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1: K&K Audio / Lundahl Transformers, RE: To friends and former customers of KandKAudio (0.00)
Posted by Jim Dowdy on 2024-02-20, 06:32:11 (73.54.140.214)
Kevin was a true prince of a guy. RIP my friend .......
2: MagneQuest/Peerless Forum, pair EXO-173 wanted (0.00)
Posted by Jim Dowdy on 2023-11-03, 04:55:24 (73.54.140.214)
PPS in nickel preferred. Thanks .......
3: Tube DIY Asylum, RE: Well then... (0.00)
Posted by Jim Dowdy on 2023-10-09, 04:21:33 (73.54.140.214)
Your post is a non-sequitur. TK made the blanket statement: "No one here wants to hear about LoMu." He was obviously incorrect - because some of us do. .......
4: Tube DIY Asylum, I do! (0.00)
Posted by Jim Dowdy on 2023-10-04, 10:40:53 (104.188.249.225)
nt .......
5: MagneQuest/Peerless Forum, RE: Mike's passing (0.00)
Posted by Jim Dowdy on 2023-04-01, 09:23:50 (76.17.122.68)
Jeez - what a bummer! As I posted on the DIY Asylum, Mike and I only met in person a couple of times, but spent untold hours on the phone together. One of my favorite memories is Mike's over-the-top .......
6: Tube DIY Asylum, RE: Sad News : Mike LaFevre / Magnequest has Passed Away (0.00)
Posted by Jim Dowdy on 2023-04-01, 08:49:21 (76.17.122.68)
Aw man - what a bummer! What a great guy Mike was! We only met a few times in person, but spent many, many hours on the phone together. RIP brother. .......
7: Tube DIY Asylum, except when he's not (0.00)
Posted by Jim Dowdy on 2023-03-05, 16:03:48 (76.17.121.229)
nt .......
8: Tube DIY Asylum, re: Should I recap my mx-110z? (0.00)
Posted by Jim Dowdy on 2023-03-05, 16:00:12 (76.17.121.229)
Yes. .......
9: MagneQuest/Peerless Forum, RE: Altec 17173 Choke Specifications (0.00)
Posted by Jim Dowdy on 2021-12-21, 12:25:33 (71.14.2.78)
Sorry for the delayed post - I don't log in here too often anymore. As I recall, Mike told me that the original was spec'd for 2 mA unbalanced current. Mike said his version was "better balanced" than .......
10: General Asylum, RIP Pierre (0.00)
Posted by Jim Dowdy on 2021-08-11, 17:53:42 (107.205.5.144)
What a gentleman, a true lover of music, and an all-around class act! Ave atque vale. .......
11: Tube DIY Asylum, Heyboer Update (0.00)
Posted by Jim Dowdy on 2021-07-14, 17:47:40 (107.205.5.144)
I just received my Heyboer Power Transformer order today! .......
12: Tube DIY Asylum, RE: Heyboer Gone? (0.00)
Posted by Jim Dowdy on 2021-07-10, 11:44:18 (107.205.5.144)
I spoke with Phil just a few days ago about a Power Transformer order. .......
13: MagneQuest/Peerless Forum, BAC-300 query (0.00)
Posted by Jim Dowdy on 2021-06-11, 17:43:03 (107.205.5.144)
Does anyone have a pair of BAC-300s that they want to get rid of? What is their inductance and approx dcr? .......
14: MagneQuest/Peerless Forum, Me too! (0.00)
Posted by Jim Dowdy on 2021-04-18, 07:39:22 (107.205.5.144)
M6/Ni pinstripe preferred. .......
15: MagneQuest/Peerless Forum, your rant (0.00)
Posted by Jim Dowdy on 2021-02-05, 13:28:50 (107.205.5.144)
I continue to hold out hope that Mike will choose to end his sabbatical and return to making the world safe for truth, justice, and the American way. In my estimation: Hammond is OK; Heyboer is good; .......
16: Tube DIY Asylum, RE: Preamp: 5842 w/output transformers (0.00)
Posted by Jim Dowdy on 2020-11-06, 07:39:09 (107.205.5.144)
I'm guessing the transformers are MQ 5k:600r units, indicating a gain of about 20 dB, and an output impedance of under 600 ohms. I don't know the Alps pot you are speaking of, but it should work. ::: .......
17: Tube DIY Asylum, superb - thanks Dave! (nt) (0.00)
Posted by Jim Dowdy on 2020-08-06, 02:13:42 (107.205.5.144)
nt .......
18: Tube DIY Asylum, +1 nt (0.00)
Posted by Jim Dowdy on 2020-05-18, 10:17:58 (107.205.5.144)
nt .......
19: General Asylum, RE: Art Dudley RIP (0.00)
Posted by Jim Dowdy on 2020-04-15, 21:29:56 (107.205.5.144)
A truly nice guy who told it like it was. Listener Magazine was a breath of fresh air! .......
20: Tube DIY Asylum, well stated Eli! (0.00)
Posted by Jim Dowdy on 2019-09-28, 05:45:54 (107.205.5.144)
This applies to all engineering. .......
21: Tube DIY Asylum, while you're at it (0.00)
Posted by Jim Dowdy on 2019-09-12, 07:24:30 (107.205.5.144)
Try your favorite 0.1 uf caps with 180k. The knee moves to 8.8 Hz, but if Paul Joppa can be happy with 8.8 Hz, I think most people would be content ;-) .......
22: Tube DIY Asylum, problems? (0.00)
Posted by Jim Dowdy on 2019-09-09, 20:10:59 (107.205.5.144)
One of the beauties of DIY is that what matters is how it sounds to you. You could keep the 0.1 uf coupling cap and reduce the grid resistor to 330k and maintain full-range response. .......
23: Tube DIY Asylum, more (0.00)
Posted by Jim Dowdy on 2019-09-09, 17:15:55 (107.205.5.144)
Everything Chip says is 100% correct. As long as you have provided an adequate load for V1, and as long as your coupling cap is of a reasonable value; I've found that tubes generally sound better with .......
24: Tube DIY Asylum, +2 (0.00)
Posted by Jim Dowdy on 2019-09-09, 01:56:06 (107.205.5.144)
You could probably drop the grid resistor to 150k. .......
25: SET Asylum, Stephens perhaps? (0.00)
Posted by Jim Dowdy on 2019-08-23, 10:36:11 (107.205.5.144)
This reminds me of a schematic that Shishido-san shared with me many years ago - designed to drive a 1950s 500 ohm Stephens setup. .......
26: OTL Asylum, Stephens link (0.00)
Posted by Jim Dowdy on 2019-08-15, 07:57:06 (107.205.5.144)
Lots of interesting material here - scroll down for info on their OTL amplifier. .......
27: OTL Asylum, RE: Somewhere I have an old hi-fi mag from the 50's and... (0.00)
Posted by Jim Dowdy on 2019-08-13, 11:15:43 (107.205.5.144)
Stephens and Philips Norelco offered high impedance speakers with matching OTL amplifiers. I believe the high impedance Stephens TruSonic speakers were 500 ohms; while Philips Norelco had both 400 oh .......
28: Tube DIY Asylum, declared illegal in the US in 1979 (nt) (0.00)
Posted by Jim Dowdy on 2019-08-10, 18:14:58 (107.205.5.144)
nt .......
29: Tube DIY Asylum, as controversial as this may sound... (0.00)
Posted by Jim Dowdy on 2019-06-19, 19:08:30 (107.205.5.144)
I'm guesstimating that I've done more experimentation with tube amps/linestages than 98+% of the folks out there...and, I tend to believe that John Hogan had it right: "Directly heated tubes simply so .......
30: Tube DIY Asylum, I believe Dennis is correct here... (0.00)
Posted by Jim Dowdy on 2019-06-19, 19:00:59 (107.205.5.144)
Having said that: I believe that driving paralleled output tubes is quite a bit more complex than one might initially derive from his remarks. .......
31: Tube DIY Asylum, "actually, it's rather easy" + "air is just distortion" (0.00)
Posted by Jim Dowdy on 2019-06-16, 15:48:53 (107.205.5.144)
The Asylum has been around for about 20 years now... Assuming this post represents 'common knowledge'; we've not moved forward one iota. .......
32: Tube DIY Asylum, "you just like listening to distortion..." (0.00)
Posted by Jim Dowdy on 2019-06-15, 06:54:57 (107.205.5.144)
Excellent post! .......
33: Tube DIY Asylum, my opinion (0.00)
Posted by Jim Dowdy on 2019-03-08, 13:46:16 (107.205.5.144)
Not attempting to be controversial, but in my experience: a) nothing is as overall neutral sounding as the Duelund cast copper capacitors - however, they *do* slightly limit low-level detail and dyna .......
34: Tube DIY Asylum, RE: my suggestion (0.00)
Posted by Jim Dowdy on 2019-02-16, 12:59:46 (107.205.5.144)
Vinnie: My apologies, I misread your grid-to-ground resistor as being 600k (not 60k). Please ignore my suggestion. FWIW: 0.1 uf and 60 kohms yields a first-order rolloff at 26.5 Hz. This will produ .......
35: Tube DIY Asylum, my suggestion (0.00)
Posted by Jim Dowdy on 2019-02-16, 12:22:25 (107.205.5.144)
Decrease R(g) to 150k and increase the size of your coupling cap to 0.22 uf. .......
36: Tube DIY Asylum, RIP Sakuma-san (0.00)
Posted by Jim Dowdy on 2019-01-05, 05:56:28 (107.205.5.144)
Susumu Sakuma left this world on December 14, 2018. Ave atque vale. .......
37: MagneQuest/Peerless Forum, Great news! (0.00)
Posted by Jim Dowdy on 2018-12-05, 19:53:29 (107.205.5.144)
Thanks for posting, George! .......
38: Tube DIY Asylum, 'good enough' (0.00)
Posted by Jim Dowdy on 2018-11-02, 06:31:07 (174.218.29.92)
Just my opinion, but I'd definitely go for the 105 degrees C option. .......
39: OTL Asylum, a more legible MQ36 schematic (0.00)
Posted by Jim Dowdy on 2018-08-25, 00:54:31 (107.205.5.144)
Can be found here: .......
40: Tube DIY Asylum, just curious... (0.00)
Posted by Jim Dowdy on 2018-07-18, 11:35:20 (107.205.5.144)
Where have you settled? Would love to catch up... .......
41: Tube DIY Asylum, elinear (0.00)
Posted by Jim Dowdy on 2018-07-15, 12:51:55 (107.205.5.144)
Have never experimented with elinear - I'm especially curious to see how well elinear performs in a directly-coupled setup. Only one set of UL taps, though... .......
42: Tube DIY Asylum, and, I know a guy with a truck! (nt) (0.00)
Posted by Jim Dowdy on 2018-07-15, 11:13:54 (107.205.5.144)
nt .......
43: Tube DIY Asylum, PP UL HY69/1269 (0.00)
Posted by Jim Dowdy on 2018-07-15, 10:00:46 (107.205.5.144)
Currently collecting parts: Choke-tail pair 6SL7 input/phase-splitter directly-coupled to the Hytron output tubes. Nickel pinstripe MQ 565 OPTs. Primarily for use below 250 Hz - my first push-pull am .......
44: Tube DIY Asylum, cool link! (0.00)
Posted by Jim Dowdy on 2018-07-07, 09:19:53 (47.215.225.183)
Thanks for posting! .......
45: Vintage Asylum, Thanks, Hoosier and Mondial (nt) (0.00)
Posted by Jim Dowdy on 2018-06-14, 18:00:57 (107.205.5.144)
nt .......
46: Vintage Asylum, thanks, Mondial! (0.00)
Posted by Jim Dowdy on 2018-06-14, 15:55:28 (107.205.5.144)
No - I'm putting together a vintage system, and am currently looking for an active tube crossover. Please post your EC-21 schematic. .......
47: Vintage Asylum, thanks - I've seen that (0.00)
Posted by Jim Dowdy on 2018-06-14, 14:40:44 (107.205.5.144)
Do you have an EC-21 schematic? Any user experience out there? .......
48: Vintage Asylum, Audio Research EC-2 vs EC-21 (0.00)
Posted by Jim Dowdy on 2018-06-14, 07:42:00 (107.205.5.144)
Can anyone tell me the difference(s) between these two crossovers? Thanks! .......
49: MagneQuest/Peerless Forum, RE: May I ask what you are planning to do with them? (0.00)
Posted by Jim Dowdy on 2018-05-30, 14:10:11 (99.170.225.28)
PP UL Hytron HY-69s. .......
50: MagneQuest/Peerless Forum, got a pair - thanks! (0.00)
Posted by Jim Dowdy on 2018-05-29, 12:47:33 (99.170.225.28)
nt .......
51: MagneQuest/Peerless Forum, Wanted: all nickel or nickel pinstripe MQ-565s (0.00)
Posted by Jim Dowdy on 2018-05-25, 17:56:52 (99.170.225.28)
I'm looking for a pair of all nickel (or nickel pinstripe) MQ-565s. Thanks! Mike approved this posting. .......
52: Tube DIY Asylum, +1 (0.00)
Posted by Jim Dowdy on 2018-04-27, 07:58:57 (99.170.225.28)
I've had great results with the Russian connectors! .......
53: Tube DIY Asylum, ping (0.00)
Posted by Jim Dowdy on 2018-04-08, 06:52:12 (99.170.225.28)
Jim: I'm interested in the nickel pinstripe MQ565 OPTs, if they are still available. Jim Dowdy .......
54: Tube DIY Asylum, +1 for Valve Wizard! (nt) (0.00)
Posted by Jim Dowdy on 2018-03-27, 19:34:59 (99.170.225.28)
nt .......
55: Tube DIY Asylum, seeing vs not seeing (0.00)
Posted by Jim Dowdy on 2018-03-09, 10:29:23 (99.170.225.28)
My point was that it's what you hear that matters. .......
56: Tube DIY Asylum, if you can't see it... (0.00)
Posted by Jim Dowdy on 2018-03-08, 16:00:28 (99.170.225.28)
This about what you hear, not what you see (or measure). If you find that multiple bypasses improve your musical enjoyment, then go for it! .......
57: Tube DIY Asylum, RE: 213a rectifier (0.00)
Posted by Jim Dowdy on 2018-03-02, 15:01:00 (99.170.225.28)
Wow - definitely appear to be half-wave - was not expecting a top cap! Is filament thoriated? .......
58: Tube DIY Asylum, 213a rectifier (0.00)
Posted by Jim Dowdy on 2018-03-02, 13:57:35 (99.170.225.28)
No idea - bear in mind that Cetron is relatively new to the tube game; so, I'm somewhat skeptical that they would be motivated to reproduce such a vintge design. FWIW: I always considered the UX-213 .......
59: Tube DIY Asylum, RCA UX-213 rectifier (0.00)
Posted by Jim Dowdy on 2018-03-01, 13:20:55 (99.170.225.28)
I don't know if this helps, but the RCA UX-213 was the predecessor to the 280/80 rectifier. .......
60: Tube DIY Asylum, SE 2A3 example (0.00)
Posted by Jim Dowdy on 2017-12-31, 11:27:32 (99.170.225.28)
With unbypassed R(k)s wired in parallel between channels: 800 + [(750/2) * (4.2 + 1)] = 2,750 ohms Works great with a 9k OPT! .......
61: Tube DIY Asylum, tie R(k)s together (0.00)
Posted by Jim Dowdy on 2017-12-31, 08:02:24 (99.170.225.28)
I'd suggest that you try running the cathode resistors in parallel between channels. .......
62: Tube DIY Asylum, not being critical (0.00)
Posted by Jim Dowdy on 2017-12-25, 09:23:27 (99.170.225.28)
Was not criticizing the sonics of the 125ESE - just agreeing with TK and buffy that the measurements appeared to correlate to Hammond's published specs. .......
63: Tube DIY Asylum, +2 (0.00)
Posted by Jim Dowdy on 2017-12-23, 21:04:19 (99.170.225.28)
Agree. .......
64: General Asylum, Oh my! (0.00)
Posted by Jim Dowdy on 2017-10-25, 09:05:37 (99.170.225.28)
I absolutely adored Fats!!! RIP. Jim .......
65: Tube DIY Asylum, RE: It just dawned on me that you.. (0.00)
Posted by Jim Dowdy on 2017-09-02, 14:49:57 (174.218.2.0)
Virtually all on the inductors in question reach/exceed critical inductance. I'd encourage you to try it and let us know how it sounds. NOTE: the vast majority of my experimentation has involved mer .......
66: Tube DIY Asylum, theoretically agree... (0.00)
Posted by Jim Dowdy on 2017-09-02, 11:49:00 (174.218.2.0)
Sorry, I don't have an explanation. I've just found that a small cap (typically 0.1 to 0.33 uf) seems to sound a bit better. .......
67: Tube DIY Asylum, all valid points... (0.00)
Posted by Jim Dowdy on 2017-09-02, 11:29:15 (174.218.2.0)
Although I suspect the vast majority of valve rectifiers actually prefer a small capacitor (approx 0.47 uf or less) before L1. .......
68: Tube DIY Asylum, congrats! (0.00)
Posted by Jim Dowdy on 2017-08-15, 13:44:47 (71.14.2.78)
Eli: Congrats on hitting retirement - please keep us posted on your Class B 46 project. Jim .......
69: Tube DIY Asylum, but, how does it sound? (0.00)
Posted by Jim Dowdy on 2017-07-19, 18:32:12 (67.191.244.86)
With the 417A/5842, I've had good luck with 180 ohm carbon comp grid stoppers (in combination with a ferrite bead). YMMV. .......
70: SET Asylum, Fond memories (0.00)
Posted by Jim Dowdy on 2017-06-12, 08:31:45 (71.14.2.78)
I only met Don once - at his store circa '96 (I believe). What a great guy! RIP Don. .......
71: General Asylum, Gregg Allman (0.00)
Posted by Jim Dowdy on 2017-05-27, 15:53:54 (98.20.161.108)
Wow, I grew up with Gregg Allman. Thanks for all the great music - RIP. .......
72: Tube DIY Asylum, 3B28s are a drop in replacement to 866s like ripple is a drop in replacement to wine (0.00)
Posted by Jim Dowdy on 2017-04-02, 06:28:17 (40.138.182.159)
What a great analogy! Thanks for the graphs - I've been curious about it for years. Jim .......
73: Tube DIY Asylum, Of course I have! (0.00)
Posted by Jim Dowdy on 2017-03-22, 14:30:41 (40.132.4.50)
Many of us have...but that does not imply that the theory is therefore 'dead on.' A 4-tube bridge of mercury vapor rectifiers operating into an L-filter sounds best 99.9% of the time. Does this comp .......
74: Tube DIY Asylum, there are limits to friendship... (0.00)
Posted by Jim Dowdy on 2017-03-02, 07:31:04 (173.184.91.142)
I consider both Tube Wrangler and Dr Low Mu friends - but I don't use the 7B4/12AX7/12BZ7 in my 2A3 amps. .......
75: General Asylum, RIP George Michael (0.00)
Posted by Jim Dowdy on 2016-12-25, 16:41:12 (24.156.98.186)
nt .......
76: Tube DIY Asylum, 845 (0.00)
Posted by Jim Dowdy on 2016-11-28, 08:42:11 (173.186.15.222)
I have built a couple of SE 845 amplifiers - neither of them utilized ITs. .......
77: Tube DIY Asylum, 6K OPT for paralleled SE GM-70 (0.00)
Posted by Jim Dowdy on 2016-11-27, 07:14:23 (162.195.207.149)
Andrea Ciuffoli estimates the R(p) of the GM70 to be 2k3, and I have no reason to question that figure. I prefer the copper-plate version of the GM70. .......
78: Tube DIY Asylum, choke (0.00)
Posted by Jim Dowdy on 2016-11-26, 06:08:47 (162.195.207.149)
Power supply choke for the four GM70s will carry approx 430 mA. Parallel SE GM70s will not be parafed - each OPT will be 6k, and designed for about 215 mA. .......
79: Tube DIY Asylum, on the drawing board (0.00)
Posted by Jim Dowdy on 2016-11-25, 11:06:35 (162.195.207.149)
Is a PSE GM70 IT-driven by 46... .......
80: Tube DIY Asylum, RE: Heater Supply? (0.00)
Posted by Jim Dowdy on 2016-11-22, 14:36:24 (173.186.15.222)
Filaments are DC. For years now, I've been threatening to use tungar rectifiers to accomplish this ;-) .......
81: Tube DIY Asylum, RE: I've had the pleasure of hearing Mr. Dowdy's GM70 (0.00)
Posted by Jim Dowdy on 2016-11-22, 14:34:16 (173.186.15.222)
Thanks for the kind words! .......
82: Tube DIY Asylum, The problem was... (0.00)
Posted by Jim Dowdy on 2016-11-19, 17:44:15 (173.184.77.152)
that I had it firmly cemented in my mind that 866s operate on 5.0 volt filaments...therefore, I continued to miss the obvious! :-) .......
83: Tube DIY Asylum, CR inversion (0.00)
Posted by Jim Dowdy on 2016-11-19, 15:28:56 (173.184.77.152)
Ha - thanks, Eli! While we're at it: did you ever make progress on that (Class B) PP 46 amp you were talking about? .......
84: Tube DIY Asylum, RE: the circuit is parafeed (nt) (0.00)
Posted by Jim Dowdy on 2016-11-19, 15:26:29 (173.184.77.152)
Let me get the rectifier issue squared away and I'll provide more info. .......
85: Tube DIY Asylum, RE: True Confessions (0.00)
Posted by Jim Dowdy on 2016-11-19, 15:25:02 (173.184.77.152)
Thanks, George: it's been at least 40 years since I've felt quite this stupid ;-) .......
86: Tube DIY Asylum, the circuit is parafeed (nt) (0.00)
Posted by Jim Dowdy on 2016-11-19, 13:21:33 (173.184.77.152)
nt .......
87: Tube DIY Asylum, I love the GM70! (0.00)
Posted by Jim Dowdy on 2016-11-19, 12:53:34 (173.184.77.152)
All-around, it's my favorite output tube. .......
88: Tube DIY Asylum, True Confessions (0.00)
Posted by Jim Dowdy on 2016-11-19, 11:36:43 (173.184.77.152)
Recently completed a SE EML30A>GM70 amp, utilizing a 4-tube bridge of 866s for rectification. Things sounded good: B+ and Bias measured perfectly...but about 20 hours in, I began losing rectifiers. I .......
89: Tube DIY Asylum, agree (0.00)
Posted by Jim Dowdy on 2016-11-17, 09:21:13 (173.184.77.152)
It's on my list... :-) .......
90: Tube DIY Asylum, 7905 (nt) (0.00)
Posted by Jim Dowdy on 2016-11-15, 10:13:24 (173.184.77.152)
nt .......
91: General Asylum, RIP Leonard Cohen (0.00)
Posted by Jim Dowdy on 2016-11-10, 19:19:21 (173.184.41.207)
http://www.nytimes.com/2016/11/11/obituaries/leonard-cohen-dies.html?_r=0 .......
92: Tube DIY Asylum, of course, Doug is correct... (0.00)
Posted by Jim Dowdy on 2016-10-11, 13:24:54 (40.134.86.130)
nt .......
93: Tube DIY Asylum, RE: low voltage 845-845 SET amp? (0.00)
Posted by Jim Dowdy on 2016-10-03, 13:55:16 (173.184.86.84)
As I understand it, the only difference between the 845 and the 211 (or 203A) is the pitch of the grid wire. Wouldn't that be a better solution to addressing the problem of gain, while still being 'cl .......
94: General Asylum, Indeed - he will be missed. (nt) (0.00)
Posted by Jim Dowdy on 2016-04-22, 11:05:05 (162.230.26.55)
RIP .......
95: General Asylum, RE: Paul Kantner of Jefferson Airplane Dead (0.00)
Posted by Jim Dowdy on 2016-01-29, 15:37:45 (162.230.26.55)
What a unique brain/talent...I was privileged to see him perform many times; I was never disappointed. Ave atque vale! .......
96: General Asylum, Glen Frey RIP (0.00)
Posted by Jim Dowdy on 2016-01-18, 14:13:08 (162.230.26.55)
A very sad month for rock 'n' roll! .......
97: General Asylum, Tony Glynn - RIP (0.00)
Posted by Jim Dowdy on 2015-10-21, 17:19:26 (162.230.26.55)
The original Mr. Lowther America: Tony Glynn, died on October 15th. Tony was an iconoclastic lover of music...he was my friend, and I admired the hell out of him. Salud! .......
98: Tube DIY Asylum, yawn (0.00)
Posted by Jim Dowdy on 2015-01-29, 19:24:52 (24.99.22.29)
Are you serious? .......
99: Tube DIY Asylum, ??? (0.00)
Posted by Jim Dowdy on 2015-01-29, 19:23:09 (24.99.22.29)
Is your point that perhaps 10% thought otherwise? If so, what does that imply? .......
100: Tube DIY Asylum, YMMV (0.00)
Posted by Jim Dowdy on 2015-01-29, 19:12:36 (24.99.22.29)
But I've engaged in literally dozens of listening tests, and the MV rectified L-filter always wins. .......
101: Tube DIY Asylum, RE: Whoa (0.00)
Posted by Jim Dowdy on 2015-01-29, 19:05:55 (24.99.22.29)
I am certainly open to other's opinions/experiences; but if you've built literally dozens of power supplies and find one approach consistently sounds best, it is folly to pretend otherwise. ::: TOPIC: .......
102: Tube DIY Asylum, my multiple insecurities quake at your machismo (0.00)
Posted by Jim Dowdy on 2015-01-29, 18:53:36 (24.99.22.29)
I suggested that you try an approach that I believe sounds better. I am unsure what my suggestions have to do with Dennis Fraker...or anyone else. My sole motivation was to assist (you and) the DIY c .......
103: Tube DIY Asylum, should everyone have the same preference? (0.00)
Posted by Jim Dowdy on 2015-01-29, 18:09:15 (24.99.22.29)
For full-range musical reproduction, I believe so. .......
104: Tube DIY Asylum, was it not as it was in the old days? (0.00)
Posted by Jim Dowdy on 2015-01-29, 18:01:07 (24.99.22.29)
Jeff Medwin is among my oldest of audio acquaintances; and I will never forget/deny his influence. One of my very earliest audio recollections goes back to around 1981: I had a highly-modified Stereo .......
105: Tube DIY Asylum, I have listened... (0.00)
Posted by Jim Dowdy on 2015-01-29, 17:19:49 (24.99.22.29)
to many, many similar supplies...and they all sound like absolute crap compared to a simple MV-rectified dual L-filter. Have you compared? .......
106: Tube DIY Asylum, Crazy Eddie (0.00)
Posted by Jim Dowdy on 2015-01-29, 16:58:48 (24.99.22.29)
That's a good question. Ed and I used to actively trade parts back in the '90s - I saw him at several of the VSACs, but lost track of him about 10 years ago...would love to know where he is. He always .......
107: Tube DIY Asylum, fixing a hole (0.00)
Posted by Jim Dowdy on 2015-01-29, 16:47:14 (24.99.22.29)
1) find a piece of wood 2) drill a hole larger than the diameter of the capacitor you are wishing to mount 3) fill area around capacitor with beeswax (or paraffin) 4) enjoy .......
108: Tube DIY Asylum, polite BS/sarcasm (0.00)
Posted by Jim Dowdy on 2015-01-29, 16:40:47 (24.99.22.29)
Exactly how does one kindly answer such a question? The benefits are that it sounds better. .......
109: Tube DIY Asylum, OTS (0.00)
Posted by Jim Dowdy on 2015-01-29, 16:36:52 (24.99.22.29)
I'm in metro Atlanta, GA - the only Oregon (Portland area) tube guys I recall are Gary Pimm and Ed Billeci. I know that Lynn Olsen was originally from there as well... Does that help? ::: TOPI .......
110: Tube DIY Asylum, no expectations (0.00)
Posted by Jim Dowdy on 2015-01-29, 16:20:01 (24.99.22.29)
You should try it if you are curious about exploring sound and the possibilities of higher fidelity. However, if you are fearful of having your preconceptions challenged, you should run in the opposi .......
111: Tube DIY Asylum, the point (0.00)
Posted by Jim Dowdy on 2015-01-29, 15:53:46 (24.99.22.29)
Have you tried it? Have you listened? .......
112: Tube DIY Asylum, indeed (0.00)
Posted by Jim Dowdy on 2015-01-29, 15:52:01 (24.99.22.29)
Its all about you. .......
113: Tube DIY Asylum, thanks for your post (0.00)
Posted by Jim Dowdy on 2015-01-29, 15:48:27 (24.99.22.29)
But: I have not advocated 'modern power supplies' (nor do I even know what that means), and I do not consider my posts to be noise. .......
114: Tube DIY Asylum, what kind of question is that? (0.00)
Posted by Jim Dowdy on 2015-01-29, 15:37:14 (24.99.22.29)
All I can suggest at this point is to compare it to a non-regulated mercury-vapor rectified L-filter...and let us all know what you think. .......
115: Tube DIY Asylum, WTF?!?!?!? (0.00)
Posted by Jim Dowdy on 2015-01-29, 15:10:31 (24.99.22.29)
What are you talking about? I challenge you to find any of my posts that were not directed at trying to assist the DIY community. I sell (at most) five amplifiers per year, and have never once hawked .......
116: Tube DIY Asylum, life changing schematics (0.00)
Posted by Jim Dowdy on 2015-01-29, 14:57:00 (24.99.22.29)
You may see a number of my schematics on the Yahoo 'Boat Anchors' forum. If you will send me an email, I will be glad to supply additional schematics - please indicate the amplifier design/voltage/cu .......
117: Tube DIY Asylum, It is indeed a start... (0.00)
Posted by Jim Dowdy on 2015-01-29, 14:33:59 (24.99.22.29)
But, do you really consider it to be significantly (and/or superior) to a bazillion other approaches to power supply designs? More importantly: have you listened? .......
118: Tube DIY Asylum, 'the things I have to say aren't necessarily simple or easy to understand' (0.00)
Posted by Jim Dowdy on 2015-01-29, 14:18:14 (24.99.22.29)
Yah - perhaps one day we will all be able to comprehend your magnificence. .......
119: Tube DIY Asylum, OK - but, where are your schematics? (nt) (0.00)
Posted by Jim Dowdy on 2015-01-29, 13:52:54 (24.99.22.29)
NT .......
120: Tube DIY Asylum, resignation (0.00)
Posted by Jim Dowdy on 2015-01-29, 13:50:01 (24.99.22.29)
So...once again, you're admitting that you have no schematics of value to post. .......
121: Tube DIY Asylum, obsession(s) with tiny differenences... (0.00)
Posted by Jim Dowdy on 2015-01-29, 13:31:29 (24.99.22.29)
Exactly why do you continue to post? Aren't these 'tiny' obsessions what this is all about? While I do not endorse everything Jeff/Dennis posit - the fact remains that they continue to post real idea .......
122: Tube DIY Asylum, RE: round plate 46 tube? (0.00)
Posted by Jim Dowdy on 2015-01-22, 13:13:24 (24.99.22.29)
That's really interesting - I've owned at least fifty 46 tubes and have never seen one similar. .......
123: SET Asylum, I'm with Tre'... (0.00)
Posted by Jim Dowdy on 2015-01-18, 13:45:06 (24.99.22.29)
I'm still pondering how V2 functions as drawn. .......
124: Tube DIY Asylum, agree with Al (0.00)
Posted by Jim Dowdy on 2015-01-18, 13:37:43 (24.99.22.29)
I've done the same thing (with chokes) on a few breadboards - the inductor was chosen based upon dcr and current handling capability. This should be equally applicable to the primary of an OPT. ::: T .......
125: SET Asylum, RE: Corrected Schematic.... (0.00)
Posted by Jim Dowdy on 2015-01-18, 05:37:36 (24.99.22.29)
The schematic shows no bias reference for the grid of V2. [R(g) or grid choke.] .......
126: Tube DIY Asylum, perhaps you meant charlatans? (0.00)
Posted by Jim Dowdy on 2015-01-16, 15:40:25 (24.99.22.29)
And, who are those charlatans? .......
127: Tube DIY Asylum, best post of 2015! (0.00)
Posted by Jim Dowdy on 2015-01-16, 15:34:31 (24.99.22.29)
GEO: A magnificent post - in my estimation, obtaining the best out of 'old crappy records' is 95+% about what this is all about. Jim .......
128: Tube DIY Asylum, cop outs (0.00)
Posted by Jim Dowdy on 2015-01-16, 15:25:01 (24.99.22.29)
Enjoy your high colonic(s)...the DIY community anxiously awaits your latest/greatest audio contributions. .......
129: Tube DIY Asylum, ars longa vita brevis (0.00)
Posted by Jim Dowdy on 2015-01-16, 15:07:41 (24.99.22.29)
I strongly prefer to be lumped in with those who celebrate music vs those who advocate high-end-audio colonics. .......
130: Tube DIY Asylum, a 'wobbly' supply (0.00)
Posted by Jim Dowdy on 2015-01-16, 14:38:41 (24.99.22.29)
Having established that I do not require a basic course in electronics, are you now changing the subject? This post is not about Dennis Fraker or Jeff Medwin (or anyone else). While I understand multi .......
131: Tube DIY Asylum, a fundamental course in electronics (0.00)
Posted by Jim Dowdy on 2015-01-16, 13:44:52 (24.99.22.29)
I have made no claims about "being a guru;" however, I do claim to be a music lover with functional hearing. I have a BS in Mathematics with an EE minor (and a minor in Philosophy as well). I also hav .......
132: Tube DIY Asylum, Validation... (0.00)
Posted by Jim Dowdy on 2015-01-16, 13:16:25 (24.99.22.29)
My nonsense?!? In order to avoid misquoting you, I am requesting that you reiterate your statement regarding one's inability to hear the difference between power supply inductors measuring thousands o .......
133: Tube DIY Asylum, a reminder re: "delusional idiots" (0.00)
Posted by Jim Dowdy on 2015-01-16, 10:52:57 (24.99.22.29)
This post is from someone who insists you cannot hear the difference in a low dcr power supply choke (approx 20 ohms or less) vs one of several thousand ohms. .......
134: Tube DIY Asylum, my experience with K40s (0.00)
Posted by Jim Dowdy on 2015-01-15, 10:28:11 (24.99.22.29)
I find K40s to be among the best power supply bypass caps - especially so when you consider their price. I have never experienced a failure. .......
135: Tube DIY Asylum, bypassing (0.00)
Posted by Jim Dowdy on 2015-01-01, 09:58:54 (24.99.22.29)
First off, I would like to reiterate what Michael Samra said: for a given system, the smallest coupling cap you can get away with is almost always going to sound better than a comparable larger capaci .......
136: Tube DIY Asylum, Sakuma 845 (0.00)
Posted by Jim Dowdy on 2014-12-31, 06:49:32 (24.99.22.29)
I've have heard Randy Carter's Sakuma-inspired 'il Monstro' on multiple occasions. It sounds great! .......
137: Tube DIY Asylum, no (0.00)
Posted by Jim Dowdy on 2014-12-31, 06:46:47 (24.99.22.29)
Sorry - my first VSAC was in 1999, I believe. .......
138: Tube DIY Asylum, RE: This is the closest I could get (0.00)
Posted by Jim Dowdy on 2014-12-31, 06:41:24 (24.99.22.29)
Googling 'Sakuma VSAC 1997', gives me a blackdahlia.com webpage link that has a brief write-up plus photos. Alternatively, David Smith has posted a path to this page (above). VSAC was sponsored by Bot .......
139: Tube DIY Asylum, sorry (0.00)
Posted by Jim Dowdy on 2014-12-31, 02:15:42 (24.99.22.29)
I tried multiple times to edit - but for some bizarre reason, the system automatically truncates my link. You'll have to do a Google search for 'Sakuma VSAC 1997'...an alternative is to try the method .......
140: Tube DIY Asylum, Sakuma at VSAC 1997 (0.00)
Posted by Jim Dowdy on 2014-12-30, 18:41:46 (24.99.22.29)
Susumu Sakuma was the guest of honor at VSAC 1997, in Silverdale, WA. He brought a couple of his mono amplifiers from Japan and provided an audio concert on a single Altec A-7. Do a Google search for .......
141: SET Asylum, audio advice for the deaf (0.00)
Posted by Jim Dowdy on 2014-12-28, 18:14:13 (24.99.22.29)
This post is from someone who believes that you cannot hear the difference in an 18 ohm PS choke vs one of several thousand ohms. .......
142: SET Asylum, 'at least you're honest about it' (0.00)
Posted by Jim Dowdy on 2014-12-28, 18:11:37 (24.99.22.29)
Do you truly sneer at those who believe that the musical experience is what is most important? It is definitely true that, given a choice between intellectual posturing vs enjoying the music, I always .......
143: SET Asylum, irrelevant? (0.00)
Posted by Jim Dowdy on 2014-12-28, 16:36:35 (24.99.22.29)
How imperious - exactly how is it irrelevant? You, Gusser, and others suggest that how something sounds is of little or no importance. I say it is. Are you sincerely suggesting that people buy Wavel .......
144: SET Asylum, the point may not be the same as my point (0.00)
Posted by Jim Dowdy on 2014-12-28, 16:05:36 (24.99.22.29)
My point is that people purchase SET amps because they hear something that they like. Arguments about the superiority of this topology vs that topology (or the associated charts/measurements/graphs) .......
145: SET Asylum, probably true... (0.00)
Posted by Jim Dowdy on 2014-12-28, 12:40:30 (24.99.22.29)
but completely beside the point. And, I seriously doubt any of them contain PS inductors of a thousand ohms or more. .......
146: SET Asylum, the tired old "I heard an improvement" (0.00)
Posted by Jim Dowdy on 2014-12-27, 13:59:16 (24.99.22.29)
I'd bet that the vast majority of SET amps are purchased because someone "heard an improvement." .......
147: SET Asylum, my vote for best SET Asylum post of 2014! (0.00)
Posted by Jim Dowdy on 2014-12-27, 13:02:06 (24.99.22.29)
Thank you, Larry. .......
148: Tube DIY Asylum, a few Sakuma style amps (0.00)
Posted by Jim Dowdy on 2014-12-27, 12:21:43 (24.99.22.29)
Thomas Meyer of Vinylsavor has built multiple amplifiers inspired by Sakuma - here's a link to his 45>45 amp: http://vinylsavor.blogspot.com/2014/03/pure-45-bliss-part-1.html Search his website for ot .......
149: Tube DIY Asylum, P.S. (0.00)
Posted by Jim Dowdy on 2014-12-26, 11:02:50 (24.99.22.29)
This circuit appears to be dissipating in excess of 15 Watts per output tube (max recommended is 12 Watts). According to the tube curves, at these voltages, the minimum R(k) value should be approx 250 .......
150: Tube DIY Asylum, RE: puzzled once more.... (0.00)
Posted by Jim Dowdy on 2014-12-26, 09:48:37 (24.99.22.29)
Assuming the tubes are all good, my guess is that your cathode resistor is problematic. It could also be in the cathode bypass cap - try disconnecting the cap. I would recommend installing a screen st .......
151: Tube DIY Asylum, Re: Schematic shows 114v which makes more sense (0.00)
Posted by Jim Dowdy on 2014-12-21, 19:18:25 (24.99.22.29)
Yes - was not trying to give you a hard time. As I indicated below, I've built enough 845/GM70 amps to know that those numbers weren't correct. .......
152: Tube DIY Asylum, Thanks, Tre' (0.00)
Posted by Jim Dowdy on 2014-12-21, 19:09:52 (24.99.22.29)
Sorry I did not communicate better...I've built enough 845/GM70 amps to know that the original sim numbers were incorrect. The Cary manual indicates 987 v at the plate of the 845 and 114 v at the cath .......
153: Tube DIY Asylum, no (0.00)
Posted by Jim Dowdy on 2014-12-21, 18:09:54 (24.99.22.29)
I have only been looking at the output stage, and have posted nothing about the 300B. .......
154: Tube DIY Asylum, basic assumptions unchanged (0.00)
Posted by Jim Dowdy on 2014-12-21, 17:55:15 (24.99.22.29)
RCA curves are attached. Once again: 893.6 vpk never gets anywhere near a possible bias point of -89 v...and, drawing 79.4 mA under these parameters does not appear possible. Assuming the above numbe .......
155: Tube DIY Asylum, I am not a Spice Guy, but... (0.00)
Posted by Jim Dowdy on 2014-12-21, 15:10:27 (24.99.22.29)
The 845 op points shown do not make sense. According to the 845 curves, 893.6 vpk never gets anywhere near a possible bias point of -89 v. Using similar logic, drawing 79.4 mA under these parameters .......
156: Tube DIY Asylum, RE: 813 verses 4e27 who has tried both? (0.00)
Posted by Jim Dowdy on 2014-12-16, 06:47:19 (24.99.22.29)
Those are the curves I used - have fun. .......
157: Tube DIY Asylum, RE: 813 verses 4e27 who has tried both? (0.00)
Posted by Jim Dowdy on 2014-12-15, 14:54:53 (24.99.22.29)
I have tried both, but only in triode-wired SE mode - in that setup, I preferred the 4E27. Based upon memory, op point was approx 750 vpk @ 125 mA into an 8k OPT. .......
158: SET Asylum, properly designed driver stages (0.00)
Posted by Jim Dowdy on 2014-12-14, 18:35:41 (24.99.22.29)
One can argue that any properly designed driver will not distort driving any following stage. .......
159: SET Asylum, RE: 1KV DC Link Cap (0.00)
Posted by Jim Dowdy on 2014-12-14, 10:44:18 (24.99.22.29)
Wima also offers the DC Link caps rated for 800 and 900 v. Mouser has many of them in stock. .......
160: Tube DIY Asylum, agree (0.00)
Posted by Jim Dowdy on 2014-12-12, 04:24:44 (24.99.22.29)
The Lundahls wired in common mode are my favorite. .......
161: SET Asylum, Amperite octal time delay relay tube (0.00)
Posted by Jim Dowdy on 2014-12-06, 09:58:09 (24.99.22.29)
Assuming you are operating with a nominal line voltage of 120 v, I recommend keeping the B+ transformer separate from filaments/bias, and install one of the Amperite TDRs on the primary of the B+ tran .......
162: SET Asylum, octal possibilities (0.00)
Posted by Jim Dowdy on 2014-12-06, 05:59:47 (24.99.22.29)
Assuming you are sticking with triodes, the 6SF5, 2C52, and 6SL7 are all possibilities. .......
163: Tube DIY Asylum, you are correct (0.00)
Posted by Jim Dowdy on 2014-12-04, 14:56:51 (24.99.22.29)
I have edited my post for clarity. .......
164: Tube DIY Asylum, RE: update (0.00)
Posted by Jim Dowdy on 2014-12-04, 12:22:34 (24.99.22.29)
Vinnie: I preferred the coke-bottle Mullard EF37A to the 310A, 6J7, 6SJ7, 6C6, etc front-ends...but (to the best of my knowledge), I have never heard a 328. Please note: my experience is with a direct .......
165: Tube DIY Asylum, "this concept is fundamental" (0.00)
Posted by Jim Dowdy on 2014-12-04, 10:07:06 (24.99.22.29)
So, how do we test this allegedly fundamental concept? Perhaps more importantly: what would constitute proof or failure? I glean from the majority of your posts that how something sounds is of no con .......
166: Tube DIY Asylum, are you suggesting... (0.00)
Posted by Jim Dowdy on 2014-12-03, 20:46:01 (24.99.22.29)
that a properly designed L-C-L-C supply with huge L1 and L2 inductors, and several Farads of capacitance in the C1 position would make quality a non-consideration for C2? .......
167: Tube DIY Asylum, ALL DHTs lend themselves to filament bias (0.00)
Posted by Jim Dowdy on 2014-12-03, 20:31:19 (24.99.22.29)
Its simply a question of how much heat are you willing to work around. .......
168: Tube DIY Asylum, RE: Duelund Copper Cast Polarity (0.00)
Posted by Jim Dowdy on 2014-12-03, 07:37:24 (24.99.22.29)
That is the same information that Michael Tehan (former Duelund importer) provided to me. However, that is not an indication that the cap has a specific plus and minus terminal - what is being indicat .......
169: Tube DIY Asylum, agree (0.00)
Posted by Jim Dowdy on 2014-12-03, 07:34:39 (24.99.22.29)
I have never achieved good sonic results with tuned PS chokes. .......
170: Tube DIY Asylum, Tre's Excel spreadsheeet (0.00)
Posted by Jim Dowdy on 2014-12-03, 07:00:36 (24.99.22.29)
Yes - the spreadsheet is excellent! I've been intending to post a thank you note, Tre. .......
171: Tube DIY Asylum, P.S. (0.00)
Posted by Jim Dowdy on 2014-12-02, 14:29:33 (24.99.22.29)
The above op point yields a G(v) of approx - 57 v. .......
172: Tube DIY Asylum, RE: GM 70 (0.00)
Posted by Jim Dowdy on 2014-12-02, 14:27:45 (24.99.22.29)
Please bear in mind that I have only used the GM70 in single-ended mode. For the copper-plates, I recommend approx 685 vpk @ 105 mA per tube - cathode-bias only...a 14 to 16k plate-to-plate primary Z .......
173: Tube DIY Asylum, RE: Time to build an Amp.....Power Tube Selection (0.00)
Posted by Jim Dowdy on 2014-12-02, 12:50:58 (24.99.22.29)
My recommendation would be a very conservatively run PP copper-plate GM70...you'll get an easy 25 to 30 Watts with zero feedback. FWIW: I prefer the 6SN7 LTP phase-inverter with a choke in the cathod .......
174: Tube DIY Asylum, RE: 46 bias (0.00)
Posted by Jim Dowdy on 2014-11-29, 17:56:07 (24.99.22.29)
All of my experience with the 46 is at the 'standard' 250 vpk @ 22 mA operating point. I've heard second-hand rumors of folks running higher voltages/currents, but I've never tried it. Having said th .......
175: SET Asylum, RE: 32 Ohm Drivers // 32 Ohm OPTs (0.00)
Posted by Jim Dowdy on 2014-11-29, 10:14:05 (24.99.22.29)
My earlier posts were a response to Mr. Steady's original question - I had not read the entire thread. In my experience, very few high-frequency drivers sound good when wired in series. .......
176: SET Asylum, RE: if money wasn't a consideration... (0.00)
Posted by Jim Dowdy on 2014-11-29, 09:56:16 (24.99.22.29)
For ultimate fidelity, I do not believe much can rival an OPT that has been designed for a specific output tube/op point and a specific speaker. .......
177: SET Asylum, if money wasn't a consideration.. (0.00)
Posted by Jim Dowdy on 2014-11-29, 09:25:15 (24.99.22.29)
I'd have an OPT custom-wound with desired primary (for a specific tube and op point) and a 32 ohm secondary. .......
178: Tube DIY Asylum, Yes, I am calling you a liar (0.00)
Posted by Jim Dowdy on 2014-11-27, 15:22:31 (24.99.22.29)
Intelligent readers will be able to discern reality. .......
179: Tube DIY Asylum, 'in another portion of the thread' (0.00)
Posted by Jim Dowdy on 2014-11-27, 14:35:48 (24.99.22.29)
And, that is my point: If we are incredibly fortunate...after endless pseudo-intellectual posturing...you might *finally* get around to trying to offer assistance... .......
180: Tube DIY Asylum, delusion (0.00)
Posted by Jim Dowdy on 2014-11-27, 14:27:10 (24.99.22.29)
Your posts have had nothing to do with Vinnie's original question. .......
181: Tube DIY Asylum, what business is this of yours? (0.00)
Posted by Jim Dowdy on 2014-11-27, 14:11:57 (24.99.22.29)
Are you suggesting that I should seek your permission to post in the future? Must everyone on the TubeDIY Forum also bow down to your (allegedly obvious) intellectually superiority...or do the rules o .......
182: Tube DIY Asylum, what am I missing? (0.00)
Posted by Jim Dowdy on 2014-11-27, 13:30:28 (24.99.22.29)
Did Vinnie ask for your opinion on how to improve the phase-inverter? .......
183: Tube DIY Asylum, 'armchair quarterbacks' (0.00)
Posted by Jim Dowdy on 2014-11-27, 13:26:55 (24.99.22.29)
Vinnie posted, looking for help with an amplifier design that is rightly considered a DIY classic. You (and TK) chose to ignore the substance of Vinne's post and instead (yet again...ad nauseum), util .......
184: Tube DIY Asylum, simplistic claims (0.00)
Posted by Jim Dowdy on 2014-11-27, 11:33:19 (24.99.22.29)
I also said that the phase-inverter is identical to many classic push-pull designs. But, yes, I do believe that the fact that the amplifier sounds good is of critical importance. .......
185: Tube DIY Asylum, phase-inverter (0.00)
Posted by Jim Dowdy on 2014-11-27, 10:20:52 (24.99.22.29)
The phase-inverter is identical to many classic push-pull amplifiers. I've heard the amplifier and thought it sounded quite good. .......
186: Tube DIY Asylum, 'the curse of understanding' (0.00)
Posted by Jim Dowdy on 2014-11-26, 19:19:57 (24.99.22.29)
Please post two or three of your designs that are indicative of your all-encompassing mastery of amplifier design. .......
187: Tube DIY Asylum, BS (nt) (0.00)
Posted by Jim Dowdy on 2014-11-26, 12:57:38 (24.99.22.29)
nt .......
188: SET Asylum, Mexican Radio (0.00)
Posted by Jim Dowdy on 2014-11-24, 13:20:40 (24.99.22.29)
nt .......
189: SET Asylum, RE: 'it is not the same tube internally' (0.00)
Posted by Jim Dowdy on 2014-11-23, 16:54:37 (24.99.22.29)
I hear you - but I'm still unconvinced that the biggest difference is not (all but) eliminating the grid to plate capacitance. .......
190: SET Asylum, 'it is not the same tube internally' (0.00)
Posted by Jim Dowdy on 2014-11-23, 14:01:56 (24.99.22.29)
Are you quite certain of this? You may be correct - but it seems to me that it was too easy to simply take a 6J7 and move the grid connection to the base. .......
191: SET Asylum, that's not just any front-end tube... (0.00)
Posted by Jim Dowdy on 2014-11-23, 07:10:26 (24.99.22.29)
It's a coke bottle Mullard EF37A - in my estimation, the very best of the 6J7 equivalents! .......
192: SET Asylum, Link to Thorsten's Legacy 300B (0.00)
Posted by Jim Dowdy on 2014-11-23, 06:24:09 (24.99.22.29)
I have no experience with this circuit - provided for informational purposes. .......
193: SET Asylum, "6J7 has lower distortion than 6SJ7" (0.00)
Posted by Jim Dowdy on 2014-11-23, 06:17:58 (24.99.22.29)
The external grid cap is most likely the biggest contributor to the lower distortion. In general, I've found that tubes with separate grid/plate caps sound better. .......
194: SET Asylum, 6C6 in the WE 91A (0.00)
Posted by Jim Dowdy on 2014-11-22, 09:37:28 (24.99.22.29)
I am not an expert in WE gear, but the attached file is an original WE 91A schematic that clearly labels V1 as a 6C6. I cannot make out the T3 power transformer model number, but it is clearly connect .......
195: SET Asylum, RE: WESTERN ELECTRIC 91A CLONE DISCUSSION (0.00)
Posted by Jim Dowdy on 2014-11-22, 06:00:39 (24.99.22.29)
I'd encourage you to try one of the three 91A variants mentioned in this thread (in no particular order): Joe Roberts' version from Sound Practices #1, or Paul Joppa's parafeed variant of the above, o .......
196: SET Asylum, what are your expectations? (0.00)
Posted by Jim Dowdy on 2014-11-20, 14:41:34 (24.99.22.29)
I was also unaware that you were attempting to be humorous - but, I'm a nerd and often miss such things...this is not a personal attack; however, you appear to have a vendetta against Dennis Fraker an .......
197: SET Asylum, 'I think we could all hear that' (0.00)
Posted by Jim Dowdy on 2014-11-20, 14:27:31 (24.99.22.29)
I have serious doubts that 'we could all hear that.' I'm not saying that you could not; nor am I suggesting that some relatively small percentage of people listeners would be able to hear it on their .......
198: SET Asylum, partially bypassed R(k) (0.00)
Posted by Jim Dowdy on 2014-11-18, 19:48:36 (24.99.22.29)
A partially bypassed R(k) is one in which some portion of the R(k) has a bypass cap and some portion of it does not. To use a specific example (one that I am listening to as I type this): the cathode .......
199: SET Asylum, words have meaning (0.00)
Posted by Jim Dowdy on 2014-11-18, 18:37:12 (24.99.22.29)
I am not attempting to be argumentative, but it does not matter what may or may not have become common usage on the internet; the words in use here have a very clear meaning. Any cap (of any size) th .......
200: SET Asylum, definitions (0.00)
Posted by Jim Dowdy on 2014-11-17, 20:42:07 (24.99.22.29)
If an R(k) has a parallel cap connected from cathode to ground, it is fully bypassed. The amount of capacitance may be inadequate for full range performance, but that is a different issue. ::: TOPIC .......
201: Tube DIY Asylum, my opinion (0.00)
Posted by Jim Dowdy on 2014-11-13, 17:37:37 (24.99.22.29)
Yes, the Black Gates were the best sounding electrolytics ever...but I never found them to sound any better than a run-of-the-mill ASC oiler. And (for considerably less money) you never had to be con .......
202: Tube DIY Asylum, ? (0.00)
Posted by Jim Dowdy on 2014-11-06, 16:53:59 (24.99.22.29)
Tre: I'm not trying to be difficult, but I re-read all of your posts in this thread and did not find any example of your amp with partially bypassed R(k) caps. Your 11/5/2014 (07:44:15 am) post stated .......
203: Tube DIY Asylum, RE: On what? (0.00)
Posted by Jim Dowdy on 2014-11-06, 08:07:09 (24.99.22.29)
We disagree that one can not properly design an amplifier with unbypassed or partially bypassed R(k)s. .......
204: Tube DIY Asylum, We disagree - nt (0.00)
Posted by Jim Dowdy on 2014-11-06, 06:56:24 (24.99.22.29)
nt .......
205: Tube DIY Asylum, "a matter of opinion" (0.00)
Posted by Jim Dowdy on 2014-11-05, 15:11:31 (24.99.22.29)
I interpreted your original post to imply that any amp without fully bypassed R(k)s was, by definition, inferior...and that is what I responded to. Obviously, one's design choices will be predicated .......
206: Tube DIY Asylum, according to me (0.00)
Posted by Jim Dowdy on 2014-11-05, 09:59:17 (24.99.22.29)
And according to a number of other designers whose opinions I value and who have excellent ears. I was responding to what I read in your post as an implication that any amp without fully bypassed R(k .......
207: Tube DIY Asylum, "Cathodes not fully bypassed" (0.00)
Posted by Jim Dowdy on 2014-11-05, 08:55:20 (24.99.22.29)
There are many times when an unbypassed or partially bypassed R(k) sounds better. .......
208: Tube DIY Asylum, RE: my experience with KT88/6550 (0.00)
Posted by Jim Dowdy on 2014-11-04, 05:20:50 (24.99.22.29)
My first amp was a Heath W5, and I spent years modifying UL-wired EL34 and KT88/6550 amps. These days, I prefer the sound of directly-heated triodes - but its fun to remember those UL days! ::: TOPIC .......
209: Tube DIY Asylum, Miller effect and tubes with plate caps (0.00)
Posted by Jim Dowdy on 2014-11-03, 05:22:51 (24.99.22.29)
One of the benefits of plate caps is that it offers optimal distance between the grid and the plate. This makes for extremely low input capacitance, which tends to make Miller effect a non-issue. I a .......
210: Tube DIY Asylum, my favorite 2A3 op point (0.00)
Posted by Jim Dowdy on 2014-11-02, 13:52:10 (24.99.22.29)
240 vpk @ approx 53 mA into a 5k load. FWIW: this is about 85% of max rated dissipation. .......
211: Tube DIY Asylum, my experience with KT88/6550 (0.00)
Posted by Jim Dowdy on 2014-11-02, 06:04:50 (24.99.22.29)
In my experience, the KT88/6550 consistently sounded best at about 80 to 85% of max dissipation. Note: all of my experimentation was UL-wired, fixed-bias push-pull into 90 dB or higher speakers. Prima .......
212: General Asylum, The world rocks just a little less hard today (0.00)
Posted by Jim Dowdy on 2014-10-25, 12:00:43 (24.99.22.29)
:-( .......
213: Tube DIY Asylum, triode-wired 7788 anecdotes (0.00)
Posted by Jim Dowdy on 2014-10-09, 18:53:55 (24.99.22.29)
While my experience with triode-wired 7788s is limited to a single application [with my choice of six different Amperex tubes]; I had zero problems from Day 1. In contrast, I found the 6C45/6S45 MUCH .......
214: SET Asylum, I can't believe anyone would modify a current WAVAC amp... (0.00)
Posted by Jim Dowdy on 2014-09-22, 01:58:13 (24.99.22.29)
But, I'd love to see and hear about the results ;-) .......
215: Tube DIY Asylum, RE: No (0.00)
Posted by Jim Dowdy on 2014-09-13, 06:36:48 (24.99.22.29)
Thanks for the info, Ed. I'd suspected Alesa Vaic may be involved. .......
216: Tube DIY Asylum, perhaps I need to re-read the entire thread... (0.00)
Posted by Jim Dowdy on 2014-09-08, 16:07:40 (24.99.22.29)
I'm not being critical, just trying to understand - given the overall expense of this undertaking: a) is DanL attempting to limit "full A2 capability?" b) does a 10 mA (stereo) bias supply vs a 50 mA .......
217: Tube DIY Asylum, Yah, but (0.00)
Posted by Jim Dowdy on 2014-09-08, 13:12:24 (24.99.22.29)
I couldn't bring myself to recommend a zener ;-) .......
218: Tube DIY Asylum, RE: couldn't you... (0.00)
Posted by Jim Dowdy on 2014-09-08, 10:49:19 (24.99.22.29)
Thanks for the explanation, TK. Off the top of my head, I was guesstimating a 2k7 5 Watter would work (which would draw approx 18 mA per channel) - so, you'd probably need a bias supply that could sup .......
219: Tube DIY Asylum, couldn't you... (0.00)
Posted by Jim Dowdy on 2014-09-08, 10:18:50 (24.99.22.29)
Eliminate the diode and install an appropriately sized resistor in parallel with C3? .......
220: Tube DIY Asylum, RE: Ayon AA 62B (0.00)
Posted by Jim Dowdy on 2014-09-08, 06:58:23 (24.99.22.29)
I was attracted by the Ayon AA 62B's R(p) of 470 ohms. But, they are unavailable for DIY; and, even if you own an Ayon 62B amp, replacement tubes are $1,600 each! At that price, I'll stick with GM70s .......
221: Tube DIY Asylum, No (0.00)
Posted by Jim Dowdy on 2014-09-07, 17:24:02 (24.99.22.29)
The tube is only available for use in Ayon amplifiers. If you own an AA 62B amplifier and need to replace a tube, they cost $1,600 each. .......
222: Tube DIY Asylum, just found out: AA 62B is a proprietary product - nt (0.00)
Posted by Jim Dowdy on 2014-09-07, 14:06:26 (24.99.22.29)
nt .......
223: Tube DIY Asylum, Ayon AA 62B (0.00)
Posted by Jim Dowdy on 2014-09-07, 12:01:49 (24.99.22.29)
Has anyone experimented with this tube? Any info would be appreciated - thanks. .......
224: Tube DIY Asylum, please elaborate re: K-horns (0.00)
Posted by Jim Dowdy on 2014-09-05, 18:34:49 (24.99.22.29)
Are you saying the realm above 375 Hz is problematic? .......
225: Tube DIY Asylum, 300B experiments (0.00)
Posted by Jim Dowdy on 2014-09-02, 22:04:53 (24.99.22.29)
By 'explored,' I am referring to experimentation/listening to what sounded best to me on my system. I used newly manufactured WE tubes and the vast majority of the listening was bi-amped (listening to .......
226: Tube DIY Asylum, "all opinions...converge" (0.00)
Posted by Jim Dowdy on 2014-09-02, 13:29:00 (24.99.22.29)
Perhaps if we were able to listen without bias/prejudice [into similar, practical speakers], opinions might converge. But, in the real world - we need to accept that they do not...and, that is one of .......
227: MagneQuest/Peerless Forum, MQ 30 W parafeed OPTs for sale (0.00)
Posted by Jim Dowdy on 2014-08-29, 05:56:11 (24.99.22.29)
The MQ FS-100 plate chokes have been sold. Still have a pair of the 30 Watt M4, Kraft paper, with Exolinear windings FS-100 PFs available for $550 - free shipping in the US. Mike approved this relisti .......
228: Tube DIY Asylum, RE: SRPP SPICE Results (0.00)
Posted by Jim Dowdy on 2014-08-24, 21:29:36 (24.99.22.29)
Thanks, TK - your efforts are greatly appreciated! While I was aware that the SRPP load must be above some certain point, I'd not considered what happens when that load greatly exceeds that point. : .......
229: Tube DIY Asylum, Huh? (0.00)
Posted by Jim Dowdy on 2014-08-24, 16:30:06 (24.99.22.29)
Author Gordon Rankin refers to it as an SRPP multiple times in the article. In your estimation, exactly what sized R(g) would make it function as a proper SRPP? .......
230: Tube DIY Asylum, I'm curious... (0.00)
Posted by Jim Dowdy on 2014-08-04, 13:34:08 (24.99.22.29)
What is the application? It sounds like a very specialized application - you'd almost certainly have to seek something custom-wound. .......
231: Tube DIY Asylum, info (0.00)
Posted by Jim Dowdy on 2014-07-24, 08:01:47 (24.99.22.29)
Lew: Emission Labs currently manufactures the AZ4 mesh-plate rectifier - this link contains info on that tube, plus some basic info on some of the others mentioned by Andy. .......
232: SET Asylum, RE: GM70 anecdote (0.00)
Posted by Jim Dowdy on 2014-06-24, 13:00:00 (24.99.22.29)
I travel a reasonable amount - so I'd guesstimate that it averages out to something like 200 days per year of 4+ hours per day. .......
233: SET Asylum, GM70 anecdote (0.00)
Posted by Jim Dowdy on 2014-06-24, 09:56:52 (24.99.22.29)
I've been using the same pair of copper plate GM70s since 2001 with no problems. 20.0 vdc on the filaments, running 685 vpk. .......
234: SET Asylum, half-wave rectification (0.00)
Posted by Jim Dowdy on 2014-06-03, 15:39:09 (24.99.22.29)
There are arguments for experimenting with half-wave rectification, but it is not adequately addressed in this schematic. Half-wave rectification pushes the nasties down to a lower frequency (60/50 H .......
235: SET Asylum, VT52 (0.00)
Posted by Jim Dowdy on 2014-06-03, 09:47:32 (24.99.22.29)
The VT52 is also known as the 2C45 and/or the '45 Special.' See the link below for more info. I'm running mine with 7.0 vac on the filaments; 340 vdc plate-to-ground with an R(k) of 1k35 ohms (two 2k7 .......
236: SET Asylum, RE: Nature Sound Permalloy OPT (0.00)
Posted by Jim Dowdy on 2014-06-03, 09:09:19 (24.99.22.29)
Glad to help. If their OPTs are anywhere near as nice as their permalloy chokes, they should sound wonderful! I would recommend keeping current draw below 75 mA (though that's probably not a concern w .......
237: SET Asylum, RE: Nature Sound Permalloy OPT (0.00)
Posted by Jim Dowdy on 2014-06-03, 08:47:14 (24.99.22.29)
The Nature Sound SE OPTs were permalloy transformers designed for 8 Watts and max unbalanced DC of approx 75 mA. The more common NS-30 had a single 3k primary, while the NS-70 had multiple primary tap .......
238: Tube DIY Asylum, you should have your OPTs by Christmas (0.00)
Posted by Jim Dowdy on 2014-05-25, 08:55:31 (24.99.22.29)
I have ordered multiple items from Pieter and they always seem to take about a year to arrive. .......
239: Tube DIY Asylum, Tre is correct (0.00)
Posted by Jim Dowdy on 2014-05-25, 08:53:05 (24.99.22.29)
The Output Transformers would not be able to handle the unbalanced DC in single-ended mode. .......
240: Tube DIY Asylum, SE47 guitar amp (0.00)
Posted by Jim Dowdy on 2014-04-16, 08:53:52 (50.147.222.176)
One of my favorite SE guitar tubes - I used AC filaments into an 8k OPT and had no major hum. Please keep us posted. .......
241: Tube DIY Asylum, RE: Help with finding cooling caps for big eimac pentodes please. (0.00)
Posted by Jim Dowdy on 2014-04-02, 18:24:17 (50.147.222.176)
Eimac HR-5 plate caps (for the 4E27) are available on eBay or from a number of online suppliers. The 3C24 uses the HR-1, which is equally available. 4-65A uses the HR-6, although any 3/8" cap can be a .......
242: Tube DIY Asylum, my 6AH4 linestage op points (0.00)
Posted by Jim Dowdy on 2014-04-02, 14:52:32 (50.147.222.176)
180 vpk, drawing approx 24 mA - bias -15 v. Each plate loaded with paralleled pair of 5k6 12 W Mills resistors. Cap-coupled output using a pair of nickel grid chokes...input uses 50k Goldpoint attenua .......
243: Tube DIY Asylum, 6AH4 vs 6CK4 linestage (0.00)
Posted by Jim Dowdy on 2014-04-02, 07:55:12 (50.147.222.176)
I've used the 6AH4 in a couple of builds - a great tube! It sounds best at higher currents...but, it was too noisy with AC on the filaments. Have never tried the 6CK4 - anyone have some recommended .......
244: Tube DIY Asylum, Thanks! (nt) (0.00)
Posted by Jim Dowdy on 2014-03-20, 18:49:02 (50.147.222.176)
nt .......
245: Tube DIY Asylum, I'm curious (0.00)
Posted by Jim Dowdy on 2014-03-20, 10:22:45 (50.147.222.176)
Which DHP are you using? .......
246: Tube DIY Asylum, also... (0.00)
Posted by Jim Dowdy on 2014-03-19, 14:41:54 (50.147.222.176)
Shigeki Yamamoto - famous for his Teflon sockets and his 45 amp kit. And: Soya Susumu - auteur of the directly-coupled dynamic A2 circuit. .......
247: Tube DIY Asylum, 46 op points (0.00)
Posted by Jim Dowdy on 2014-03-19, 14:34:02 (50.147.222.176)
I made a bad joke one time about running the 46 in UL mode - and a number of people took me seriously. So sorry...it now seems impossible to quell that poor attempt at humor. The 46 is a wonderful tu .......
248: Tube DIY Asylum, also not known .... (0.00)
Posted by Jim Dowdy on 2014-03-19, 11:24:27 (50.147.222.176)
While Shishido-san loved SE circuitry, he was not a fan of horns. Much of the reason he pursued A2 designs was to find the perfect amp for his beloved Spendor BC-1s. .......
249: Tube DIY Asylum, changing the primary impedance of OPTs (0.00)
Posted by Jim Dowdy on 2014-03-09, 18:44:17 (50.147.222.176)
Cleet: The primary impedance of an OPT is based upon the R(p) of the output tube and the stepdown ratio of the OPT to the speaker being driven. Additionally, the chosen inductance of the OPT is based .......
250: Tube DIY Asylum, they make great PS bypass caps (nt) (0.00)
Posted by Jim Dowdy on 2014-01-24, 08:47:04 (50.147.222.176)
nt .......
251: SET Asylum, Rectification? (0.00)
Posted by Jim Dowdy on 2014-01-19, 09:52:43 (50.147.222.176)
I'm curious about the rectification - can you provide details? Thanks. .......
252: Tube DIY Asylum, a significant... (0.00)
Posted by Jim Dowdy on 2014-01-10, 17:56:00 (50.147.222.176)
A significant part of my point is that this test is not about sonic timbre/accuracy. .......
253: Tube DIY Asylum, Yep - its Simon! (0.00)
Posted by Jim Dowdy on 2014-01-10, 14:44:16 (50.147.222.176)
I scored 77.8% as well...although I'm unsure what this has to do with Tube DIY Audio. .......
254: Tube DIY Asylum, agree (0.00)
Posted by Jim Dowdy on 2013-12-17, 10:08:19 (24.156.94.75)
While I have not compared the two, there's no doubt that (for a non-commercial product) I would choose the ES-025. .......
255: Tube DIY Asylum, "without bypassing sounded better to me" (0.00)
Posted by Jim Dowdy on 2013-12-09, 15:39:53 (50.147.222.176)
If you thought it sounded better without the bypass cap, why would you consider adding a bypass cap? .......
256: Tube DIY Asylum, yes (0.00)
Posted by Jim Dowdy on 2013-12-05, 18:23:42 (50.147.222.176)
I was suggesting wiring the two channels in parallel. In my experience, any 'problems' are overwhelmed by the sonic advantages. YMMV. .......
257: Tube DIY Asylum, not necessarily (0.00)
Posted by Jim Dowdy on 2013-12-05, 11:51:32 (50.147.222.176)
Using a 2A3 for example: the 'standard' cathode resistor is 750 ohms; if you wire them in parallel, your effective plate resistance is: (750/2) x (4.2 + 1) + 800 = 2.75 kohms This works extremely well .......
258: Tube DIY Asylum, in my experience... (0.00)
Posted by Jim Dowdy on 2013-11-04, 13:42:36 (50.147.222.176)
Chip is correct with the majority of 9 pin miniature tubes - but, I will note two exceptions: 1) Output tubes (in particular the EL84) sound best as close to 6.3 v as reasonably possible, and 2) high .......
259: Tube DIY Asylum, try the Magnequest Asylum page (0.00)
Posted by Jim Dowdy on 2013-10-18, 11:15:29 (50.147.222.176)
I suggest you post on the Magnequest Asylum page. Jim .......
260: Tube DIY Asylum, what Ralph said (0.00)
Posted by Jim Dowdy on 2013-10-01, 15:06:27 (50.147.222.176)
Lew: I don't know your exact schematic, but my guess is that there is a problem with the bias supply. Its a shame when a problem takes out tubes as rare/cool as the 7241. Jim .......
261: Tube DIY Asylum, output impedance (0.00)
Posted by Jim Dowdy on 2013-07-06, 11:54:19 (50.147.222.176)
I believe Scott was pointing out that you have approx 300 ohms at the primary of the OPT. Actual output z will be less than 1 ohm. .......
262: Tube DIY Asylum, not stupid (0.00)
Posted by Jim Dowdy on 2013-05-22, 20:02:41 (65.6.132.235)
I can certainly accept that many may believe this approach should be avoided. However, this is DIY audio - there is nothing inherently stupid about this approach. .......
263: Tube DIY Asylum, yes (0.00)
Posted by Jim Dowdy on 2013-04-18, 16:36:03 (65.6.132.235)
Although Iczerman is encouraged to chime in as well. .......
264: Tube DIY Asylum, CMC (0.00)
Posted by Jim Dowdy on 2013-04-18, 15:33:17 (65.6.132.235)
Could you please provide more specifics about your CMC experiments? .......
265: MagneQuest/Peerless Forum, RE: For Sale: one pair 8k cobalt B7s (0.00)
Posted by Jim Dowdy on 2013-03-27, 10:48:50 (65.6.132.235)
Thanks, X! .......
266: MagneQuest/Peerless Forum, For Sale: one pair 8k cobalt B7s (0.00)
Posted by Jim Dowdy on 2013-03-25, 10:51:23 (65.6.132.235)
Mike provided the OK for me to list these for sale. One pair NOS 8k cobalt B7s for sale - $600/pair or best offer. Jim .......
267: Tubes Asylum, 6A5 (0.00)
Posted by Jim Dowdy on 2013-01-29, 14:36:19 (65.6.132.235)
An odd tube - very similar to the 6B4G. The majority of the ones I've seen appear to be as you described: a center-tapped 6B4; 'though some have what I can only describe as a 'sleeve' around the heat .......
268: Tube DIY Asylum, I was there... (0.00)
Posted by Jim Dowdy on 2013-01-28, 14:25:16 (65.6.132.235)
when Tex was conducting the experiment - and the green LEDs sounded best in this application. .......
269: Tube DIY Asylum, Wright phono stage (0.00)
Posted by Jim Dowdy on 2013-01-27, 17:13:21 (65.6.132.235)
When discussing bang-for-buck products, I still believe very little can touch the George Wright phono stage. .......
270: Tube DIY Asylum, no (0.00)
Posted by Jim Dowdy on 2013-01-21, 13:24:14 (65.6.132.235)
I built to see what sounded best. Easy enough to try. .......
271: Tube DIY Asylum, you are correct (0.00)
Posted by Jim Dowdy on 2013-01-21, 12:14:09 (65.6.132.235)
But you're well below anything audible. .......
272: Tube DIY Asylum, comparison (0.00)
Posted by Jim Dowdy on 2013-01-21, 11:45:50 (65.6.132.235)
You can easily compare the sound with unbypassed cathode resistors. Which sounds better? To compare bypassed cathode resistors, look at a SE 2A3 run at standard op points: Listen to your setup with .......
273: Tube DIY Asylum, gossip (0.00)
Posted by Jim Dowdy on 2013-01-21, 09:16:40 (65.6.132.235)
In my experience (as long as they are adequately rated), a shared biasing resistor sounds better. .......
274: Tube DIY Asylum, no (0.00)
Posted by Jim Dowdy on 2012-12-19, 14:00:05 (24.121.161.57)
If you don't like what they have to say, skip by their posts. Problem solved. .......
275: Tube DIY Asylum, RE: Oil coupling caps (0.00)
Posted by Jim Dowdy on 2012-07-09, 14:49:00 (24.248.85.3)
The Jensens that I have the most experience with are in (silver-colored) aluminum cans with an orange-ish plastic covering. Jensen now offers 4 case options: aluminum, paper, copper, and ceramic - I .......
276: Tube DIY Asylum, RE: Oil coupling caps (0.00)
Posted by Jim Dowdy on 2012-07-08, 09:00:07 (24.248.85.3)
Both are very good caps. In my experience, the Jupiter caps will add less of their own sonic signature, but the Jensen copper-foil oilers have a lovely tone that can be addictively synergistic. ::: T .......
277: Tube DIY Asylum, fellatious arguments (0.00)
Posted by Jim Dowdy on 2012-04-18, 12:35:18 (24.248.85.3)
Fellatious arguments are what got Bill Clinton in trouble with Monica Lewinsky. .......
278: General Asylum, RIP Jim Marshall (0.00)
Posted by Jim Dowdy on 2012-04-05, 10:17:34 (24.248.85.3)
nt .......
279: Tube DIY Asylum, WE 421A (0.00)
Posted by Jim Dowdy on 2012-01-21, 10:17:05 (65.6.132.235)
Another big advantage of the WE 421A is that it (unlike the 6AS7) can reliably be found with matching tube halves. .......
280: Tube DIY Asylum, which product? (0.00)
Posted by Jim Dowdy on 2012-01-20, 07:03:44 (65.6.132.235)
It might be helpful to know which of George's products you need help with. For example: I've got pretty detailed info on his phono pre. Jim .......
281: Tube DIY Asylum, 6AH4 into a 1:1 trannie (nt) (0.00)
Posted by Jim Dowdy on 2012-01-08, 08:31:48 (65.6.132.235)
nt .......
282: SET Asylum, copper-plate GM70 (0.00)
Posted by Jim Dowdy on 2011-12-27, 17:22:01 (65.6.132.235)
Any two-stage, all-DHT design should perform extremely well. .......
283: SET Asylum, RE: Tamura VL-208 (0.00)
Posted by Jim Dowdy on 2011-11-29, 13:24:08 (74.131.88.70)
João: Send me an email if you're interested in purchasing NOS VL-208s. Jim .......
284: Tube DIY Asylum, RE: WE/TJ 101D & 26 (0.00)
Posted by Jim Dowdy on 2011-10-21, 05:08:56 (65.6.132.235)
The 26 requires battery filaments in my estimation; even then it won't beat the original WE 101D. Sorry, but I have no experience with the TJs. Jim .......
285: Tube DIY Asylum, RE: 2A3 Project with Eimac driver (0.00)
Posted by Jim Dowdy on 2011-09-25, 15:52:55 (65.6.132.235)
I have built several similar amps - the first one about 10 years ago. In my experience, the 3C24 is happier (and sounds better) with a plate voltage of at least 400 v. Jim .......
286: Tubes Asylum, RE: Anybody bought from USSR-Tubes.com? (0.00)
Posted by Jim Dowdy on 2011-08-06, 08:07:12 (24.246.180.130)
My experience matches Ironbut's: good tubes, but delivery to the USA was s-l-o-w. Jim .......
287: Tube DIY Asylum, ESL 57 iron (0.00)
Posted by Jim Dowdy on 2011-08-06, 08:04:37 (24.246.180.130)
Go Dave, go! And keep us all posted. Jim .......
288: Tube DIY Asylum, screen drive (0.00)
Posted by Jim Dowdy on 2011-07-26, 05:07:58 (24.246.180.130)
Screen drive is best suited for modern high-perveance tubes (like the EL509). I love the look of the old Telefunken pentodes, but would recommend a push-pull design similar to the old Lorenz LVA/B 30 .......
289: MagneQuest/Peerless Forum, PP 300B (0.00)
Posted by Jim Dowdy on 2011-07-16, 14:10:12 (24.246.180.130)
The AS-250 looks like push-pull 300B territory to me. I have a good friend running stacked ESL 57s with a similar amp; he is using a small amount of negative feedback. Good luck and keep us posted! .......
290: Amp/Preamp Asylum, Yes! (0.00)
Posted by Jim Dowdy on 2011-07-14, 10:57:44 (24.246.180.130)
Will gladly provide references. Jim .......
291: Tube DIY Asylum, I agree with Chris... (0.00)
Posted by Jim Dowdy on 2011-07-04, 09:17:27 (24.246.180.130)
A tough road - here's a link showing a Shishido-style 805: .......
292: Tube DIY Asylum, Johnson sockets (0.00)
Posted by Jim Dowdy on 2011-06-24, 07:31:24 (24.246.180.130)
I am not an expert in Johnson sockets, but I have only seen one type of Johnson Septar. Of course, I have only seen one type of Johnson 813 socket as well. ;-) Jim .......
293: Tube DIY Asylum, agree (0.00)
Posted by Jim Dowdy on 2011-06-23, 16:09:07 (24.246.180.130)
Most of my septar experience is with the 826, but its hard to beat the old Johnson sockets. As Al says: the Chinese are OK, and the HATs fall apart. I also like the Yamamotos, but they are pricey. J .......
294: Tube DIY Asylum, RE: DCAudioDIY Room at Capital Audiofest (0.00)
Posted by Jim Dowdy on 2011-06-21, 06:58:41 (24.246.180.130)
Very cool - I'll see you there! Jim .......
295: SET Asylum, I'm still here! (0.00)
Posted by Jim Dowdy on 2011-05-17, 08:24:25 (67.42.173.110)
While its true that I have been a full-time grad student for the past couple of years - I am still actively building amplifiers for customers. I am currently at a customer's place in Montana setting u .......
296: Tube DIY Asylum, 300B as pass tubes (0.00)
Posted by Jim Dowdy on 2011-05-17, 08:19:15 (67.42.173.110)
The last major production run of WE 300Bs was for pass tubes by the FAA and NASA. (I'm referring to the pre-Whitener WE here.) .......
297: Tubes Asylum, Re: Fender Reissued Reverb tank (0.00)
Posted by Jim Dowdy on 2011-04-23, 10:34:50 (24.246.180.130)
Thanks for the report. I've got one of the high-impedance Accutronics units awaiting some attention...just gotta graduate first! Jim .......
298: Tube DIY Asylum, 18 Watt.com (0.00)
Posted by Jim Dowdy on 2011-03-31, 03:32:21 (24.246.180.130)
It's still operational. I believe you need to register with the Wattkins.com forum for access. .......
299: Tube DIY Asylum, RIP Allen (0.00)
Posted by Jim Dowdy on 2011-02-28, 21:08:00 (24.246.180.130)
I'll never forget first meeting Allen at one of the VSACs. His lectures were standing room only!! RIP Allen. Jim .......
300: Tube DIY Asylum, RE: 6SF5GT in Guitar Front End? (0.00)
Posted by Jim Dowdy on 2011-02-19, 10:07:01 (151.199.107.158)
I love them in this application! But as others have noted, they can be microphonic. Jim .......
301: OTL Asylum, all things being equal... (0.00)
Posted by Jim Dowdy on 2010-12-19, 11:28:34 (24.246.180.130)
I'm of the opinion that a SEPP stage sounds better than a cathode-follower stage. .......
302: SET Asylum, agree re: 12B4 (0.00)
Posted by Jim Dowdy on 2010-10-24, 10:41:02 (24.246.180.130)
12B4 is a great-sounding tube! .......
303: Tube DIY Asylum, :-) (0.00)
Posted by Jim Dowdy on 2010-06-24, 10:36:55 (173.21.198.156)
I spent five or six years attempting to get those Acoustat amps to function for longer than a few months at a time - fond memeories and fun times, but ultimately frustrating! .......
304: Tubes Asylum, RE: 6HA5 tube (0.00)
Posted by Jim Dowdy on 2010-06-19, 07:32:46 (173.21.198.156)
EC900 is cross-listed as 6HA5/6HM5. Both are high-mu triodes. .......
305: Tubes Asylum, Taylor 825 (0.00)
Posted by Jim Dowdy on 2010-06-18, 09:40:45 (173.21.198.156)
I am unfamiliar with tube tester; you can find 825 tube data here: .......
306: Tube DIY Asylum, Wow (0.00)
Posted by Jim Dowdy on 2010-05-26, 12:39:14 (173.21.198.156)
That's beautiful, Jeff! .......
307: Tube DIY Asylum, Errors in quotations (0.00)
Posted by Jim Dowdy on 2010-05-17, 15:39:17 (173.21.198.156)
Your quotation is spurious; the quote I believe you are referring to is: "And I sincerely believe, with you, that banking establishments are more dangerous than standing armies; and that the principle .......
308: Tube DIY Asylum, RE: OT: Leaving tube audio for an indefinite period (0.00)
Posted by Jim Dowdy on 2010-04-17, 10:02:54 (173.21.198.156)
Best wishes, Kurt! .......
309: SET Asylum, raw parts cost (0.00)
Posted by Jim Dowdy on 2010-04-12, 11:14:57 (173.21.198.156)
The raw parts cost of my basic SE GM70 amplifier is approx $8,000 - this does not include chassis work. .......
310: Tube DIY Asylum, Yes indeed (0.00)
Posted by Jim Dowdy on 2010-03-09, 20:00:10 (173.21.198.156)
Thank you, Pete! .......
311: Tube DIY Asylum, LTP (0.00)
Posted by Jim Dowdy on 2010-01-08, 11:21:17 (173.21.198.156)
If phase inversion is necessary, I generally prefer a transformer. Having said that, I've had good luck using a variation of the LTP, the choke-tail pair. Here's an example of one: .......
312: MagneQuest/Peerless Forum, AV20 vs EML20B (0.00)
Posted by Jim Dowdy on 2009-12-27, 10:05:21 (173.21.198.156)
AVVT is no longer in business - 'tho it is possible that you might find some NOS pairs around. Aside from glancing at the EML20B curves to make sure they were close to my AV20 op points, I have not st .......
313: MagneQuest/Peerless Forum, AV20 (0.00)
Posted by Jim Dowdy on 2009-12-27, 07:51:10 (173.21.198.156)
Jeff: While it has a number of other nice applications, the Dowdy plate choke was originally designed for the AVVT forerunner of the EML 20B, the AV20. The op points I ended up with for the AV20: B+ .......
314: SET Asylum, Yes - indeed (0.00)
Posted by Jim Dowdy on 2009-12-25, 17:12:06 (173.21.198.156)
Happiest of holidays to all! .......
315: Tubes Asylum, Shuguang 6L6GCR experience (0.00)
Posted by Jim Dowdy on 2009-12-24, 09:37:42 (173.21.198.156)
I've only used them in a guitar amp, but the Shuguang 6L6GC perform well and are as tough as nails! .......
316: Tube DIY Asylum, my thoughts (0.00)
Posted by Jim Dowdy on 2009-12-20, 16:26:41 (173.21.198.156)
I'm unsure exactly how much power you are going for...but if I were building an A1 304TL, I'm fairly certain that I'd be looking at the EML 20 (or 30). .......
317: Tube DIY Asylum, 826 set-up (0.00)
Posted by Jim Dowdy on 2009-12-20, 13:22:54 (173.21.198.156)
I'm using 0.22 uf Duelund with a nickel MQ BCP-16 grid choke. 826 plate choke is 550 Hy nickel jobber from Dave Slagle, paralleled with a 330k carbon comp resistor. 826 op points: 510 v @ 9.2 mA; -8. .......
318: Tube DIY Asylum, I understand... (0.00)
Posted by Jim Dowdy on 2009-12-20, 13:16:33 (173.21.198.156)
'Cuz I had to try it also :-) Let me know what you think...it may be (to some extent) a system synergy issue. .......
319: Tube DIY Asylum, more on the 826 (0.00)
Posted by Jim Dowdy on 2009-12-20, 13:12:06 (173.21.198.156)
I'd probably keep it simple and cap-couple; but I'm sure others would disagree. I generally tend to believe that the only reason to transformer-couple is if you are gaining something by the use of th .......
320: Tube DIY Asylum, my opinion (0.00)
Posted by Jim Dowdy on 2009-12-20, 12:58:03 (173.21.198.156)
I have tried the 3C24 front-end with a number of thoriated output tubes, including the 75TL/TH and the 250TL. In my experience, the glorious clarity and razor-sharp imaging of the 3C24 is a near-perfe .......
321: Tube DIY Asylum, 826 (0.00)
Posted by Jim Dowdy on 2009-12-20, 12:31:26 (173.21.198.156)
I offer the 826 as an option for folks who are averse to the exposed plate caps of the 3C24. The additional gain is also nice; but I can tell very little sonic difference between the 826 and the 3C24. .......
322: Tube DIY Asylum, driver thoughts (0.00)
Posted by Jim Dowdy on 2009-12-20, 11:51:42 (173.21.198.156)
I love the 3C24, but the only thoriated filament output tube that I've really liked it with was the copper-plate GM70. .......
323: Tube DIY Asylum, Have your cake and eat it too... (0.00)
Posted by Jim Dowdy on 2009-12-19, 14:38:54 (173.21.198.156)
My mind boggles when I consider every possible combination/permutation that I've analyzed/listened to over the past 3+ decades...but I must admit that I've never tried combination bias. Happy holidays .......
324: Tube DIY Asylum, 845 bias (0.00)
Posted by Jim Dowdy on 2009-12-19, 11:22:13 (173.21.198.156)
With all due respects to Bro Eli, I personally prefer the sound of self-biased 845s/GM70s. .......
325: SET Asylum, 421A vs 5998? (0.00)
Posted by Jim Dowdy on 2009-12-15, 13:29:52 (173.21.198.156)
Hmmm - I could've sworn I posted a response to this. In any case, I'll try again: the 421A exhibits better section matching than just about any other pass tube available; its sonics are also a bit mor .......
326: Tubes Asylum, Yes! (0.00)
Posted by Jim Dowdy on 2009-12-12, 11:37:28 (173.21.198.156)
I'd suggest that the 450TL is a more sane choice. .......
327: SET Asylum, RE: SE guitaramp (0.00)
Posted by Jim Dowdy on 2009-12-03, 10:31:44 (173.17.29.24)
I agree with FenderLover - the best all around SE guitar amp output tube is the 6V6...triode output stages generally aren't worth wasting your time with when it comes to guitar. All of the above is of .......
328: K&K Audio / Lundahl Transformers, Yes, indeed - Beautiful work! (nt) (0.00)
Posted by Jim Dowdy on 2009-11-27, 09:24:24 (173.17.29.24)
nt .......
329: Tube DIY Asylum, RE: Mundorf Silver Oil vs Silver/Gold Oil (0.00)
Posted by Jim Dowdy on 2009-11-25, 05:42:18 (173.17.29.24)
I have only tried the Mundorf Gold Oil Supremes on one occasion. They sound very musical, and may be just about perfect in some set-ups - but for my application, I found them a bit lacking in ultimate .......
330: Tube DIY Asylum, RE: Mundorf Silver Oil vs Silver/Gold Oil (0.00)
Posted by Jim Dowdy on 2009-11-24, 17:35:08 (173.17.29.24)
I've had excellent results with the Mundorf Silver/Gold/Oil Supremes. They do take at least 50 hours to really settle in. .......
331: SET Asylum, Re: Do you prefer 3C24 or 841 as driver? (0.00)
Posted by Jim Dowdy on 2009-11-05, 18:10:15 (173.17.29.24)
It is difficult to provide an easy one-size-fits-all answer. Do you prefer chocolate, vanilla or strawberry? If you prefer strawberry today, are you allowed to prefer vanilla tomorrow...or chocolate n .......
332: SET Asylum, Re: 801A (0.00)
Posted by Jim Dowdy on 2009-11-05, 13:05:45 (173.17.29.24)
I have indeed heard the 801A on a number occasions - as Dave says, it sounds like a muscular 10/10Y. However, I have not personally experimented/built with the 801A. .......
333: Tubes Asylum, reminder (0.00)
Posted by Jim Dowdy on 2009-11-05, 13:02:07 (173.17.29.24)
The specs for the 6F5 and 6SF5 are indeed similar to one-half of a 12AX7...that means you would need a pair of these octals to replace a single 12AX7. .......
334: Tubes Asylum, Even single ended... (0.00)
Posted by Jim Dowdy on 2009-11-02, 17:29:02 (173.17.29.24)
Josh was well beyond 200 SE Watts at VSAC 2003: .......
335: SET Asylum, No lance... (0.00)
Posted by Jim Dowdy on 2009-11-02, 17:09:12 (173.17.29.24)
I'm an advocate of all-DHT designs...in fact, I recommend that you consider the high-mu cousin of the 801, the 841. .......
336: Tube DIY Asylum, "a bit dull in the wrong amp..." (0.00)
Posted by Jim Dowdy on 2009-11-01, 09:22:25 (173.17.29.24)
Thanks for the nudge Kurt. I'll give the 7119 another shot...I thought they sounded "dull" compared to the 7044, but I've only experimented with them on one occasion. .......
337: OTL Asylum, Oy is right! (0.00)
Posted by Jim Dowdy on 2009-10-19, 08:34:49 (173.17.29.24)
I'm curious: what the proposed tube line-up/circuit? .......
338: Tube DIY Asylum, I agree with Eli (0.00)
Posted by Jim Dowdy on 2009-10-14, 07:18:23 (173.17.29.24)
If you are not using high Gm tubes, I see no reason for grid stoppers. If you need grid stoppers, I recommend carbon comp. .......
339: SET Asylum, Sakuma inspired SE (0.00)
Posted by Jim Dowdy on 2009-10-12, 11:48:43 (173.17.29.24)
845 > 845 il Monstro - and it sounds as good as it looks! .......
340: Tube DIY Asylum, Good reminder, Larry (0.00)
Posted by Jim Dowdy on 2009-08-29, 11:26:47 (173.19.65.224)
Section 2 of the 'EM7 definitely begins to sound hard above 150 vpk. .......
341: Tube DIY Asylum, too far? (0.00)
Posted by Jim Dowdy on 2009-08-28, 22:06:38 (173.19.65.224)
Afar and agleam, like a valley of dream, Still mocks you - the land beyond. Robert W. Service .......
342: Tube DIY Asylum, Man, Gordon Holt & George Wright gone in one day! (0.00)
Posted by Jim Dowdy on 2009-08-25, 08:35:04 (173.19.65.224)
Last Thursday was a devastating one for the audiophile community. I wrote a bit about George on the Bottlehead Forum; he truly was one of the good guys. J. Gordon Holt was the first person I ever enco .......
343: Bottlehead Forum, RIP George (0.00)
Posted by Jim Dowdy on 2009-08-24, 07:59:21 (173.19.65.224)
I still recall being blown away by the intense passion on display in George's room at VSAC 2001! What a great guy George was; and what a tremendous loss to our community! Even today, I cannot figure .......
344: Tubes Asylum, what? (0.00)
Posted by Jim Dowdy on 2009-08-18, 15:56:56 (173.19.65.224)
Mr. McShane is mentioned because the original poster mentioned him. The reality is that no one has heard every 6SN7 out there in every possible configuration. Trust your ears. .......
345: Tube DIY Asylum, 6CJ3 would have been my recommendation (nt) (0.00)
Posted by Jim Dowdy on 2009-08-18, 15:47:03 (173.19.65.224)
nt .......
346: Tube DIY Asylum, Chinese food? (0.00)
Posted by Jim Dowdy on 2009-08-12, 08:18:15 (173.19.65.224)
If you are a fan of Chinese food, I'd recommend you try Little Szechuan on Buford Highway in Chamblee. .......
347: Tubes Asylum, Russian EL509 (0.00)
Posted by Jim Dowdy on 2009-08-12, 08:15:46 (173.19.65.224)
I have no experience with the EL509 in traditional triode mode, but it works extremely well as a screen-driven output stage. Link is provided as an example only; I have never heard Bob Danielak's amp. .......
348: Tubes Asylum, Yes... (0.00)
Posted by Jim Dowdy on 2009-05-28, 11:00:31 (173.19.65.224)
I bought several Eimac 35Ts just because they looked so good! .......
349: Tubes Asylum, 307A (0.00)
Posted by Jim Dowdy on 2009-05-20, 08:11:48 (173.19.65.224)
It would be incorrect to say I am "using it" - I picked up some 307As to run as the [pentode-wired] front-end of a Thorsten-inspired 300B amp [WE 91A semi-clone]; and that was the vast majority of my .......
350: Tubes Asylum, Based upon my extremely limited experience... (0.00)
Posted by Jim Dowdy on 2009-05-19, 17:20:32 (173.19.65.224)
Based upon my extremely limited experience, I'd have to go with the 307A. .......
351: MagneQuest/Peerless Forum, Congrats! (nt) (0.00)
Posted by Jim Dowdy on 2009-05-15, 10:18:03 (173.19.65.224)
NT .......
352: Tube DIY Asylum, Yes - welcome back! (nt) (0.00)
Posted by Jim Dowdy on 2009-05-11, 15:51:00 (173.19.65.224)
nt .......
353: Tube DIY Asylum, RE: Nobu Shushido, triode amplifier designer (0.00)
Posted by Jim Dowdy on 2009-05-04, 07:49:43 (173.19.65.224)
I'm going on memory here, but I believe Shishido-san was 59 years old when he died. .......
354: MagneQuest/Peerless Forum, in my experience... (0.00)
Posted by Jim Dowdy on 2009-04-29, 14:53:57 (173.19.65.224)
Maybe it's just me, but in my experience, the 112A is about 110% of a 26 :-) The lack of filament hum hassle is icing on the cake. .......
355: Tube DIY Asylum, Nick's preamp (0.00)
Posted by Jim Dowdy on 2009-04-29, 08:57:49 (173.19.65.224)
Nick is a smart guy, and his preamp looks pretty darn good to me! I've only heard it once, on a completely unknown system, but it seemed to perform well. .......
356: SET Asylum, I avoid these threads (0.00)
Posted by Jim Dowdy on 2009-04-28, 03:50:06 (173.19.65.224)
I avoid these threads because they're boring. The same people essentially repeat themselves over and over. .......
357: Bottlehead Forum, parts not discontinued... (0.00)
Posted by Jim Dowdy on 2009-04-22, 07:44:42 (173.19.65.224)
Can NOS tubes, such as the 5687 be used? I ask because it's readily available from AES, but is not in current production. .......
358: SET Asylum, more re: 841 (0.00)
Posted by Jim Dowdy on 2009-04-17, 11:04:23 (173.19.65.224)
I'm thinking the mu was pretty close to 30 utilizing the Magnequest EXO-99 plate choke...it was plenty of voltage swing for my 2-stage SE 2A3. 385 vdc was the B+ measurement at the plate [to ground]. .......
359: SET Asylum, 841 (0.00)
Posted by Jim Dowdy on 2009-04-17, 06:47:38 (173.19.65.224)
I've never really experimented much with the 801A, but can tell you that the 841 sounds very similar to the 10/10Y - just with more gain. Crisp and super-clean with nice frequency extension, it mates .......
360: SET Asylum, all the best DHTs (0.00)
Posted by Jim Dowdy on 2009-04-14, 13:37:03 (173.19.65.224)
Consider the 841 or the 3C24; I've had good luck with both in 2-stage all-DHT amplifiers. .......
361: Tube DIY Asylum, JEEZ!!! (0.00)
Posted by Jim Dowdy on 2009-04-07, 15:31:08 (173.19.65.224)
Exactly what is the problem here? A member offers a transformer; providing honest specifications; but it's not "good enough?" Well, golly gee, what might qualify as "good enough?" Can no one ever m .......
362: Tube DIY Asylum, Tango NC-15 (0.00)
Posted by Jim Dowdy on 2009-04-02, 10:19:23 (173.19.65.224)
It is an interstage transformer, most commonly used with the 6SN7/6J5. .......
363: Tube DIY Asylum, RE: DC heater? (0.00)
Posted by Jim Dowdy on 2009-03-29, 09:03:43 (173.19.65.224)
I utilized DC, but never gave AC a shot. .......
364: Tube DIY Asylum, RE: DC heater? (0.00)
Posted by Jim Dowdy on 2009-03-28, 18:19:24 (173.19.65.224)
Yes. .......
365: Tube DIY Asylum, 6AH4 (0.00)
Posted by Jim Dowdy on 2009-03-28, 11:32:29 (173.19.65.224)
Best non-DHT linestage I ever built used the 6AH4 - it replaced a 12B4 and I never regretted the change. B+ was 180 vdc, and I'm guessing that I was drawing about 27-28 mA...I can try to dig up my not .......
366: SET Asylum, PAT-4157 (0.00)
Posted by Jim Dowdy on 2009-03-24, 10:41:12 (173.19.65.224)
No tease intended - we were talking about Plitron OPTs, and I thought it worth mentioning. Tube lineup is: EF86 > 12DW7 > 2 x 6C19 choke-tail PI d-ced to 4 x EL84s; with a pair of GZ34 rectifiers. ::: .......
367: SET Asylum, Plitron OPTs (0.00)
Posted by Jim Dowdy on 2009-03-23, 22:58:07 (173.19.65.224)
I've experimented with the PAT-3025, the PAT-3035, the PAT-3050 and the HQ-5090; however, the majority of my experience is with the '3035 (300B) and the '5090 (250TL). All performed superbly, but in .......
368: Tubes Asylum, 3C24 as output tube (0.00)
Posted by Jim Dowdy on 2009-03-17, 08:15:08 (173.19.65.224)
I have no personal experience, but the "classic" operating point is 300 v @ 75 mA into 3.5 k load; this is with a positive bias supply of 35 v. I believe these op points originated with Soya Susumu, b .......
369: Tubes Asylum, RE: Identify this rectifier? (0.00)
Posted by Jim Dowdy on 2009-03-16, 13:30:14 (173.19.65.224)
I agree with Ed - it looks like a re-based Telefunken mesh-plate rectifier, probably an RGN 2504. .......
370: MagneQuest/Peerless Forum, welcome (0.00)
Posted by Jim Dowdy on 2009-03-16, 09:55:13 (173.19.65.224)
Hayesville is a couple of hours west of me; I'm about 15 miles south of Asheville, near the airport. Drop me an email when you get settled in and we'll try to have a get-together (including Anand). :: .......
371: MagneQuest/Peerless Forum, Sold! (0.00)
Posted by Jim Dowdy on 2009-03-16, 07:58:34 (173.19.65.224)
Thanks, TS *and* Mike! .......
372: MagneQuest/Peerless Forum, hi (0.00)
Posted by Jim Dowdy on 2009-03-15, 13:36:51 (173.19.65.224)
I just sent you an offsite note - hope we have a chance to hook up sometime. .......
373: Tubes Asylum, RE: 3c24 help (0.00)
Posted by Jim Dowdy on 2009-03-15, 12:38:16 (173.19.65.224)
That is an excellent operating point; I've had good luck with B+ anywhere between 300 and 450 vdc [same R(k)]. .......
374: MagneQuest/Peerless Forum, cobalt OPTs for sale (0.00)
Posted by Jim Dowdy on 2009-03-14, 09:22:06 (173.19.65.224)
Mike very graciously gave me permission to list this pair of parafeed output transformers for sale: Pinstriped cobalt/M4 TFA-2004 Jrs; 3k primary, 9 or 16 ohm secondary. These are the channel-frame ve .......
375: Tube DIY Asylum, RE: Looking for a mono copy of JC Morrison's 'Strange Days' (0.00)
Posted by Jim Dowdy on 2009-03-10, 18:13:50 (173.19.65.224)
I've been told the same thing about my sense of humor. .......
376: Tube DIY Asylum, RE: Looking for a mono copy of JC Morrison's 'Strange Days' (0.00)
Posted by Jim Dowdy on 2009-03-10, 13:04:38 (173.19.65.224)
Glad someone got it ;-) .......
377: Tube DIY Asylum, Looking for a mono copy of JC Morrison's 'Strange Days' (0.00)
Posted by Jim Dowdy on 2009-03-09, 12:13:20 (173.19.65.224)
Top price paid! .......
378: Vinyl Asylum, Tool - Greenville, SC 2008 (0.00)
Posted by Jim Dowdy on 2009-02-14, 10:47:27 (173.19.65.224)
Would also have to rank Hendrix at Atlanta Pop Festival 1970, and Pink Floyd Atlanta 1977 in the top 3. .......
379: MagneQuest/Peerless Forum, Happy 20th MQ! (nt) (0.00)
Posted by Jim Dowdy on 2009-02-10, 14:31:22 (173.19.65.224)
nt .......
380: OTL Asylum, RE: Covi Mark II (0.00)
Posted by Jim Dowdy on 2009-02-04, 12:14:04 (173.19.65.224)
Sorry, for any confusion. Click on 'Tubes' (under the Amplifier heading): .......
381: MagneQuest/Peerless Forum, rest up! (0.00)
Posted by Jim Dowdy on 2009-02-04, 11:39:49 (173.19.65.224)
Take care of yourself, bro. Believe it or not, I was going to call and order another pair of FS-100 plate chokes this week...but, it was only to have an extra pair on the shelf. .......
382: OTL Asylum, Covi Mark II (0.00)
Posted by Jim Dowdy on 2009-02-04, 11:33:20 (173.19.65.224)
Try posting this question over at the DIY Audio Tube Forum. Kevin Kennedy hangs out there and he should have the info you seek. .......
383: Tube DIY Asylum, agreed (0.00)
Posted by Jim Dowdy on 2009-01-20, 15:29:51 (173.19.65.224)
Jeez guys - lighten up. Jeff posts something he likes. You are free to accept it or reject it. From my perspective, that is the purpose of this forum. End of story. I've encountered many things over t .......
384: MagneQuest/Peerless Forum, RE: Thanks, guys! I'll just stick to 6.3V. nt (0.00)
Posted by Jim Dowdy on 2009-01-04, 07:39:36 (173.19.65.224)
I have limited experience with this tube, but a B+ of 14 v and a 1k cathode resistor worked quite well. This results in a current draw of approx 0.9 mA [and a G(v) of about -0.9 v]. I also recommend .......
385: OTL Asylum, SE OTLs (0.00)
Posted by Jim Dowdy on 2009-01-04, 07:29:43 (173.19.65.224)
I agree that phase inversion is a significant weak point. I've built two different SE OTLs and they sounded mighty nice. .......
386: Tube DIY Asylum, RE: UL wired driver? (0.00)
Posted by Jim Dowdy on 2008-12-30, 13:16:03 (173.19.65.224)
UL operation is still a bit mysterious to me...can you enlighten us a bit re: op point, inductance, and UL tap point? Which curves are you referring to? .......
387: Tube DIY Asylum, RE: UL wired driver? (0.00)
Posted by Jim Dowdy on 2008-12-30, 13:12:47 (173.19.65.224)
Again, the post was made somewhat in jest; the 46 was never really designed for tetrode use. Still, I do find the idea intriguing... I'd guesstimate that anything over about 100 Hy would work. ::: TO .......
388: Tube DIY Asylum, RE: UL wired driver? (0.00)
Posted by Jim Dowdy on 2008-12-30, 08:41:25 (173.19.65.224)
The posting was made somewhat in jest - but you can do it using a center-tapped plate choke. Mike LaFevre posted something similar a while back on the MQ Forum. .......
389: Tube DIY Asylum, UL wired 46 (0.00)
Posted by Jim Dowdy on 2008-12-29, 14:48:21 (173.19.65.224)
I've always wanted to try that one! .......
390: OTL Asylum, NYAL/Futterman OTLs (0.00)
Posted by Jim Dowdy on 2008-12-29, 12:04:21 (173.19.65.224)
Try contacting George Kaye: .......
391: Tube DIY Asylum, Nice work! (nt) (0.00)
Posted by Jim Dowdy on 2008-12-24, 15:56:58 (173.19.65.224)
nt .......
392: Tube DIY Asylum, Dan's Quark amp (0.00)
Posted by Jim Dowdy on 2008-12-18, 08:40:46 (173.19.65.224)
I remember that amp - Dan was using the super-exotic cobalt parafeed OPTs with Litz secondaries. Dan's design evolved from the 26; he moved on to the 112A and finally ended up with the 01A as his pre .......
393: Vinyl Asylum, picking and choosing (0.00)
Posted by Jim Dowdy on 2008-12-14, 14:51:48 (173.19.65.224)
I don't know all of the LPs, but Kirsten Flagstad absolutely slays me every time! The Argo ASMF titles are generally excellent - 'though I prefer the Boccherini side of this one. Scherchen can be ridi .......
394: OTL Asylum, Philips AD3800AM inductance (0.00)
Posted by Jim Dowdy on 2008-12-08, 17:00:29 (12.214.254.102)
Aldovan: I just measured the 3 AD3800s for you - (at 1 Khz) they were between 26 and 30 mHy. Jim .......
395: SET Asylum, RE: Philips AD3800AM and AD9710AM speakers clones (0.00)
Posted by Jim Dowdy on 2008-12-08, 14:29:10 (12.214.254.102)
I posted a response on the OTL forum...let me know if you need more info. .......
396: OTL Asylum, RE: Philips AD3800AM and AD9710AM speakers clones (0.00)
Posted by Jim Dowdy on 2008-12-08, 14:25:10 (12.214.254.102)
I have three AD3800s, and quite a few other 800 ohm Philips drivers - the lowest measure 560 ohms; but overall, they average about 620 ohms. I hope you find this helpful. .......
397: Tube DIY Asylum, RE: 25W Guitar Amplifier with 3E29 (0.00)
Posted by Jim Dowdy on 2008-11-29, 11:40:15 (12.214.254.102)
I'd love to see the schematic...thanks! .......
398: Tube DIY Asylum, Longview (0.00)
Posted by Jim Dowdy on 2008-11-28, 15:25:44 (12.214.254.102)
nt .......
399: Tube DIY Asylum, 3C24 plate choke (0.00)
Posted by Jim Dowdy on 2008-11-25, 07:04:35 (12.214.254.102)
I've used the 600 Hy Magnequest EXO-99s with great success! Never tried the Herbies... .......
400: Tube DIY Asylum, RE: DC coupled SE 3C24-PX4 (0.00)
Posted by Jim Dowdy on 2008-11-24, 17:22:28 (12.214.254.102)
I've never tried the PX4, but the 3C24 > PX25 combo is wonderful! .......
401: SET Asylum, RE: SET guitaramp (0.00)
Posted by Jim Dowdy on 2008-11-23, 08:20:15 (12.214.254.102)
I've experimented with SET guitar amps and BobbyJ is generally correct. However, I have had excellent results with Fender Champ-type circuits driving big triodes - 6SJ7 > 6V6 > GM70 - in other words, .......
402: Tube DIY Asylum, DHT linestage (0.00)
Posted by Jim Dowdy on 2008-11-22, 07:46:29 (12.214.254.102)
As long as you're driving reasonable loads, in my opinion, a 71A or a PX25 into a 1:1 is the ultimate choice. .......
403: K&K Audio / Lundahl Transformers, indeed (0.00)
Posted by Jim Dowdy on 2008-11-20, 08:37:13 (12.214.254.102)
Hope you're feeling much better, Kevin! .......
404: Tube DIY Asylum, I'm sure it's just a typo... (0.00)
Posted by Jim Dowdy on 2008-11-13, 17:24:14 (12.214.254.102)
but, the mu of the 841 is 30. .......
405: Tube DIY Asylum, welcome back HP (0.00)
Posted by Jim Dowdy on 2008-11-13, 13:16:01 (12.214.254.102)
You're not *really* Harry Pearson, are you? :-) .......
406: Tube DIY Asylum, propaganda machines (0.00)
Posted by Jim Dowdy on 2008-11-13, 07:38:27 (12.214.254.102)
Many engineers have polluted the field of audio with their pronouncements of superiority, based upon their own ego-driven pet theory of the moment...one that almost invariably ignores the reality of h .......
407: Tube DIY Asylum, EL34 grid stopper (0.00)
Posted by Jim Dowdy on 2008-11-07, 13:43:36 (12.214.254.102)
For audio application, I'd start with 330 ohm carbon comps and work my way down from there. .......
408: Tube DIY Asylum, 2k output Z (0.00)
Posted by Jim Dowdy on 2008-11-06, 08:33:47 (12.214.254.102)
The only Lundahl input transformer I have any experience with is the 1544A; and it definitely sounded best with a source Z of 200 ohms or less. I'm speculating that the 1676 would perform similarly (t .......
409: Tube DIY Asylum, I'm curious, Steve (0.00)
Posted by Jim Dowdy on 2008-11-06, 06:11:54 (12.214.254.102)
What is the output impedance of your linestage? .......
410: Tube DIY Asylum, more re: my 2 cents (0.00)
Posted by Jim Dowdy on 2008-11-05, 04:11:18 (12.214.254.102)
As a general rule, a tube with a transconductance of less than 8 to 10k isn't likely to oscillate in most audio applications/environments. .......
411: Tube DIY Asylum, my 2 cents (0.00)
Posted by Jim Dowdy on 2008-11-04, 14:27:12 (12.214.254.102)
I avoid grid stoppers whenever possible. .......
412: Bottlehead Forum, congrats, truegrit! (0.00)
Posted by Jim Dowdy on 2008-10-29, 08:23:22 (12.214.254.102)
What a joy twins are! Mine are now 17 year-old seniors in high school...I'm anticipating feeling *very* poor over the next 4-5 years! ;-) .......
413: Tube DIY Asylum, getting serious (0.00)
Posted by Jim Dowdy on 2008-10-28, 14:06:21 (12.214.254.102)
How many manufacturers choose to supply photos of the underside of their products to DIYers who are obviously never going to purchase anything? Even more importantly: how many manufacturers would be .......
414: Tube DIY Asylum, 75TH: what Op Point? (0.00)
Posted by Jim Dowdy on 2008-10-18, 12:10:02 (12.214.254.102)
395 v B+, drawing approx 21 mA [-4.9 G(v)]; loaded with a 250 Hy nickel plate choke, courtesy of Dave Slagle. .......
415: Tube DIY Asylum, mmmmmmmmmmm 75THs (0.00)
Posted by Jim Dowdy on 2008-10-18, 11:11:23 (12.214.254.102)
I *love* 75THs - best front-end for my GM70 amp I've ever heard! .......
416: High Efficiency Speaker Asylum, Hi Ed (0.00)
Posted by Jim Dowdy on 2008-10-16, 14:57:00 (12.214.254.102)
The AC1s are the only speaker that I'm aware of that are made of 100% hardwood - no MDF...not even plywood - and, that by itself makes for an *extremely* expensive undertaking. I have no idea what sor .......
417: Tube DIY Asylum, thanks Doug! (nt) (0.00)
Posted by Jim Dowdy on 2008-10-13, 09:37:42 (12.214.254.102)
.......
418: Tube DIY Asylum, 5-125 UL curves anyone? (0.00)
Posted by Jim Dowdy on 2008-10-08, 12:16:55 (12.214.254.102)
Can anyone provide UL curves for the 5-125 (aka 4E27)? Thanks. .......
419: Tube DIY Asylum, agree (0.00)
Posted by Jim Dowdy on 2008-10-04, 09:54:25 (12.214.254.102)
Either PP 845s or GM70s would get my vote. .......
420: Tube DIY Asylum, RE: 30W PP (0.00)
Posted by Jim Dowdy on 2008-10-03, 15:16:22 (12.214.254.102)
It looks similar to an amp I built quite a few years ago. 27/56 > Tango IT for phase inversion > PP 6BX7 directly-coupled to PP 300Bs. I used a center-tapped choke to load the 'BX7 plates. It worked .......
421: Tube DIY Asylum, RE: Your favorite PP power tube (not triode) (0.00)
Posted by Jim Dowdy on 2008-09-27, 20:40:52 (12.214.254.102)
The best push-pull pentode amp I've ever heard was Doug Piccard's 5-125A. .......
422: Tube DIY Asylum, 6A5 and 6CK4 (0.00)
Posted by Jim Dowdy on 2008-09-25, 10:56:45 (12.214.254.102)
6A5 and 6CK4 are single IDHTs with a 6.3 v filament that will provide 10 W in push-pull. The 6BL7, 6080/6AS7, 6336, 7236 and WE421A are dual triodes that fit your criteria. However, the 6A5 is the onl .......
423: Tube DIY Asylum, give everyone a no money down ninja loan and then feign surprise when they default (nt) (0.00)
Posted by Jim Dowdy on 2008-09-22, 10:28:38 (12.214.254.102)
.......
424: Tube DIY Asylum, Bartolucci (0.00)
Posted by Jim Dowdy on 2008-09-07, 15:15:44 (12.214.254.102)
I've had good luck with the Bartolucci items I've purchased. Yes, delivery can be frustratingly slow, but that applies to a significant number of suppliers. .......
425: Tube DIY Asylum, 3C24s (0.00)
Posted by Jim Dowdy on 2008-09-05, 08:47:51 (12.214.254.102)
While I've never used the 3C24 as an output tube, I've used them many times as input/driver tubes...and, my experience is that they sound much better with a B+ of 400 vdc or more. So, if it were me, I .......
426: Tube DIY Asylum, nice approach (0.00)
Posted by Jim Dowdy on 2008-08-27, 07:02:15 (12.214.254.102)
That's how I do it most of the time. .......
427: Bottlehead Forum, RE: Joe Bonamassa (0.00)
Posted by Jim Dowdy on 2008-08-18, 06:54:29 (12.214.254.102)
He put on an absolutely fabulous show in Greenville, SC just a few months ago - highly recommended! .......
428: SET Asylum, agree (0.00)
Posted by Jim Dowdy on 2008-08-16, 07:23:05 (12.214.254.102)
I generally use a 0.22 uf to a 0.47 uf oil cap prior to my first choke. .......
429: Tube DIY Asylum, RIP Walt (0.00)
Posted by Jim Dowdy on 2008-08-01, 11:23:38 (12.214.254.102)
Walt had more influence in this hobby than most will ever realize. He was always a class act and he'll be missed. .......
430: SET Asylum, excellent point (0.00)
Posted by Jim Dowdy on 2008-07-25, 08:02:37 (12.214.254.102)
In fact, all of are best known for their work with SE transmitting triodes: Kondo - 211 Komuro - 845 Shishido - 805, 833 and more .......
431: Tube DIY Asylum, RE: Good candidates for octal low mu single triode (0.00)
Posted by Jim Dowdy on 2008-07-21, 09:08:36 (12.214.254.102)
6AH4: mu = 8; R(p) = 1800 BTW: 6BL7 is a twin triode. .......
432: Tube DIY Asylum, Loftin-White generalities (0.00)
Posted by Jim Dowdy on 2008-07-17, 14:52:34 (12.214.254.102)
The original Loftin-White amplifiers all utilized the 24A tetrode as the input tube. While a few variants exist with pentodes in the V1 position; Nobu Shishido's 1970 design, utilizing a paralleled 1 .......
433: Vinyl Asylum, Mono Stones (0.00)
Posted by Jim Dowdy on 2008-07-09, 15:07:07 (12.214.254.102)
Without a doubt, the first five Rolling Stones' LPs are best experienced in glorious UK Decca mono..."Beggars Banquet" and "Let It Bleed" are also best in Decca mono. But; what about 'Satanic Majestie .......
434: Tubes Asylum, RE: Best high Mu tube (0.00)
Posted by Jim Dowdy on 2008-07-06, 09:44:53 (12.214.254.102)
Best is always going to be dependent upon your circuitry requirements; but overall, I prefer the sound of the 6SL7, followed by the 12AV7. .......
435: MagneQuest/Peerless Forum, BAC-120? (0.00)
Posted by Jim Dowdy on 2008-07-02, 14:51:52 (12.214.254.102)
Is the BAC-120 no longer available? .......
436: Tubes Asylum, Rugged 6V6 tubes for guitar amp? (0.00)
Posted by Jim Dowdy on 2008-07-02, 05:35:57 (12.214.254.102)
The current production JJ 6V6S are very rugged tubes...and they sound great to boot. .......
437: SET Asylum, hysteresis losses (0.00)
Posted by Jim Dowdy on 2008-07-01, 06:57:22 (12.214.254.102)
I'm not really a magnetics guy, but I believe there are going to be hysteresis losses in just about all applications where there is current in a core. .......
438: SET Asylum, current-canceling OPT (0.00)
Posted by Jim Dowdy on 2008-06-30, 09:18:08 (12.214.254.102)
A tertiary winding provides DC [usually from a filament supply] to the secondary to 'cancel out' a major portion of the DC on the primary. .......
439: SET Asylum, it would be interesting... (0.00)
Posted by Jim Dowdy on 2008-06-29, 17:29:42 (12.214.254.102)
It would be very interesting to compare this approach with either: a) well-executed parafeed, or b) a SE OPT with minimal air-gap due to utilizing current-cancellation in the secondary. .......
440: Tube DIY Asylum, "an engineer would be content..." (0.00)
Posted by Jim Dowdy on 2008-06-29, 13:24:26 (12.214.254.102)
There are hundreds of commercial audio products that have wonderful measurements and sound like garbage. .......
441: Tubes Asylum, KR 300BXLS Tubes (0.00)
Posted by Jim Dowdy on 2008-06-16, 09:07:14 (12.214.254.102)
Drop me an offsite note. .......
442: Tube DIY Asylum, good one, Doc! (0.00)
Posted by Jim Dowdy on 2008-06-15, 09:54:31 (12.214.254.102)
:-) .......
443: Tube DIY Asylum, caps (0.00)
Posted by Jim Dowdy on 2008-06-15, 04:43:01 (12.214.254.102)
"As DIY'ers we should be trying to get caps out of the circuit anyway." I disagree. In my opinion, removing caps from a circuit is no more important than getting resistors out of a circuit; or optimi .......
444: MagneQuest/Peerless Forum, cool (0.00)
Posted by Jim Dowdy on 2008-06-14, 15:29:27 (12.214.254.102)
Put me down for a pair of those UL chokes. .......
445: Tube DIY Asylum, done! (nt) (0.00)
Posted by Jim Dowdy on 2008-06-07, 12:02:34 (12.214.254.102)
.......
446: Tube DIY Asylum, my opinion (0.00)
Posted by Jim Dowdy on 2008-05-16, 08:04:16 (12.214.254.102)
First off, I'd caution you that just because Vitamin Qs sound great in an amp, it does not necessarily follow that they'll sound as good in small signal applications. I like the sound of vintage carbo .......
447: Tube DIY Asylum, agreed re: the pot (nt) (0.00)
Posted by Jim Dowdy on 2008-05-15, 11:20:50 (12.214.254.102)
.......
448: Tube DIY Asylum, Jeremy Epstein (0.00)
Posted by Jim Dowdy on 2008-05-15, 07:53:53 (12.214.254.102)
Jeremy built a pretty cool one: .......
449: Bottlehead Forum, speechless indeed! (0.00)
Posted by Jim Dowdy on 2008-05-13, 04:54:27 (12.214.254.102)
Beautiful job! .......
450: Tube DIY Asylum, RE: DIY guitar amps (0.00)
Posted by Jim Dowdy on 2008-04-30, 07:53:32 (12.214.254.102)
My personal favorite is a SE HY69 - send me an offsite note and we'll discuss. .......
451: Tube DIY Asylum, DIY guitar amps (0.00)
Posted by Jim Dowdy on 2008-04-30, 06:58:07 (12.214.254.102)
"Doing this guitar amp stuff from scratch is very annoying" I could not disagree more - mindlessly cloning a 50 year old design is the most brain-dead and boring approach imaginable. If all you want .......
452: SET Asylum, I'm fairly certain that (0.00)
Posted by Jim Dowdy on 2008-04-21, 09:58:02 (12.214.254.102)
Josh's guitar amp utilizes a 211. .......
453: Tube DIY Asylum, more re: A2 and IITs (0.00)
Posted by Jim Dowdy on 2008-04-15, 10:17:01 (12.214.254.102)
Tango was bought out by it's employees a few years ago and is now known as Tango/ISO - their product line is now significantly smaller. The S-2014s are available only by special order - contact Koji @ .......
454: Tube DIY Asylum, A2 and IITs (0.00)
Posted by Jim Dowdy on 2008-04-15, 07:19:41 (12.214.254.102)
As Dave indicated, the inverted operation is a big deal, especially in terms of bandwidth. According to Nobu Shishido, Tango developed special winding techniques to obtain high freq response with thei .......
455: OTL Asylum, single tube EL509 OTL (0.00)
Posted by Jim Dowdy on 2008-04-06, 23:46:50 (12.214.254.102)
About 1 Watt into 8 ohms - see: .......
456: Tube DIY Asylum, guitar amp theory (0.00)
Posted by Jim Dowdy on 2008-03-30, 16:35:43 (12.214.254.102)
My advice is to study, study, study the classic circuits! And listen to every amp you can find. I've built a few variations of the Angela PSE amp. If you want the bluesy tone of the original Champ, yo .......
457: SET Asylum, preserved output tubes (0.00)
Posted by Jim Dowdy on 2008-03-15, 13:04:05 (12.214.254.102)
I have a NOS WE 205D that has been stored in an immersion circulator of extra virgin olive oil at 21.5 degrees Celsius - I change the oil every 2,500 hours; and have established a trust fund to ensure .......
458: SET Asylum, my opinion (0.00)
Posted by Jim Dowdy on 2008-03-06, 12:56:13 (12.214.254.102)
You have the manners of a baboon. .......
459: Tube DIY Asylum, EL509 (0.00)
Posted by Jim Dowdy on 2008-02-18, 04:52:59 (12.214.254.102)
EL509 works extremely well with screen-drive...mine used a 6C45. Here's Bob Danielak's take on one: .......
460: Tube DIY Asylum, I understood completely (0.00)
Posted by Jim Dowdy on 2008-02-09, 10:24:33 (12.214.254.102)
For the most part, I'm teasing the Patricia Barber crowd ;-) But, how many people are really listening to live music of any kind on a regular basis? I listen to live rock/blues several times a week; I .......
461: Tube DIY Asylum, my live reference (0.00)
Posted by Jim Dowdy on 2008-02-09, 06:03:39 (12.214.254.102)
Is a Marshall JCM800...preferably on 11 ;-) .......
462: Tubes Asylum, RE: curves for 20A (0.00)
Posted by Jim Dowdy on 2008-02-08, 07:09:40 (12.214.254.102)
The old AVVT AV20A curves are usually 'close enough' .......
463: Tube DIY Asylum, Jensen Cu-foil cap failure (0.00)
Posted by Jim Dowdy on 2008-01-15, 09:52:32 (12.214.254.102)
I've never had a failure with the Jensen Cu-foil caps. You might try the ones rated for 1kv; or, as Paul suggested, you might try the Mundorfs rated for 1.2kv. .......
464: SET Asylum, RE: KR VV 52B filament requirements? (0.00)
Posted by Jim Dowdy on 2007-12-17, 07:49:50 (12.214.254.102)
6.0 volts AC or DC 2.5 A .......
465: Tube DIY Asylum, elders, ears, etc. (0.00)
Posted by Jim Dowdy on 2007-12-15, 09:54:26 (12.214.254.102)
I built my first tube amp in 1970; and by the early '80s, I thought I was pretty good at it...that's about the time that I met Jeff Medwin. He and his mentor Bob Fulton were the first people I'd ever .......
466: Tube DIY Asylum, RX21A (0.00)
Posted by Jim Dowdy on 2007-12-13, 07:44:32 (12.214.254.102)
Sorry, no pics. The globe RX21s look a lot like the 75TL; in fact I believe that Josh used them on his 75TL amp, because they were so similar in appearance. .......
467: Tubes Asylum, RE: The story of 6AS7G "Coke Bottle"? (0.00)
Posted by Jim Dowdy on 2007-12-07, 07:57:21 (12.214.254.102)
I'm not an expert in 6AS7s either, but I do know that Tung-Sol, GE and Chatham also made them. .......
468: SET Asylum, SE OTL (0.00)
Posted by Jim Dowdy on 2007-12-06, 04:35:19 (12.214.254.102)
How about a single-ended OTL amp utilizing a directly-coupled screen-driven EL509? Cap-coupled cathode follower output, with a bit of NFB to really irritate the purists. 6C45 should make a decent dri .......
469: OTL Asylum, RE: 300B OTL (0.00)
Posted by Jim Dowdy on 2007-12-02, 07:33:02 (12.214.254.102)
Sorry Lew, I misunderstood your earlier post; I thought you were talking about putting a CCS load on the output stage. The 2A3 driver I mentioned above was a traditional plate follower. .......
470: OTL Asylum, RE: 300B OTL (0.00)
Posted by Jim Dowdy on 2007-12-01, 08:07:55 (12.214.254.102)
I built a single-ended OTL that utilized a 2A3 driver. Output stage was a single 6C33 [cap-coupled cathode follower] - I thought the DHT driver added some nice tone to the mix. I don't know enough abo .......
471: Tube DIY Asylum, the doctor is always right (0.00)
Posted by Jim Dowdy on 2007-11-29, 09:01:11 (12.214.254.102)
My only experience with the 75TL was as a driver tube for the GM70...so, my recommendation was simply a starting point that I knew was safe. Jeffrey and Dr. Dave have considerably more experience re: .......
472: Tube DIY Asylum, 75TL op points around 700 v (0.00)
Posted by Jim Dowdy on 2007-11-28, 06:12:26 (12.214.254.102)
I've never used the 75TL as an output tube, but I'd suggest that you start with a 500 ohm resistor [rated for at least 10 Watts] and tweak from there...that should put your current draw at approx 65 m .......
473: OTL Asylum, 300B OTL (0.00)
Posted by Jim Dowdy on 2007-11-26, 09:38:44 (12.214.254.102)
I've never heard the 300B OTL, nor do I know anyone who has. But, a few questions to ask yourself about such an undertaking are: 1) do you like the sound of the 300B/2A3/45 as cathode-followers? 2) do .......
474: Tube DIY Asylum, ALESSANDRO capacitors? (0.00)
Posted by Jim Dowdy on 2007-11-08, 12:09:40 (12.214.254.102)
I'm fairly certain that they are Jensen capacitors. .......
475: OTL Asylum, miniature triode OTLs (0.00)
Posted by Jim Dowdy on 2007-11-05, 07:01:16 (12.214.254.102)
Futterman's first OTL utilized the 12B4, and Transcendent makes a couple of OTLs that utilize the 6C19pi. .......
476: SET Asylum, ditto (nt) (0.00)
Posted by Jim Dowdy on 2007-10-31, 10:16:33 (12.214.254.102)
.......
477: MagneQuest/Peerless Forum, RE: Under the hood (0.00)
Posted by Jim Dowdy on 2007-10-12, 07:58:36 (12.214.254.102)
Wow - that's a tightly packed underside! Nice work. .......
478: Tube DIY Asylum, Oswald's Mill Audio website (0.00)
Posted by Jim Dowdy on 2007-10-09, 09:09:57 (12.214.254.102)
Check it out: .......
479: MagneQuest/Peerless Forum, I'd be interested (nt) (0.00)
Posted by Jim Dowdy on 2007-10-07, 08:36:52 (12.214.254.102)
.......
480: Tube DIY Asylum, agree with Gordon (0.00)
Posted by Jim Dowdy on 2007-10-04, 09:02:23 (12.214.254.102)
I'd also recommen changing the 71A's cathode bypass cap to a 10 uf ASC or GE oiler. .......
481: Tubes Asylum, sorry (0.00)
Posted by Jim Dowdy on 2007-09-30, 08:28:47 (12.214.254.102)
but I have no idea. .......
482: Tubes Asylum, Brook 12A (0.00)
Posted by Jim Dowdy on 2007-09-28, 07:58:41 (12.214.254.102)
I've never seen a 'K-1' schematic, but here's the original: .......
483: Bottlehead Forum, RIP Bruce (0.00)
Posted by Jim Dowdy on 2007-09-21, 08:41:46 (12.214.254.102)
What a guy - I always admired that Porsche-powered VW camper of his! .......
484: MagneQuest/Peerless Forum, GM70 (0.00)
Posted by Jim Dowdy on 2007-09-19, 07:40:34 (12.214.254.102)
mu is approx 6.5. Data follows: .......
485: Tube DIY Asylum, you need to understand that (0.00)
Posted by Jim Dowdy on 2007-09-07, 14:00:30 (12.214.254.102)
Shindo designs involve intricate seventh and eighth dimensional quantum mechanical concepts that cannot even be printed on two-dimensional paper. .......
486: High Efficiency Speaker Asylum, Just beautiful! (nt) (0.00)
Posted by Jim Dowdy on 2007-09-04, 08:41:40 (12.214.254.102)
.......
487: Bottlehead Forum, exact dates? (0.00)
Posted by Jim Dowdy on 2007-08-12, 08:35:10 (12.214.254.102)
Will the show run Fri-Sun or Sat -Mon? Or is something else planned? .......
488: Tube DIY Asylum, triode-wired 4-65A (0.00)
Posted by Jim Dowdy on 2007-08-07, 10:00:13 (12.214.254.102)
Dave from the Oregon Triode Society had one in the VSAC 2003 Craftsmen's room [sorry, I do not recall his surname]. You can see a photo about halfway down this page: .......
489: Tube DIY Asylum, very very cool! (nt) (0.00)
Posted by Jim Dowdy on 2007-07-23, 11:31:45 (12.214.254.102)
.......
490: Bottlehead Forum, I'll be there! (0.00)
Posted by Jim Dowdy on 2007-07-14, 07:22:55 (12.214.254.102)
Most likely as an exhibitor...looking forward to it! .......
491: Tube DIY Asylum, Everyone I know (0.00)
Posted by Jim Dowdy on 2007-07-08, 16:41:48 (12.214.254.102)
has the same dismal opinion of them. .......
492: Tube DIY Asylum, yes...and (0.00)
Posted by Jim Dowdy on 2007-07-01, 09:12:03 (12.214.254.102)
The average reader of this forum is exposed to more Hg via dental fillings than they would ever encounter during a lifetime of listening to an amplifier that utilizes Hg vapor rectifiers. .......
493: Tube DIY Asylum, break what? (0.00)
Posted by Jim Dowdy on 2007-07-01, 07:24:39 (12.214.254.102)
A flourescent light bulb? A mercury vapor rectifier? A thermometer? I've accidentally broken all of the above in my house and did not call in Hazmat. Suggesting that CFL lightbulbs are 100% safe while .......
494: Tube DIY Asylum, Hazmat? (0.00)
Posted by Jim Dowdy on 2007-06-30, 20:21:14 (12.214.254.102)
What bullshit. If MV rectifiers offend/scare you; OK...but upon exactly what science do you base your belief that a CFL bulb has minimal risk [vs an Hg rectifier]? .......
495: Tube DIY Asylum, more anecdotal evidence (0.00)
Posted by Jim Dowdy on 2007-06-28, 10:43:30 (12.214.254.102)
I first began using mercury vapor rectifiers in the early 1990s. Within only a few years, I began losing hair...dang, I'd never made the connection before! Fortunately, my teeth are still doing pretty .......
496: DIY HiFi Forum, TentLabs (0.00)
Posted by Jim Dowdy on 2007-06-21, 10:56:22 (12.214.254.102)
My experience with TentLabs has been 100% positive. .......
497: Tube DIY Asylum, 3C24 (0.00)
Posted by Jim Dowdy on 2007-06-21, 04:14:24 (12.214.254.102)
Depending a bit upon how you run them, plate resistance of the 3C24 is in the 13k to 14k range. .......
498: Tube DIY Asylum, RIP 18watt.com (0.00)
Posted by Jim Dowdy on 2007-05-17, 11:03:49 (12.215.238.134)
One of the very best of the DIY guitar amp pages is no more...I'll certainly miss it! .......
499: K&K Audio / Lundahl Transformers, technology to the rescue (0.00)
Posted by Jim Dowdy on 2007-05-11, 11:31:28 (12.215.238.134)
.......
500: SET Asylum, 300B (0.00)
Posted by Jim Dowdy on 2007-05-07, 06:31:34 (12.215.238.134)
300B works extremely well at 320 vpk @ 70 mA - output is about 6.5 Watts, I believe. .......
Found total of 500 records, Query: , Author: Jim Dowdy in All Forums, Time: 1 sec.