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1: General Asylum, Who's in Southern Oregon? (0.00)
Posted by groverg on 2008-11-13, 22:19:45 (68.186.127.129)
Recently moved to Medford, OR from DC area. Miss my audio and DIY buddies! I'd love to know who's in the area. Drop me a line if you like. .......
2: Vinyl Asylum, London Blueback Guide? (0.00)
Posted by groverg on 2007-03-06, 22:35:31 (71.210.12.230)
Does anyone know how to obtain a copy of the Audiophiles Guide to London Bluebacks? It appears to exist but I can't find any information on who published it or where to purchase it. Any info would be .......
3: Bottlehead Forum, Re: Need help from the builder savants... (0.00)
Posted by groverg on 2006-09-01, 13:06:43 (151.200.151.152)
Just to satisfy the curiosity of the helpful contributors, I took a look at Elliot's amp today. I've never looked at a Jolida and was sort of amused to to see it uses the same circuit as an Eico HF87- .......
4: Tube DIY Asylum, Re: 1N4007 HV for 211 B+ supplies (0.00)
Posted by groverg on 2005-02-05, 18:20:02 (68.239.127.36)
Certainly you can build a bridge with 1n4007s. I would strongly recommend using UF4007s, and using at *least* 3 in series for each leg of the bridge. Same for 1n4007. You want these guys to stay well .......
5: Tube DIY Asylum, Re: Are you meeting critical inductance? (0.00)
Posted by groverg on 2005-01-26, 17:22:07 (68.239.65.17)
I'd use at least 10H for the input choke. 10mA of bleeder should be safe enough. A swinging choke would be fine. Check out www.surplussales.com. With the current input choke you're probably whapping t .......
6: Tube DIY Asylum, Re: Questions for groverg.... (0.00)
Posted by groverg on 2005-01-19, 11:11:44 (68.239.73.134)
I use RatShack 18G solid hookup wire sheathed in 14G silicone-impregnated sleeving from www.weicowire.com. For terminals, I used a combination of heavy-duty tag boards from surplus HV power supplies a .......
7: SET Asylum, Re: Response Audio Ultimate Dared SVP 845 (0.00)
Posted by groverg on 2005-01-16, 18:01:01 (68.239.73.134)
Sounds like a pretty extensive mod, and the V-Caps alone are going to run $200-300. I friend of mine just had me put V-Caps in his 845SE amp and I have to say they're really, really good. .......
8: Tube DIY Asylum, Not much help but... (0.00)
Posted by groverg on 2005-01-14, 18:01:23 (68.239.73.134)
Antique used to carry them, don't see them now. They were mighty cheesy, though, don't know if they'd hold up. Haven't seen anything else like them. .......
9: Tube DIY Asylum, Re: Ideal B+ delay time for DHT's - 300B/2A3. (0.00)
Posted by groverg on 2005-01-10, 13:09:46 (68.239.73.134)
It's the input and driver tubes you want to worry about more than the DHTs. Some 6SN7s, depending on the suffix (wgb, etc.) can take 10-15 seconds to come up (they were designed that way). So I'd say .......
10: Tube DIY Asylum, Re: I'll third Grover here. (0.00)
Posted by groverg on 2005-01-09, 20:15:18 (68.239.73.134)
Hey, glad it worked for you. It really was fun, I'll be going back to it soon. .......
11: Tube DIY Asylum, Re: I'll third Grover here. (0.00)
Posted by groverg on 2005-01-09, 20:14:22 (68.239.73.134)
No, actually I kept cathode bias cause I didn't like the clipping characteristics of fixed bias on this particular case. I did use 6B4Gs, then played around with 300Bs and even 6336s. But if you just .......
12: Tube DIY Asylum, Re: To breadboard or not - that is the question. (0.00)
Posted by groverg on 2005-01-08, 20:40:27 (68.239.73.134)
I've got good news and bad news :-). The good news is that if you breadboard an amp you're tempted to keep trying new things and it's a lot easier to and more fun to do that on a breadboard, and you g .......
13: Tube DIY Asylum, Re: still there but getting better I think (0.00)
Posted by groverg on 2005-01-08, 01:42:26 (68.239.73.134)
Making sure all filament supplies are properly grounded will help. It could be noise injected from a poorly-made power tranny--I'm not that versed in that area. You certainly seem to have done everyth .......
14: Tube DIY Asylum, Re: shorted inputs....no change, still got buzz from both channels (nt) (0.00)
Posted by groverg on 2005-01-06, 23:57:57 (68.239.73.134)
Now I'm recalling hearing a "buzzy" early Jolida in a shop once. Hmmmm. Could it be a bad power tranny is injecting noise? I'm not familiar with how that could happen, but I suppose it's possible. If .......
15: Tube DIY Asylum, Re: shorted inputs....no change, still got buzz from both channels (nt) (0.00)
Posted by groverg on 2005-01-06, 23:51:42 (68.239.73.134)
So it's definitely in the amp somewhere and not coming from a source or bad interconnect. I think you're correct in that if a filtering cap had failed or if the filtering were insufficient you would h .......
16: Tube DIY Asylum, Re: Interesting observation... (0.00)
Posted by groverg on 2005-01-06, 23:22:22 (68.239.73.134)
I suggested it as a precaution. Vinnie was experiencing a problem with the amp, but we later tracked it down to a faulty EL34. Vinnie, you have my permission to remove the grid-stopper :-). ::: TOPIC: .......
17: Tube DIY Asylum, Re: the dreaded "buzzzz" problem (0.00)
Posted by groverg on 2005-01-05, 14:01:53 (68.239.73.134)
Okay. Well, it sounds like everything is in order. Is the output transformer taking B+ from the first set of caps? If so it's possible that ripple is still too high for quiet operation. Is this your o .......
18: Tube DIY Asylum, $29 elsewhere if you do a search (nt) (0.00)
Posted by groverg on 2005-01-05, 13:23:40 (68.239.73.134)
. .......
19: Tube DIY Asylum, Re: Good Push Pull 2A3 or 300B Designs? (0.00)
Posted by groverg on 2005-01-05, 13:16:13 (68.239.73.134)
This is a wonderful-sounding design, and very easy to build: http://www2u.biglobe.ne.jp/~tossie/F2A3PP-E.html I like it with the negative feedback implemented, which you can do on any 5K PP tranny by .......
20: Tube DIY Asylum, Re: the dreaded "buzzzz" problem (0.00)
Posted by groverg on 2005-01-05, 13:05:02 (68.239.73.134)
Is the buzz there when you short the inputs of the amp, with no source attached? Could you explain the power supply again? You mention full-wave and voltage-doubler--which is it? Full-wave would use f .......
21: Tube DIY Asylum, Re: best coupling caps vs. $$ for vitage theatre amps. (0.00)
Posted by groverg on 2005-01-04, 21:17:13 (68.239.73.134)
I've tried some Auricaps and found them warm but clean and extended. Very good for the price, IMHO. .......
22: Tube DIY Asylum, Re: cathode bias balance control (0.00)
Posted by groverg on 2005-01-03, 13:38:48 (68.239.73.134)
Oh, yeah, the CT choke would be a problem for fixed bias. Well, forget that :-). But to answer the question--no, the two hum pots would balance the filaments on each tube, but the third pot would only .......
23: Tube DIY Asylum, Re: cathode bias balance control (0.00)
Posted by groverg on 2005-01-03, 11:18:17 (68.239.73.134)
I take it you haven't built the amp yet. You may find that you don't have a problem, given that the filament transformer's winding may effectively cancel most of the noise. But it's a tricky issue and .......
24: Tube DIY Asylum, Re: changed to UF4007, need others opinions? (0.00)
Posted by groverg on 2004-12-30, 18:36:06 (141.156.13.223)
Oh, yes. .......
25: Tube DIY Asylum, Re: changed to UF4007, need others opinions? (0.00)
Posted by groverg on 2004-12-29, 20:15:05 (141.156.13.223)
Depends on your voltage. At 120VAC, one is sufficient in my experience. .......
26: Tube DIY Asylum, Re: Thanks Russ... (0.00)
Posted by groverg on 2004-12-29, 17:39:29 (141.156.13.223)
Both Mouser and Digikey carry line isolation trannies. Look for chassis-mount, dual-bobbin types, Hammond, Triad or Magnetek. Use the 240V primaries and 115 secondaries as Russ suggests and you'll get .......
27: Tube DIY Asylum, Re: Yes, but no luck : ( (0.00)
Posted by groverg on 2004-12-29, 15:32:43 (141.156.13.223)
Vinnie, hook up the secondaries of the "noisy" tranny to some terminal strips, fire it up, measure the AC voltages from each side to the center tap, and see if they are producing equal voltages. ::: T .......
28: Tube DIY Asylum, Re: changed to UF4007, need others opinions? (0.00)
Posted by groverg on 2004-12-28, 17:45:27 (141.156.13.223)
UF4007 is vastly better-sounding than 1N4007. Just as you describe--greater clarity and detail. I prefer them to Hexfreds. Let them break in for a week and they'll smooth out and pretty much disappear .......
29: Tube DIY Asylum, Re: 845 update and more questions.... (0.00)
Posted by groverg on 2004-12-28, 17:39:05 (141.156.13.223)
Regarding the hum you got from the other power tranny--it sounds to me like one secondary wasn't working properly, giving you a half-wave supply which would be noisier than a full-wave. It might be da .......
30: Tube DIY Asylum, Re: Can 2A3 be used as Cathode Follower ? (0.00)
Posted by groverg on 2004-12-28, 09:32:32 (141.156.13.223)
I may be wrong, but I would think that filament noise would be injected into the 845's grid. .......
31: Tube DIY Asylum, Re: Looks like we DON"T have a preamp problem... (0.00)
Posted by groverg on 2004-12-27, 11:10:55 (141.156.13.223)
Vinnie, why don't you call me at 301-699-8227 and I'll call you back on my dime--don't worry it doesn't cost me anything. .......
32: Tube DIY Asylum, Re: Looks like we got a preamp problem... (0.00)
Posted by groverg on 2004-12-27, 09:23:56 (141.156.13.223)
The power tranny and the output cap would appear to be fine. The power tranny may be buzzing because you're powering it off the variac. We'll look into that more later. Here's what I would do next: Re .......
33: Tube DIY Asylum, Re: Looks like we got a preamp problem... (0.00)
Posted by groverg on 2004-12-26, 20:06:47 (141.156.13.223)
It wouldn't hurt to tie one to the relay terminals. Let me know when you get back to it. .......
34: Tube DIY Asylum, Re: Looks like we got a preamp problem... (0.00)
Posted by groverg on 2004-12-26, 17:25:21 (141.156.13.223)
Hang in there, we're making progress. We can probably solve it tonight. .......
35: Tube DIY Asylum, Re: And... (0.00)
Posted by groverg on 2004-12-26, 17:24:14 (141.156.13.223)
Yes, now that you have the filaments grounded! Before you had -130 on the grid, plus probably +70 volts on the cathode, effectively given you a grid bias voltage of -200 or more (in relation to the ca .......
36: Tube DIY Asylum, Re: Looks like we got a preamp problem... (0.00)
Posted by groverg on 2004-12-26, 17:21:28 (141.156.13.223)
If the oscillation is subtle, it can take a while for it to ramp itself up and set the amp to singing. Have you tried a grid-stopper on the input pins of the 6N7? If not, solder a 1K carbon resistor r .......
37: Tube DIY Asylum, And... (0.00)
Posted by groverg on 2004-12-26, 14:46:20 (141.156.13.223)
Measure the negative bias voltage from the grid pin to GROUND. .......
38: Tube DIY Asylum, Re: Back to the Drawing Board.... (0.00)
Posted by groverg on 2004-12-26, 14:44:30 (141.156.13.223)
Aaaaaahhhh... You're using a 1000 ohm/25W resistor between the filament CT and ground, along with -130 volts on the grid? If so, in effect you're "double-biasing" the 845. You're running the tube way .......
39: Tube DIY Asylum, Re: Back to the Drawing Board.... (0.00)
Posted by groverg on 2004-12-26, 11:38:17 (141.156.13.223)
Well, okay, here we go :-). First, reapply the bypass cap to the 6N7 cathode since this seemed to stabilize it more. Next, remove the preamp from the circuit, short the input of the amp with a shortin .......
40: Tube DIY Asylum, Re: Very high Gm microwave triode (0.00)
Posted by groverg on 2004-12-26, 04:32:11 (141.156.13.223)
Richard Sears made a spectacular-sounding phono stage with these. He had a lot of trouble matching them, though, and microphony was a problem. If you're curious you can visit his home page at http://w .......
41: Tube DIY Asylum, Re: What is happening??? (0.00)
Posted by groverg on 2004-12-25, 18:52:12 (141.156.13.223)
I'm also wondering about that bias supply running from a Variac. Something's not right about that, but I can't put my finger on it. That may be the point where some kind of instability is being introd .......
42: Tube DIY Asylum, Re: What is happening??? (0.00)
Posted by groverg on 2004-12-25, 18:47:13 (141.156.13.223)
Oh well! :-( There must be some kind of phase shift going on between the circuit and your version of the PS. See my post above. .......
43: Tube DIY Asylum, Re: need to see a schematic (0.00)
Posted by groverg on 2004-12-25, 18:43:56 (141.156.13.223)
Below are the schematics for the circuit and PS. Tell us how your version differs from the schematic, and we'll see if we can spot anything. I've built this about 20 times and never had the problem yo .......
44: SET Asylum, Re: Do You Know Which 845 Is The Best Tube? (0.00)
Posted by groverg on 2004-12-25, 18:28:32 (141.156.13.223)
I've heard the 845B in several amps and they are way better than the stock Chinese 845s, for not much more money. Cleaner, airier, closer to the open sound of the NOS 845s, though not quite of that ca .......
45: Tube DIY Asylum, Re: What is happening??? (0.00)
Posted by groverg on 2004-12-25, 09:05:49 (141.156.13.223)
Yeah, you've got a lot of gain there for the K-horns. No, unparalleling the 6N7 won't change the gain. Remove the cathode bypass cap on the 6N7 for now and see if that settles it down. You may notice .......
46: Tube DIY Asylum, Re: Correcting Posts??? (0.00)
Posted by groverg on 2004-12-25, 07:30:53 (141.156.13.223)
Look at the bottom of the page containing your post. There's a "Delete" link. .......
47: Tube DIY Asylum, Re: What is happening??? (0.00)
Posted by groverg on 2004-12-25, 07:29:42 (141.156.13.223)
No, you're right, I've heard "bypass" used for the decoupling caps too. What you're using is fine. It's unlikely to be a power supply or OPT problem--the 125ese shouldn't have any problem here. I thin .......
48: Tube DIY Asylum, Re: What is happening??? (0.00)
Posted by groverg on 2004-12-25, 05:28:39 (141.156.13.223)
Okay. First, we miscommunicated about the caps. I was referring to the PS caps. Since you have a PS in place I'm sure it's fine, whatever you used will work--PIO is okay, whatever you like to get the .......
49: Tube DIY Asylum, Re: Glassware Tube Design Software (0.00)
Posted by groverg on 2004-12-22, 20:36:37 (141.156.13.223)
I agree with kyle that these programs have their limitations, but what they do, they do well and are easy to use. I like them because they help me learn about the relationships between various circuit .......
50: SET Asylum, Re: First timer... (0.00)
Posted by groverg on 2004-12-18, 09:01:35 (141.156.13.223)
Other components perhaps, but tubes shouldn't change very much after a few hours in circuit. .......
51: Tube DIY Asylum, Re: How do you guys size voltage drop resistors for watts dissipated? (0.00)
Posted by groverg on 2004-12-13, 08:27:30 (151.200.119.112)
Normally your safety factor should be fine and the resistors may get warm but not smoke. Two possibilities: one. the resistors have some kind or oil or varnish coating which is burning off due to the .......
52: Tube DIY Asylum, Re: 7.5V Filament Transformer for 801 (0.00)
Posted by groverg on 2004-11-29, 12:56:40 (151.200.119.112)
1. You can run the 801s at 6.3 volts, probably without significantly shortening their life, per Steve Bench's website; 2. Fair Radio (www.fairradio.com) has some nice multi-secondary trannies with 7.5 .......
53: Tube DIY Asylum, Re: Oh, and... (0.00)
Posted by groverg on 2004-11-27, 15:33:16 (151.200.119.112)
I'm sure the problem is AC on the 845 filaments. I don't think you'll ever get it quiet enough. Try a CRC DC supply with Schottky rectifiers, and a 4A common-mode choke from Mouser or Digikey between .......
54: Tube DIY Asylum, Re: 300b vs 845 "wrong" (0.00)
Posted by groverg on 2004-11-27, 14:10:21 (151.200.119.112)
All right, John, I'll back off here :-). I'm curious though--what OPT did you use and what sort of power and filament supplies? .......
55: Tube DIY Asylum, Re:which tube?.. tried a 46 Lynn???? (0.00)
Posted by groverg on 2004-11-26, 11:34:45 (151.200.151.212)
Hmmm, just as a heads up, I wouldn't agree with that. I've played around alot with the 46 and to my ears it has a "warmer" sound indicating a little more harmonic emphasis than the 45, and a more forw .......
56: Tube DIY Asylum, Re: What do you mean terminating??? (0.00)
Posted by groverg on 2004-11-26, 11:31:14 (151.200.151.212)
My filament supply is a simple one using Schottky rectifiers and decent filter caps, CRC, with a common-mode choke from Mouser between the supply and the filaments. For whatever reasons, it eliminates .......
57: Tube DIY Asylum, Re: 300b vs 845 (0.00)
Posted by groverg on 2004-11-25, 17:51:30 (151.200.151.212)
Charlie, you've brought up a very good point. I've been building on wood so long now I've forgotten what an effect is has on the sound, particularly with the 845. Those 845 amps of Dave P.'s probably .......
58: Tube DIY Asylum, Oh, and... (0.00)
Posted by groverg on 2004-11-25, 16:56:41 (151.200.151.212)
As for hum, it's hard to say--my first guess would be the filament supplies. What are you using in this respect? .......
59: Tube DIY Asylum, Re: 300b vs 845 (0.00)
Posted by groverg on 2004-11-25, 16:55:11 (151.200.151.212)
I use the Magnequest FS-100, 10K. I've tried ElectraPrint 10K OPTs, which were okay buy not as liquid as the MQs, and Tamura F-2013s, which better the Magnequests in openness and neutrality of tone. : .......
60: Tube DIY Asylum, Re: 300b vs 845 (0.00)
Posted by groverg on 2004-11-25, 10:09:50 (151.200.151.212)
Sorry, John, but I have to say that this is about the most inaccurate description of the 845 sound I've come across. You tried it yourself and these are the results you got?? In my experience it's exa .......
61: Tube DIY Asylum, Re: 300b vs 845 (0.00)
Posted by groverg on 2004-11-25, 09:53:19 (151.200.151.212)
Vinnie, try terminating a 10V DC filament supply with a common mode choke and you may change your tune. .......
62: SET Asylum, Re: Can a SET amp with KT 88 be built? (0.00)
Posted by groverg on 2004-11-24, 17:45:59 (151.200.151.212)
Can quite figure out what GEO is trying to say, unless he means that you can't build a S(ingle) E(nded) T(riode) amp with a pentode, but of course you can if you triode-strap it. You can also build a .......
63: Tube DIY Asylum, Re: single chasis vs mono blocks? (0.00)
Posted by groverg on 2004-11-20, 21:05:09 (151.200.151.212)
I dunno, Vinnie--the monoblock approach would seem to make a lot of sense. Better channel separation, less drag on the PS, etc. OTOH, I've built some pretty sweet-sounding stereo amps with a single PS .......
64: Tube DIY Asylum, Re: 845 at "medium" power (0.00)
Posted by groverg on 2004-11-19, 18:03:34 (151.200.151.212)
Does that CT choke give you a step-up? .......
65: Tube DIY Asylum, Re: 845 at "medium" power (0.00)
Posted by groverg on 2004-11-19, 17:58:28 (151.200.151.212)
You could do a parafeed 845 with 70mA plate chokes and your 5.5K OPTs. As I posted above, you'll probably only get 7-8 watts, and it may not sound optimal, but I'm willing to bet it'll pump out more m .......
66: Tube DIY Asylum, Re: 845 at "medium" power (0.00)
Posted by groverg on 2004-11-19, 17:48:16 (151.200.151.212)
Sorry, I took down the schematic some time ago. If you want to email me through the asylum, I'll be happy to email a copy back. I think the first prototype I built ran at about 700VDC, with a Magneque .......
67: Tube DIY Asylum, Re: sounds like a good idea,,,,,nt (0.00)
Posted by groverg on 2004-11-10, 15:33:17 (151.200.151.212)
Sorry, Tre, that should have been addressed to you. .......
68: Tube DIY Asylum, Re: My DIY PP 6B4G short on power......... (0.00)
Posted by groverg on 2004-11-10, 15:28:47 (151.200.151.212)
Jimmy, as a very brilliant amp designer once told me, "Forget the curves." The 6528 may indeed produce a certain distortion signature, but I have heard it single-ended and in PP and if it's set up pro .......
69: Tube DIY Asylum, Re: My DIY PP 6B4G short on power......... (0.00)
Posted by groverg on 2004-11-09, 19:55:21 (151.200.151.212)
I had the same problem. Here's an off-the-wall idea. Get ahold of some 6528 regulator dual-triodes, drop on in each channel, and use a 330 ohm (or slightly higher) 20W cathode resistor for each channe .......
70: Tube DIY Asylum, Re: Swinging v non swinging chokes, SUBJECTIVE (0.00)
Posted by groverg on 2004-10-29, 20:57:08 (151.200.151.212)
Hey Dave that's a helpful thought--originally I was using 5R4s but with the 83s it would seem that I could lose or reduce the resistors. I'll try it. .......
71: Tube DIY Asylum, Re: Swinging v non swinging chokes, SUBJECTIVE (0.00)
Posted by groverg on 2004-10-29, 17:03:52 (151.200.151.212)
I parallel each 83 with 50 ohm resistors feeding each plate. I used 83s because I could with choke input :-) though I still find it beneficial to preheat the filaments. The stereo PP circuits draws ab .......
72: Tube DIY Asylum, Re: Swinging v non swinging chokes, SUBJECTIVE (0.00)
Posted by groverg on 2004-10-27, 12:59:12 (151.200.151.212)
I've had exactly the opposite impression, Jeff. I've never cared for LC supplies much untill I tried a swinging choke. For some reason it sounded much better to me and I've stuck with it for my PP amp .......
73: Tube DIY Asylum, Re: Hammond versus One Electron Power transformer (0.00)
Posted by groverg on 2004-10-26, 13:59:03 (151.200.151.212)
The One Electron BFT is a terrific tranny, built like a rock--and the price is now lower at tubesandmore.com. I especially like the resistive filament windings that ensure accurate filament voltage wh .......
74: Tube DIY Asylum, Re: d'oh, but... (0.00)
Posted by groverg on 2004-10-21, 15:06:11 (151.200.61.182)
I don't know much about the CCS application, but you can certainly have a combination of positive cathode voltage and negative grid voltage. Depending on the voltage the cathode sees, you adjust the g .......
75: Tube DIY Asylum, Re: Design articles needed.... (0.00)
Posted by groverg on 2004-10-19, 10:35:01 (141.156.11.116)
Gordon Rankin's SE 807 article from Sound Practices is a great primer on designing simple 2-stage SE amps. You could do worse than order the back-issue CD from Joe Roberts. You can reach him at jrober .......
76: SET Asylum, Re: Please, help me out with the iron layout! (0.00)
Posted by groverg on 2004-10-19, 10:29:17 (141.156.11.116)
Looks pretty good to me. One suggestion: How about left input jack and volume pot on one side, right input and pot on the other--it'll reduce the wiring length, which can make some difference at the i .......
77: Tube DIY Asylum, Re: Source question (0.00)
Posted by groverg on 2004-10-19, 04:14:13 (141.156.11.116)
I think maybe you're thinking too hard about it :-) But for the sake of argument, you could take a mono CD and scope the two channels to see if they're identical. There are numerous very fine, mid-50s .......
78: Tube DIY Asylum, Huh? (0.00)
Posted by groverg on 2004-10-18, 17:38:11 (141.156.11.116)
Don't hear anything about Heathkit???!!!! Er, I think many people consider the Heathkit Williamson series tyo be highly desirable. I'd take a pair of W4s with Acrosound transformers any day over a Dyn .......
79: SET Asylum, Re: Cable survey (0.00)
Posted by groverg on 2004-10-18, 11:19:40 (141.156.11.116)
I have a friend who swears by Golden Cross, and they seem to my ears to be an excellent cable. I don't know if you'll do much better. But if you want to have some cheap fun and perhaps shatter some de .......
80: Tube DIY Asylum, Re: instability now introduced (0.00)
Posted by groverg on 2004-10-16, 21:19:25 (141.156.11.116)
You've either got some RF or oscillation of some sort. The tipoff is when you apply a meter to the circuit and it stabilizes. Sometimes just moving some wires around can set these things off. Are you .......
81: SET Asylum, Re: 'nother question.. (0.00)
Posted by groverg on 2004-10-16, 10:06:33 (141.156.11.116)
"ECC31s would be nice, too." Yes, if you can find them :-). No, I never tried a differential configuration. Even in parallel mode you still have 11K plate resistance and only about 6 mA of current. Th .......
82: SET Asylum, Re: Just found... (0.00)
Posted by groverg on 2004-10-16, 07:22:24 (141.156.11.116)
You can use the 6N7 G or GT (they sound a little different, the G being more airy and the GT being a little more focused and 3-D) or a 6A5 or a 53, depending on what sockets you want to use and what f .......
83: SET Asylum, Re: driver suggestions for 10 (0.00)
Posted by groverg on 2004-10-15, 21:58:07 (141.156.11.116)
If you go with a 76 preamp, or even with the PAS, you might try a parallel 6N7 to drive the 10. The gain should be about right and it's a really sweet, 3-D sound, compliments the "coolness" of the 10 .......
84: SET Asylum, Re: driver suggestions for 10 (0.00)
Posted by groverg on 2004-10-15, 14:53:07 (141.156.11.116)
It depends on how much gain you need. What preamp are you using? .......
85: Tube DIY Asylum, Thank you! nt (0.00)
Posted by groverg on 2004-10-14, 19:53:56 (141.156.11.116)
. .......
86: Tube DIY Asylum, Re: Another take (0.00)
Posted by groverg on 2004-10-14, 15:47:29 (141.156.11.116)
Very interesting, thanks! I'd like to see the previous section about degenrative amplifiers, if it's not too much trouble. .......
87: SET Asylum, Re: 845 & 211/VT-4 amps (0.00)
Posted by groverg on 2004-10-14, 13:53:38 (141.156.11.116)
Yes, many transmitting amps did use "driver" amps. I question whether you'll hear what the 845 or 211 can really sound like this way, especially single-ended. If you're going to build a 1KV PS, it's o .......
88: Tube DIY Asylum, Re: excessive heater voltage (0.00)
Posted by groverg on 2004-10-13, 19:55:00 (141.156.11.116)
That's too high. You need to insert a dropping resistor in series with the supply. What tubes are you running and how many? .......
89: Tube DIY Asylum, Re: Magnavox Preamp (0.00)
Posted by groverg on 2004-10-06, 21:28:51 (141.156.11.116)
A lot of the old console setups had some unique shortcuts and features. There may be a built in compensation circuit, as suggested below, for the console's speaker compliment. There may also be some k .......
90: SET Asylum, Just to clarify... (0.00)
Posted by groverg on 2004-10-05, 20:19:49 (141.156.11.116)
My comment about the 211 seems a little negative--it's not. I just meant that it's a real different tube with a different sound. A lot of people prefer it to the 845. .......
91: Tube DIY Asylum, Re: Thanks Grover... (0.00)
Posted by groverg on 2004-10-05, 13:00:41 (141.156.11.116)
On second thought, how about something with more transconductance, like a 5687? Leave the cathode unbypassed, put 47K on the grid and send the feedback from plate to grid with a .1uF cap and a 100K po .......
92: Tube DIY Asylum, Re: Thanks Grover... (0.00)
Posted by groverg on 2004-10-05, 12:57:19 (141.156.11.116)
You could try a 6SN7, that would be a good place to start, I think. .......
93: SET Asylum, Re: what about the 211? (nt) (0.00)
Posted by groverg on 2004-10-05, 12:54:14 (141.156.11.116)
A pear to go with your apple and your orange :-). A smooth, neutral sound to my ears, very unlike the sturdy warmth of the 845. .......
94: SET Asylum, Re: Apples and oranges (0.00)
Posted by groverg on 2004-10-05, 12:52:05 (141.156.11.116)
No, the 845 and 805 are identical in size and build. .......
95: Tube DIY Asylum, Re: Where to order custom power transformers? Help! (0.00)
Posted by groverg on 2004-10-05, 10:56:07 (141.156.11.116)
I've always wanted to try his stuff--I've heard VERY good comments about his work--but I also heard he was very hard to get ahold of. I assume you've had a good experience. What was the turn-around ti .......
96: SET Asylum, Re: 805 vs 845 (0.00)
Posted by groverg on 2004-10-05, 10:47:23 (141.156.11.116)
Where does that notion come from--reviews of the Wavac amps? I've never heard that, but maybe it's so. Anyway, it's apples and oranges, IMHO. The 805 requires positive grid bias, which in my experienc .......
97: Tube DIY Asylum, Re: Modifying what i have, im new to home audio (0.00)
Posted by groverg on 2004-10-04, 21:58:08 (141.156.11.116)
Replace the PAS-4 with an inexpensive tube preamp, maybe the AES preamp from Cary Audio, or see if you can find a PAS-3 tube pre on eBay. The solid-state Dyna pres are pretty nasty, IMHO. Otherwise yo .......
98: Tube DIY Asylum, Re: More (0.00)
Posted by groverg on 2004-10-04, 10:46:15 (141.156.11.116)
Got it, thanks, Tre. .......
99: Tube DIY Asylum, Re: More (0.00)
Posted by groverg on 2004-10-04, 05:34:35 (68.239.104.134)
But don't PP transformers have a limit, even with AC current, in terms of how much imbalance they can handle? Could you have, for instance, an all-nickel PP transformer for a Class A circuit? ::: TOPI .......
100: Tube DIY Asylum, Re: beware the 'black box' sim.... (0.00)
Posted by groverg on 2004-10-03, 21:44:24 (68.239.66.91)
Oh your poor wife :-). I hope plastic surgery wasn't required. Now we're playing the "Whaddayaknow-I-can-reach-this" game. You wait til Daddy's across the room absorbed in figuring out why his music t .......
101: Tube DIY Asylum, Re: Yikes!!! I didn't mean to get the same old argument started, especially... (0.00)
Posted by groverg on 2004-10-03, 21:15:36 (68.239.66.91)
Okay, the end-to-end change in voltage, yes. Thanks, both of you. Now, what do we gain? :-) Seriously, can we use materials that wouldn't otherwise tolerate any current differences, which would risk s .......
102: Tube DIY Asylum, Re: Here Come The Worms!!! (0.00)
Posted by groverg on 2004-10-03, 21:02:02 (68.239.66.91)
George, I have a custom preamp designed by someone who uses local plate-to-grid feedback wrapped around the input stage, with a series pot, as a volume control. I can tell you that the results are qui .......
103: Tube DIY Asylum, Re: Yikes!!! I didn't mean to get the same old argument started, especially... (0.00)
Posted by groverg on 2004-10-03, 20:45:18 (68.239.66.91)
Ahaaaa. That starts to penetrate. Thanks Dave. .......
104: Tube DIY Asylum, Re: beware the 'black box' sim.... (0.00)
Posted by groverg on 2004-10-03, 20:40:38 (68.239.66.91)
True, but it at least helps you see and understand some of the relationships, doesn't it? Have you seen the software? .......
105: Tube DIY Asylum, Re: Yikes!!! I didn't mean to get the same old argument started, especially... (0.00)
Posted by groverg on 2004-10-03, 20:36:32 (68.239.66.91)
I see what you're saying. Bear with me if you can. We keep the DC off the OPT. (Interesting point about not needing the parafeed caps if we don't ground the CT.) But in order for the transformer to wo .......
106: Tube DIY Asylum, Re: 2A3/6B4G or 300B, for example... (0.00)
Posted by groverg on 2004-10-03, 20:24:11 (68.239.66.91)
No, I don't think this is correct. Damir posted some power-out calculations somewhere below, and they pretty much agree with what PP Calc tells me. FOR YOUR PURPOSES I think you must assume that with .......
107: Tube DIY Asylum, Re: To 300B or not to 300B, that is the question.... (0.00)
Posted by groverg on 2004-10-03, 20:09:50 (68.239.66.91)
This is why I gave up and went to PP 6528s. ;-) My recent PP 300B experiments were based on a quad of EH 300Bs. Pretty, but not the last word in resolution, I'm afraid. The TJ globe mesh plates I borr .......
108: Tube DIY Asylum, Re: Composite plate curves for P-P (0.00)
Posted by groverg on 2004-10-03, 20:02:13 (68.239.66.91)
Just another comment regarding PP loading and composite curves which some might find useful. Broskie's PP Calculator does a lot of work for math idiots like me. It lets you play with loads, operating .......
109: Tube DIY Asylum, Re: Yikes!!! I didn't mean to get the same old argument started, especially... (0.00)
Posted by groverg on 2004-10-03, 19:53:56 (68.239.66.91)
Oh, my. I would have automatically assumed that with parafeed PP, you would ground the OPT's primary CT. Don't we have to have a return to earth for the AC signal passing through the two halves of the .......
110: Tube DIY Asylum, Re: Composite plate curves for P-P (0.00)
Posted by groverg on 2004-10-03, 19:37:15 (68.239.66.91)
That's a very good point, Dave, if I take your meaning correctly. I was thinking that if we leave that made-to-order 5K p-p tranny on the shelf and start from scratch, what is the ideal load for PP 2A .......
111: Tube DIY Asylum, Re: Correct... (0.00)
Posted by groverg on 2004-10-03, 19:27:24 (68.239.66.91)
I hope you're not referring to me. Just because I'm trying to understand how a PP circuit operates doesn't mean I don't know what I'm doing when I apply high voltages to an amplifier circuit. Frankly .......
112: Tube DIY Asylum, Re: Composite plate curves for P-P (0.00)
Posted by groverg on 2004-10-03, 11:43:14 (68.239.66.91)
Thank you, Pete. That clarifies it for me. A chicken-or-egg type question: One half of the PP transformer winding, mechanically speaking, is 1/4 Rpp. In Class A PP, does each tube "see" 1/2 Rpp becau .......
113: SET Asylum, Re: 845 Tubes, Billington Gold, Valve Art & KR Audio (0.00)
Posted by groverg on 2004-10-01, 18:57:45 (68.239.113.194)
www.supertnt.com .......
114: SET Asylum, Re: 845 Tubes, Billington Gold, Valve Art & KR Audio (0.00)
Posted by groverg on 2004-10-01, 12:41:45 (68.239.113.194)
Try the SuperTNT 845B--$150 per matched pair, three reports to me that they are excellent, way better than stock Chinese. .......
115: Tube DIY Asylum, Re: well Piano man... (0.00)
Posted by groverg on 2004-09-30, 09:53:55 (68.239.66.111)
Good points, Doug. I don't know how Broskie constructs his CAD programs. Is it just a Spice model with a GUI? Dunno. I'll take a look at the points you raise--PP Calc offers a pretty comprehensive set .......
116: Tube DIY Asylum, Re: well Piano man... (0.00)
Posted by groverg on 2004-09-30, 09:45:15 (68.239.66.111)
Input power was kept at full grid voltage, i.e. 45 volts. Third harmonic distortion went up significantly, like .8%, in the SE circuit with the lower load, more like a .3% change in the PP circuit. :: .......
117: Tube DIY Asylum, Re: well Piano man... (0.00)
Posted by groverg on 2004-09-30, 05:57:58 (68.239.66.111)
Using SE CAD and PP Calculator I can construct two circuits, one for SE and one for PP. Leaving aside transformer specs, which I cannot duplicate between the two programs, the results for 2A3s operati .......
118: Tube DIY Asylum, Re: PP amplifier measured data (0.00)
Posted by groverg on 2004-09-30, 05:36:27 (68.239.66.111)
So the "composite tube" represented by the graph isn't a reality, but a mathematical convenience? Or is it a true representation of what happens when we essentially have two tubes operating in series .......
119: Tube DIY Asylum, Re: Parallel 6SL7 sections. (0.00)
Posted by groverg on 2004-09-28, 19:26:52 (68.239.123.67)
At such low currents I don't think you have to worry too much about one tube hogging the current--though I could be wrong. As for sound, I often use parallel 6N7s as input stages, and have found that .......
120: Tube DIY Asylum, Re: Yes! (0.00)
Posted by groverg on 2004-09-22, 09:42:48 (151.200.52.86)
You make some good points. Try replacing DC on the 6SL7 and 6SN7 with AC filaments. See if you can find a source of 4-5 amp E-core common-mode chokes in your area--they should be available from a majo .......
121: Tube DIY Asylum, Re: Sonic charateristic on 845 and 300B (0.00)
Posted by groverg on 2004-09-22, 04:37:14 (151.200.52.86)
The biggest culprit is probably the DC filament supply on the 845. This will definitely lend a dry, harsh sound to the tube. Get a pair of common mode inductors from alliedelec.com, part no. 967-8600, .......
122: Tube DIY Asylum, Re: Would $500 be a good price to pay for a SFL-1 .... (0.00)
Posted by groverg on 2004-09-21, 19:32:27 (151.200.52.86)
Yes, I think that would be very fair. .......
123: Tube DIY Asylum, Re: Is A 2.5" Greenlee Punch Really $143? (0.00)
Posted by groverg on 2004-09-21, 18:15:42 (151.200.52.86)
Scout around on eBay. That's where I bought mine. .......
124: Tube DIY Asylum, Re: For twice the money, is Sonic Frontiers SFL-1 twice as good as a Dynaco PAS-2 ? (0.00)
Posted by groverg on 2004-09-21, 16:27:59 (151.200.52.86)
IMHO, the Sonic Frontiers pre was one of the better mass-produced, mid-priced pres in recent years. With careful tube selection, it can sound pretty darn good, much better, I think, than the PAS. If y .......
125: Tube DIY Asylum, Re: Sonic charateristic on 845 and 300B (0.00)
Posted by groverg on 2004-09-21, 10:48:12 (151.200.52.86)
This doesn't surprise me. Generally it takes more work to get a comparable sweetness from the 845, whereas the 300B is much more forgiving and amenable. What kind of filament supply did you use, as op .......
126: SET Asylum, Re: TNT? (0.00)
Posted by groverg on 2004-09-21, 09:37:05 (151.200.52.86)
No, they're not pricey, around $150 per pair, I think. I use paralleled 6N7GT -> triode-wired EL34 -> 845. You can use anything you want, of course, but I'd recommend something more powerful than a 6S .......
127: SET Asylum, Re: I just might go for it. thanks....nt (0.00)
Posted by groverg on 2004-09-20, 15:26:13 (151.200.52.86)
Correction--the 845bs are from TNT. .......
128: Tube DIY Asylum, Sound Practices CD (0.00)
Posted by groverg on 2004-09-20, 10:23:50 (151.200.52.86)
This is the latest info I have from Joe Roberts, as of 2/2004. The email link looks strabge but that's he wrote: "You can still snag a CD direct from me for 29.95, pay-o-pal , check, or real money. I .......
129: SET Asylum, Re: sorry, what are the meanings of "DC degeneration" and "stacked supply designs"? nt (0.00)
Posted by groverg on 2004-09-19, 22:17:18 (151.200.52.86)
"Stacked supplies" means you have two supplies, one for each tube in the circuit. Let's say the driver supply is 150 VDC. The output tube supply is 300VDC. In a normal direct-coupled circuit with one .......
130: Tube DIY Asylum, Re: Circuit Design Progress? (0.00)
Posted by groverg on 2004-09-19, 22:01:45 (151.200.52.86)
The Valve CD is available from bottlehead.com, and the Sound Practices CDs can be had via Joe Roberts, former editor of the mag, but it's hard to track him down right now. Maybe someone will chime in .......
131: SET Asylum, Re: what does anyone have to say about se845 amps (0.00)
Posted by groverg on 2004-09-19, 21:57:23 (151.200.52.86)
I have found that 845s deliver far more "apparent" power than a 300B. Even at modest voltages like 750-800 VDC, putting out maybe 10 watts at best, they will power speakers that make a 300B cringe. Ju .......
132: SET Asylum, Re: would the tube rectifier would have similar B+ delay effects? (nt) (0.00)
Posted by groverg on 2004-09-19, 21:54:27 (151.200.52.86)
Yes, a 5AR4, GZ37, 5V4 or even a pair of TV damper diodes would provide a suitable slow turn-on for a direct-coupled circuit. .......
133: Tube DIY Asylum, Great! (0.00)
Posted by groverg on 2004-09-19, 13:54:53 (151.200.52.86)
. .......
134: Tube DIY Asylum, Re: Circuit Design Progress? (0.00)
Posted by groverg on 2004-09-19, 11:38:40 (151.200.52.86)
I think there have been some very interesting developments in the past 15 years, a lot of them thanks to the DIY community and those who cater to it. Some of them mimic or improve upon older designs, .......
135: SET Asylum, Re: replacing all tubes in a tube amplifier once a year is quite costly esp I seldom use new tubes... (nt) (0.00)
Posted by groverg on 2004-09-19, 10:54:43 (151.200.52.86)
As I said, you may not have to replace them once a year--it depends on how many hours you run the amp and the quality of the tubes. As Doc B. says, they can last for years at a time. They're going to .......
136: SET Asylum, Re: "replacing the tubes, say, once a year..." you mean replacing the 2A3's once a year...nt (0.00)
Posted by groverg on 2004-09-18, 17:37:41 (68.239.73.178)
No, I meant replacing all tubes, especially the driver, since a change in the driver tube's operating point will change the way the 2A3 operates. It may not be once a year, it depends on how often you .......
137: SET Asylum, Re: direct-coupling between 2A3 and driver stage (0.00)
Posted by groverg on 2004-09-18, 14:10:08 (151.200.58.89)
With proper care and feeding, a simple direct-coupled 2A3 design shouldn't give you problems. Over the course of months you will want to check your operating voltages to make sure nothing is out of li .......
138: Tube DIY Asylum, Re: Two SE transformers versus one PP transformer (0.00)
Posted by groverg on 2004-09-17, 10:51:25 (68.239.65.165)
Thanks, Mike. .......
139: Tube DIY Asylum, Re: an additional reference (0.00)
Posted by groverg on 2004-09-17, 08:17:02 (68.239.65.165)
Yes, but we also have clear references to a Class A PP circuit seeing 1/2 Raa--at least at *at some point*. I assume Doug's question is, is there a clearer way to graph or somehow model the PP circui .......
140: Tube DIY Asylum, Re: my fav example (0.00)
Posted by groverg on 2004-09-17, 08:10:06 (68.239.65.165)
True enough! Now, if you took two SE transformers and connected them in series but out of phase, would they behave the same as two single SE transformers, or would they behave like a PP transformer? O .......
141: Tube DIY Asylum, Re: my fav example (0.00)
Posted by groverg on 2004-09-17, 07:41:08 (68.239.65.165)
True, but if the point is that two Class A tubes in PP *always* see 1/2 Raa, that wouldn't be the case, would it? The load is dynamic. .......
142: Tube DIY Asylum, Re: I Have Concerns About Single-Ended PSRR... (0.00)
Posted by groverg on 2004-09-17, 07:26:44 (68.239.65.165)
Any sort of negative feedback would reduce noise, wouldn't it? It's in opposite phase, no? .......
143: Tube DIY Asylum, Re: my fav example (0.00)
Posted by groverg on 2004-09-17, 07:16:34 (68.239.65.165)
Mark's example involves static voltage measurements and static loads, is that correct? Does it really reflect the actual behavior of two tubes with constantly changing dynamic characteristics interact .......
144: Tube DIY Asylum, Re: The practical app. of the PP Class A load question (0.00)
Posted by groverg on 2004-09-17, 07:09:05 (68.239.65.165)
I suppose there's nothing to stop you from plotting it as a single-ended device with 1/2 Raa as the load and assume 2X Po. But the more I read the more it seems that that doesn't represent what's goin .......
145: Tube DIY Asylum, Re: Chassis - DIY? (0.00)
Posted by groverg on 2004-09-16, 16:11:11 (68.239.65.165)
Sorry, I misunderstood your post :-) .......
146: Tube DIY Asylum, Re: What the HELL?!? (0.00)
Posted by groverg on 2004-09-16, 13:43:46 (68.239.65.165)
Try unbolting the PT if you can and rotating it some, see if this helps. Phono stages are a b*tch to get quiet. I think isolating the PS by a good long umbilical would be a good idea anyway, and might .......
147: SET Asylum, Re: in the current schematic BOTH filaments are floated to around 50V (via the point A connection), floating both no goo (0.00)
Posted by groverg on 2004-09-16, 13:29:27 (68.239.65.165)
Any time the cathode is raised a certain voltage above the grounded filament supply, you put some degree of stress on the heater-to-cathode insulation. Normally we don't worry about this as it involve .......
148: Tube DIY Asylum, Re: What the HELL?!? (0.00)
Posted by groverg on 2004-09-16, 05:35:34 (68.239.65.165)
If you're getting 60Hz, it sounds like you've got some magnetic coupling from your transformer placement. .......
149: Tube DIY Asylum, Re: mystery tubes (0.00)
Posted by groverg on 2004-09-16, 05:33:57 (68.239.65.165)
I don't know what that is, but it's extremely inadvisable to build a power amp without a power transformer to isolate the circuit from the mains. .......
150: SET Asylum, Re: in the current schematic BOTH filaments are floated to around 50V (via the point A connection), floating both no goo (0.00)
Posted by groverg on 2004-09-16, 05:29:37 (68.239.65.165)
Either way is fine. It was just a suggestion. Since you're building it on one chassis and you have the extra filament supply, you have the option to float the upper halves of the SRPP and keep the bot .......
151: SET Asylum, Re: so... what is the advantage of floating one filament and grounding the other...(NT) (0.00)
Posted by groverg on 2004-09-15, 12:19:03 (68.239.65.165)
The upper half of the SRPP is going to see its cathode at 90 volts or more above ground. Since the max h/k voltage permissible for the 6SL7 is 90 volts, you'll have to split the difference between the .......
152: SET Asylum, Yes... (0.00)
Posted by groverg on 2004-09-15, 11:29:27 (68.239.65.165)
...that way you can float the one heater and keep the other grounded. Just a thought. .......
153: SET Asylum, Re: power transformer for 2A3(SE) or 6B4G (SE or PP): please comment (0.00)
Posted by groverg on 2004-09-15, 09:28:30 (68.239.65.165)
Looks lovely, I'm sure the amp will sound great. I would use the two 6.3 volt taps otherwise--one for the bottom halves of the SRPP stages and the other, floated by 90 volts, for the top halves. ::: T .......
154: Tube DIY Asylum, Re: Can Rectifier Tubes Be Paralleled? (0.00)
Posted by groverg on 2004-09-10, 18:17:01 (68.239.65.165)
John gave you the best answer, but just as a correction, unless I misunderstood you--your power transformer secondary would connect to a pair of resistors, one going to each plate of the rectifier tub .......
155: Tube DIY Asylum, Re: Can Rectifier Tubes Be Paralleled? (0.00)
Posted by groverg on 2004-09-10, 05:45:49 (68.239.65.165)
I think if you add a resistor in series with each plate, say 50 ohms/10 watts, this should equalize the current sharing between the tubes. I parallel the plates in a single tube for each leg of the re .......
156: Tube DIY Asylum, Re: What is a better input match for a 6900 driver ecc99 ,5687or7199? nt (0.00)
Posted by groverg on 2004-09-09, 13:39:02 (68.239.107.34)
You CAN get too much of a good thing :-). Unless I'm mistaken, the 5687 and it's cousins have rather high input capacitances and this can theoretically hobble the bandwidth of the amp and make the inp .......
157: Tube DIY Asylum, Re: Fixed Bias Supply - Shopping for Power Trans. Got advice ? (0.00)
Posted by groverg on 2004-09-09, 13:34:16 (68.239.107.34)
Allied and Mouser carry Hammond or Magnetek/Triad isolation transformers--dual-bobbin types that are very cheap. That's what I use. .......
158: Tube DIY Asylum, Re: adapter woes (0.00)
Posted by groverg on 2004-09-06, 17:26:17 (151.200.141.22)
I use adapters for 76s in an octal relay socket for my breadboards. I follow the connections for a 6J5--3 for plate, 5 for grid, 8 for cathode and 2 and 7 for the filaments. Then if you plop them in a .......
159: Tube DIY Asylum, Re: Quesrions for those knowledgeable about tube preamp circuits. (0.00)
Posted by groverg on 2004-08-28, 08:02:36 (151.200.10.116)
A lot of the "boutique" tube designers have turned to "newer" tubes, like the Russion 6C45 and 6H30, which are sturdy, high-transconductance tubes capable of conveying a lot of detail in very simple c .......
160: SET Asylum, Re: SET balanced DC filament? (0.00)
Posted by groverg on 2004-08-28, 07:57:10 (151.200.10.116)
Good question! Getting SETs quiet with AC is a real art--careful layout, wiring schemes AND well-made DHTs with well-constructed filaments. If you need the extra quiet of DC on the filaments, you can .......
161: Tube DIY Asylum, Re: SE tube amp schematics... (0.00)
Posted by groverg on 2004-08-27, 13:54:28 (151.200.10.116)
Try here: http://tubesall.hihome.com/tube.htm .......
162: SET Asylum, Re: Power Conditioners with SET based systems (0.00)
Posted by groverg on 2004-08-27, 13:52:42 (151.200.10.116)
I agree with Jack that the Tice conditioners work very well. I've heard them on several SE systems. .......
163: SET Asylum, Re: SET balanced DC filament? (0.00)
Posted by groverg on 2004-08-26, 10:13:38 (151.200.10.116)
You can choose to either ground the negative leg of the supply or use balancing resistors or a pot across the filaments. It won't effect the hum, AFAIK. It may effect the sound, at least I have found .......
164: Tube DIY Asylum, Re: PP 2A3 amp - question (0.00)
Posted by groverg on 2004-08-26, 07:04:57 (151.200.10.116)
Yes, it's a bleeder. .......
165: Tube DIY Asylum, Re: Filament voltage ? (0.00)
Posted by groverg on 2004-08-25, 21:24:26 (151.200.10.116)
Well, we just had a somewhat contentious thread about this not far below. :-) .......
166: Tube DIY Asylum, Re: for those of us who already own good interstages.... (0.00)
Posted by groverg on 2004-08-25, 21:22:44 (151.200.10.116)
Gee, your guess is as good as mine. I'm using some old Magnequest Brooklyns, which aren't made anymore. I guess I'd try the Magnequest Dynaco ST-70 replacements, but there are lots of other options. : .......
167: Tube DIY Asylum, Re: What to replace the 6A6? (0.00)
Posted by groverg on 2004-08-25, 21:19:44 (151.200.10.116)
Oh, yes, sorry! 6N7G or GT. There's also an octal version of the 76, the 6P5G or GT. I'd go for the G versions of both. OR*** if you want to go with 2.5 volt filaments throughout, using a single suppl .......
168: Tube DIY Asylum, Re: Socrates, Langmuir and the Encyclopaedia of Ignorance. (0.00)
Posted by groverg on 2004-08-25, 20:47:55 (151.200.10.116)
That's an excellent link, Mark, thank you. Very enlightening. .......
169: Tube DIY Asylum, Re: Books are the treasures of the past. But it is for us to scrutinize their true values. (0.00)
Posted by groverg on 2004-08-25, 20:46:46 (151.200.10.116)
The article is found below. Very interesting. .......
170: Tube DIY Asylum, Re: while im at it... sweaty resistors! (0.00)
Posted by groverg on 2004-08-25, 20:00:04 (151.200.10.116)
Okay, I'll apologize for the gulp :-). That's a helpful set of measurements. It's likely the power resistor has drifted in value, not surprising for it's age. But that's not critical at the moment. Ac .......
171: Tube DIY Asylum, Re: PP 2A3 amp (0.00)
Posted by groverg on 2004-08-25, 19:37:05 (151.200.10.116)
It's a wonderful-sounding amp and has been making the rounds at some DIY meets here with high approval ratings. Here's the circuit: http://www2u.biglobe.ne.jp/~tossie/F2A3PP-E.html .......
172: Tube DIY Asylum, Re: Hey.......... (0.00)
Posted by groverg on 2004-08-25, 14:35:41 (151.200.10.116)
Agreed! .......
173: Tube DIY Asylum, Re: "it was repeatable and audible easily to 100ths of an ohm" (0.00)
Posted by groverg on 2004-08-25, 12:32:34 (151.200.10.116)
Could it be that the effect of the paralleled resistors themselves causes the change in sound, as opposed to the change in ohmic value? .......
174: Tube DIY Asylum, Re: while im at it... sweaty resistors! (0.00)
Posted by groverg on 2004-08-25, 11:13:57 (151.200.10.116)
Gulp :-). Okay, if you measure the DC voltage from the output of the rectifier to ground, and it's unreasonably low, like below 100 volts, you may have a problem. I gulped because before suggesting th .......
175: Tube DIY Asylum, Re: First amp from scratch and a few questions. (0.00)
Posted by groverg on 2004-08-25, 11:08:23 (151.200.10.116)
You can try a choke between the first and second caps--you may like what it does to the sound, or not. 5H/150mA should suffice. I do have a question about the alkaline battery, however. It's possible .......
176: Tube DIY Asylum, Re: they always fall back on 'creativity'... (0.00)
Posted by groverg on 2004-08-25, 10:28:49 (151.200.10.116)
You're right, Joel, I don't know you. I can only judge you by your posts to the asylum. By the same token, you don't know many of us. And I think it's fatuous to imply that someone you don't know, who .......
177: Tube DIY Asylum, Re: while im at it... sweaty resistors! (0.00)
Posted by groverg on 2004-08-25, 05:00:48 (151.200.10.116)
Hmmm. You've got a challenge there. :-( The smoking power resistor isn't a good sign. Sounds like your B+ is getting grounded somewhere to draw so much current through that resistor, but I could be wr .......
178: Tube DIY Asylum, Re: while im at it... sweaty resistors! (0.00)
Posted by groverg on 2004-08-24, 21:33:02 (151.200.10.116)
Er, no offense, but you'd better slow up, there, snuck :-). The hum sounds like a lack of power supply filtering, which may mean mis-wired filter caps, or a possible short in the power supply. And tha .......
179: Tube DIY Asylum, Re: Problem has been resolved. (0.00)
Posted by groverg on 2004-08-24, 21:28:35 (151.200.10.116)
Well, that's good news--an easy fix, though a pain to track down! .......
180: Tube DIY Asylum, Re: Burn in strikes again (0.00)
Posted by groverg on 2004-08-24, 17:21:42 (68.239.108.115)
I'm wondering what it must be like to live in a world where your imagination is limited by strict adherence to RDH and Crowhurst. Not that these aren't fine books, but according to their precepts John .......
181: Tube DIY Asylum, Re: Confusion resulting from a vintage amp project. (0.00)
Posted by groverg on 2004-08-22, 10:51:53 (68.239.104.217)
It sounds like the center tap of the transformer isn't grounded. Have you checked that connection? .......
182: Tube DIY Asylum, Re: Changing PS filter Chokes (0.00)
Posted by groverg on 2004-08-17, 10:42:37 (151.200.52.146)
"35" probably means 35 Henries. Why do you want to change it? .......
183: SET Asylum, Re: From Push-Pull to SET (0.00)
Posted by groverg on 2004-08-10, 09:39:46 (138.88.0.194)
Provided the amps prove to be a good match with your speakers, I think you'll like the clarity and transparency of the SE amps, the relaxing ease of the sound, and the sense of realism and tonal verac .......
184: Tube DIY Asylum, Re: Curious about magnetism and sound... (0.00)
Posted by groverg on 2004-08-03, 21:20:59 (141.156.182.24)
Now, Henry... "It's easy sometimes to declare a subjective observation to be nonsense based on too little information, and then have to revise that position when a deeper understanding comes along." B .......
185: Tube DIY Asylum, Re: pleese help with micro 3.5 amp (0.00)
Posted by groverg on 2004-08-03, 21:06:47 (141.156.182.24)
The resistor values are for the two halves of the 6SL7 together. Wire the plate, grid and cathode pinns in parallel and use the values given in the schematic. .......
186: SET Asylum, Re: Volume control distortion (0.00)
Posted by groverg on 2004-07-29, 12:13:09 (141.156.161.106)
Probably the pot is either dirty or defective. Try some spray-on contact cleaner or replace the pot. .......
187: SET Asylum, Re: input impedance question (0.00)
Posted by groverg on 2004-07-28, 17:43:25 (141.156.161.106)
Definitely leave the 100K resistor to ground in place. You want somethting to tie the input grid to ground. Otherwise, if you lose a connection to the amp for any reason, the input tube's grid will fl .......
188: SET Asylum, Re: Why can I hear biwiring on an HE + SET rig? (0.00)
Posted by groverg on 2004-07-14, 06:33:20 (151.200.238.42)
Various theories have been put forth as to why bi-wiring sounds different, though some claim it's a crock. I've always preferred bi-wiring on my ProAcs. .......
189: Tube DIY Asylum, Re: Gird stopper hookup (0.00)
Posted by groverg on 2004-07-11, 12:58:37 (138.88.92.162)
A safer bet is one grid-stopper per grid pin. Also, running such a high gm tube in parallel is asking for trouble :-). You may have to resort to further tricks-shielding the tube, plate stoppers, etc. .......
190: SET Asylum, Re: Thanks Ongaku problem solved by "groverg" (0.00)
Posted by groverg on 2004-07-11, 12:55:06 (138.88.92.162)
Great! It didn't occur to me that the caps are mislabeled in the schematic, but I guess that would be so since it's a negative voltage supply. .......
191: SET Asylum, Re: Ongaku circuit wrong ? (0.00)
Posted by groverg on 2004-07-10, 16:25:44 (138.88.34.112)
I assume you are measuring +200 and -200 volts on the =/- supply? If so, then carefully go over your wiring and connections for the CF stage grid bias circuit. Make the sure you don't have a short to .......
192: Tube DIY Asylum, Re: How do I pull a signal from my amp to a sub? (0.00)
Posted by groverg on 2004-07-05, 17:09:42 (138.88.148.143)
I don't think so, and it never came up when my "guru" set up my sub for me. You could check the specs of the Hsu and see what the load is, but I don't think it's a problem. Yes, thin wire would be goo .......
193: Tube DIY Asylum, Re: Stick the 'R' in the primary... (0.00)
Posted by groverg on 2004-07-05, 13:27:10 (151.200.243.199)
Are you sure, Doug? I've found it takes a heftier resistor to handle the 5-10VAC primary drop than in the secondary... .......
194: Tube DIY Asylum, Re: tube designations/names (0.00)
Posted by groverg on 2004-07-05, 11:50:34 (151.200.243.199)
There's an online explanantion of this somewhere, but anyway the numbers describe various aspects of the tube's construction. The beginning number is almost always the filament voltage, and the ending .......
195: Tube DIY Asylum, Re: How do I pull a signal from my amp to a sub? (0.00)
Posted by groverg on 2004-07-05, 11:43:37 (151.200.243.199)
Most subs have high-level and low-level inputs. It sounds like you are feeding the Toshiba directly into the Darling. You could split the output of the Tosh to feed both the amp and the sub's low-leve .......
196: Tube DIY Asylum, Re: How do I reduce 6.3VAC 6amps to 6.3VAC 2amps. (0.00)
Posted by groverg on 2004-07-05, 11:33:21 (151.200.243.199)
You don't need to. Technically speaking, the new transformer will produce the same voltage, it just has the capacity to handle more current. However, in real world applications, a transformer with a h .......
197: Tube DIY Asylum, You need never... (0.00)
Posted by groverg on 2004-07-02, 21:28:38 (141.156.220.81)
...be ashamed to show me anything. If you'd ever seen my breadboards-of-death you wouldn't be shy. :-) Yes, chokes to close to the PT can be a problem. Try moving them and also rotating them to reduce .......
198: Tube DIY Asylum, Re: newbie question on Transformers . . . (0.00)
Posted by groverg on 2004-07-02, 19:59:32 (141.156.220.81)
If you have the model number, we might be able to dredge up a schematic on the web which would tell you what's what in the amp and what might be usable for another project. Chances are it would be goo .......
199: Tube DIY Asylum, Re: Hum Hunting (0.00)
Posted by groverg on 2004-07-02, 19:56:47 (141.156.220.81)
The fact that you have lower hum with the B+ off doesn't really mean anything. You may have some magnetic-field coupling between transformers and/or chokes, or there may be some wiring or grounding is .......
200: Tube DIY Asylum, Does your wife know... (0.00)
Posted by groverg on 2004-07-02, 17:28:54 (141.156.220.81)
...you took that picture? ;-) She gorgeous! Congratulations! .......
201: Tube DIY Asylum, Re: What about Bob? (0.00)
Posted by groverg on 2004-06-28, 08:53:08 (151.200.246.88)
Bob is fine and very busy at work and tinkering with cars and the occasional audio project, as far as I know. He still contributes to the Sound Practices listserv (Joelist) but only occasionally. ::: .......
202: SET Asylum, Great! nt (0.00)
Posted by groverg on 2004-06-18, 14:54:55 (138.88.156.135)
. .......
203: SET Asylum, Re: Problem on 300B tube? (0.00)
Posted by groverg on 2004-06-17, 09:16:44 (138.88.37.221)
The most likely culprits are: 1) A leaky coupling capacitor allowing DC voltage to pass to the grid of the 300B from the previous stage, thus ramping up the bias and current of the 300B; 2) If it's a .......
204: Tube DIY Asylum, Re: Hi Grover, did you use the 6A6?.......... (0.00)
Posted by groverg on 2004-06-14, 19:35:13 (141.156.33.210)
The 6N7 is a direct octal substitute. The glass G or GT would be preferable to the metal version, IMHO. .......
205: Tube DIY Asylum, Re: Interesting (0.00)
Posted by groverg on 2004-06-14, 19:33:05 (141.156.33.210)
Well, it just goes to show, ya never know :-). Maybe it's the 6B4s in place of the 2A3s and the maple block breadboards. This circuit just sings on my ProAcs. Have no idea how it would sound elsewhere .......
206: Tube DIY Asylum, Re: Nice...Real Nice (0.00)
Posted by groverg on 2004-06-13, 16:07:54 (138.88.126.40)
I've never been that big on the 76, like many folks are, but I do love the 6N7 and use it in a lot of my SE experiments. I had already played around with a similar front end using 6SN7s, but I was loo .......
207: Tube DIY Asylum, Re: PP topology: Compact vs fi-primer PP (0.00)
Posted by groverg on 2004-06-13, 11:34:28 (138.88.126.40)
I don't know if you want to get into DHTs, but I ran across this circuit online and breadboarded it, substituting 6B4Gs for the 2A3s. It's absolutely gorgeous sounding. 10 watts output. I used a Hammo .......
208: Tube DIY Asylum, Correction.. (0.00)
Posted by groverg on 2004-06-10, 17:41:55 (138.88.151.178)
I should have said "bias voltage", not "bias resistor". .......
209: Tube DIY Asylum, Re: Need help with load line when plates in parallel (0.00)
Posted by groverg on 2004-06-10, 17:39:56 (138.88.151.178)
Russ, I played around with Tube Cad and this is what appears to happen, graphically speaking anyway. All else remaining the same--plate load, B+, bias resistor value--try simply doubling the increment .......
210: Tube DIY Asylum, Re: Rebuilding tube amps (0.00)
Posted by groverg on 2004-06-08, 17:09:31 (141.156.167.108)
By acceptable, you mean "audiophile approved" ? ;-) I wouldn't break the bank here. Allied Electronics or Digikey can supply just about everything you need. Panasonic power supply caps, 1% metal film .......
211: Tube DIY Asylum, Re: How much grid current does a 845 need in fixed bias configuration ?? (0.00)
Posted by groverg on 2004-06-08, 17:02:38 (141.156.167.108)
The 845 wasn't really designed for positive grid swings so there should be no grid current to speak of. With a mu-follower or SRPP, it's the output impedance of the driver that counts rather than the .......
212: Tube DIY Asylum, Ditto! (0.00)
Posted by groverg on 2004-06-08, 14:26:49 (141.156.167.108)
. .......
213: SET Asylum, Correction... (0.00)
Posted by groverg on 2004-06-06, 14:54:26 (138.88.95.115)
Magnequest has a whole new series, the Robin Hood, which will suit your purposes if you want to go that way. .......
214: SET Asylum, Re: 807's, KT 66's as single ended monoblocks (0.00)
Posted by groverg on 2004-06-06, 14:49:15 (138.88.95.115)
I'm guessing 8-10 watts. I did a KT88 UL SE and it was plenty of power for my ProAcs. BTW, Magnequest is now making a UL version of the DS-025. This is what I used and it's very sweet, but there are o .......
215: Tube DIY Asylum, Re: Rebuilding tube amps (0.00)
Posted by groverg on 2004-06-05, 18:17:54 (138.88.95.115)
No, you're not crazy at all. It's a great way to learn about tube amp design and construction. There are numerous tube primers around, others could recommend them--Morgan Jones' book is mentioned freq .......
216: SET Asylum, Re: 807's, KT 66's as single ended monoblocks (0.00)
Posted by groverg on 2004-06-05, 18:12:18 (138.88.95.115)
You might want to try the KT66 is SE ultralinear--good power, near-triode sound and very agreeable over all. There are numerous circuits, you can google them. The only caveat is you need an SE ultrali .......
217: Tube DIY Asylum, Re: ABOUT WESTCAP (0.00)
Posted by groverg on 2004-05-30, 19:51:14 (151.200.247.196)
You can find a lot of surplus WestCaps here: http://www.surplussales.com/Capacitors/NP-MetalC.html .......
218: Tube DIY Asylum, Re: Choke ratings ? (0.00)
Posted by groverg on 2004-05-24, 14:04:13 (138.88.139.150)
I have several of these. Chicago Standard potted, square can with rounded corners. .......
219: Tube DIY Asylum, Re: Got an idea for a interstage tranny-coupled 2A3, read & comment? (long) (0.00)
Posted by groverg on 2004-05-19, 20:09:59 (138.88.93.102)
My first question would be, why do you want to use an IT? Unless it's an awfully good one you're probably going to lose some bandwidth, top and bottom. Secondly, if you want to try an IT, I wouldn't r .......
220: Tube DIY Asylum, Re: I am not going to read it...anytime soon that is. (0.00)
Posted by groverg on 2004-05-15, 18:54:36 (138.88.138.184)
I believe Dan Cheever died of cancer several years ago. .......
221: SET Asylum, I agree... (0.00)
Posted by groverg on 2004-05-15, 18:45:00 (138.88.138.184)
...the preamp can dominate and it is hard to find the magic formula. But a 6SN7 line stage is a good start and you could do worse :-). .......
222: SET Asylum, Re: Some SET advice please (0.00)
Posted by groverg on 2004-05-15, 12:06:56 (138.88.138.184)
IMHO you've received some good advice below, including not running the amps through PS power plant (if you are) and trying a preamp with the CD player. I will only add that, while I've not heard the s .......
223: Tube DIY Asylum, Re: thanks for the seriously good advice... (0.00)
Posted by groverg on 2004-05-09, 17:41:21 (151.200.246.87)
I am very happy with a version of the JE Labs PP 2A3 amp modified to accomodate 300Bs. I used a 760VCT power tranny with a GZ37 rectifier, 4uF paper-in-oil 600VDC cap, 2H/300mA choke, 47uF, netting 43 .......
224: Digital Drive, Re: Has anyone tried putting adhesive CD printing labels on Commercial CDs? (0.00)
Posted by groverg on 2004-05-07, 14:38:39 (138.88.158.204)
One possible problem is that heat from some units may cause the paper labels to buckle or somehow interfere with the mechanism. I use to label CDs to send to a duplication firm, and they told me not t .......
225: Tube DIY Asylum, Re: safety check request... (0.00)
Posted by groverg on 2004-05-05, 14:52:00 (138.88.158.204)
I've used these, they're wonderful trannies. They don't get much safer than this :-). .......
226: Tube DIY Asylum, Re: capacitors (0.00)
Posted by groverg on 2004-05-01, 21:13:08 (138.88.94.149)
The Jupiters are very nice as coupling caps, very rich midrange especially and a very natural sound. I'm a bit torn as they seem to be a bit short of detail on the top end, but then again that could b .......
227: Tube DIY Asylum, Re: Other Chinese DHTs: 805 and 813 (0.00)
Posted by groverg on 2004-04-21, 10:50:52 (138.88.141.130)
I haven't tried them at 500VDC, but I suppose you could. The 813 can be triode-strapped and run similarly to an 845 with with lower voltage drive demands. An 845 at 500VDC/80mA needs about 60 volts dr .......
228: Tube DIY Asylum, Re: ? for Mark Kelly (0.00)
Posted by groverg on 2004-04-19, 15:50:25 (141.156.164.129)
It would maximise gain, cancel even harmonics (if it's a CT choke or IT with opposed windings), it would provide better balance between phases and it would linearize the voltage output of the driver. .......
229: Tube DIY Asylum, Re: help me finding a tube (0.00)
Posted by groverg on 2004-04-17, 10:01:59 (141.156.180.3)
How about a 46? .......
230: SET Asylum, Re: Which 300B design (0.00)
Posted by groverg on 2004-04-16, 21:01:14 (141.156.180.3)
You have a long memory, Tom :-). I recall I did post something to that effect somewhere, though I don't recall that I used the exact components that Herb prescribes. Tastes don't change but building s .......
231: Tube DIY Asylum, Or... (0.00)
Posted by groverg on 2004-04-14, 19:29:35 (141.156.180.3)
It might be easier to float one of the input jacks on the amp :-). .......
232: SET Asylum, Re: Which 300B design (0.00)
Posted by groverg on 2004-04-13, 18:41:25 (141.156.180.3)
No, I don't believe the Reichert is analytical in any way, at least the version of it I've experimented with. IMHO it's hard to get a 6SN7 to sound "analytical" :-). The 91 clone is very elegant and o .......
233: SET Asylum, Re: Which 300B design (0.00)
Posted by groverg on 2004-04-12, 21:19:53 (141.156.180.3)
Well, I like the 91 clone okay but compared to the Reichert it's sweeter and more polite. "Flesh and Blood" describes the Reichert pretty well. .......
234: SET Asylum, Re: Which 300B design (0.00)
Posted by groverg on 2004-04-11, 08:24:05 (141.156.180.3)
The Fi Primer and the JE Labs are essentially the same design. I'd build the Reichert. .......
235: Tube DIY Asylum, Re: Transformer catalogs (0.00)
Posted by groverg on 2004-04-10, 10:59:18 (141.156.180.3)
Got any Kenyon stuff? .......
236: Tube DIY Asylum, Re: Parafeed Transformer Primary Impedance (0.00)
Posted by groverg on 2004-04-08, 19:50:30 (141.156.180.3)
Yes, the impedance should remain the same; the primary inductance is what you want to increase with the parafeed tranny. .......
237: Tube DIY Asylum, Re: 211 SET - anyone out there built them? 2A3 comparison? (0.00)
Posted by groverg on 2004-04-08, 10:58:55 (141.156.180.3)
Wow. There's no real comparison I can think of between a 2A3 amp and a 211 amp. :-) The 211 has a big, smooth, neutral sound in my experience, just nothing like the 2A3 or 300B. The Ongaku is a great .......
238: Tube DIY Asylum, Re: What's the load? (0.00)
Posted by groverg on 2004-04-06, 13:38:59 (141.156.180.3)
I'll butt in, if I may :-). I don't think you need to change the amp's input resistance. I too was puzzled that there are no output grounding resistors indicated in the schematic. I would put 1 meg re .......
239: SET Asylum, Re: Mastersound Reference 845 (0.00)
Posted by groverg on 2004-04-06, 13:31:06 (141.156.180.3)
There are very slight electrical differences, but basically yes, you can drop it in. Tom is correct, the 6900 is a dramatic upgrade, and I do mean dramatic. It throws a bigger sound stage and has none .......
240: Tube DIY Asylum, Re: PSU switch on, 20 seconds later = large spkr cone movements, then OK (0.00)
Posted by groverg on 2004-03-31, 20:26:08 (141.156.180.3)
Well, all resistance/capacitance combinations will combine to create (mostly) low frequency poles or cutoffs, just like in a speaker crossover. This combines with all the other low frequency poles in .......
241: Tube DIY Asylum, Re: PSU switch on, 20 seconds later = large spkr cone movements, then OK (0.00)
Posted by groverg on 2004-03-31, 19:27:06 (141.156.180.3)
Possibly some additive LF poles with the longer B+ chain causing some temporary instability while the B+ settles down or the tubes fully conduct? What's the circuit? .......
242: Tube DIY Asylum, Re: Help with SE Amp design in the 4/04 Audio Express (0.00)
Posted by groverg on 2004-03-31, 19:15:59 (141.156.180.3)
You would take the supply points for the second channel from the same places as the channel shown. In other words, the output tube for both channels would be supplied by the tap on the power supply as .......
243: Tube DIY Asylum, Re: Anyone know what happened to Jute ? (0.00)
Posted by groverg on 2004-03-30, 17:43:13 (141.156.180.3)
He's right under your nose. .......
244: Tube DIY Asylum, Re: Do I have an OP transformer problem (semi-newby question) (0.00)
Posted by groverg on 2004-03-29, 11:31:20 (141.156.180.3)
I think you have the primaries mixed up. Some PP outputs use solid leads to plates, striped leads to screen. Others do it differently, like blue striped to plate, green striped to screen, blue solid t .......
245: Tube DIY Asylum, Re: Does anybody have experience in Mu follower feeding to 845 ? (0.00)
Posted by groverg on 2004-03-29, 11:26:09 (141.156.180.3)
Not sure I understand. Am I confusing RMS with peak voltage? Perhaps. You could raise the plate resistor a bit to get more headroom. The reason I would choose a simple parallel plate follower is that .......
246: Tube DIY Asylum, Re: Does anybody have experience in Mu follower feeding to 845 ? (0.00)
Posted by groverg on 2004-03-28, 20:14:07 (141.156.180.3)
About 15 mA. .......
247: Tube DIY Asylum, Re: Does anybody have experience in Mu follower feeding to 845 ? (0.00)
Posted by groverg on 2004-03-28, 07:51:44 (141.156.180.3)
You can do it without the mu follower. Parallel a 6SN7GTB, use a 15K plate resistor and 1k on the cathode with bypass. It'll swing 200 volts or more. Just be sure to use a GTB which will take 400 plat .......
248: Tube DIY Asylum, Re: Opinions wanted on two drivers for LARGE swing (0.00)
Posted by groverg on 2004-03-26, 13:29:37 (141.156.180.3)
How about just a center-tapped choke (or the primaries of a small PP output transformer) on the PP driver stage? Then cap couple to the output stage, a la Brook. This may alleviate the bandwidth probl .......
249: Tube DIY Asylum, Re: Teething troubles. (0.00)
Posted by groverg on 2004-03-25, 19:41:06 (141.156.180.3)
Try removing C1 from each channel of the preamp. .......
250: Tube DIY Asylum, Re: and even more good news :) (0.00)
Posted by groverg on 2004-03-25, 13:59:44 (141.156.180.3)
Yes, you can have a lot of fun indeed. Try the 7408, a 6V6 variant, or the 5932, a mil-spec 6L6. Or KT66. I even subbed a KT90 for the EL34 driver in the 845SE I helped a friend build, and he likes th .......
251: Tube DIY Asylum, Oh, and... (0.00)
Posted by groverg on 2004-03-24, 17:31:15 (141.156.180.3)
...of course bypass the whole 6V6 cathode resistance. .......
252: Tube DIY Asylum, Re: Lkg for Design Walkthrough for Direct Coupling (0.00)
Posted by groverg on 2004-03-24, 17:24:06 (141.156.180.3)
Why can't you use a 6J5 or 6SN7 at 100 plate volts? They sound pretty good down there. You only need to swing, what, about 20 volts to drive the 6V6, no? Don't use a 6BX7, the input capacitance is too .......
253: Tube DIY Asylum, Re: Static-like noise when playing piano music (0.00)
Posted by groverg on 2004-03-10, 14:10:02 (141.156.33.252)
Piano recordings contain some pretty fierce transients. You might be experiencing clipping somewhere in the circuit. .......
254: Tube DIY Asylum, Re: What Are Bypass Caps? (0.00)
Posted by groverg on 2004-03-07, 17:30:44 (138.88.133.104)
Usually "bypass cap" refers to a capacitor which is placed in parallel with the resistor connected from a tube's cathode pin to ground. The cathode resistor provides a way of biasing a tube and settin .......
255: SET Asylum, Re: I Have The Response One SC (0.00)
Posted by groverg on 2004-02-25, 19:47:20 (138.88.132.95)
I couldn't really say. If you'd heard from others that this combination works well, then it's probably a safe bet. It certainly stands a better chance than a 300B amplifier, which I'm almost certain w .......
256: SET Asylum, Re: I Have The Response One SC (0.00)
Posted by groverg on 2004-02-25, 14:50:29 (138.88.132.95)
I have a fair amount experience with the One SC and IMHO it is not well suited for low-powered SET amplifiers. I have heard it perform beautifully with modest PP tube amps of 20-30 wpc. That doesn't m .......
257: SET Asylum, Don't worry, Jack... (0.00)
Posted by groverg on 2004-02-24, 21:25:49 (151.200.238.114)
...I didn't take it that way at all. As I say, I was glad to see some different experiences. It really is so system-dependent. .......
258: SET Asylum, Re: What do you think of the Sovtek 2A3 monoplate? <nt> (0.00)
Posted by groverg on 2004-02-24, 10:41:37 (151.200.238.114)
Oh, there's no doubt about it, Tom. Yes, they were in my pentode-driven 300B project. I think I was using a 6688 at the time. The amps were quite a hit at a local DIY meeting, but only after we switch .......
259: SET Asylum, Re: I totally disagree (0.00)
Posted by groverg on 2004-02-23, 14:32:57 (151.200.238.114)
The EH's are very rolled off in my system, the TJs rather bright, almost harsh. Depends on the OPT, circuit, cables, etc., I suppose. Glad you posted a different view, I'd rather my post wasn't taken .......
260: SET Asylum, Re: What do you think of the Sovtek 2A3 monoplate? <nt> (0.00)
Posted by groverg on 2004-02-23, 13:29:12 (151.200.238.114)
I found them kinda dull in my setup, but a lot of other people like them. OTOH, my EH 300Bs sounded nice at home and stank up the joint at a DIY meet on some horn speaks. Go figure. There's really no .......
261: SET Asylum, Re: Need opinions about sound differences between 45, 2A3, and 300B? (0.00)
Posted by groverg on 2004-02-23, 09:59:53 (138.88.44.80)
Very generally speaking, 2A3s are very warm and mid-rangey, with a slightly burry sound, at least in my experience. I think of them as "warm and fuzzy" and a lot of people like this. I'm talking about .......
262: SET Asylum, Re: Wavelength Gemini vs ASL & dehavilland 845 SETs (0.00)
Posted by groverg on 2004-02-22, 12:20:34 (138.88.44.80)
You're talking about two completely different designs and philosophies. The 845 requires a more complex circuit than the 45 as well as a more complicated power supply. Plus the ASLs, as excellent as t .......
263: SET Asylum, Re: Help neede with 805 tubes (0.00)
Posted by groverg on 2004-02-18, 09:31:53 (141.156.32.241)
How much current are you running through the 805s? Some transmitting tubes are designed to be run "in the red", so to speak, meaning red plates are normal, some are not. I'm not sure the 805 is a "red .......
264: Tube DIY Asylum, Re: Reliability of new Chinese Valve Art 845s? (0.00)
Posted by groverg on 2004-02-17, 20:05:01 (138.88.144.37)
I know two people using them, probably for a year or more now, no problems. .......
265: SET Asylum, Re: Tube rectified/regulated or solid state fro SET amps??? (0.00)
Posted by groverg on 2004-02-15, 12:35:04 (138.88.99.139)
While tube rectified supplies can do some nice things at lower voltages, I've found that at 1000VDC and up a tube-rectified supply can be unweildy to implement and all the more prone to sag and murky .......
266: Tube DIY Asylum, Re: Q for "SE Amp CAD" by TubeCAD.com users (0.00)
Posted by groverg on 2004-02-08, 09:20:24 (141.156.186.27)
No, it will only do tetrodes and pentodes in triode mode. .......
267: SET Asylum, Re: Did I just destoryed my 300B? (0.00)
Posted by groverg on 2004-02-03, 14:42:08 (138.88.14.230)
Everything is probably all right. You won't know unless you put them on a scope, but if the amp is working okay now and sounds okay, I would carry on. .......
268: Tube DIY Asylum, Re: SET VT52 amplifier; 12-14mV hum noise is too high? (0.00)
Posted by groverg on 2004-02-02, 16:55:34 (138.88.17.207)
Based on my experience, a 6.3 volt DHT with AC on the filaments is going to be too noisy, period. I assume what you're reading on the plate of the 6A3 is 100Hz rectified filament noise. You can get a .......
269: Tube DIY Asylum, Re: Distortion from Certain CD Tracks (0.00)
Posted by groverg on 2004-02-01, 06:29:25 (138.88.17.207)
Proprius is a small, independent label, probably using minimal recording techniques for high-quality sound. Choral works are notoriously difficult to record. It's entirely possible that there's some d .......
270: Tube DIY Asylum, Re: pentode vs triode 300B driver (0.00)
Posted by groverg on 2004-01-31, 12:20:03 (138.88.17.207)
Go to www.triodedick.com, click on "Projects" and look at the Caesar amplifier, or look at some of the other amps. I think this is what you want. .......
271: Tube DIY Asylum, Re: power transformer/rectifier tube options (0.00)
Posted by groverg on 2004-01-29, 11:10:26 (138.88.94.6)
You could use a 5U4 by placing a voltage-dropping resistor in series with the filament leads. BUT a 6CA4 draws 1 amp of filament current while a 5U4 draws 3 amps--quite a difference. It would probably .......
272: Tube DIY Asylum, Re: Opinions Needed About Harmon Kardon (0.00)
Posted by groverg on 2004-01-28, 11:33:42 (141.156.32.214)
A VERY good deal, IMHO. The preamp is very nice and modify-able, with a good phono stage, the tuner is nice enough and the amp is a classic, albeit one with both fans and detractors. *Provided* it's a .......
273: Tube DIY Asylum, Re: SE/PP Transformer Question (0.00)
Posted by groverg on 2004-01-26, 21:40:07 (141.156.32.214)
The primary of a PP output transformer essentially consists of two opposite windings. When you attached power tubes to the windings, the current from from the two tubes cancels out and there is no DC .......
274: Tube DIY Asylum, Re: Cathode Feedback (0.00)
Posted by groverg on 2004-01-26, 21:31:37 (141.156.32.214)
I'm interested that the amp cited above uses both cathode feedback and NFB. Did you try both? .......
275: Tube DIY Asylum, Re: KT90 SE UL update (0.00)
Posted by groverg on 2004-01-26, 19:31:02 (141.156.32.214)
Well, I'll have to do some listening to confirm this. It's certainly better than without the feedback connection (I think), and I'm not sure there's much difference between the cathode feedback and gl .......
276: Tube DIY Asylum, Re: KT90 SE UL update (0.00)
Posted by groverg on 2004-01-26, 18:03:20 (141.156.32.214)
I'm not sure what you mean--could you explain just a little further? .......
277: Tube DIY Asylum, Re: KT90 SE UL update (0.00)
Posted by groverg on 2004-01-26, 18:01:56 (141.156.32.214)
Thanks for the reference. Nice article and very relevant. I'll study it. .......
278: Tube DIY Asylum, Re: MagneQuest ??? (0.00)
Posted by groverg on 2004-01-26, 17:57:33 (141.156.32.214)
I think a lot of us have swapped or resold Magnequest iron over the years. Mike has always seemed happy to answer questions about his iron regardless of how one may have obtained it :-). .......
279: Tube DIY Asylum, KT90 SE UL update (0.00)
Posted by groverg on 2004-01-26, 13:40:13 (141.156.32.214)
The driver-to-screen-tap connection proved to be just marginally stable, even with a good deal of straightening out of the LF poles. Global feedback worked pretty well, about 4-5dB, and sounded pretty .......
280: Tube DIY Asylum, Re: MagneQuest ??? (0.00)
Posted by groverg on 2004-01-26, 13:09:57 (141.156.32.214)
I see. I'm sorry, I didn't read carefully enough. I guess you should email Mike LaFevre via the website and ask. If you're in a hurry :-) you could put an ohmmeter across each pair to find out which o .......
281: Tube DIY Asylum, Re: MagneQuest ??? (0.00)
Posted by groverg on 2004-01-26, 11:20:23 (141.156.32.214)
Go to www.magnequest.com, click on "Products" and look at the specs for the FS-030. You'll find the hook-up instructions there. .......
282: Tube DIY Asylum, Re: Tamura Output transformers opinions needed (0.00)
Posted by groverg on 2004-01-25, 11:57:01 (138.88.130.162)
It's no secret I'm a Magnequest user and really like the FS-100 with my 845s, but I helped a friend build an SE 845 with the Tamura F-2013 and it's a gorgeous piece of iron--transparent, open and deta .......
283: Tube DIY Asylum, Re: Meanwhile, back in Frankenstein's Lab........ (0.00)
Posted by groverg on 2004-01-24, 18:52:16 (138.88.136.199)
You have an output transformer on the 2A3 amp? If so, just use the primary as a choke load and cap couple to the 845 grid. Or just use a plate choke on the 2A3 in place of an OPT. .......
284: Tube DIY Asylum, Re: Single-ended KT90 UL design and question (0.00)
Posted by groverg on 2004-01-24, 06:14:47 (151.200.241.100)
I've thought about that, Alan, and you may be right. It could be just the thing. Another topology I'll have to try! .......
285: Tube DIY Asylum, Re: Single-ended KT90 UL design and question (0.00)
Posted by groverg on 2004-01-24, 06:14:47 (151.200.241.100)
I've thought about that, Alan, and you may be right. It could be just the thing. Another topology I'll have to try! .......
286: Tube DIY Asylum, Aaaargh. (0.00)
Posted by groverg on 2004-01-22, 21:15:55 (138.88.94.44)
Tried the choke decoupling. Seemed to be better. Then I played around with some bypass cap values. Turns out this thing is wildly sensitive to LF oscillation. Rats. I'm going to pow-wow with some deep .......
287: Tube DIY Asylum, Aaaargh. (0.00)
Posted by groverg on 2004-01-22, 21:15:55 (138.88.94.44)
Tried the choke decoupling. Seemed to be better. Then I played around with some bypass cap values. Turns out this thing is wildly sensitive to LF oscillation. Rats. I'm going to pow-wow with some deep .......
288: Tube DIY Asylum, Re: 6JS7GT vs. EF86? (0.00)
Posted by groverg on 2004-01-22, 21:05:11 (138.88.94.44)
I like the 6SJ7 better, and good ones are easier to come by. In fact I very much like the red-can RCA 5963. Less microphonic, more focused and smooth to my ears. .......
289: Tube DIY Asylum, Re: 6JS7GT vs. EF86? (0.00)
Posted by groverg on 2004-01-22, 21:05:11 (138.88.94.44)
I like the 6SJ7 better, and good ones are easier to come by. In fact I very much like the red-can RCA 5963. Less microphonic, more focused and smooth to my ears. .......
290: SET Asylum, Antique Sound Laboratory Limited 1006(845) Amplifier (Tube) (0.00)
Posted by groverg on 2004-01-22, 21:03:21 (138.88.94.44)
The aluminum chassis is an upgrade--I find aluminum contributes much less resonance than steel. And don't knock those Chinese 845s :-). They're pretty darn good. Try the Valve Arts, they're a bit of a .......
291: SET Asylum, Antique Sound Laboratory Limited 1006(845) Amplifier (Tube) (0.00)
Posted by groverg on 2004-01-22, 21:03:21 (138.88.94.44)
The aluminum chassis is an upgrade--I find aluminum contributes much less resonance than steel. And don't knock those Chinese 845s :-). They're pretty darn good. Try the Valve Arts, they're a bit of a .......
292: Tube DIY Asylum, Re: Tame that B+ (0.00)
Posted by groverg on 2004-01-22, 11:59:25 (138.88.2.42)
Wow, that's very high for a 760VCT tranny. What rectifier are you using? The extra capacitance shouldn't have that much effect, and I suspect you're maxing out the caps even after warm-up. Have you me .......
293: Tube DIY Asylum, Re: Tame that B+ (0.00)
Posted by groverg on 2004-01-22, 11:59:25 (138.88.2.42)
Wow, that's very high for a 760VCT tranny. What rectifier are you using? The extra capacitance shouldn't have that much effect, and I suspect you're maxing out the caps even after warm-up. Have you me .......
294: Tube DIY Asylum, Re: Sorry no answers but rather questions (0.00)
Posted by groverg on 2004-01-22, 11:54:25 (138.88.2.42)
The Tango U-808 is still available and can be used as an SE UL load. Hammond 1600 series have UL taps. I've heard ElectraPrint will add UL taps. And maybe Mikey will make another run of these UL DS-02 .......
295: Tube DIY Asylum, Re: Sorry no answers but rather questions (0.00)
Posted by groverg on 2004-01-22, 11:54:25 (138.88.2.42)
The Tango U-808 is still available and can be used as an SE UL load. Hammond 1600 series have UL taps. I've heard ElectraPrint will add UL taps. And maybe Mikey will make another run of these UL DS-02 .......
296: Tube DIY Asylum, Re: Is 845 definietly better than 211 (sonically) ? (0.00)
Posted by groverg on 2004-01-22, 11:12:52 (138.88.2.42)
Two totally different sounds, is all I can say. You'll find people who prefer one or the other. I like the 845 better myself but it's awfully hard to drive compared to the 211. I've found that the 211 .......
297: Tube DIY Asylum, Re: Is 845 definietly better than 211 (sonically) ? (0.00)
Posted by groverg on 2004-01-22, 11:12:52 (138.88.2.42)
Two totally different sounds, is all I can say. You'll find people who prefer one or the other. I like the 845 better myself but it's awfully hard to drive compared to the 211. I've found that the 211 .......
298: Tube DIY Asylum, Re: Single-ended KT90 UL design and question (0.00)
Posted by groverg on 2004-01-22, 11:08:36 (138.88.2.42)
Good point, Jim. I'll adjust the coupling caps. I looked at the amp last night and found that in fact I'm using 220uF after the choke. I'll adjust the schematic to reflect this. I'll add a more for th .......
299: Tube DIY Asylum, Re: Single-ended KT90 UL design and question (0.00)
Posted by groverg on 2004-01-22, 11:08:36 (138.88.2.42)
Good point, Jim. I'll adjust the coupling caps. I looked at the amp last night and found that in fact I'm using 220uF after the choke. I'll adjust the schematic to reflect this. I'll add a more for th .......
300: Tube DIY Asylum, Re: Single-ended KT90 UL design and question (0.00)
Posted by groverg on 2004-01-22, 11:05:52 (138.88.2.42)
The feedback is small. Amp sounded pretty good with a standard RC-coupling arrangement, but Douglas mentioned the screen-tap/driver stage thing, so I thought I'd try it and it just smoothed things out .......
301: Tube DIY Asylum, Re: Single-ended KT90 UL design and question (0.00)
Posted by groverg on 2004-01-22, 11:05:52 (138.88.2.42)
The feedback is small. Amp sounded pretty good with a standard RC-coupling arrangement, but Douglas mentioned the screen-tap/driver stage thing, so I thought I'd try it and it just smoothed things out .......
302: Tube DIY Asylum, Re: Single-ended KT90 UL design and question (0.00)
Posted by groverg on 2004-01-22, 11:02:09 (138.88.2.42)
Yes, I did try two stages. I have a very low-gain front end so I need a lot of gain in the amp. So I tried a pentode driver. But I have to say I like the naturalness and weighty sound of this triode c .......
303: Tube DIY Asylum, Re: Single-ended KT90 UL design and question (0.00)
Posted by groverg on 2004-01-22, 11:02:09 (138.88.2.42)
Yes, I did try two stages. I have a very low-gain front end so I need a lot of gain in the amp. So I tried a pentode driver. But I have to say I like the naturalness and weighty sound of this triode c .......
304: Tube DIY Asylum, Re: Ideas and a question (0.00)
Posted by groverg on 2004-01-22, 10:58:54 (138.88.2.42)
It occurred to me last night that remving the bypass would leave the LF at the input wide open, perhaps contributing to the problem. I might adjust the first stage bypass to form a reasonable cut off .......
305: Tube DIY Asylum, Re: Ideas and a question (0.00)
Posted by groverg on 2004-01-22, 10:58:54 (138.88.2.42)
It occurred to me last night that remving the bypass would leave the LF at the input wide open, perhaps contributing to the problem. I might adjust the first stage bypass to form a reasonable cut off .......
306: Tube DIY Asylum, Re: try this (0.00)
Posted by groverg on 2004-01-22, 10:55:53 (138.88.2.42)
That's two votes for choke decoupling of the first stage. Easy enough to do, I'll try it. It struck me last night that removing the first stage bypass would essentially eliminate any LF cutoff there a .......
307: Tube DIY Asylum, Re: try this (0.00)
Posted by groverg on 2004-01-22, 10:55:53 (138.88.2.42)
That's two votes for choke decoupling of the first stage. Easy enough to do, I'll try it. It struck me last night that removing the first stage bypass would essentially eliminate any LF cutoff there a .......
308: Tube DIY Asylum, Re: Sorry no answers but rather questions (0.00)
Posted by groverg on 2004-01-22, 10:51:25 (138.88.2.42)
Good question. They are Maqnequest DS-025s with UL taps which I bought from another DIYer ages ago. Maybe Mike can tell us what the screen taps are? .......
309: Tube DIY Asylum, Re: Sorry no answers but rather questions (0.00)
Posted by groverg on 2004-01-22, 10:51:25 (138.88.2.42)
Good question. They are Maqnequest DS-025s with UL taps which I bought from another DIYer ages ago. Maybe Mike can tell us what the screen taps are? .......
310: Tube DIY Asylum, Re: HALF of a 2A3 (0.00)
Posted by groverg on 2004-01-21, 22:16:33 (138.88.2.42)
The standard operating point of 275 Vp and 36mA comes to 9.9 watts, so one would assume it could handle 10 :-). .......
311: Tube DIY Asylum, Re: HALF of a 2A3 (0.00)
Posted by groverg on 2004-01-21, 22:16:33 (138.88.2.42)
The standard operating point of 275 Vp and 36mA comes to 9.9 watts, so one would assume it could handle 10 :-). .......
312: Tube DIY Asylum, Single-ended KT90 UL design and question (0.00)
Posted by groverg on 2004-01-21, 21:17:47 (138.88.2.42)
I've put up a schematic of something I've been working on. It's a single-ended, ultralinear KT90 design. I built it in stereo with a single supply because it sounds nice and doesn't waste tubes or tra .......
313: Tube DIY Asylum, Single-ended KT90 UL design and question (0.00)
Posted by groverg on 2004-01-21, 21:17:47 (138.88.2.42)
I've put up a schematic of something I've been working on. It's a single-ended, ultralinear KT90 design. I built it in stereo with a single supply because it sounds nice and doesn't waste tubes or tra .......
314: Tube DIY Asylum, Re: hum - as usual (0.00)
Posted by groverg on 2004-01-21, 16:24:20 (138.88.2.42)
This is completely natural. When you apply B+ and the tubes develop current, the hum should diminish considerably. The figures most people cite for hum on their SE amps is with the B+ applied. You're .......
315: Tube DIY Asylum, Re: hum - as usual (0.00)
Posted by groverg on 2004-01-21, 16:24:20 (138.88.2.42)
This is completely natural. When you apply B+ and the tubes develop current, the hum should diminish considerably. The figures most people cite for hum on their SE amps is with the B+ applied. You're .......
316: Tube DIY Asylum, Re: too hot? (0.00)
Posted by groverg on 2004-01-21, 13:28:07 (138.88.138.249)
Oh, I see. GE says 10 W. Anyway I agree that it's not worth what is probably a small benefit in sound, if any. .......
317: Tube DIY Asylum, Re: too hot? (0.00)
Posted by groverg on 2004-01-21, 13:28:07 (138.88.138.249)
Oh, I see. GE says 10 W. Anyway I agree that it's not worth what is probably a small benefit in sound, if any. .......
318: Tube DIY Asylum, Re: Output ripple (0.00)
Posted by groverg on 2004-01-21, 10:39:32 (138.88.138.249)
It might be because he's running the tube so low. Some time ago, while breadboarding some DHT output tubes, I used AC on the filaments and was rewarded with dead quiet! I thought I'd discovered the Ho .......
319: Tube DIY Asylum, Re: Output ripple (0.00)
Posted by groverg on 2004-01-21, 10:39:32 (138.88.138.249)
It might be because he's running the tube so low. Some time ago, while breadboarding some DHT output tubes, I used AC on the filaments and was rewarded with dead quiet! I thought I'd discovered the Ho .......
320: Tube DIY Asylum, Re: too hot? (0.00)
Posted by groverg on 2004-01-21, 10:27:22 (138.88.138.249)
How do you get 140%? 225 x .05 = 11.25, which would only be 12.5% over the 10 watt max for this tube. Am I calculating it wrong? Nonetheless it is higher than recommended. They'd probably take it with .......
321: Tube DIY Asylum, Re: too hot? (0.00)
Posted by groverg on 2004-01-21, 10:27:22 (138.88.138.249)
How do you get 140%? 225 x .05 = 11.25, which would only be 12.5% over the 10 watt max for this tube. Am I calculating it wrong? Nonetheless it is higher than recommended. They'd probably take it with .......
322: SET Asylum, Re: JE Labs simple 2a3 power supply (0.00)
Posted by groverg on 2004-01-17, 06:19:58 (138.88.42.232)
If you adjust the input capacitor to somewhere between 1 and 2 uF, the voltage can be kept lower than with the full capacitance indicated in the schematic. You will not get as much ripple reduction, h .......
323: Tube DIY Asylum, Re: Can somebody share a simple, but good sounding (to your ears is ok) PSE or PP 2A3 circuit (0.00)
Posted by groverg on 2004-01-16, 12:41:14 (138.88.42.232)
How about this? http://www.angela.com/catalog/how-to/JE_Labs/PP_2A3/ .......
324: Tube DIY Asylum, Re: Push pull can work great!!! (0.00)
Posted by groverg on 2004-01-13, 01:03:29 (138.88.42.246)
You don't have to convince me that 845s are great, and do everything you claim for them :-). I'm happy to hear you got them working in this PP arrangement. That should prove me wrong and encourage And .......
325: Tube DIY Asylum, Re: Says Who? (0.00)
Posted by groverg on 2004-01-13, 01:00:19 (138.88.42.246)
I agree with you, but current trends would appear to indicate otherwise. Judging by some recent threads, you're stated average is generous, to say the least. .......
326: Tube DIY Asylum, Re: Choice of Rectifier Diodes (0.00)
Posted by groverg on 2004-01-13, 00:56:51 (138.88.42.246)
Good point. I should have mentioned that I use them very conservatively, like 300 volts. I have used them in series with no problems. .......
327: Tube DIY Asylum, Re: How do I "load" my amps' speaker outputs? (0.00)
Posted by groverg on 2004-01-13, 00:54:44 (138.88.42.246)
Radio Shack sells an 8 ohm power resistor for just this sort of thing. .......
328: Tube DIY Asylum, Re: Choice of Rectifier Diodes (0.00)
Posted by groverg on 2004-01-12, 17:44:41 (141.156.170.141)
I use UF4007s these days for just about all my HV needs :-). After a few days of break-in I can't hear them. As for DC on the 211s, you almost have to. I don't know any way to get the hum quiet otherw .......
329: Tube DIY Asylum, Re: How robust is Hammond iron? (0.00)
Posted by groverg on 2004-01-12, 12:21:14 (141.156.170.141)
I agree with Chris in that "robust" is not a term I would apply to 200-series Hammonds :-(. But I believe you could use the filament tap in this case without running into trouble. I've found bigger pr .......
330: Tube DIY Asylum, Re: 845s at low voltage (300-400v) (0.00)
Posted by groverg on 2004-01-12, 12:18:38 (141.156.170.141)
I haven't done the curves, but for PP 845s at, say, 500VDC, Class A, you'd probably need 10K P-P. In AB1 maybe you could get away with 6.6K, which is a pretty standard offering, but I don't know how m .......
331: Tube DIY Asylum, Re: I ain't there quite yet..... (0.00)
Posted by groverg on 2004-01-12, 12:08:44 (141.156.170.141)
Vinnie, if you attend a symphony concert and then rush home and compare your system to what you just heard, you're asking for trouble :-). Having said that, I have a friend who attends concerts regula .......
332: Tube DIY Asylum, Re: PP advantages for a preamp. (0.00)
Posted by groverg on 2004-01-09, 10:54:46 (138.88.91.226)
I agree with Joel in terms of the distortion and cancellation advantages. If you want to read about Lynn Olsen's Raven PP preamp, go to http://www.nutshellhifi.com/triode1.html .......
333: Tube DIY Asylum, Jeff, you rejoined the party at the wrong time. (0.00)
Posted by groverg on 2004-01-08, 17:13:04 (151.200.246.7)
I'm reminded of a scene from a WWII comedy, in which a grizzled traffic cop is trying to order some new recruits out of the middle of the street. They won't budge and he begins to berate them for diso .......
334: Tube DIY Asylum, Re: There you go exposing me! (0.00)
Posted by groverg on 2004-01-08, 16:38:49 (151.200.246.7)
The nominal gain of an EL34 triode-strapped is 11. .......
335: Tube DIY Asylum, Re: Is there a site that I can learn to read Schematics? (0.00)
Posted by groverg on 2004-01-04, 08:47:07 (141.156.163.183)
Go to Google and type in "how to read a schematic" and you will find numerous brief primers that can get you started. .......
336: Tube DIY Asylum, Re: You've read my mind (0.00)
Posted by groverg on 2004-01-02, 19:41:36 (138.88.96.32)
I think I heard about the 300B and grid current from something Gordon Rankin posted a while back--it may be that you can run the 300B in A2 but Gordon was quite adament about not doing so, and based o .......
337: Tube DIY Asylum, Correction (0.00)
Posted by groverg on 2004-01-02, 14:27:17 (138.88.96.32)
I misspoke toward the end of my post. Power output can depend on the bias arrangement used, but that was not my point. .......
338: Tube DIY Asylum, Re: It is an amazing article but...... (0.00)
Posted by groverg on 2004-01-02, 14:21:36 (138.88.96.32)
Okay. First of all I can't seem to download the circuit you pointed to so I can't really comment. I know there are SE designs that use a combination of self- and fixed bias but the reasons for this ar .......
339: Tube DIY Asylum, Re: Does self-bias SE give better clipping charateristic ??? (0.00)
Posted by groverg on 2004-01-01, 14:36:53 (138.88.96.32)
Go to https://secure32.softcomca.com/southernelectricaudio_com/library.html and read Herbert Ravenswood's article, "The Fixed Bias Story". Generally speaking, a self-biasing SE amplifier will exhibit .......
340: SET Asylum, Re: Western Electric 91A copy (0.00)
Posted by groverg on 2003-12-31, 10:55:07 (138.88.144.119)
The original WE91 was used to amplify very low-level signals from movie projectors, which required two pentode gain stages. For modern line level signals like CD players, a single 310A or 6SJ7 is suff .......
341: Tube DIY Asylum, Re: Tell me more. (0.00)
Posted by groverg on 2003-12-30, 20:29:14 (138.88.144.119)
I think Dave answered your question better than I put it :-). .......
342: Tube DIY Asylum, Re: Here's where I may be confused: (0.00)
Posted by groverg on 2003-12-30, 20:26:06 (138.88.144.119)
1. You're teaching me something! 2. I think that's correct. 3. I think others can give you better advice on a CF output stage than I could. Interesting topic, I'm glad you posted about it. ::: TOPIC:: .......
343: Tube DIY Asylum, Re: EF86 linestage - initial listen - CF ideas? (0.00)
Posted by groverg on 2003-12-30, 19:19:15 (138.88.144.119)
Have you tried unbypassing the cathode resistor? Why not try the feedback? Wrap a few dB around it, you should only need a touch to reduce the gain. You might like it :-). .......
344: Tube DIY Asylum, Re: DC-coupled 6H30Pi might work too, and for fewer mA? (0.00)
Posted by groverg on 2003-12-30, 19:12:19 (138.88.144.119)
Just watch your voltage-output capabilities on the second stage. Even with a choke load, you want to give it enough room to operate comfortably. .......
345: Tube DIY Asylum, Oh, wait... (0.00)
Posted by groverg on 2003-12-30, 19:09:32 (138.88.144.119)
I just noticed you're doing a cathode-follower output stage. Wow, that'll need a lot of drive voltage. I'm not familiar enough with this topology to really comment. I will say that you could just as e .......
346: Tube DIY Asylum, Re: Hmm... Thanks. Maybe 6EM7 as input/driver? (0.00)
Posted by groverg on 2003-12-30, 18:57:06 (138.88.144.119)
I was going to mention the 6EM7 as an alternative, without having to swap out the original socket. .......
347: Tube DIY Asylum, Re: 8W 6AS7 CF - Check my work? (0.00)
Posted by groverg on 2003-12-30, 17:44:12 (138.88.144.119)
Looks fine to me, but that second 6SN7 is running at about 3 mA. I think you're going to notice an appreciable loss of high frequency information due to the extremely high input capacitance if the 6AS .......
348: Tube DIY Asylum, Thanks! nt (0.00)
Posted by groverg on 2003-12-22, 18:16:21 (138.88.154.132)
. .......
349: Tube DIY Asylum, Question to others... (0.00)
Posted by groverg on 2003-12-19, 18:51:30 (151.200.246.40)
How did the "damping factor" controls on some old amps work? Like the Fisher "Z-matic"... .......
350: Tube DIY Asylum, Re: SE amp cad and I are not agreeing .... (0.00)
Posted by groverg on 2003-12-15, 19:51:52 (138.88.34.61)
The instructions are pretty sparse and I don't know of anywhere to find more. Vin would be determined by the voltage output of the previous stage. Vin is there to tell you if you are over- or under-dr .......
351: Tube DIY Asylum, Re: SE amp cad and I are not agreeing .... (0.00)
Posted by groverg on 2003-12-14, 18:31:30 (141.156.216.47)
I don't think SE Cad will allow you to model direct-coupled circuits. The "input voltage" is the AC signal voltage seen by the grid. I don't think there's any way to specify a reference voltage for th .......
352: Tube DIY Asylum, Re: Resistor value for triode connected EF86-EF804 (0.00)
Posted by groverg on 2003-12-14, 13:37:50 (141.156.216.47)
I don't think you need a resistor. At least, I've never used them in small-signal applications like this. .......
353: Tube DIY Asylum, Re: Here's an idea for a really cheap 811A A2 design (0.00)
Posted by groverg on 2003-12-14, 03:08:54 (141.156.216.47)
Jim, see Bob Danielak's A2 design. .......
354: SET Asylum, Re: Anyone explain auto-bias to me? (0.00)
Posted by groverg on 2003-12-14, 03:02:03 (141.156.216.47)
There are three elements to a power triode--the plate, the grid, and the cathode. The cathode glows in the center of the tube and emits electrons. The grid is a finely wound wire between the cathode a .......
355: Tube DIY Asylum, Re: Specs (0.00)
Posted by groverg on 2003-12-12, 18:20:21 (138.88.10.76)
Hey, dude, you've heard the MQ DS-025, at the last DIY meet we all attended at Dave's. It was on my pentode-driven 300B amp. .......
356: Tube DIY Asylum, Re: mythology from the mouth of babes... (0.00)
Posted by groverg on 2003-12-10, 15:59:03 (141.156.222.223)
Well, I was just asking, there's no need to be rude. Your post wasn't specific enough for me to tell exactly what you were saying. If microphonics have an audible effect, isn't it possible that some p .......
357: Tube DIY Asylum, Re: mythology from the mouth of babes... (0.00)
Posted by groverg on 2003-12-10, 13:23:48 (141.156.222.223)
You don't think microphonics have any effect on the sound of a tube amplifier? .......
358: Tube DIY Asylum, Re: Real RCA's?? (0.00)
Posted by groverg on 2003-12-07, 05:40:09 (138.88.17.114)
RCA 5U4gs are not that rare, so far as I know. There wouldn't be much point in substituting Chinese or Soviet models. I have a lot of these and they look like the real thing to me. .......
359: SET Asylum, Re: Voices- females -BIllie the absolute best! (0.00)
Posted by groverg on 2003-12-06, 07:28:11 (138.88.147.129)
You've reminded me of another favorite of mine: Dinah Washington "Dinah Jams", Mercury/Verve CD .......
360: SET Asylum, You didn't include Liza Minelli so you're okay (nt) (0.00)
Posted by groverg on 2003-12-05, 23:39:43 (138.88.147.129)
. .......
361: SET Asylum, Re: Voices (0.00)
Posted by groverg on 2003-12-02, 21:06:35 (138.88.43.170)
Oh yes, Blossom Dearie is lovely through SETs--the song njjohn refers to can be heard on "Once Upon a Summerime" from Verve, one of my favorite of her many albums--every number is a surprise and a tre .......
362: Tube DIY Asylum, Re: Inquiring Minds want to Know! (0.00)
Posted by groverg on 2003-11-26, 21:00:14 (138.88.154.105)
Oh, you'll hear them. If you don't, you might want to look into the rest of your system :-). Remember, though, that you're not only hearing changes in the operating point of the tube itself, but also .......
363: Tube DIY Asylum, Re: Another tranny question, y'all (0.00)
Posted by groverg on 2003-11-26, 17:50:24 (138.88.154.105)
The RCA data sheet. .......
364: Tube DIY Asylum, Re: Well, you've lost me then.... (0.00)
Posted by groverg on 2003-11-26, 14:24:44 (138.88.154.105)
You're right, I confused myself :-). .......
365: Tube DIY Asylum, Re: Another tranny question, y'all (0.00)
Posted by groverg on 2003-11-26, 14:22:18 (138.88.154.105)
By my math 3 x Ra for an 845 is 5100. But you have to look at the curves and load lines, too, particularly with a tube like the 845 which can operate over a wide range of voltages and currents. If you .......
366: Tube DIY Asylum, No. (nt) (0.00)
Posted by groverg on 2003-11-24, 20:45:13 (141.156.222.167)
. .......
367: Tube DIY Asylum, Re: How much hum could an 845 hum if an 845 could hum, hum? (0.00)
Posted by groverg on 2003-11-24, 15:41:08 (141.156.161.172)
Your best bet is to use a 20VCT tranny and tie the cathode resistor to the CT. Then you get cancellation from the windings. Thta's the only way I've gotten AC quiet enough to tolerate with the 845. A .......
368: SET Asylum, Re: Trying to find 1000uf 350-500v lytics (0.00)
Posted by groverg on 2003-11-24, 12:21:38 (141.156.161.172)
You need surplus computer-grade electrolytics. Try www.fairradio.com, www.surplussales.com, www.goldmine-elec.com, www.alltronics.com, or do a web search for other surplus capacitor dealers. For examp .......
369: Tube DIY Asylum, Re: power transformer (0.00)
Posted by groverg on 2003-11-23, 20:45:45 (141.156.187.251)
This is an extremely well-made tranny. I would add that the filament taps are resistive, so you never get over-voltage. .......
370: Tube DIY Asylum, Re: 10Y PP OPT (0.00)
Posted by groverg on 2003-11-21, 19:01:02 (141.156.187.251)
You really need 15K plate-to-plate. Very hard to find. You could use an 8K p-p tranny, such as those designed for el84s, and hook an 8 ohm load to the 4 ohm tap to reflect a higher impedance back to t .......
371: SET Asylum, Re: Ok I was right about the type of tube but now I'm really confused. (0.00)
Posted by groverg on 2003-11-15, 06:58:34 (138.88.41.37)
Same old mystery again. eh? Well, I'm willing to take another shot at it. What preamp are you using? .......
372: Tube DIY Asylum, Re: Punching holes in Aluminium chassis. (0.00)
Posted by groverg on 2003-11-14, 12:52:42 (138.88.94.171)
Do an eBay search for "greenlee" and you will find individual punches and sets for reasonable prices. Note that the "SlugBuster" sets are for conduits and are larger than the standard "Knockout" sets. .......
373: Tube DIY Asylum, Re: 10K:16 ohm VS 5K:8 ohm OPT difference? (0.00)
Posted by groverg on 2003-11-14, 12:43:33 (138.88.94.171)
There was a long and rather contentious thread about this some time ago, but I believe that if you use only half the primary without loading the other half, the tube will only see 1/4 of the full prim .......
374: SET Asylum, Re: What does a 6V6 sound like ? (0.00)
Posted by groverg on 2003-11-10, 17:15:34 (138.88.151.44)
Well I suppose it's silly to try to generalize, but I'll take a stab at it :-). I've always found the 6V6 to have a very sweet, clean sound, a little on the thin side, not a lot of weight on the botto .......
375: SET Asylum, Re: Triodes sounding sharp (0.00)
Posted by groverg on 2003-11-08, 07:11:01 (138.88.151.44)
Are you trying all these tubes in the same position? If you are, the 6189 is a 12AU7 substitute while the other two are 12AX7s. If the circuit is designed for 12AX7s then the 6189 may not be operating .......
376: SET Asylum, Re: The wiper of the pot may not be clean or something in the path <nt> (0.00)
Posted by groverg on 2003-11-07, 12:07:09 (141.156.214.193)
If it becomes a recurring issues, you can replace each pot with a pair of 50-100 ohm resistors, say 3 watts. This will accomplish the same thing as the pot without the possibility of loss of contact. .......
377: SET Asylum, Re: It has to do with using DC on the hum pots (0.00)
Posted by groverg on 2003-11-07, 12:04:19 (141.156.214.193)
But even with DC filaments, a hum pot can be an effective way to bridge the positive and negative legs, thus reducing the difference in potential between the two end of the filaments. All the same, if .......
378: SET Asylum, Re: Can anyone explain this? (0.00)
Posted by groverg on 2003-11-04, 12:26:16 (138.88.151.86)
Oh, I remember now, sorry to make you repeat it. I can only think of two things, first that the treated tubes aren't working right in the circuit, even if they do test well, but the only way to tell w .......
379: SET Asylum, Oh, and... (0.00)
Posted by groverg on 2003-11-04, 02:56:11 (138.88.136.133)
You don't have to be a techie to post in this forum :-). Your question is a tough one, and I think the answer probably lies in a number of small variables, not one big problem. .......
380: SET Asylum, Re: Can anyone explain this? (0.00)
Posted by groverg on 2003-11-04, 02:54:43 (138.88.136.133)
What speakers are you using with the Wavacs? What's curious to me, especially considering keto's response, is that this is a three-stage amplifier, so not much is demanded of the 12AT7 in terms of out .......
381: Tube DIY Asylum, Re: beautiful curves... (0.00)
Posted by groverg on 2003-11-03, 13:11:05 (138.88.136.133)
This is a nice little tube, very similar to the 6N7 but a little drier and crisper in presentation. You can get them dirt cheap. Run the two halves in parallel and it makes a nice input stage with rea .......
382: SET Asylum, Re: Is a 6336A a good canidate for a SE amp? (0.00)
Posted by groverg on 2003-11-02, 19:03:01 (138.88.136.133)
There was a recent thread in the DIY asylum about the 6336. I've done an SE design which I like very much, and Paul Searce has an even simpler one that looks great. But I doubt you'll get more than 8 .......
383: SET Asylum, Re: Thanks for the help. (0.00)
Posted by groverg on 2003-11-01, 20:52:01 (138.88.136.133)
Oh good! Since it's a three-stage design, you aren't asking much from the 12AT7 to drive the second stage, so I figured one of the 12AT7s had to be underperforming in a big way. Glad you're getting re .......
384: Tube DIY Asylum, Re: Monoblocks vs. stereo amplifiers (0.00)
Posted by groverg on 2003-11-01, 18:02:44 (138.88.136.133)
Wisdom has it that a monoblock for each channel will give you better stereo separation and isolation, better power and generally a more muscular sound. Having said that, there are a lot of beautiful-s .......
385: SET Asylum, Re: Help please for an old audiophile who knows little about tubes. (0.00)
Posted by groverg on 2003-10-31, 15:29:38 (138.88.136.133)
The only thing I can think of is that, though they may sound better, something about the cryo treatment damaged the tubes and they are not operating properly in the circuit, causing distortion. Do you .......
386: Tube DIY Asylum, 2E22 (nt) (0.00)
Posted by groverg on 2003-10-31, 11:43:40 (138.88.136.133)
. .......
387: SET Asylum, ...or just pathologically insecure. (0.00)
Posted by groverg on 2003-10-29, 17:14:36 (138.88.136.133)
. .......
388: Tube DIY Asylum, Huh? (0.00)
Posted by groverg on 2003-10-27, 17:38:15 (141.156.179.179)
The WE91B uses a 390K resistor on the 300B grids. Unless the amp is fixed bias, 270K should be perfectly stable. .......
389: Tube DIY Asylum, Re: What do you think the sonic difference between SE and PP ? (0.00)
Posted by groverg on 2003-10-27, 11:25:05 (141.156.179.179)
The better PP amps I've heard to date use a differential phase splitter, and I've always gotten better results myself from this topology. I haven't heard Lynn Olsen's Amity project, though the theory .......
390: SET Asylum, Re: Baltimore places of interest in SET (0.00)
Posted by groverg on 2003-10-27, 05:52:49 (141.156.179.179)
There may be some local meetings of DIY groups around that time--DCAUDIODIY just had theirs, but you might check the Bottlehead forum asnd see when they are planning a meet, it would be enlightening, .......
391: Tube DIY Asylum, Re: What do you think the sonic difference between SE and PP ? (0.00)
Posted by groverg on 2003-10-26, 17:18:35 (138.88.126.71)
It's relatively easy to build a good-sounding SE amplifier. Because of the nature of SE, there's a natural coherence and stability to the soundstage, and while an SE circuit may add harmonic coloratio .......
392: Tube DIY Asylum, Re: I can answer that! (0.00)
Posted by groverg on 2003-10-24, 20:06:18 (138.88.126.71)
Sure, people do it all the time. The point is, the further upstream you can separate the power chains, the less effect one channel's current demands will have on the other. .......
393: Tube DIY Asylum, Hey Paul... (0.00)
Posted by groverg on 2003-10-24, 12:24:17 (138.88.126.71)
Interesting. Looking at the spec sheet for the 6336, it appears that the Rp shoots up to 600 ohms, in your case, and about 800 at my operating point. Gm also drops dramatically. So the loads we use ma .......
394: Tube DIY Asylum, Re: "Baby 845" amp (0.00)
Posted by groverg on 2003-10-24, 12:13:07 (138.88.126.71)
No, nor are 6336s to my knowledge, but there are a lot of NOS out there. They come and go in spates on eBay. .......
395: Tube DIY Asylum, Re: I can answer that! (0.00)
Posted by groverg on 2003-10-24, 12:12:11 (138.88.126.71)
Er, well, use two rectifiers powered from the same plate transformer. Gives you as close to a monoblock PS withoyt the extra weight and space, I guess. .......
396: Tube DIY Asylum, Re: I use either a 55 or a 76 with a 6J5 follower and . . (0.00)
Posted by groverg on 2003-10-24, 12:09:16 (138.88.126.71)
Well, Allen makes excellent points in his post and he is far more learned than I on these matters, but I can't imagine needing a grid-stopper on a 76, unless you have serious local RF problems, like a .......
397: Tube DIY Asylum, Re: How do you determine that a grid stopper is needed?? . . (0.00)
Posted by groverg on 2003-10-24, 12:07:20 (138.88.126.71)
Search around online. There are several tutorials out there. .......
398: Tube DIY Asylum, So what are playing CDs with, a nail and a tin can? (0.00)
Posted by groverg on 2003-10-23, 19:59:48 (141.156.183.25)
. .......
399: Tube DIY Asylum, Re: I can answer that! (0.00)
Posted by groverg on 2003-10-23, 19:22:53 (141.156.183.25)
After the rectifier, or before if you want :-) .......
400: SET Asylum, Re: Baltimore places of interest in SET (0.00)
Posted by groverg on 2003-10-23, 18:04:24 (141.156.183.25)
When are you planning to visit? .......
401: Tube DIY Asylum, Re: I can answer that! (0.00)
Posted by groverg on 2003-10-23, 16:22:01 (141.156.183.25)
Doug, I think those were 6528s, with a gritty power supply and sub-optimal driver. I hesitated, thinking of that last attempt. But this sounds much sweeter. .......
402: Tube DIY Asylum, Re: I can answer that! (0.00)
Posted by groverg on 2003-10-23, 16:20:01 (141.156.183.25)
Probably not. Why use twice the tubes (like mine)? You could split the power supply to each channel, though. .......
403: Tube DIY Asylum, I'm a good person and people like me! :-) nt (0.00)
Posted by groverg on 2003-10-23, 15:00:08 (141.156.183.25)
. .......
404: Tube DIY Asylum, I can answer that! (0.00)
Posted by groverg on 2003-10-23, 14:58:05 (141.156.183.25)
It's stereo, Vinnie. Each channel uses half a 12AX7, half a 5687 and half a 6336. Very cool, Paul! .......
405: Tube DIY Asylum, Re: "Baby 845" amp (0.00)
Posted by groverg on 2003-10-23, 11:31:07 (141.156.183.25)
The 6528 is very nice and requires a lot less drive. A friend of mine has a little commercial SE amp he sells that runs the 6528 at about 380VDC/60mA into 2.5K with fixed bias, in a circuit somewhat s .......
406: Tube DIY Asylum, Re: "Baby 845" amp (0.00)
Posted by groverg on 2003-10-23, 11:27:40 (141.156.183.25)
Hey, that's nice, Paul. Gives me some ideas :-). I used two gain stages because I have a low-output front end. How long have you been running them now? Any problems with failure or red plates? What 63 .......
407: Tube DIY Asylum, Re: How do you determine that a grid stopper is needed?? . . (0.00)
Posted by groverg on 2003-10-23, 11:22:36 (141.156.183.25)
In the case of HF oscillation, my understanding is that though it may not be audible, it can stress the circuit and components. Only a 'scope will show you the problem. With most low-to-medium gm tube .......
408: Tube DIY Asylum, Re: "Baby 845" amp (0.00)
Posted by groverg on 2003-10-22, 20:12:27 (141.156.183.25)
I should mention it's probably only 6-8 watts, with a tailwind :-). But it drives my ProAc 2 speaks as loud as I like it. .......
409: Tube DIY Asylum, "Baby 845" amp (0.00)
Posted by groverg on 2003-10-22, 19:55:22 (141.156.183.25)
I've been putting off rebuilding my 845 amps, so in the meantime I thought I'd breadboard a 300B amp to tide me over. Eh. Then I tried some old graphite-plate Valve Art 5300Bs and liked it better. The .......
410: Tube DIY Asylum, Re: Inrush Limiter (0.00)
Posted by groverg on 2003-10-21, 10:55:58 (141.156.222.155)
First, you don't want the bias voltage to slow-start, and you don't need to worry as the current draw is minimal,as I said, maybe a couple mA. The bias supply should be tied to the filaments, so it go .......
411: Tube DIY Asylum, Re: Inrush Limiter (0.00)
Posted by groverg on 2003-10-20, 20:26:38 (138.88.17.52)
Brian, is this for the 845 project? If so, why do you feel you need an inrush limiter? The bias circuit draws very little, if any, current and is immediately stabilized by the resistance to ground any .......
412: Tube DIY Asylum, Re: Safe to try 5751 in SoundValve pre (line stage)? (0.00)
Posted by groverg on 2003-10-20, 16:47:29 (138.88.17.52)
They're safe to substitute but I don't think they'll reduce the gain that much. Third step is too loud? You've got a real mismatch. What amp are you using? It might ber easier to modify the amp... ::: .......
413: Tubes Asylum, Curcio Dynaco Schematic? (0.00)
Posted by groverg on 2003-10-15, 12:58:34 (138.88.150.212)
Does anyone have a schematic for the Curcio Dynaco board? A friend of mine is trying to fix one. Perhaps an owner has a schematic he could mail or email me? TIA. .......
414: Tube DIY Asylum, Dyna Curcio Schematic? (0.00)
Posted by groverg on 2003-10-15, 12:57:17 (138.88.150.212)
Does anyone have a schematic for the Curcio Dynaco board? A friend of mine is trying to fix one. Perhaps an owner has a schematic he could mail or email me? TIA. .......
415: SET Asylum, Re: HELP! I am in middle of the roads between Classic, Ultrapath and Parafeed and really (0.00)
Posted by groverg on 2003-10-15, 04:48:21 (138.88.150.212)
How much power do you want? What kind of speakers do you plan to drive? Are you going to use a preamp or do you want an "integrated" design with full gain? I'd start by banishing from your mind the t .......
416: Tube DIY Asylum, Re: Look at "exubri"s bidding behavior.......... (0.00)
Posted by groverg on 2003-10-13, 14:07:34 (138.88.150.212)
Kinda cute that the most recent items he has up for auction are being bid by "private" bidders. And love those responses to negative feedback--"BIDDER UNREASONABLE!" and "Even winders need a break!" : .......
417: Tube DIY Asylum, Re: Given those figures (0.00)
Posted by groverg on 2003-10-12, 20:52:03 (138.88.150.212)
Well, 7316s are on another level, IMHO. If I had to use a 12AU7 I would use the 7316. A much cleaner-sounding tube. .......
418: Tube DIY Asylum, Re: Given those figures (0.00)
Posted by groverg on 2003-10-12, 07:36:39 (141.156.168.89)
That doesn't necessarily follow. I've always found that the 12AU7 has an overly "warm" signature to my ears, which may be accounted for in some measure by the higher distortion figures. Certainly the .......
419: Tube DIY Asylum, Re: I would expect my caps (0.00)
Posted by groverg on 2003-10-10, 15:28:49 (141.156.168.89)
"...the best sounding parts are more fragile by their very nature..." I'm sorry, but that's a ridiculous thing to say. I have a great many NOS, mil-spec paper in oil caps made 50 years ago that have n .......
420: Tube DIY Asylum, Re: Tranny update 2 - Grover (0.00)
Posted by groverg on 2003-10-09, 20:30:04 (141.156.168.89)
Well, I guess it means you have a tranny with some 6+ volt secondaries and, what was it, 245? Sounds like maybe a voltage conversion tranny or something. .......
421: Tube DIY Asylum, Re: GroverG, what do you make of this? (0.00)
Posted by groverg on 2003-10-09, 11:29:57 (141.156.168.89)
Yup. Now wire the primaries in parallel, apply AC and measure what you get on the secondary pairs. .......
422: Tube DIY Asylum, Re: GroverG, what do you make of this? (0.00)
Posted by groverg on 2003-10-08, 11:48:36 (141.156.168.89)
Okay, wait a minute. Are you saying that all pins except 1,2,3,4,11 and 12 show continuity with each other? What we need to know is what of pins show continuity with which other pins... .......
423: Tube DIY Asylum, Re: GroverG, what do you make of this? (0.00)
Posted by groverg on 2003-10-07, 20:27:04 (151.200.237.98)
First, I think the primaries are separate windings, to be connected either in parallel for 120 or in series for 240, so that would explain that. Next, they all seem to be in pairs--no sets of three or .......
424: Tube DIY Asylum, Re: Coupling cap conundrum (0.00)
Posted by groverg on 2003-10-07, 01:21:57 (138.88.159.65)
You need to parallel them to double the value. If you put them in series the values are halved. .......
425: Tube DIY Asylum, Re: Tranny Question (0.00)
Posted by groverg on 2003-10-05, 15:37:54 (138.88.159.65)
Disconnect all AC, take a multimeter set to 2K ohms and measure from one pin to another. Mark what pins show continuity with each other and what the resistances are and we can go from there. Figure yo .......
426: Tube DIY Asylum, Re: Output tranny: 325/40ma What tube? (0.00)
Posted by groverg on 2003-10-03, 12:02:47 (138.88.159.65)
How about a direct-coupled 45 SET? .......
427: Tube DIY Asylum, Re: Possible Problem found! (0.00)
Posted by groverg on 2003-09-29, 20:55:27 (138.88.159.65)
If you have some DC offset between the circuit ground and the chassis, yes, this would certainly cause problems. It would effectively add some positive bias to the grids, for starters. Let us know if .......
428: Tube DIY Asylum, Re: Also... update! (0.00)
Posted by groverg on 2003-09-29, 16:53:31 (138.88.159.65)
Triode Kingdom is dead on, if you don't have a grid resistor on G2 then do so, it will stabilize that tube. Yes, 12AX7s are used in preamps--with a ton of feedback which reduces the gain significantly .......
429: Tube DIY Asylum, Re: Also... (0.00)
Posted by groverg on 2003-09-27, 20:11:08 (138.88.159.65)
Well, with the pot possibly miswired and turned all the way in one direction, you're opening the pot all the way to 50K and allowing the tube to work properly. As for the seond stage, have you tried s .......
430: Tube DIY Asylum, Re: Power ratings only (0.00)
Posted by groverg on 2003-09-27, 05:36:25 (141.156.215.94)
If MusicCD can measure the resistance of the primaries they should match the HF22 schematic and that will tell him how the connections go. I used these in a recent project but I took it apart and can' .......
431: Tube DIY Asylum, Also... (0.00)
Posted by groverg on 2003-09-27, 05:31:37 (141.156.215.94)
What kind of pot are you using? Is it a linear pot or a log pot? Sounds like it's connected incorrectly, for starters. The center lug should not be grounded. It sounds as though you've got the pot wir .......
432: Tube DIY Asylum, Re: 6N1P linestage problem found, but... (0.00)
Posted by groverg on 2003-09-27, 05:27:56 (141.156.215.94)
Well, wait a minute. You're using a cascade, that is, two sections of the tube in series? Is it a direct-coupled scheme? Are you using a plate-follower direct-coupled to a cathode follower stage? Do y .......
433: SET Asylum, Re: Link to your 845 homepage? (0.00)
Posted by groverg on 2003-09-25, 12:22:06 (141.156.215.94)
I've posted a fresh copy of the schematic here. .......
434: SET Asylum, Gee... (0.00)
Posted by groverg on 2003-09-24, 21:07:22 (141.156.33.63)
Thanks for the kind words, Roger and Larry. To answer the original question, I'm afraid I haven't heard any commercial 845 amps lately. I'd certainly like to, if only to get a sense of what kind of so .......
435: SET Asylum, Re: 845 vs 300b vs... (0.00)
Posted by groverg on 2003-09-24, 21:02:06 (141.156.33.63)
I heard the 805s years ago, I don't know if they were running 845s or 211s at that point. I certainly didn't care for the sound--dark and thick, with a sort of one-note quality. I don't know what was .......
436: SET Asylum, Re: 845 vs 300b vs... (0.00)
Posted by groverg on 2003-09-24, 11:58:55 (141.156.178.159)
VERRRRRY generally speaking, IMHO, the 300B/2A3 have the classic mid-range magic, the amazing "you-are-there-ness" that draws people to SET. The 45 is cooler and more even-handed but equally if not mo .......
437: Tube DIY Asylum, Re: done some homework (0.00)
Posted by groverg on 2003-09-20, 09:01:49 (141.156.177.184)
Sounds like a choke-input supply. You might try a hefty bleeder after the second choke to pull the voltage down so myou can troubleshoot the rest of the circuit. Two 25K/25W ceramic resistors in serie .......
438: SET Asylum, Re: Very few homebrews have voltage regulators.. (0.00)
Posted by groverg on 2003-09-20, 06:54:03 (141.156.214.170)
The best line conditioners I have heard yet are the Tice. They work nicely with SET amps and actually improve the sound as opposed to muckingm it up. .......
439: Tube DIY Asylum, Mad Dogs and Maffias (0.00)
Posted by groverg on 2003-09-18, 12:37:14 (138.88.143.83)
Crawl back under your rock, Jute. Your creative writing exercises are wasting bandwidth in a worthy forum. .......
440: Tube DIY Asylum, I think you're onto something nt (0.00)
Posted by groverg on 2003-09-16, 13:38:04 (138.88.134.97)
. .......
441: Tube DIY Asylum, Re: TJ 45 update (0.00)
Posted by groverg on 2003-09-12, 11:38:59 (141.156.162.221)
The mesh plates have a perforated plate that is somewhat transparent--you can see the filaments clearly when they are lit. Originally mesh plate tubes like the 27 or 50 or some others had true mesh, o .......
442: SET Asylum, Re: What's your problem? More rambling 45 thoughts (0.00)
Posted by groverg on 2003-09-12, 11:31:46 (141.156.162.221)
Could it also have something to do with the box plate structure? I find the 45, 71A, 50 and 10Y all share something of that cool, neutral, detailed sound, though in different measures. Never heard a s .......
443: Tube DIY Asylum, Re: 6B4G Schematic (0.00)
Posted by groverg on 2003-09-12, 01:11:44 (151.200.237.184)
You're a better man than I!! I'm long on experimentation and short on theory :-). I'd love to hear how it goes. .......
444: Tube DIY Asylum, Re: 6B4G Schematic (0.00)
Posted by groverg on 2003-09-11, 21:37:36 (151.200.237.184)
I don't know :-). I've worked off other designs and then tweaked the percentage based on listening. So I guess I spoke a little out of turn! But if you can find a design that is similar, like an Eico .......
445: SET Asylum, Re: "You're right, I've NEVER heard any 45s and I can't tell the difference between a 45 and mud hen" (0.00)
Posted by groverg on 2003-09-11, 20:06:22 (151.200.237.184)
Get off your high horse, Robert, the lack of oxygen up there is affecting your brain. I've experimented with a sizeable number of tube topologies over the past ten years. I've heard the 45 on many occ .......
446: SET Asylum, Oh thank you, Harold... (0.00)
Posted by groverg on 2003-09-11, 14:48:06 (151.200.237.184)
...for condescending to keep it simple. You're right, I've NEVER heard any 45s and I can't tell the difference between a 45 and mud hen. And unlike other DIYers I NEVER get discouraged about diminishi .......
447: Tube DIY Asylum, Re: 6B4G Schematic (0.00)
Posted by groverg on 2003-09-11, 12:17:22 (151.200.237.184)
I'd go with cathode bias, I just think it sounds better on 6B4Gs and it's a lot less work. Sure, use damper diodes as rectifiers--cheap and clean, with low voltage drop. 6SN7s have a very slow warm-u .......
448: Tube DIY Asylum, Re: 6B4G Schematic (0.00)
Posted by groverg on 2003-09-10, 21:00:32 (151.200.237.184)
Well, it's just a Williamson with an extra gain stage in front--for what I'm not sure, maybe low-level sources like ceramic cartridges or something, I don't think the feedback is high enough to warren .......
449: Tube DIY Asylum, Re: Reducing input sensitivity on a LEAK stereo 20? (0.00)
Posted by groverg on 2003-09-06, 17:59:02 (141.156.188.64)
Triode Kingdom offered a good tip below. You could try replacing the 12AX7s with 5751s, that might reduce the overall gain without affecting the feedback circuit. I *think* you could even replace the .......
450: Tube DIY Asylum, Re: what is the best way to reduce poweramp input sensitivity ? (0.00)
Posted by groverg on 2003-09-06, 10:16:31 (141.156.188.64)
Altering the feedback is a tricky proposition. You would have to increase it, which could lead to overshoot at the input and ringing at the output. You could scope it to maske sure you have a clean si .......
451: Tube DIY Asylum, Re: A Couple of Suggestions........ (0.00)
Posted by groverg on 2003-09-04, 13:05:05 (141.156.188.64)
Oh, Mike, that's a good idea! I've always used both sections of a 5687, never one at a time. Someone else once suggested grounding the unused section but I'd forgotten about it. .......
452: Tube DIY Asylum, Re: 5687 operating point stability - sorry for crossposting (0.00)
Posted by groverg on 2003-09-03, 12:23:27 (141.156.188.64)
Well...maybe you got a bad batch. They are certainly prone to long warm-up periods, and will shift quite a bit over the course of an hour after turn-on. And I've had several samples behave badly. Did .......
453: Tube DIY Asylum, Re: 5687 operating point stability - sorry for crossposting (0.00)
Posted by groverg on 2003-09-03, 11:10:50 (141.156.188.64)
Well, that shouldn't be a problem. Have you tried grid-stoppers, or some sort of mechanical shielding? .......
454: Tube DIY Asylum, Re: 5687 operating point stability - sorry for crossposting (0.00)
Posted by groverg on 2003-09-01, 18:46:34 (141.156.188.64)
What value of grid resistor are you using? .......
455: SET Asylum, Re: Morning Grover.... (0.00)
Posted by groverg on 2003-08-31, 18:00:07 (141.156.188.64)
Yes, you can just drop it in. .......
456: SET Asylum, Re: Assemblage 300B SET -- how good? (0.00)
Posted by groverg on 2003-08-31, 09:16:09 (141.156.188.64)
I've spent a little time with the Assemblage. It is a great bargain and is built like a tank. Sonically I find it a bit on the dry side compared to other SET amps I've heard. The cathode-follower driv .......
457: Tube DIY Asylum, Re: Dynaco PAS (0.00)
Posted by groverg on 2003-08-30, 05:18:41 (141.156.188.64)
Have you tried different tubes? Perhaps some low-noise military grades would help. .......
458: Tube DIY Asylum, Re: Toroid Corp of Maryland (0.00)
Posted by groverg on 2003-08-29, 20:49:41 (141.156.188.64)
I was merely pointing out that changing to a toroidal transformer is not necessary. A readily available EI replacement transformer is likely to solve the problem, will be cheaper and will have all the .......
459: Tube DIY Asylum, Re: Toroid Corp of Maryland (0.00)
Posted by groverg on 2003-08-29, 12:13:52 (141.156.188.64)
This is not inherent in EI trannies. In your case it's likely that the insulation has been compromised by heat, age or storage, so the windings have loosened and are vibrating causing noise and excess .......
460: Tube DIY Asylum, Re: Toroid Corp of Maryland (0.00)
Posted by groverg on 2003-08-29, 12:11:32 (141.156.188.64)
Why would it hum at all, unless it were poorly made or defective? Properly built EI trannies shouldn't make any noise. .......
461: Tube DIY Asylum, Re: Freed transformer (0.00)
Posted by groverg on 2003-08-25, 16:29:20 (138.88.97.104)
Working volts means the actual continuous DC voltage for which the tranny insulation is rated. .......
462: Tube DIY Asylum, Re: parafeed and fixed bias (0.00)
Posted by groverg on 2003-08-25, 15:06:51 (138.88.97.104)
Keep the bias pot as small as possible! Remember, the portion of the pot's resistance seen by the grid to ground will change as you adjust the pot; if you make the pot too big, you're going to alter s .......
463: Tube DIY Asylum, Re: Replacement RCA sockets (0.00)
Posted by groverg on 2003-08-24, 19:47:25 (138.88.138.90)
You can get something much better, Kimber or Cardas or whatever, from Michael Percy, Handmade or another of the DIY suppliers. .......
464: Tube DIY Asylum, Re: parafeed and fixed bias (0.00)
Posted by groverg on 2003-08-24, 19:45:55 (138.88.138.90)
Use a 10K pot for bias with 47K fixed resistor to the grid; it will keep the grid resistance more stable. .......
465: Tube DIY Asylum, Re: LM350 regulated DC PSU & HUM problem (0.00)
Posted by groverg on 2003-08-20, 23:26:30 (141.156.187.46)
Yes, there is such a thing. Consider that your music signal passes through this pot just as it passes through the cathode resistor and bypass cap. If the pot is noisy, tracks poorly or is cheaply made .......
466: Tube DIY Asylum, Re: Soldering a gound buss to the Bugle (0.00)
Posted by groverg on 2003-08-19, 19:55:25 (138.88.2.61)
Sounds like you have routed the buss fine. Some layouts are more sensitive to ground loops than others, only experimentation will tell. I would suggest, however, using 14 gauge wire for the buss, prec .......
467: Tube DIY Asylum, Re: LM350 regulated DC PSU & HUM problem (0.00)
Posted by groverg on 2003-08-19, 19:51:26 (138.88.2.61)
Are you using a hum-balancing pot on the 300B filaments? .......
468: Tube DIY Asylum, Thanks for report, Gordon nt (0.00)
Posted by groverg on 2003-08-19, 18:22:58 (138.88.92.127)
. .......
469: Tube DIY Asylum, Re: Q:SE and feedback... (0.00)
Posted by groverg on 2003-08-18, 11:49:01 (138.88.17.180)
People I know who are more familiar with feedback circuits tell me that the parallel pf cap value is very dependent on the specific output tranny used, that it prevents ringing. It's best optimized wi .......
470: SET Asylum, Re: Mono or Stereo 300B Amp (0.00)
Posted by groverg on 2003-08-18, 11:40:47 (138.88.17.180)
I agree with Datubie--use Cerafines or Panasonic TSHA's for the power supply. BGs on the bypasses, I think this is very important, though Nichicon Muses are pretty good, but for a few extra dollars th .......
471: SET Asylum, Re: Mono or Stereo 300B Amp (0.00)
Posted by groverg on 2003-08-17, 16:11:14 (138.88.36.182)
I agree. A stereo amp with nice outputs is a lot more enjoyable than monoblocks with cheaper iron. Stereo amps can be very sweet, with nice focus and coherence. .......
472: SET Asylum, Re: SET amp perfered (0.00)
Posted by groverg on 2003-08-16, 08:11:36 (138.88.11.179)
I am fond of the 845 for my own projects but I am not impressed by the Cary 805s--I felt the same thing you did each time I've heard them. I heard the Sophias in a limited demo but couldn't really tel .......
473: Tube DIY Asylum, Nice! nt (0.00)
Posted by groverg on 2003-08-14, 21:34:05 (138.88.11.179)
. .......
474: Tube DIY Asylum, Re: CM chokes in filaments. (0.00)
Posted by groverg on 2003-08-14, 14:52:49 (138.88.11.179)
I'm not clear if the CMC blocks noise from the supply, or even does so at useful frequencies. It may simply be a matter of adding some extra series resistance, I don't know. But it does seem to add fo .......
475: Tube DIY Asylum, Re: cmc chokes (0.00)
Posted by groverg on 2003-08-14, 14:45:17 (138.88.11.179)
You don't need to order 50--that's just the price-break point. But I see they are out of stock until November. How much current capacity do you need? You could order two of the DN4606-ND for each fila .......
476: Tube DIY Asylum, Re: Do you stay with auto-bias? <nt> (0.00)
Posted by groverg on 2003-08-13, 20:35:26 (138.88.11.179)
It depends on what tube you are talking about. I prefer cathode bias for a 300B or 2A3, but fixed bias with an 845. .......
477: Tube DIY Asylum, Re: Cathode Bias with VR Tubes (0.00)
Posted by groverg on 2003-08-13, 18:18:44 (138.88.11.179)
I have and didn't particularly care for the sound--rather sterile to my ears. .......
478: Tube DIY Asylum, Re: How do you wire them up? (0.00)
Posted by groverg on 2003-08-13, 14:03:48 (138.88.11.179)
Each CMC has two section. Consult the diagram on the catalogue page. One section is wired in series with the positive filament leg, the other in series with the negative leg. Place the CMC after the l .......
479: Tube DIY Asylum, Re: CM chokes in filaments. (0.00)
Posted by groverg on 2003-08-13, 13:23:38 (138.88.96.190)
I couldn't begin to tell you why they work, but for me they make a significant difference in the "acceptability" of the sound of DC filaments on the 10Y and the 845. Maybe there are other ways to do i .......
480: Tube DIY Asylum, Re: part numbers? (0.00)
Posted by groverg on 2003-08-13, 13:19:28 (138.88.96.190)
Digikey part numbers DN4600-ND (47uH at 3.5A) or DN4606-ND (150uH at 2.8A). I use the former for the 845. .......
481: Tube DIY Asylum, Re: CM chokes in filaments. (0.00)
Posted by groverg on 2003-08-13, 11:08:51 (138.88.96.190)
I have found that the smaller the CMC the better (Digikey's offerings). With larger CMCs (from Allied) I feel I begin to "hear" the choke, and detect some smearing etc. The smaller CMCs seem to bring .......
482: Tube DIY Asylum, Re: How do you calculate the tube operating points for Class A PP? (0.00)
Posted by groverg on 2003-08-12, 18:27:21 (138.88.96.190)
Read the Norman Crowhurst articles at http://www.audioxpress.com/resource/audioclass/index.htm You'll need the curves for the tube in question. If you cannot find them, then you may be able to find a .......
483: Tube DIY Asylum, Re: Makes sense... (0.00)
Posted by groverg on 2003-08-11, 06:05:29 (138.88.96.190)
With PP the filament hum is cancelled out, at least in most cases. You still have to take care to assure low noise. .......
484: Tube DIY Asylum, Re: "if i did they would not go near my stereo without instruction and appreciation" (0.00)
Posted by groverg on 2003-08-10, 18:47:15 (138.88.96.190)
My girl being only four months old and fairly immobile at this point, I'd been thinking about what sort of devices might eventually keep curious hands away from the stereo, open CD and record racks, a .......
485: Tube DIY Asylum, Re: Advantages of direct over indirectly heated tubes? (0.00)
Posted by groverg on 2003-08-10, 18:07:12 (138.88.96.190)
Mechanically it's a PITA, since you do not have the cathode to eliminate noise from the filament supply :-). Seriously, you're removing one element, the cathode sleeve, from the signal, so the filamen .......
486: Tube DIY Asylum, Re: Authentic Custom Magnequests? (0.00)
Posted by groverg on 2003-08-09, 15:42:57 (138.88.96.190)
If they have nickel lams they are probably meant for parafeed and are not designed to handle any current on the primary. .......
487: Tube DIY Asylum, Re: Choke Input DC Supply for Filaments (0.00)
Posted by groverg on 2003-08-09, 10:39:50 (141.156.185.217)
I have found that a small CMC helps restore body to the sound of a DHT with DC filaments. I've tried choke-filtered DC supplies without much luck, finding them a little "thick" sounding. Don't know wh .......
488: Tube DIY Asylum, Re: Parallelling an Input Tube (0.00)
Posted by groverg on 2003-08-08, 06:02:27 (141.156.185.217)
What's the bias voltage on the 12AX7 cathode? Some CD players may be putting out more volts than the grid can handle. .......
489: Tube DIY Asylum, Re: What is the best RCA Tube Manual to start with? (0.00)
Posted by groverg on 2003-08-06, 03:20:41 (138.88.0.57)
Actually the best all-purpose tube data book I've found is the 1972 GE manual. It only lists short data but it covers most of the US types out there and is a handy reference for checking specs, maximu .......
490: Tube DIY Asylum, Re: DC supply to 300B filament (0.00)
Posted by groverg on 2003-08-04, 21:29:10 (141.156.178.167)
You've got a 5VDC supply with two legs, one negative and one positive. Attach each leg to one end of the tube's filament, pins 1 and 4. To bias the cathode (which is the filament in a 300B) you attach .......
491: Tube DIY Asylum, Re: DC supply to 300B filament (0.00)
Posted by groverg on 2003-08-04, 18:28:14 (141.156.178.167)
Absolutely not! If you ground the filament supply you'll short the cathode bias resistor and the tube will run at ) volts bias and burn up. Connect both ends of the DC supply across the filaments of t .......
492: Tube DIY Asylum, Re: Clipping in high frequency area. (0.00)
Posted by groverg on 2003-08-01, 13:27:15 (138.88.33.232)
Not enough power, it sounds like. Transients from a mic'ed soprano can be pretty tough for an amp to handle. .......
493: Tube DIY Asylum, Re: What gives with Sakuma's amps... (0.00)
Posted by groverg on 2003-08-01, 12:17:24 (138.88.33.232)
Regarding low-uF caps in the power supply, I've seen it argued that you get a faster, tighter sound from an SET. Certainly a lot of classic tube equipment, like Lamda supplies and old theater and ham .......
494: Tube DIY Asylum, Re: What gives with Sakuma's amps... (0.00)
Posted by groverg on 2003-08-01, 06:01:38 (138.88.33.232)
If you read the old ham radio texts, this is the classic "brute force" power supply. 8 and 10 uF were pretty standard values in the 1940's, considered plenty of filtering for a CLCL supply. I have not .......
495: Tube DIY Asylum, Re: Need 310 VAC sec. @ 400 ma. but don't want to pay $600 for 2 custom wounds. Any ideas? (0.00)
Posted by groverg on 2003-07-29, 17:44:38 (138.88.42.184)
That sounds like a good plan. Get it up and running, see if it satisfies your system needs, then you can upgrade the iron, and other things as well. .......
496: Tube DIY Asylum, Re: Need 310 VAC sec. @ 400 ma. but don't want to pay $600 for 2 custom wounds. Any ideas? (0.00)
Posted by groverg on 2003-07-29, 16:11:06 (138.88.42.184)
Well, not using chokes is fine as far as I'm concerned :-). I have no idea why he would have the power trannies custom wound, but it's possible he just couldn't find anything off the shelf to suit his .......
497: Tube DIY Asylum, Re: Need 310 VAC sec. @ 400 ma. but don't want to pay $600 for 2 custom wounds. Any ideas? (0.00)
Posted by groverg on 2003-07-28, 20:15:11 (138.88.144.15)
I'll bet he used a bridge because that's the transformer he had handy :-). If all else fails, a fw rectifier won't change the circuit significantly and might make your search for a proper power tranny .......
498: Tube DIY Asylum, Re: Need 310 VAC sec. @ 400 ma. but don't want to pay $600 for 2 custom wounds. Any ideas? (0.00)
Posted by groverg on 2003-07-28, 17:52:10 (138.88.144.15)
Sure. If you're on a budget, use a Hammond 272JX, 300-0-300/250mA with a full wave ct configuration instead of a bridge. With the 115VAC primaries, you'll get a about 620VAC CT. It won't sound any dif .......
499: Tube DIY Asylum, Re: 845 DC Schematics (0.00)
Posted by groverg on 2003-07-27, 23:03:14 (138.88.144.15)
It depends on what sound you want and how much power you need. You can drag 10wpc or more out of a 300B, but only 4-5 watts out of an 845 at the same voltages (under 500VDC). But as a lot of folks on .......
500: SET Asylum, Re: SET amp and Sonus Faber Concertino's (0.00)
Posted by groverg on 2003-07-27, 22:49:37 (138.88.144.15)
I could be completely wrong, but it's hard to imagine an SE 300B driving the Sonus Fabers to any good effect. .......
Found total of 500 records, Query: , Author: groverg in All Forums, Time: 1 sec.