"Richard Harrison" bravely wrote to "All" (02 Mar 05 10:35:29)
--- on the heady topic of " Say what you mean."

RH From: (Richard Harrison)
RH Xref: aeinews rec.radio.amateur.antenna:26249

RH Asimov wrote:
RH "Let`s look at it from the dynamic point of view (loss in a Class A
RH amplifier)."

RH The no-signal loss of a Class A amplifier is 100%. It equals volts x
RH amps and appears in the amplifier. Now feed a signal to the ideal
RH amplifier set just below the clipping level. Average d-c power is
RH unchanged from the unloaded and no-signal conditions.

RH Connect a matched load resistor to the amplifier output. If physically
RH small, the resistor may become warm with heat that were it not for the
RH load would be otherwise dissipated in the amplifier. Input power to
RH the Class A amplifier is unchanging.
[,,,]
RH Power output from a Class A amplifier cools it.

Okay, it cools. Enough said. I was confusing it with Class B which
does warm up the heatsink. ;-)

A*s*i*m*o*v

.... May you find the light and walk the mountain tops.

Asimov wrote:
"I was confusing it with Class B which does warm up the heatsink"

True. Class B amplifiers can be single-ended for R-F if used with the
right tank circuit to supply the missing 1/2-cycle. More often they are
push-pull to reduce harmonics.

SSB final amplifiers are biased to near current cut-off. During
modulation gaps, current falls to nearly zero. When current is zero, so
is the dissipation.

Reg mentioned the blistering heat of the 6N7. Thai`s my recollection too
when getting nearly 10 watts of audio from the small twin-triode
octal-based metal tube. Reduce the audio volume and the heat is reduced
simultaneously.

Best regards, Richard Harrison, KB5WZI