Today I picked up where I left off. I spent the day updating the high voltage regulator section (no more overheating, yay!) and designing a tremolo circuit. Originally I intended to leave out the tremolo in favor of a tone control, but enough folks have pointed out to me since then that tremolo is an essential part of the classic Wurly sound. So I tweaked the tone control circuit a little, and added a vactrol-based tremolo oscillator. It turned out sounding pretty cool; the tremolo effect seems to be accompanied by a slight filter modulation… an appealing sound.

I’ve left the circuit running for several hours as a burn-in period and it appears stable.

I have also decided to re-name the project WurlyBrain… its just easier to say than Electric Piano Amplifier 200.

At this point I need to prepare a revised PCB layout and send it off to pcbex.com. I’ll write another post as soon as I have units ready for production. In the meantime, let me know if you are interested.