(How much) POWER supply

[andrew ivimey]

not a prob, just a query.

No one doubts that to have loads of spare power in a PSU for single ended valves is a good idea.

Surely, this is so too for solid state amplifiers.

But when one gets down to the tiny level of ... an i.c. ridden phono pre-amplifier then would a beefy power supply that could supply, say, 2 amps of power when only about 200 milliamps is specc'd. -Is there any point in going for the (relatively) big one ?????

intuitively, why not, but what about in practice really ???

[petercom]

IMO the main differences between power supplies are due to:

1. Noise
2. Output impedance
3. Meeting demand

For a preamp you can usually rule out 3. unless your supply is very weedy, so that just leaves the first two. You might just find, depending on design, that a beefy supply does better on both terms than a weedy one. But that doesn't mean that you can't design an elegant, low noise, low impedance supply that just meets the circuit demand current.

[andrew ivimey]

Thanks Peter, that looks sensible advice and I think I can cover each condition.

[Ianm2]

yes it makes me laugh a little bit when you see a phono stage with a couple of chips in it, and a small transformer that is still overspecced, and they do a big monster upgrade one and say amazing increase in sound quality.

hmpph....

[JerryT]

And then you try the 'big monster' and discover you do prefer the sound......

Don't forget we work in an AC to DC world - and the bigger the transformer the less ripple you generate on the DC as the current draw changes (in response to the music).

I think Peter's comments about noise, and noise rejection are also very significant here.

If only life were simple!

Jerry

[Ianm2]

yes but if the supply is already regulated the ripple is negligible

[NickG]

We can argue till blue in face about what should make no difference. I guess the thing to do is try it. If it sounds the same, then our theory still stands, if it sounds different then our theory is broken.

[Ray P]

Its the quality that matters, not the size.

That's why I'm looking forward to experimenting with some constant current shunt regulated supplies, courtsey of Paul Hynes, for the B+ in my Bottlehead Paraglows.

Ray

[NickG]

It will be interesting to see what you find Ray, I am very pleased with the effect of changing a conventional supply to one using a valve shunt regulator. I guess the circuit I use is supplying about 70ma to the 45 stage at the moment, but should be able to supply more than enough to drive your paraglows.

Actually, just thought, it will be interesting to see if the CCS shunt supply in my phono stage does it any favours at the phono get together.

[Ray P]

Nick, I'll report back in due course.

The stock Paraglows use a constant current source on the driver stage and the improvement over that when I applied the Paraglow 2 mod, which consists of constant current shunt regulation on the driver tubes (uses half of a 6N1P for the driver valve and the other half for the shunt regulation) was well worth while.

Ray