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Old 4th January 2020
Originally Posted by Jay Rose View Post
Looked closer at your first photo. The 70.7v tap clearly shows this was a piece of public address equipment... AFAIK, that's the only application that uses "constant-voltage" distribution to multiple speakers. (Each speaker had a transformer with a 70.7 V primary, and a bunch of secondary taps marked in watts, so you could easily set how much power went to that room. No messing with impedance... just make sure your total secondary wattage didn't exceed the amp. There was also 25v constant voltage, which had the additional advantage of class II wiring.)

Then I went to an archive of RCA catalogs, and looked at the PA amps in an early 70s version. None of them looked like your box. RCA's front panels were very different.

RCA -did- have PA amps in the "SA" series (I think it stood for 'speech amplifier'). But never SAGG as far as I know. And as far as I could determine, all of them also had MI ordering/stock numbers somewhere on them.

This does have an 8ohm tap, my thoughts were to use it more as a guitar type amp, if it sounded any good. Looks to be all germanium on the inputs, with plug in transformer options. I got a bunch of octal plug transformers and sockets i could mount transformers too.

Ill poke around more for the mi number.