[Lowfer] 1 W OUTPUT STAGE TYPE

[JD]

I've used MOSFETs in the past myself, but it appears ampifiers using 
complementary pair switching BJTs are most common nowadays.  The standard 
"Lyle Koehler final" you've undoubtedly run across is pretty tolerant of 
tuneup conditions, even with inexpensive transistors; whereas you sometimes 
need a very robust FET to survive the waveforms it may have to endure under 
less than ideal adjustment.  Neither output stage seems to have a 
significant efficiency advantage, and neither is at all hard to drive from 
everyday CMOS for the 1-watt power level.

John