"Tim Martin" wrote in message
...
So; suppose we have a sound reinforcement system, with an ordinary class
AB
amplifier, whose manufacturer says it can deliver say 250 watts per
channel
or more at some distortion level. And we are using it for a pub band rock
performance, and towards the end of the evening, it's at or close to full
power, with speakers putting out 120dB or so.

Os this amplifier working in Class A some of the time and Class B some of
the time, or what?

Class A/B doesn't mean Class A sometimes, and class B sometimes. It means
that the output devices are biased somewhere between Class A and B, and that
a quiescent current does flow all the time - the device/s never fully switch
off as in class B, but are not on full all the time as in Class B.

It's a bit like gray - between black and white, but never black or white.


geoff