In article , Jim Lesurf
wrote:
In article , Rob
wrote:
Jim Lesurf wrote:


I know you don't know everything about every amplifier, but could you
explain what the average punter should look for in an amplifier to
avoid these issues? The sorts of questions I can ask a manufacturer
for example?

The primary question is, "Is your power amplifier unconditionally
stable?"

A "yes" response should go a long way to removing any risk or worry,
although there is still some chance they are wrong, or that there can be
some alteration in behaviour at a low level.

I should perhaps have added a subsidiary question, "Does your power
amplifier have a high output impedance at (audio) HF?"

A "yes" response would indicate you should avoid cables with high shunt
capacitance as the interaction between cable and amp could affect the audio
HF response.

A problem here is to quantify 'high output impedance' at high audio
frequencies, particularly because - as has already been explained - some
output series inductance is advisible as a way of helping to ensure
unconditional stability.

FWIW I'd tend to say an amp should have an output impedance not much more
or less than a couple of micro Henries at audio HF. But this does depend on
other details, etc. So other values may be fine - depending on
circumstances.

Slainte,

Jim

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