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