For identification: that circuit board is probably factory made, and probably in Japan in the 1970s. Guya, Elk, other less-common brands. If the rectifiers are "green pills" then is sure from Japan.
You have the power supply drawn wrong. It is the Voltage Doubler. There's two kinds, Google will help.
Unless you find that some scrap of this is Very Collectable, I'd be inclined to chisel it back to iron and good(?) sockets/wires, lose ALL that iffy patchwork wiring, un-bushed holes, and vintage cheese-board.
> any inspiration that the builder may have followed
"Stuff it and see"??
The output stage is basic Fender but with EL34. Oddly the Presence network is permanently on.
The tone control IS classic Fender, you just drew it tangled. There may be small differences which I don't care to trace.
The mixer.... that's a LOW level mixer. It distorts easy. I wouldn't put it before a lossy tone control. For a few more parts it cudda been a 5F6A stage.
The preamps are unexceptional until you spot the 1Meg feedback from Vol pot to grid. That will give a LOW input impedance, perhaps 20K. (67K including the input resistors.) Which will suck the treble off a guitar. Which may be why the Presence network is permanently on.
If you prefer to do as little as possible, play as-is, then clip the 1M NFB around preamps. That may be bright, snip the 0.1u across the 4.7K to get no-Presence. That may be an OK amp. If it strains, mod the mixer stage to be more like the 5F6A (passive mix, gain, cathode-follower). 5F6A *works*. 5881 or EL34 is a matter of taste (and bias). Using a voltage-doubler supply is unimportant (and all you can do with this low HV winding).
Topic: Mystery Amp (Read 6429 times)