audio-talk

Good points well made Mark, an excellent summary I think.

Nick wrote: ↑Wed Apr 11, 2018 10:47 pm IMHO, a good power supply never hurts. PSRR is not a simple subject, and its rarely constant with frequency. Allen Wright makes a very important point in his book, along the lines of "points in the circuit that should stay fixed, should never move, and points that should move, should have nothing stopping them moving."

Good points also. This book Nick? Not cheap, but worth it?

http://www.vacuumstate.com/?rubrik=1&ka ... 6984048749

All of which is interesting in context of Steve's latest 2A3 adventures.

Its a good read, but I was lucky I think in not buying it for many years, when I finally did, both myself and Andrew was amused to find we had developed the same circuits. It would have been far less fun to have just got them from the book in the first place

I'd just like to point out here that it was not I but t'other Andrew. But I agree with what Mark just said.

You mean cheep Chinese boards.....Stamped NVA.
Or
NVA boards stamped....Made in China.



Mmmm.....DISCUSS..

Nanook of the North wrote: ↑Sat Apr 14, 2018 9:19 pm You mean cheep chink boards.....Stamped NVA.
Or
NVA boards stamped....Made in China.



Mmmm.....DISCUSS..

I sincerely hope you are not trying to initiate any form of conflict ?

Now dont be silly Phill.

And are you admin now........

Nanook of the North wrote: ↑Sat Apr 14, 2018 9:27 pm And are you admin now........

Certainly not Jammy.

Who........

pre65 wrote: ↑Sat Apr 14, 2018 9:31 pm

Nanook of the North wrote: ↑Sat Apr 14, 2018 9:27 pm And are you admin now........

Certainly not Jammy.

17,000 posts and not admin.........wow

I'd call it a day if I were U.

So,it is Jammy.

Who.........

Thinking yesterday about recently departed Richard Dunn, I decided to bring my NVA A60 clone out of hibernation and tidy up the rat’s nest of an interior.

Parts of the bus bar grounding system were replaced with new, because the existing was so covered in solder blobs and lethal wiry spikes it was frankly a disgrace. The outputs of the supplies to the circuit board power rails were uprated to 17 Amp wire.

I also took the time to upgrade my P20 passive control unit by fitting a TOCOS 10K log pot and converting it to take 3 inputs, simply by moving the reference washer on the selector switch to number “3” and wiring the “direct” input to the newly created position. So now there is no source direct facility, but the extra input makes more sense and is more valuable to me.

It’s as quiet as the grave when idling, which it ought to be, but the last iteration was not as quiet because I was basically crap at SS power supplies, which gave Richard much amusement. I’m not that clever at SS even now but I’m starting to get there (I think).

Anyone know of a good primer, so I can learn about solid state power control circuitry, eg timed relays, soft-starts etc?

Tried some new power supply bypass caps, but removed them PDQ, as they just didn’t work. This time however upon removing them I have cleaned up the busbars where the bypasses were rather than simply cutting off the leads. Tidiness doncha know.

Maybe it’s a characteristic of Richard’s circuit, but adding anything other than what is essential to make the things function seems to result in a retrograde step in terms of sound quality. Maybe also, the 10,000uF, 80V, SuperTech slit-foil power supply capacitors I bought from Hi-Fi Collective, simply don’t need bypasses on them.

I know Richard had been of that opinion, as he told me last year, that he’d tried Denis Morecroft’s (DNM) original slit-foil electrolytics back in the late ‘80s and had found them excellent sounding without needing to be bypassed. He had however declined to use them as they were too expensive at the time. He’d therefore decided to continue to use “normal” PSU caps with film bypasses as the then new slit-foil types would have pushed up his prices too far.

Anyway, the OTL has been put away for the Summer as it was making the room too hot and the missus was complaining. Mind you I can see her point, it was sweltering in the front room the other night. It’ll reappear in the Autumn/Winter season.

It’s nice to have more than one amp.

Interesting bit of tweakery to the power supply this afternoon:
The power rail capacitors were made up of 16800uF each rail consisting of a 10,000uF Supertech slit-foil combined with 6800uF of “normal” Samwaha “Audio Grade” electrolytics.

So this afternoon, I removed the 6800uF Samwahas from each rail, leaving just a single 10000uF slit-foiler per side. The result has been quite lovely. The treble performance of the A60 clone has improved to such an extent, that it rivals my OTL amplifier. I didn’t expect this, but I’ll take it nonetheless.

The Supertech slit-foil caps are modern versions of Denis Morecroft’s originals and are a joint venture between Morecroft and Supertech. They are the best power supply caps I’ve heard, for transistor amps, but what do I know? This is the only transistor amp I’ve ever put a power supply to.

link https://www.hificollective.co.uk/compon ... itors.html

I’m starting to wonder what the four-terminal versions will do.

link https://www.hificollective.co.uk/compon ... itors.html