I'd like to bring up the the subject of the Master/Slave switch.
It has been suggested that amps used by major acts like Hendrix and Mountain were modified to have a Master/Slave switch and one or two jacks on the back. This allowed one amp to drive several other slave amps. I've ask Conrad about this subject and he didn't respond. How were the switch and jacks connected?
Yeah, I've heard the same thing in regards to some amps used by Felix Pappalardi in Mountain (which could have actually been the same amps Hendrix/Redding used). I think it's on the Sunn Shack 2?
Ah, here it is, discussing a 2000s used by Felix:
"Numerous features separate this set from a stock model, including the addition of a 120/240V switch for world travelers, a slave output with a mysterious switch allowing a number of heads to be controlled from a single set of controls, and an additional output jack. "
Other than that, I have no idea about how they were worked into the circuitry or anything else about them, but I'd sure love to know too.