Another DIY SS Amplifier with NVA Boards

[Dr Bunsen Honeydew]

What make of transformer is that.

[SteveTheShadow]

What make of transformer is that.

Its a Siga, which is a UK company.

Must be some sort of custom thing. I got it off eBay. It has three secondaries 30V, 30V and 12V, which I'm not using.

The diagrams on their website correspond to what yourself and Nick say, but nevertheless how I have it is exactly according to the markings on the transformer itself. Surely the label can't be wrong.
I get two polarities -47 and + 47 at each rail. Don't know what else I can say. It works.

[Dr Bunsen Honeydew]

Different colour coding then in this case.

[SteveTheShadow]

Aye, strange one.
Sorting the stars at the capacitor terminals has cleaned things up further. Just shows that it's those little details that make the difference. Maybe it's also time now to experiment with bypasses. I'll let things settle a bit before messing about with those.

[Lurcher300b]

Yep, I was going to suggest 1uf film caps on each cap, but got sidetracked by transformer wires

Never underestimate the fact that a short bit of wire is a resistor that matters if you pass a big enough pulse of current through it. The charging spikes for these sorts of power supplies are short in duration but can be large in current. Add that to the fact that you can hear down below the noise and its not surprising what we can hear, The bigger the transformer and the more capacitance just make the spikes bigger.

[SteveTheShadow]

Cheers Nick. So the bigger the power supply, the less sloppy you can afford to be, would seem to be the rule.

[SteveTheShadow]

OK,

So I've introduced bypasses, comprising 0.94uF worth of vintage '70s tropical fish, tone caps (2 x 0.47uF paralleled across each cap bank. They were all I could find, but close enough to 1uF for jazz I think. Another layer of hash gone; a surprising amount actually.

All in all, a good few sessions' work.

Thanks for the tips Nick and thanks again Richard for the opportunity to use the boards.

[Lurcher300b]

The 1uf is not a special value, its just what I use.

[Dr Bunsen Honeydew]

If you want more effective then you should try 3 by-passes with progressive values. I love paper in oil, but impractically large (and hard to find, mostly old stock), so I only use in speakers. Second fav is polystyrene, many values. I go in Statement amps with parallel caps like you have done and bypasses of about 8 to 10mfd and 1mfd, and 470pf, try that.

https://uk.farnell.com/c/passive-compon ... lystyrene-

[SteveTheShadow]

Thanks Richard.

I managed to find 0.1uF and 0.01uF in my parts box, to use as descending value bypasses, so these were fitted alongside the tropical fish caps. So as an approximation we have 1uF, 0.1uF and 0.01uF, going down by a factor of 10 each time.
The results are very very good. I'm well pleased.