So a few years ago my friend Jim bought a used Sofia Electric PP EL34 amp, only to learn after receiving it that the previous owner had "modified" it for 6L6's. Whatever he did, the thing never worked and kept blowing tubes and fuses. Jim took it over to Richard at Sofia to see if he could "fix" it, but Richard said it was such a mess he couldn't do anything. It sat in a closet for a few years, then when Jim and his partner retired and moved to Lewis, he sent it to me to see if I could do anything with it.
It arrived last month. What a beast--must weigh 80 pounds--and what a mess. Stuff glued to the inside, wires everywhere--just a mess. I'm a messy builder but this made me look like Engineer of the Year.
Anyway, I thought, well, decent transformers, lots of room, what can I do? Fortunately Sofia uses the same chassis for all their stereo amps, so there were a number of extra holes and stuff, plus an easily drilled sub-board.
I figured out what tubes I could add where, then hunted around for a circuit that might be fun. In my stash I came across that old PP 300B circuit from Sound Practices, by Al Bryant, "Homebrewer of the Month," who built his amps on cake pans (anyone remember that?). It was a perfect match for the chassis. I don't know of anyone ever actually building it, that I heard of. So here we go:
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