[Geoff]

Richard Crowley wrote:
"Todd H." wrote...
"Richard Crowley" writes:

"Jeff Findley" wrote ...
Most people think volume control as controlling the power output of
the amplifier. As you point out, it's not really since power
depends on the impedance of what you're driving with the amplifier.

It is equally dependent on both.
It wouldn't work any other way.

If you're driving a 100kohm cmos preamp from your headphone jack,
your ipod ain't gonna be burning a lot of battery life wiggling that
headphone output voltage against such a light load. It'd down in
the noise next to spinning the hard disk.

So you are saying that the output of ANY power amp
(whether it is the micro-power chip inside an iPod
or a 10KW rock-concert bruiser) is NOT dependent
on the input signal level? Sorry to hear that you have
no control over power amps in your world. :-)

No, he is saying that the ipod ain't driving the speakers - it's driving the
input impedence of the power amp (or whatver).

geoff