"Richard Crowley" writes:
"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, but that's certainly an interesting take on what I wrote.
My original point is that you're wrong to say that power consumption
of a an amplifier is "equally (as in 50/50) dependent on both" the
volume control and impedance of the load in all circumstances.
So, back to where the original poster I believe said he wasn't going
to use his portable mp3 player to drive his receiver anymore because
he was concerned about battery drain, and I told him not to worry much
about that....
I don't care if the volume control is on 100%, if you're driving so
light a load as a high impedance preamp input on a receiver (generally
on the 10kOhm range or higher), you're driving cmos gates. If you
know anything about electronics, you'll know that driving a cmos gate
(or moving 10kOhms in general) doesn't pull much current out of the
power supply, hence doesn't have a significant effect on battery life.
Unless of course the original 1/8" to RCA cable in question here is
partially shorted (which I suspect). In which case, this would draw
current out of the headphone amp and contribute more noticeably to battery
drain.
Best Regards,
--
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