On Fri, 07 Jan 2005 19:18:57 GMT, "Leo Lichtman"
vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email


"Vaughn" wrote: I disagree. In my experience, Watts RMS is the ONLY
meaningful measurement of the power output capability of an amplifier.
^^^^^^^^^^^^^
Vaughn, lets look at this one step at a time. RMS stands for "root mean
square." If you look at the equation for power, it is I^2 R, or E^2/R. For
DC that is very simple, but for AC, it is necessary to use an average figure
for E or I that gives the correct power. The way to get that average is to
square the instantaneous voltage or current at every instant, take an
average of the squared values, and take the square root of the
average--hence: root (meaning square root) mean (same as average) square.

The wattage rating or operating point of an amplifier is already in power
units. It is perfectly OK to talk about "average power," or "peak power,"
but RMS power suggests doing something to the numbers that has already been
done. To square, average, and take the square root again would produce a
figure that has no meaning. That's my gripe.


But if you use a standardised method of measurement (sine wave) the
RMS is the same power dissipation as DC, isn't it? So you are
measuring the ability of the amp to continuously dissipate heat,
basically.

Taking the square of a number that has _as part of its makeup_ a
squaring process of only one constituent of that number is not "doing
something that has already been done" at all.