Modifications
Overall, I'm pretty happy with the way this turned out. These are good amplifiers, but they don't have enough gain to work well in a typical home audio application, so I added pre-amp stage. Total power is about 70 watts (20 + 20 + 30) I set this one up to be used as a single channel amplifier for my "tri-amped" speakers. Now that I have this fixed up, I can rebuild the large Allen amp I have on my right channel right now. There is something wrong with it, because two of the four 6L6's run too hot.
I added some nice spring terminals for the speakers, and RCA input jacks
And a super-secret toggle switch that engages a preamplifier circuit that I built!
See the extra 12AX7 on the left side of the photo? (the only socket held in with screws)
.Here is the wiring for the extra tube, and the relay that switches it into the circuit. The tube is white ceramic with red marks on the plate pins (1 and 6). Not much room in there. Point to point wiring is a pain. I used snippets of wire insulation on most of the component leads to minimize risk of shorts. The large red wires are sheilded signal wire.
Here is another detail
It's really not as chaotic as it looks, just hard to take a good picture of.
Here is a picture of all the wiring. I replaced a number of capacitors and resistors to get the circuit into shape before I made the other modifications. I had a hard time debugging a problem that turned out to be an out-of-tolerance resistor.
Here is my super-tidy electrolytic capacitor replacement job. I added two big terminal strips, and used modern electrolytics in series to match the required voltage (about 400 volts) The small capacitor and bridge rectifier in the back are the 12v DC supply for the relay coil.
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