Chuck D. Bones
Circuit Wizard
A couple of weeks ago I breadboarded the Apocalypse Audio Thundertone. It sort of models the preamp section of the Supro Thunderbolt from the mid 60's. Mr. Linders chose to use Germanium transistors. It sounded ok, but didn't get me too excited. The TONE control had a big volume drop in the middle and I did not like the biasing. So I thought I'd take a bash at it myself. After several incarnations, one of which bore more than a passing resemblance to the Quarantine SE, I ended up with this. I managed to get one Ge transistor in there! It started out as a 3-knob pedal, but the last circuit change was adding the PRESENCE control at the end to be able to reduce the harshness with high GAIN settings. The first two stages are pretty close to the Supro and the 3rd stage is supposed to represent the phase splitter and output stage. It's a medium gain pedal that will play clean with lower GAIN settings. The breakup is gentle at first and gets more aggressive as you advance the GAIN. I also tried it with MPF4393s and it sounded the same after a little bias tweaking. Other JFETs should work too, just tweak the source resistors. I tried 2N1308 and MP38A in the 3rd stage; both worked and no bias adjustment was req'd. It's nice being able to tailor the tone before the distortion stages.
VOLUME & GAIN on the top, PRESENCE & TONE on the bottom.
VOLUME & GAIN on the top, PRESENCE & TONE on the bottom.
