"Trevor Wilson" wrote in
message
"Eeyore" wrote
in message ...


Trevor Wilson wrote:

IOW: The design is more important than the Class of
operation. Class A will
help a bad design and, at best, do nothing to a good
design.

You're assuming they all start as Class AB output stages
there.

**That's because there are essentially no Class A push
pull designs (anymore). They're all Class A/B with
different bias currents.

Agreed again. Building a truely Class A power amp that can deliver
significant amounts of power output is really a pretty awesome thing. The
OPT stage quiescent current has to be equal to the *peak* current that is
delivered to the load.

We all know that speakers can be capacitive-reactive and can jack the load
current to unexpectedly high levels. A common power amp will have +/- 80
volt DC rails and may need to deliver up to 15 amps peak to the load. So,
now the OPT is dissipating 2400 watts per channel just sitting there, not
counting internal losses.

Considering that heavy duty electrical room heaters usually top out around
1600 watts, the problem should be self-evident. We're basically talking a
power amp that duplicates the heating function of 3 room heaters and has to
be hooked up to a clothes dryer circuit.