I just acquired a Lear Sigler brand, Bogen Communications Division, 30 watt, monaural audio amplifier, model 330A Series H-57, with tubes, that has 3 empty tube sockets. Unlike the other sockets which have the tube numbers on the chassis next to the sockets, these three don't.
I would like to give this amp away, and I think I first need to insert new tubes, but I don't know what to use. :)
The other 5 sockets are marked V1 6EU7 V2 6EU7 V3 7247 V4 7868 V5 7868
Since there is only one speaker output, the 2 pairs of matching tubes seems to me to indicate push-pull stages to the amp. Yes?
The other three sockets are labled X1, X2, and X3. I've never seen such names before. Perhaps this is a secret government amplifier?
The sockets are labeled Mic, Tape 1, and Tape 2. Each has a slide switch for Hi or Lo Impedance, on top of the open backed chassis.
Is it possible that a tube is needed for Lo impedance inputs and not needed for Hi impedance? Or is it vice versa?
I would like to be able to tell the next owner, if I can find someone who wants this, what tube he should use if he has the other impedance input. Does anyone want to wager a guess? The tube sockets are 9-pin and each has clips for a tube shield. Do they still sell tube shields? I have some, but I don't know if I can find them.
Four of the tubes are the original Bogen tubes, and the other, V3, the7247, is a Telefunken tube labeled "Made in West Germany". So I guess this was repaired between 1945 and 1990. Can anyone suggest when it was made?
It also has little adjusting holes in the chassis for WMT-1 input and output, plus an RCA jack labeled "WMT-1 HIZ". Is that the same as High Z, and what would that be? :)
Any help is much appreciated.
If you are inclined to email me for some reason, remove NOPSAM :-)