PS provide less hum than a "regular" choke used for choke input PS? (0.00)
Posted by mikeyb on 2010-02-23, 07:01:39 (192.94.94.106)
Assuming that chokes have the same value, no, a 'special' choke' will not result in lower hum than a standard choke. From what I can see in the Piltron spec sheet, the difference between the choke int .......
464: Tube DIY Asylum, Lansing Enclosures (0.00)
Posted by mikeyb on 2010-02-19, 05:48:40 (192.91.75.29)
Has anybody tried one of the Lansing 'GrayBox' enclosures? If so, what was your impression? The alternative is a Hammond, which isn't available in the size I want (3 unit high, half rack width, 10" de .......
465: Tube DIY Asylum, RE: Cathode stripping on DHTs (0.00)
Posted by mikeyb on 2010-02-18, 05:45:14 (192.94.94.106)
"The damper diode IS a compromise which I won't do, (due to its cathode) in music playback,... that is what is wrong !" This is where I don't see your logic. Generally speaking, a damper diode has lo .......
466: Tube DIY Asylum, RE: Cathode stripping on DHTs (0.00)
Posted by mikeyb on 2010-02-17, 07:41:50 (192.94.94.105)
The bigger problem is in fixed bias designs, where it is important that the negative bias be applied before B+ is applied. What is so complicated about using a IDHR (indirectly heated rectifier) inst .......
467: Tube DIY Asylum, Broskie (0.00)
Posted by mikeyb on 2010-02-16, 10:15:54 (192.94.94.105)
While I really respect Broskie's technical expertise, his political opinions are obnoxious. If I wanted to listen to uninformed, conservative, 'tea party' like comments, I'd turn on AM radio and liste .......
468: Tube DIY Asylum, RE: Has anyone tried isolation transformers for AC heaters? (0.00)
Posted by mikeyb on 2010-02-16, 06:08:35 (192.91.75.29)
"How does 25A. of current sound, going through the small contact area of the wiper - with its tentative contact to the winding of the pot??" No, there will not be 25 amps of current going through the .......
469: Tube DIY Asylum, RE: euros (0.00)
Posted by mikeyb on 2010-02-15, 14:28:17 (192.91.75.29)
Darn! Those sweeds are too smart. .......
470: Tube DIY Asylum, RE: Need help removing solder (0.00)
Posted by mikeyb on 2010-02-15, 14:26:39 (192.91.75.29)
I'm really surprised that a 'wick' doesn't work. By 'wick' I assume you mean that flat copper braid that sort of looks like Litz wire ('One Step Braid No Clean', made by Easy Braid, Minneapolis, MN). .......
471: Tube DIY Asylum, RE: mikeyb - Cathode Followers (0.00)
Posted by mikeyb on 2010-02-15, 06:19:39 (192.91.75.29)
Thanks for the advice. I'm busy with the 46 preamp project at the moment, but need to build another PP 300B amp sometime. Right now, I have one of the 300B PP amps shown in the schematics built, and a .......
472: Tube DIY Asylum, RE: Using a 49 (0.00)
Posted by mikeyb on 2010-02-12, 10:43:17 (192.94.94.105)
I really can't say. I'm no drlowmu. Maybe my ear is mushy, but aside from hum and microphonics, I really can't differentiate between the sound of the DHTs I tested. Plus I was testing with a Dynaco ST .......
473: Tube DIY Asylum, In process (0.00)
Posted by mikeyb on 2010-02-12, 05:54:24 (192.91.75.30)
That's been my project for the last year+. I am including a Baxandal style tone controlin the preamp design, and so needed two 46's per channel. Testing revealed that it is not possible (with the five .......
474: Tube DIY Asylum, RE: Cathode Followers (0.00)
Posted by mikeyb on 2010-02-10, 06:14:14 (192.94.94.105)
Here are links to the schematics: Main schematic: http://webpages.charter.net/smburns/amp300bp1.pdf Bias\negative voltage supply: http://webpages.charter.net/smburns/amp300bp2.pdf HV supply: http://we .......
475: Tube DIY Asylum, That's it! (0.00)
Posted by mikeyb on 2010-02-09, 06:24:15 (192.91.75.29)
Basically, this is the amp that I am using, with the exceptions noted below. I sounds great! 1) 6N1P instead of 6SL7. The 3 dB bandwidth (into the 300B grids) using the 6N1P was about 3 times that usi .......
476: Tube DIY Asylum, Recomendations (0.00)
Posted by mikeyb on 2010-02-08, 12:51:26 (192.94.94.106)
I'm using a 6N1P (differential voltage amp) DC coupled into a 6SN7 (differential voltage amp) AC coupled into two 6S4A cathode followers that are DC coupled into the 300B grids. Personally, I can't se .......
477: Tube DIY Asylum, RE: GM70 project (0.00)
Posted by mikeyb on 2010-02-03, 11:30:37 (192.91.75.29)
I would be very concerned about using a 470K resistor from grid to ground on a GM70. Seems way to high! .......
478: Tube DIY Asylum, $1225!!! (0.00)
Posted by mikeyb on 2010-01-25, 12:10:04 (192.91.75.30)
Egads - why? There are only two connections to the pickup, so it must be mono. .......
479: Tube DIY Asylum, RE: Yes and No (0.00)
Posted by mikeyb on 2010-01-14, 07:33:38 (192.94.94.105)
Thanks - I feel better now! If I can find a spare CDE cap, I'll measure the SRF. .......
480: Tube DIY Asylum, RE: Yes and No (0.00)
Posted by mikeyb on 2010-01-14, 07:03:17 (192.94.94.105)
I'm using using 50 uFd oil filled motor runs from CDE (metalized polypropylene). .......
481: Tube DIY Asylum, Yes and No (0.00)
Posted by mikeyb on 2010-01-14, 06:29:39 (192.94.94.105)
No, the mains frequency is 60 Hz, so the primary frequency seen by the power supply caps is the 120 Hz ripple frequency. But I am concerned about the output impedance of the power supply, as a functio .......
482: Tube DIY Asylum, RE: Interesting article on capacitor loss (0.00)
Posted by mikeyb on 2010-01-13, 12:42:00 (192.91.75.30)
The statement that motor run caps can have a self resonate frequency in the low kHz region is rather scarry. I should check that out, given that my preamp power supply uses several 50 uF motor runs. : .......
483: Tube DIY Asylum, RE: The filament supply (0.00)
Posted by mikeyb on 2010-01-06, 10:58:21 (192.91.75.29)
O.K. - that makes sense. I was just hoping that you weren't thinking that the common mode choke is equivalent to a conventional single coil choke. It (the common mode choke) will do nothing for 120 Hz .......
484: Tube DIY Asylum, RE: The filament supply (0.00)
Posted by mikeyb on 2010-01-06, 06:29:44 (192.91.75.29)
What's the purpose of the 7 mH common mode choke? .......
485: Tube DIY Asylum, Hammond RMC\RMU Series enclosures (0.00)
Posted by mikeyb on 2009-12-31, 13:38:30 (192.91.75.30)
Has anyone used the Hammond RMC or RMU series of enclosures? If so, what was your impression? See link below. .......
486: Tube DIY Asylum, RE: When stacking power supplies.... (0.00)
Posted by mikeyb on 2009-12-29, 10:28:01 (192.94.94.106)
"The diodes need to all be the same"- Ronald Reagan The Ronald Regan? As in president Ronald Regan (choke choke gasp gasp). Is he an expert on tube amplifiers? When did he say that? Just curious. ::: .......
487: Tube DIY Asylum, One more comment ... (0.00)
Posted by mikeyb on 2009-12-29, 07:36:47 (192.91.75.29)
'RadioDaze' has the lowest prices on Hammond chokes that I have found. I used the 155B (6 mH, 0.3 Ohms) on my 46 preamp project. 6 mH doesn't sound like much, but it meets the critical inductance requ .......
488: Tube DIY Asylum, Will not work! (0.00)
Posted by mikeyb on 2009-12-29, 07:30:32 (192.91.75.29)
From the Murata web site, with reference to common mode chokes: "Since magnetic flux cancels out inside the ferrite core, impedance is not produced for differential mode current." In other words, a co .......
489: Tube DIY Asylum, Oh for Gods' sake! (0.00)
Posted by mikeyb on 2009-12-23, 10:34:16 (192.91.75.30)
I've been quiet up to this point, but this one is over-the-top. I'm sure the electrons care what color the insulation is. Are you really that gullible? .......
490: Tube DIY Asylum, au contraire (0.00)
Posted by mikeyb on 2009-12-23, 08:36:15 (192.94.94.105)
I think just the opposite! He is an artist - he has made the physical implementation artistically elegant, and (arguably) the electrical design less so. His emphasis has been mechanical, not electrica .......
491: Tube DIY Asylum, RE: Aluminum versus Steel (0.00)
Posted by mikeyb on 2009-12-22, 12:30:56 (192.91.75.30)
Steel is ferrous (magnetic); aluminum is not. Maybe that is the responsible for the difference that you hear. .......
492: Tube DIY Asylum, RE: Favorite program to draw diagrams with??? (0.00)
Posted by mikeyb on 2009-12-17, 08:10:16 (192.94.94.105)
I use Visio 5.0, which was a wonderful product until Microsoft bought out the company and througly screwed it up. You might try to obtain a old, pre-microsfoft version of Visio. Maybe on Ebay? ::: TOP .......
493: Tube DIY Asylum, RE: I think you're largely correct (0.00)
Posted by mikeyb on 2009-12-17, 08:07:35 (192.94.94.105)
Careful - I don't have a PHD, but I do have an ME! Transistors, particularly bipolar transistors (they aren't used much anymore, by the way) are inherently non-linear. Without the application of negat .......
494: Tube DIY Asylum, Engineers (0.00)
Posted by mikeyb on 2009-12-17, 06:05:23 (192.91.75.30)
You have to keep in mind that engineers are progmatists; "if it works then it is good" Says who? I resent that! I would tend to believe that it's management, not engineers, who have that attitude. It .......
495: Tube DIY Asylum, RE: Distortion and Oscilloscopes (0.00)
Posted by mikeyb on 2009-12-16, 08:32:57 (192.94.94.105)
It is very difficult to 'see' distortion on an oscilloscope. Even 5% distortion is hard to see. A much better technique to measure distortion is with a spectrum analyzer or 'distortion analyzer' and a .......
496: Tube DIY Asylum, RE: Low Inductance Caps (0.00)
Posted by mikeyb on 2009-12-09, 18:04:15 (97.86.232.93)
If a 22 uFd cap has adequately low impedance at 20 Hz, why wouldn't a 1 uFd cap have adequately low impedance at 20 kHz? .......
497: Tube DIY Asylum, RE: 845 or 300B (0.00)
Posted by mikeyb on 2009-12-09, 17:59:20 (97.86.232.93)
Well, I can't say that I have tried the likes of a EML300B or WE300B, nor will I ever. Maybe ignorance is bliss ... I'm happy with the gold grid EH300Bs that I have, and that's good enough for me. I'm .......
498: Tube DIY Asylum, RE: 845 or 300B (0.00)
Posted by mikeyb on 2009-12-09, 10:30:45 (192.94.94.105)
What leads you to believe that "so many various 300B's ... have so-so performance"? I've used EH gold grid 300Bs and JJ300Bs - both sound great to me. Using a 845 will force you into using a higher i .......
499: Tube DIY Asylum, Which transformer? (0.00)
Posted by mikeyb on 2009-12-08, 06:38:55 (192.91.75.30)
The power transformer or an output transformer? A power transformer should not be too difficult to replace - you can even have a custom unit made for you, from what I read. More importantly, find out .......
500: Tube DIY Asylum, RE: Low Inductance Caps (0.00)
Posted by mikeyb on 2009-12-07, 12:04:48 (192.94.94.106)
I have no idea - the data sheet of kind that I use (CDE SF series) does not state ESL. If it's say 100 nH (about 10 times that of the super caps under discussion), a 40 uFd cap would have a self reson .......
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