"mick" wrote in message
...
On Tue, 11 Aug 2009 07:57:10 +0100, David Looser wrote:

"Eiron" wrote in message
...

I wasn't criticizing Jim. I was criticizing you.


Then you are being remarkably obscure. Criticising me for what?



I think his point is that 0.001uF / 1000pF (a figure that I, admittedly,
plucked from the air) across the output is less than some cable loads. To
quote you:
"Arggh!... Plonking a 1nF capacitor across the output of a feedback
amplifier is a pretty likely way of making it unstable"

As Eiron points out, that's about 12m of Chord Silver Screen or a foot of
Townshend Isolda cable, which doesn't sound much does it?

Now, whether 1nF is enough to make any difference at all I'm not
experienced enough to know. If Jim says:
"if you just put a shunt capacitor across the output that might provoke
oscillations if the amp isn't already stable for other reasons" then
that's good enough for me. :-)

If you are right in your analysis of Eiron's point (and it sems likely) then
clearly he has little experience of this sort of thing. Yes indeed, a 1nF
capacitor connected directly across the output of an amplifier can easily
cause instability if that amplifier is not unconditionally stable.

David.