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173.18.51.34
Looking to build the ultimate 2A3 SET amp with the best of the best parts. Looking for suggestions and schematic.
Thanks in advance.
Follow Ups:
I built this one several years ago.
I used better OPT's than the 125SE pair shown.
Power tubes were JJ 2A3-40.
I used it with a pair of Klipsch Lascala's.
It sounded nothing short of excellent IMO.
mg16
Edits: 02/16/23
This would be a perfect Audio question for ChatGPT.
Let us know what "it" says.
Hmmm... Just wondering and not that I'm a pronoun guy (too old), but... Is "it" the proper pronoun for AI? I wouldn't want to hurt "it's" feelings.
I've been building 2a3 amps for a year or two in preference to 300b.
The challenge is the input stage. I've gone round the houses many, many times with different tubes and topologies and in the end I compromised slightly with a simple front end but one which is musical and has good tone to the instruments - a sound I can live with in comfort. Plus the E180CC is still a generally available tube. So this is one suggestion.
I do not know about ultimate, I do not know about greatest... but if you purchase really good iron why not build either the Seth fora push pull out of the ordinary or the Bugle for single ended?
A53,
Not that I am the best to ask. Because the 2A3 was always a compromise to me. All the current ones are 300B's with the filament folded in 1/2. 300B 5V@1.2A, fold the filament in half and you get 2.5V @ 2.4A. Just easier to make.
Single plate old ones are great but $$$.
Bi-Plates are just two starved 45's in parallel which sucks anyway you look at it.
If you want the Baby-O plans I can send them to you.
Thanks,
Gordon
J. Gordon Rankin
My Emission Labs 2A3 look to be a single plate 2A3.
And sound great.
They DO sound great! (EML).That's because they're true single-plates,
are built very well, AND ARE MADE FROM
GOOD METALLURGY, with really solid glass
envelopes, and superior internal vacuum.Biplates were made for radios. So were
45's. A single-plate 45 usually has a "W"
or "M" shaped single filament. So do Western
Electric 300B's.While these tubes are indeed pleasantly euphonic,
the skewed filament arrangement changes the
behavior of the tube to accentuating some tones
in music, and compressing others.The original RCA single-plate RCA-Cunningham
2A3 had all of its filament arranged into
straight-vertical strands welded onto horizontal
rods, one at the top of the filament structure,
another horizontal rod at the bottom of the structure.Musically, this tube is linear. They cost RCA
too much to produce (all the welding), so the
BiPlate 2A3 was made from the 45 tube's parts,
and replaced the only GOOD 2A3.Today, EML still builds the vertical, welded,
filament system as Alesa Vaic (AVVT) designed
them. This 2A3 greatly outperforms the original
RCA-Cunningham single-plate!JJ makes a lower-cost (but well designed and built)
version of this, called a JJ 2A3-40. The "40" means
forty watts max plate dissipation rating..This tube uses their 300B plate and glass
envelope, etc. The filament is a single run
of filament wire that runs on 2.5 volts by
itself. The grid system is set up for 2A3
parameters.JJ avoids the serious distortions
that are in the W.E. 300B tubes, and in single
NOS 45 tubes by arranging the single filament
to be squared-off at the top and bottom of
the filament structure, allowing the portions
of it that are exposed to the plate and grid
to run purely vertical.While this is a compromise compared
to the original RCA, and the current EML, it
is the biggest tube bargain out there. You
get excellent glass envelope, superb internal
vacuum, and extremely long life. These tubes
have decent metallurgy-- they're not the soup-can
materials of NOS radio tubes.You also get the same plate-dissipation rating
of their 300B-- 40 max. watts.JJ's 2A3-40 greatly outperforms their 300B, as
they hint at on their website. I KNOW it does
just that because I prefer to listen to them and
have thousands of hours on many examples.Although this tube is a winner, you do have to know
how to use it. It doesn't sound like any other triode--
of any kind. That's not the question, the question
is-- can you build a world-class amp around one of these?YES, and you get a lot for your money. Long life,
fatigue-free listening, superior dynamics, powerful
lows and superb, extended highs.All you have to do is a little work on your power
supply for it, and it will surprise you!-Dennis-
Edits: 03/30/22
Big J
"... only a very few individuals understand as yet that personal salvation is a contradiction in terms."
Come September I'll have 11 years on my JJ 2a3-40.
229 B+, -29v grid, 72 ma, 395 ohm cathode resistor, 2500 ohm load.
highs only in biamp config.
try it.
at what frequency do you crossover for your 2a3 biamp setup?
solid state for the bottom or something else?
I run my 2a3 amp full range into speakers that play down to roughly -6db at 50hz and then have multisub bass. works great for me and no active crossover on the full range speakers.
this was op point of IEEE paper from like 80 years ago that had calcs for finding the optimal op point for any triode. It was all theory. I think I remember it always pointed to low and hot op point.
a friend and I breadboarded a 2a3 amp and he still uses it to this day.
I think he crosses at 120hz
he uses solid state
what it does, it does well.
I like your idea. let everything just happen.
A lot has changed in 80 years. Based on my limited experience, I prefer higher voltage/lower current operating points.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
high voltage/lower current/higher load impedance operating points
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
For me, yes. Where practical, I like to run nominal loads a touch higher than what many people would think is optimal/efficient. Higher loads and inductance are not really a problem for quality custom iron, though the cost is of course greater.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Edits: 03/31/22
As long as you don't get the voltage
too high, this is the way to go, for
many reasons. You are right.
-Dennis-
No offense (if such is possible), but nice troll.
I quite like my Empress Silver monoblocks - (Parallel Single Ended).
The Vindicator is also very nice (3.5watts) sounding. Maybe find the schematics as they're probably out there. Labour and overhead are large costs for manufacturers so you can build it(them) for less.
If you go the parallel 2a3 route, would he have to go for the silver primary/silver secondary trannies that Audio Note employs in the Kageki? The last time I checked the price, they were in the $25,000 a pair range. Then there are the silver foil caps and all the other high really pricey Audio Note bits and pieces. All of just to attempt to duplicate an Audio Note amp, with not everyone agreeing it represents the "best" in 2a3 sound.
I like this family of amps (I own a Kageki), but I haven't compared it to other 2a3 amps and I have no idea how it compares with a Kondo version.
There is never full agreement on anything in audio so there is no point in seeking what impresses other people.
That's the great thing about audio in a sense is that it is not a show-off hobby like buying watches or cars.
Even within a company line-up, not everyone agrees which amp sounds best or which tube you should use for said amp.
In the big AN thread over at the Steve Hoffman forum, the fans of the gear don't even agree - some like the Lexus cable over the more expensive SPe cable - I liked the AN E Lexus speakers over the more expensive SPe speakers. Some folks like the 45 Paladin the most others like the Vindicator and others like Conquest etc.
Steve Hoffman greatly prefers their 211 amps over the 2a3 amps. I have somewhat come around to his view. I just can't afford a Tomei Kensei power amp which is a level 4 match for my M6. I am guessing that it is around $60,000. Hell, it might be cheaper to buy Marisa Tomei instead.
The Audio Note 211 amps are good at working with almost any speakers. I've had the privilege of hearing Gaku-on amps running a number of different speakers and it always sounds good. Speaking of 211 vs. 2a3, I know someone who use to own a giant 3-way horn system that utilized two pairs of Gaku-On amps for the midrange and tweeters. But, when it was determined that a Kageki on the tweeter sounded at least as good as the Gaku-On running the tweeter, the dealer/builder offered to trade a Kageki for the Gaku-On and refund the substantial difference in price. The obviously well-heeled customer decided to buy the pair of Kageki, but keep the Gaku-On as a back-up amp.
Not sure what the top Audio Note 2a3 amp cost these days but from the retail price of the top of the line silver output transformer it cannot be $25k. Price of the Perma 55 core all silver trans is (sit down please) $20,934.52 USD PER PIECE.
Oh no, just wait until The Reverend Dr Lowmu sees This! He'll tell ya to trash the 2A3 and go with three 6005/6AQ5's in parallel!!!
Seriously, the good doctor may be on to something. I'm quite sure he or his mentor will respond soon.
As TK says, there are too many ways to make a great 2A3 amp. It's like trying to write the ultimate poem, using the best of the best words. Where do you start?
But you also asked for suggestions, so I'll suggest putting some constraints on the design to focus the effort. It's like asking for the ultimate sonnet.
The first constraint is clarifying your goals - what do you mean by "ultimate 2A3?" To me, that would be an amp that expresses the sonic character of the 2A3 as purely as possible, uncorrupted by the driver, power supplies, RFI, noise, etc. You may have other goals in mind.
Given a goal, you have a standard by which to judge possible topologies, choose parts, and optimize a layout. For example, to get the most 2A3-ness, I personally would operate the 2A3 at the RCA specified voltage, current, and load impedance.
I have several 2a3 and 6C4C amps in various formats. They all use the book values of 250v, 60mA and -45v. Don't overlook the 6C4C with Rod Coleman regulators (see Lyrima, UK), it's Svetlana quality.
I've been doing some power supply experiments, and I'm currently using 1200v SIC diodes in a bridge, followed by all DC Link capacitors and a big choke. I think it stands up very well to a 5U4 based PSU.
Output transformer is simple - just buy the best you can afford. Monolith in Europe make good ones for instance.
The challenge is the driver stage. Do you go for 3 stages - if you do you can use all DHT tubes like 10Y, 45, 46 etc and indeed another 2a3. Or do you try and find the Holy Grail driver for a 2 stage amplifier? D3a, C3g in triode etc etc. Same challenge as for a 300b amp and there are plenty of threads on that. Or do you use a step-up input transformer followed by a DHT like 10Y, 47? That's the solution of Ale Moglia on Bartola Valves.
You'll find a lot of pentodes in triode suggested. On the other hand there are some true triodes with higher mu like EC86 and one or two others. And so on....
There are hundreds of ways to build a very good SET amplifier. The fundamental topology will vary from one to the next, as will the components and the distribution of costs. Lots of people can make recommendations, but there's no "ultimate" amplifier, and no definitive answer to your question.
--------------------------
Buy Chinese. Bury freedom.
Find a topology you like and then stare at if for a while.
Best Iron you can afford, best power supply you can build and best driver you can come up with?
300V @ 50ma sounds good to me but some prefer 250V @ 60ma so who knows?
Also, what's it gonna have to drive? If the speakers used aren't VERY efficient, then maybe what's the point? 100dB would be my limit for a 2A3, but that's just me wanting to run the amps as close to the first watt, or better yet just a few MILLIWATTS, as I can.
then you can go worry about a 2A3 or one of the 2A3 with additional plate dissipation. And then...
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Ok, there's no best, we all know that argument.
But the OP is looking for suggestions, so what can we give him?
... on modern amplifier design. Publications like those authored by Morgan Jones, Crowhurst, Rosenblit and many others are essential reading. Once that's been absorbed, and after the OP has searched and read the thousands of previously posted opinions about this on the major audio forums, he'll be in a position to ask a few remaining questions to help him on his way. Of course, if anyone here feels like writing a 500-page thesis on this subject, by all means...
--------------------------
Buy Chinese. Bury freedom.
So how long did it take you to get to a decision making point? and, making a prediction here, why is it so short compared to what you suggest to the OP?
All that aside, before building an ultimate amp, one should build several practice amps, as a warm up and educational experience. If nothing else, to discover what you like. Whilst engaged on this task, go and compare the results of these builds to other amplifiers. As many as you can find... :)
cheers,
Douglas
Learning to ignore the zealots that tell you that one particular way is best for you is something else to learn.
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
That 'best parts' is way too deep a rabbit hole. Add to that no common listening experience... LOL
But anyway...coupling caps ought to be Teflon dielectric, and foil electrode. Couple to choose from there. Plate load resistors; non-inductive wire wound. Mills come to mind in particular. Slightly different voicing would be the Kiwame carbon film. On that choice, who's to say one is better than the other?
Assumes resistive load vs inductors( or interstage trans-es) of course.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Then there is series feed versus parallel feed....
You have my interest here! I was just today putting in a couple of plate load resistors, for which I used older Holco black 1W types.
Is there anything very audible to gain from Mills or Kiwame?
They're bigger than the 1W Holco( which should be treated like 1/2W in order to keep 'em from getting noisy). Am not a fan of colourful components, there were super low L Mills, at perhaps 3W rating and 2x physical size of the 12W. Mike Percey had 'em loooong ago.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I've had success with those Mills precision WW. They'd be my go to if they were available.Edit: they were the MR200 series.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Edits: 02/19/22
"if they were available"...yep, that is certainly about the size of it. Would love to be able to get 'em from Mouser.
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I think Ivan 303 hit the nail on the head---WHAT speakers will be used. room size, desired volume ??? These should be your first considerations before dropping any money on a 2A3 amplifier.
IMHO, any speaker less then 100 db.sensitivity is out for any REALISTIC reproduction of most symphony and dynamic music. If you are bi or tri amping , that is a different story. Getting good woofer control is the main problem for low wattage SET amps. Using good 2A3 amps on horns can be fantastic !!
Good luck,
Joe
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