"COLIN LAMB" wrote in message
...
Push-Pull allows you to runn in other than class A, which is about 35%
efficient. However, class A can result in very good audio.

Some high end audio amplifiers are single ended class A. High power puts
out a lot of heat.

Colin K7FM

Back in the year one, Bill Orr, W6SAI, published an article (When QST was
still a technical magazine) on a single 304TL Heising modulator. I built one
to modulate a 4-400A.

Ran class A when you were talking to it, ran class C when you weren't.
Shifted the bias at a syllabic rate by rectifying a bit of the preamp audio
and applying it as forward bias when talking. Worked very well, quite
efficient, and the origin of EBC. The Electronic Bias Control bias shift
seen in 1970 and 80 Alpha RF Amplifiers to hold down plate dissipation for
class AB and B operation.

W4ZCB