I am not quite sure what this was originally for. It had a mic preamp and two stereo turntable inputs that were on modular boards. They were gone before I bought it. So are a pair of output transformers, said to be a pair of UTC A-25 units. What is left is rather interesting: a program amp that consists of a single 6AQ6 and a 6AK6 tube per channel and monitor section that consists of a single 6AQ5. It has output transformers for the 6AQ5 which are 5k to 4 ohm so it must have driven speakers, though it is unclear what drove IT. Anyway, though it is a bit rare, the 6AQ6 is not itself that weird of a choice for a program amp first stage, but the 6AK6 is a 1 watt power tube and I've never seen it used in a line amp before. I traced out the circuit and it is a fixed gain, single ended circuit with some feedback from the triode-mode 6AK6 plate to the 6AQ6 Cathode. It is a configuration I am not familiar with. I plan on keeping the circuits as-is and modifying the mixer section to work as a passive mid-side encoder/decoder using transformers. I may tweak the brute-force, tube-rectified power supply as well. We shall see.
Update: This looks like it is some kind of custom build of course, but I think it may be a Gates based on the knobs, meters, and label plaques. SO, now I am thinking about remaking it into a stereo vari-mu, like a modified Altec 436 circuit. I still think it would be neat to have the line amp in there to patch in front of or after the vari-mu.
hi, might this be what you have? If so, what a unique piece - preserve it!
ReplyDeletehttp://www.preservationsound.com/?p=2550
AUDIO magazine c 1955: plans and schematics for a radio station mixing console.