We use a 2A3 because it has a 2.5 VAC filament, and so, we can use BETTER SOUNDING AC on it !! Always do AC and NEVER do a 6A3, 6B4G, etc. Why to you think the 6 VAC tubes sell for a quarter of the price of a 2A3?? JJ 2A3-40 is THE tube to own, cost versus performance, the audio bargain of the century.
Jeff Medwin
So you are saying that Miller Capacitance doesn't exist, that you're hearing doesn't go much past 12K, or that your speakers are so bright up there anyway that you want a rolled off amp?
Hello !!
Sir,
No, you are only talking on a theoretical basis, and your theoretical concerns and "pet" design theories don't cut it in the REAL world. I have actual build and listening experieinces over the last eight years, that negates all the "theory" you want to talk about. What counts more, the real thing or a theory you read in a book and "believe in" ????
The best sounding 2A3 amp ever built is the recent / latest ones done by Dennis Fraker. No one comes close !! Go look up and read the amp reviews of his earlier 2A3 amp on his web site .... Serious Stereo out of Livingston MT.
I'm not talking theory, only you are !!!
In the end, there is simply only ONE thing, and one thing ONLY that counts...performance...how does it sound?
Jeff Medwin
Sir,
No, you are only talking on a theoretical basis, and your theoretical concerns and "pet" design theories don't cut it in the REAL world. I have actual build and listening experieinces over the last eight years, that negates all the "theory" you want to talk about. What counts more, the real thing or a theory you read in a book and "believe in" ????
The best sounding 2A3 amp ever built is the recent / latest ones done by Dennis Fraker. No one comes close !! Go look up and read the amp reviews of his earlier 2A3 amp on his web site .... Serious Stereo out of Livingston MT.
I'm not talking theory, only you are !!!
In the end, there is simply only ONE thing, and one thing ONLY that counts...performance...how does it sound?
Jeff Medwin
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I have measured and heard the roll off from 12AX7 driven 2A3's. I have also heard these amps run out of gas when pressed for more than a Watt or two. When you use a 12AX7 in this position, you either drastically sacrifice high frequency response, or you run more current and pick up extra distortion.
Either you need to correct an error in the Miller Capacitance Theory (which mind you, if you're correct and not so lazy that you can't sit down and hash it out, you could become a published physicist) or you should just admit that you like or need a rolled off amp. Miller Capacitance started as a hypotheses and has been replicated a sufficient number of times to have been adopted as a theory. Please tell me why something I can hear and measure is incorrect. Please provide evidence.
Otherwise, you'll continue coming across as a crackpot. (It kind of reminds of people who buy into the medicinal value of collodial silver, then end up with blue or gray skin because of it)
8 years isn't really much experience. I've been at this for 14 and am still learning a lot from my mentors who have 40+ years of dickering with this stuff.
Either you need to correct an error in the Miller Capacitance Theory (which mind you, if you're correct and not so lazy that you can't sit down and hash it out, you could become a published physicist) or you should just admit that you like or need a rolled off amp. Miller Capacitance started as a hypotheses and has been replicated a sufficient number of times to have been adopted as a theory. Please tell me why something I can hear and measure is incorrect. Please provide evidence.
Otherwise, you'll continue coming across as a crackpot. (It kind of reminds of people who buy into the medicinal value of collodial silver, then end up with blue or gray skin because of it)
8 years isn't really much experience. I've been at this for 14 and am still learning a lot from my mentors who have 40+ years of dickering with this stuff.
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we've already had a go at this question here: http://www.diyaudio.com/forums/tubes-valves/212673-why-do-wimpy-drivers-2a3-work-well-they-do.html
but the proof is in the pudding and I do plan, one day, to build this amplifier to determine if the sound is good, or is not good. I beg for your patience...
but the proof is in the pudding and I do plan, one day, to build this amplifier to determine if the sound is good, or is not good. I beg for your patience...
In another thread on a different forum, Lomu has demonstrated that he can't hear when his speakers are out of phase... I guess that makes the pudding expired.
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I do appreciate the words of wisdom on the theory Audiowize and I like all opportunities to improve my knowledge of the science (fyi - I have a PhD in physics). But we're not putting the design on trial here, no need to try and discredit any witnesses, we're having fun and listening to all the wonderful ideas and real world experiences that folk with a common interest care to share despite any inconsistencies between them.
Mind you, if it turns out that the frequency response is slightly rolled off at the high-end, this may turn out to be perfectly acceptable in my listening environment and I may not even notice it. I expect there will be many other areas where the performance of the amplifier is less than ideal, where tradeoffs will be accepted just because it sounds good. I will have to find out by getting the iron hot - alas not for awhile.
Mind you, if it turns out that the frequency response is slightly rolled off at the high-end, this may turn out to be perfectly acceptable in my listening environment and I may not even notice it. I expect there will be many other areas where the performance of the amplifier is less than ideal, where tradeoffs will be accepted just because it sounds good. I will have to find out by getting the iron hot - alas not for awhile.
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Case in point might be the WE91 which would be very rolled off on the top end. fWIW I've built a pair of Jeff's mono blocks though I already know they are not "pure", and yet they are the amps most often in my system. The other night I was listening to the 45rpm reissue of Brubeck's Take Five and if anything I found the top end a little bright. Clearly a system all works together. My version of the amp uses a 6sl7 and not all the tweaks Jeff proposes yet it presents music in a way that draws me in regardless of style. I had a bunch of friends over a couple of weeks ago. I was playing Hotel California, the person sitting in the "sweet spot" said, this is the most realistic sound I've ever heard. Add to that, unlike the rest of us, he had not even been drinking. 🙂 that to say, to each his own. I've tried dozens of amps. The 6SL7 driving a 2a3 gives a dynamic sound that has a great "jump factor" and yet seems to reach really deep. PSUs are low but not ultra low DCR and speakers are similar to the 4pi.
You can choose to believe whatever YOU want to believe, I have no phase-correctness hearing problem such as you infer, whatsoever. That was an interpretation of oral instructions problem.
If you are concerned about "running out of gas when pushed over one Watt" , that, IMHO, is a stupid concern.
With efficient speakers, say ALTEC or JBL well wired, we listen at 1/10th to 3/4s of a Watt 99 percent of the time. MY CONCERN is to design the best first Watt amp possible, for the power level we use 99% of the time. YOUR technique will NEVER do that, you are foolishly looking at the wrong things !!
You never did respond, .............have you heard a recent Dennis Fraker 2A3 amp on ALTECS or JBLs in a good system ?
That resolves this entire discussion. Performance is ALL that matters.
Jeff Medwin
Jeff Medwin
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Hello Audiowise,
You are 31 years old and I am 69, been sitting in front of ALTEC 604s
since I was eight years old, which was 1952. With your pedestrian
build techniques, and approach, no doubt you can't engineer a 12AX7 to
directly drive a 2A3 grid, which BTW, is easy to drive. That doesn't mean
that others, who are much more experienced than you, have not been
able to successfully implement it. They have !! It exists.
There is a commercially available amp that TOTALLY disproves what you believe !!
Have you ever HEARD the Serious Stereo 2A3 DC amp done by Dennis
Fraker? No, you have not !!
Its got the best high end of any amp I have heard, in over sixty years
of me doing audio with high efficiency speakers, etc.
There is more than one way to skin the cat, and theoretical Miller concerns and sophomoric hot rodding of tubes is NOT ever the best approach to do a
directly coupled two stage 2A3 amp.
I'm no crackpot, but, like your mentors you cite, I have four times the experience as you do. Capish ??
Jeff Medwin
When did this thread turn into an ego flame war? Most come here (the forum in general) to talk about designs ..... this thread really degenerated..... Build what you like and if you like the sound then fine, stick with it, but PLEASE stop the flaming. Geez.....
I agree 100% with you. This thread turned sour in post #102, the words written by "audiowise". See for yourself...his nasty response provoked me. My response initially was pretty even !!
Jeff Medwin
I agree about the manners.
I am referring to a commercial product, amps made by Dennis Fraker of Serious Stereo. No DATA Sy ! I am in no position to give out data that others could have. My ONLY comment would be for people to LISTEN to the basic design, and judge it, not by a graph or a meter, but by their ears.
Remember what I keep saying, PERFORMANCE only, what you hear, is what counts !! All else is not of importance.
"smbrown" has built a mild-clone ( 6SL7 DCed into a 2A3 ) and HIS listening reports ( in this thread ) seem quite enticing. He is no novice BTW !!
I have recently discussed with Mr. Brown, why half a 12AX7 would even sound better, properly implemented. Mr. Brown is hearing and getting about 65% ( my estimate ) of what Dennis' latest amps would be like.
Sy, if you want to find out about this amp design, and how it performs, come to RMAF 2014 this year, October 10-12 and visit Dennis' in Rooom 2020. Hes FUN to talk to, great guy.
I can't release data on proprietary designs, its not my place to do so. Can you make it to RMAF this year ? If not, read the amp reviews on Dennis' web page. His latest amps, not reviewed, are suppossedly even higher in performance!! Thats what he'll schlep to Denver. I'll go, just to hear it .
Jeff Medwin
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Well, in a technical forum, people will want to see actual results. And circuits.
Manners will help here. As will keeping the argument technical rather than personal.
drlowmu,
Just curious, does the 2A3 amp in question happen to be based on the Shishido 2A3 with a modified low dcr power supply?
Thanks,
Scott
Just curious, does the 2A3 amp in question happen to be based on the Shishido 2A3 with a modified low dcr power supply?
Thanks,
Scott
Recently heard on a program about hearing;that most people 70 and above have very poor HF hearing.
Phil
Phil
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Joined 2009
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Hi Scott,
The design which Jeff provided to me does borrow from the Shishido 2A3 and others. The Shishido uses both sections of the 12AX7 in parallel but Jeff recommends using only one section. The other section remains unused. I don't feel at liberty to post the material that Jeff provided me without his permission, although he does talk about his ideas in this and other forums.
My design will be heavily influenced by Jeff but there are a couple of changes I plan to try, such as the use of SS rectifiers and some PSRR enhancements. The end result will be my own. It will be a nice little valve amplifier 😀