They look like renovated amps from the early to mid 1950s, given the octal valve bases, the use of oil-paper caps, and two chokes (large & small). The other small choke and can caps may be related to a bias supply.
There was a lot of US-based Williamson amp modifications going on in that period - certainly the use of quad 807's and the need for increased diode capability than just available form a single valve, so as to increase the power rating of original Williamson from 15W.
There was a lot of US-based Williamson amp modifications going on in that period - certainly the use of quad 807's and the need for increased diode capability than just available form a single valve, so as to increase the power rating of original Williamson from 15W.
They certainly could be a custom design. However, based on the little the seller shared, I am hoping they were a commercial design and someone will have a schematic.
I did look back at my correspondence, and the seller believed these came out of a movie theater, were manufactured under the Operadio brand, and were model 1A50.
I have never been able to find any information that linked Operadio to any large amplifiers like these, however, and I have never found information on a model 1A50.
I did look back at my correspondence, and the seller believed these came out of a movie theater, were manufactured under the Operadio brand, and were model 1A50.
I have never been able to find any information that linked Operadio to any large amplifiers like these, however, and I have never found information on a model 1A50.
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