I've tested these guys, it powers up and passes signal. Sounds neat, but I never used it much (too many pre's/lazy about wiring patchbays). I never figured out the pinout of the opto compressor but it looks very much like an LA3a and I've got the opto section to react to input signals, just never figured out the output wiring. I'd be willing to give it another shot if you asked nicely.
All discrete, transformer balanced goodness. Should be easy to modify with attenuators, but they sound great as fixed gain pre's. Seem to have around 45 db of gain or so as they sit and a very cool vintage tone. They sound nice chained together from what I remember and are fantastic line amplifiers as well.
Probably circa 1960-64. Def early solid state design and built to military standards. Would be a fun winter project to tinker around with. I have some hand drawn schematics somewhere.
SOLD
