Music and Synth DIY

Circuit bending

Alesis SR16 circuit bend

About 10 years late to the party with this one but there you go.


  • patchbay for the sound ROM’s address and data lines (standard stuff)
  • LTC 1799 from with a Vactrol for pitch
  • Rubbish home made case. I can’t make cases.

Also added an LFO to control the pitch via the Vactrol, and an Electric Druid MIDICLK PIC chip to send MIDI clock to the LFO and output another clock with start, stop, continue and run +5v logic triggers to 3.5mm jacks for Eurorack integration.

This was the through hole version of the SR16. There’s at least a couple of SMD versions – if you’ve got an “AUX L/R” jack on the back, it’s a surface mount board.

The sound ROM is a TC534000P (datasheet here if you want the pinouts for the address/data lines, etc).

The vactrol needed to be calibrated to a 0-5v control voltage range, as I was using an Electric Druid “StompLFO” PIC as the LFO. I did that with the synthrotek VacPak schematic.

That’s synced to the Alesis MIDI clock with a Electric Druid’s MIDICLK PIC (they don’t sell a chip for this one, but the code is on their site). This has 2 clock outputs, so I brought clock 2 and some other triggers out to the panel for Eurorack use.

I’d say this was partially successful. It’s prone to crashing with certain patching combinations, or if more than 3 or 4 address/data lines are connected simultaneously. Googling around, it seems the through hole version is prone to noise when circuit bent if the cable carrying the lines is near one of the ICs on the board.

I tried a few things to get around that but nothing made much difference. I could try the SMD version but as I’ve already got a rackmount Alesis DM4 that I’ve done a similar thing to, I’ll probably just leave it.

Here’s a quick demo with crappy phone mic audio recording. Vactrol LFO at 1 minute 10 seconds.