Hi!

If the "outboard speaker protection device " is a "crowbar" how
do you know it was not a failure in that which knocked out the
amp ?

The device in question opens the circuit by tripping a relay (one per
channel).

The left channel of the amplifier was already dying before I was using
it anyway. At first it got weak and distorted when I turned up the
volume. It would come back to working order if I turned it back down.

Then it stayed broken, with the weak and distorted audio on the left
channel. Around that time, I put the good speakers away, got some
crappy ones and decided that I'd rather not smell them burning up.

It played for a while beyond that and then "click" ... the relay
tripped.

William