I know when Blackie was a Quasi, she did not like Infinity Quantum 5's at all when you started to move the volume up to high levels, it would blow fuses left and right
Ron,
Your post got me to thinking.
I am not sure if you or some of the other folks out there have seen the Phase Linear 400 and 700B service bulletins that were issued on the "Infinity Quantum Line Source Speakers...." or "Infinity Speakers with Watkins woofer System". These service bulletins came out around 1980/1. (See attached pdf's.)
Decades ago, I first began replacing the older slower output transistors (FPL, and XPL series transistors) with newer faster MJ15024's. One day Dean showed me on a 400 series 1 amplifier how the older devices when being driven into a 4 ohm load into clipping above 8KHz would blow the fuses and the MJ15024's would not. He then began to explain to me common mode conduction.
Anyway, since these earlier amplifiers were quasi comp amps, my guess is that either the Infinity's were causing your problems or you were driving the amps into clipping into a 4 ohm load above 8 KHz (with the older slower output transistors which were common in the quasi comp amps).
It is interesting to note that the later 400 and 700 series II service manuals did not include any information about the Infinity's. Perhaps either Infinity fixed the problem on their end or there was some design change in the Phase Linear amps that prevented any issues when driving the Infinity's. Perhaps Joe has a thought or two on this?
Ed