The Devil wrote:
On Thu, 15 Apr 2004 12:36:58 -0400, "Arny Krueger"
wrote:

That is usually the case. The early stages of the main part of the
power amp circuit often run off the same source as the output
devices. In other cases there is some built-in extra filtering.

http://www.citycom.gr/electronics/pr...l/100ampl5.gif
shows a fairly typical design. Everthing runs off the same voltage
source as the output devices.

If by 'extra filtering' you're talking about C9 and 1, then it's not
really very useful-

I'm not talking about that at all. Sorry for any possible lack of clarity. I
intended this to be an example of a power amp where everything runs off the
same basic voltage source as the output devices. In fact, that's what I
said - " Everything runs off the same voltage
source as the output devices."


-those capacitors will follow the main smoothing
capacitors and discharge through the output stage.

Agreed.

A schottky diode to
separate the main supply capacitors from local smoothing on an
isolated small signal supply would work wonders to reject rail sags
and grunge caused by the output stage.

As a rule, tweaks such as this just don't have any practical technical
advantages. Wire 'em in and there's usually no visible effect on the display
of residuals from distortion analyzer.