In article , harrogate
wrote:


Capacitors and their effects - apart from long-term drying out and the
inductance of very large values - also fall into snake oil IMHO.

There are various effects. However I'm not personally convinced they are
audible as reviewers seem to assume.

However one thing that can have effect is heat. Most amps have some sort
of temperature sensing in the output stages that are designed to
stabilise the biasing which will inevitably change with temperature. The
old way used to be a small signal transistor either glued into or onto
the surface of the heatsinks

e.g. 'Rubber zener' used to set the bias, and clamped thermally to the
output devices and drivers (ideally). The problem here is due to the times
taken for temperatures to equalise between devices. To some xtent you can't
win here as the output devices will have junction/channel temperatures
which are very different to such a bias control device in another package.
Also possible problems with asymmetric musical waveforms where the
junctions temperatures differ.


- the Japs now build specialist transistors that have this transistor
fitted internally with external access.

Neat idea. Wish I'd had these in 1980. ;- I envy modern designers for
some of the devices they now have. However I also pity them for some of the
'reviews' that have to put up with after years of hard work. That's show
biz, I guess. :-/


Leaving the amp on for perhaps an hour before use will allow the
heatsinks - and thus the bias - to thermally stabilise which could
lead to reduced crossover distortion - the main effect of poor biasing.

In some cases warm-up might make things worse. Depends upon the situation
that gives best performance and if the amp was setup warm or cold, etc.

Slainte,

Jim

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