JJ 2A3-40 DHT Single ended triode, power amplifier

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SteveTheShadow
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Re: JJ 2A3-40 DHT Single ended triode, power amplifier

Unread post by SteveTheShadow » Sat Jan 20, 2018 11:43 am

Love that video!

Eccentricity personified. :grin:
Gotta love Herb.
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Large sealed cabs, with Fane 12-250-TC 12" full range drivers.

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SteveTheShadow
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Re: JJ 2A3-40 DHT Single ended triode, power amplifier

Unread post by SteveTheShadow » Sat Jan 20, 2018 12:34 pm

I'm going to put in a few more words of wisdom from crazy Herb.

Personally in terms of my electronics efforts, I absolutely Identify with what he says below. Why? Simple!...I'm one of those unstable, arty types, who over the years, has failed to ask the right questions of those capable of answering them, so have struggled a bit as a consequence, to get beyond the "good" and move towards the "great" system.

Over to Herb, Talking about a 2A3 amp he built, with a lot of support from some very clever people:

I have a confession to make. By any rational standard, I am not qualified to design an audio amplifier. I have built every feasible circuit. I have read dozens of books and even studied in the classroom of my mentor Arthur Loesch. Still, after almost twenty years of trying, I feel radically unprepared for the chore.

I am a slow learner and I have the worst memory in the world, which may be an asset but it sure is embarrassment. I sound like a darn fool when discussing mathematical problems. I continue to ask the same dumb questions and rely on the advice and consul of guys like Steve Berger, J.C. Morrison, Komuro, Andy Grove, Kondo and Nobu Shishido. Without their help this amplifier would not exist.

On close examination, the only real talents I can muster are a basic ability to paint pictures and a potential to (sometimes) be quiet and listen. My (imagined?) capacity to glimpse a painting, read poem or visualize the forces of nature is the source of my belief that I can indeed design audio amplifiers.


What finally focussed my attention, after twelve years of building around thirty different amps, was the NVA A20/P20 I bought off Richard in the summer. The sound of this combo was a revelation and became the goal to work towards with my DIY efforts.

That my choice of amp NVA amplification, and my design of a semi-omni speaker that was a bit like an NVA Cube (horrors) resulted in a torrent of abuse and ridicule and very nearly killed my interest in hi-fi is in the record. Glad I didn't let the twats get their way (it was touch and go) in the end, as I have ended up with a cracking little system.
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Large sealed cabs, with Fane 12-250-TC 12" full range drivers.

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Lotus Seven S
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Re: JJ 2A3-40 DHT Single ended triode, power amplifier

Unread post by Lotus Seven S » Sat Jan 20, 2018 9:01 pm

I'm one of those unstable, arty types
Nice!
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SteveTheShadow
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Re: JJ 2A3-40 DHT Single ended triode, power amplifier

Unread post by SteveTheShadow » Sat Apr 14, 2018 2:25 pm

In a further development of the saga of this SET amplifier, I decided on a whim last week to chuck out most of the components from the power supply.

I'm left with a transformer, bridge rectifier, choke and a cap bank, that's it; decoupling filters between stages have gone. I reasoned that, if the Doc's KISS policy had had a major positive influence on the music making abilities of the DIY NVA I built, then the same ditching of components might do the same for a valve amp.

Well I'm extremely pleased to say that this SET now plays fantastic music. It's an excellent result and not what I expected at all.

In a valve amp, you're supposed to have decoupling filters between each stage to prevent low frequency instability or motorboating; anyway, that's what the theory says, so removing those filters could have been asking for wildly flapping speaker cones, except that nothing happened when I took out those filters except a large improvement in the quality of the music coming from the amplifier. Indeed it's surprising, just how much of the music those filters were removing from the signal.

I've tried everything to provoke LF instability and nothing has worked, the circuit remains impeturbable.

Disclaimer:
If you have a valve amp, don't try this at home. I'm not about to allow anyone to blame me for wrecked speakers.
This worked on my amp, I can't vouch for any other.
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Large sealed cabs, with Fane 12-250-TC 12" full range drivers.

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karatestu
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Re: JJ 2A3-40 DHT Single ended triode, power amplifier

Unread post by karatestu » Sat Apr 14, 2018 2:45 pm

Excellent Steve. What did you remove from the power supply then ?

I have some work to do in this department. As well as my NVA based amps, my CDP is ripe for gutting. Several ALWSR super regulators (a pfm favourite), gyrators (another pfm fave) - all of which i have no idea what to do with.
Naim, Linn & Harbeth fanboy

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Dr Bunsen Honeydew
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Re: JJ 2A3-40 DHT Single ended triode, power amplifier

Unread post by Dr Bunsen Honeydew » Sat Apr 14, 2018 3:03 pm

Adding unnecessary shite can add hi-fi, removing it can add music. But not all shite is unnecessary, my Phono stages definitely benefit from voltage regulators, but simple ones.

ALL components are shite, the only good thing is nothing. I have been saying this and publishing it (see the 1992 interview) for over 30 years. BUT nothing doesn't work, so you have to use the minimum necessary of something. That is the art in design and also the art of choosing a compromise as nothing is perfect.

Back in the beginning of hi-fi / music everything was simple, we have had decades of bullshitters and slurpers adding shite and creating what we have now. Time to go the other way.
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karatestu
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Re: JJ 2A3-40 DHT Single ended triode, power amplifier

Unread post by karatestu » Sat Apr 14, 2018 3:34 pm

Well the thing is, at the time i did a lot of these modifications i was not listening like i do now. I read about the super regs and people were saying they were brilliant (and in my particular cdp too) so i built and installed them without question. They were a huge improvement from what i remember BUT i was a detail junky at the time and probably assessing it in hifi terms.

Everything i did was adding more complexity, additional regs, more complex super regs, adding regs before regs, reducing ripple all over the place. I do remember though that adding additional independent power supplies to a circuit (where they could be split for power supply purposes) was a different kind of improvement. So were giving something its own regulator rather than it sharing a reg with something else. Maybe these were musical rather than hifi although i did not care which they were at the time. The mod that did more than any of the others was building a pfm flea powered tent labs clock and giving it a dedicated psu. Looking back that mod was definitely musical.

You see what you have started now Doc :grin: . Getting Steve and I to listen and build things in a musical sense has really opened the flood gates and made us be suspicious of everything we have learned in the past. I will have to tear my cdp apart - its not as if i didn't have enough projects on the go already :lol:
Naim, Linn & Harbeth fanboy

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SteveTheShadow
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Re: JJ 2A3-40 DHT Single ended triode, power amplifier

Unread post by SteveTheShadow » Sat Apr 14, 2018 5:03 pm

Well Stu, I know I was the same. The nature of the DIY hi-fi game is that nothing is ever complicated enough and you complicate and complicate and complicate until you disappear up your own arse; you can't help yourself. I've lost count of the number of times I've done this, and the money I've wasted is not a trivial amount. But you need to do this; perhaps not as many times as I have, but you only learn something useful by falling on your arse.

In removing the "superfluous" power supply components I knew the risks I was taking concerning the question of LF instability so there was some knowledge going on, about what I was doing.

Here's the thing though. I would never have even contemplated doing such a thing, had it not been for the Doc's offer to sell me the boards to build the DIY NVA amp. Messing about with that project brought the virtues of KISS and its effect on the music into sharp relief, and gave me the confidence to try the same kind of approach out on the valve amp.

I too am seeing things differently. A "road to Damascus" thing, but a proper one rather than one of those "yet another false dawn" kicks.
DIY NVA amplification ( roughly equivalent to NVA A60) BTE Designs passive preamp, BTE Designs Lenco L75 turntable, Rega R200 arm, Goldring E3 cartridge, NVA Phono 1
Musical Fidelity M1 DAC, AppleTV4 with Apple Music subscription, ripped CDs streamed via WD MyCloud Home Duo NAS, with PLEX media server.
Speakers - Large sealed cabs, with Fane 12-250-TC 12" full range drivers.

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karatestu
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Re: JJ 2A3-40 DHT Single ended triode, power amplifier

Unread post by karatestu » Sun Apr 15, 2018 5:50 pm

I definitely disappeared up my own arse :lol: Fortunately i have emerged from that place and have a new goal - simplicity and music.

It is easy to improve things in hifi terms - add more regulators, filter noise away at every opportunity, add lots more smoothing caps etc etc blah blah blah.
I did have a light bulb moment the other day and partially realised what my plan of attack should be. It all started with the passive pre and getting rid of the active one. I now have no input selector or attenuator switch contacts. No fuses in the amps or cdp, hell i have even got rid of the on off switches. No fuses in the plugs either as i am on a radial.

All good musical improvements. Now all my power supplies are going to be simple single capacitor jobbies. Super regulators are going to be baked off against very simple ones. One thing i know to bring big musical improvement is splitting power rails, adding more power supplies and keeping transformers WELL away from sensitive circuitry.
Naim, Linn & Harbeth fanboy

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