This is a copy of my post on the EEGSynth homepage, the original can be found here and more details are available from the EEGsynth GitHub repository.
To link the digital signal processing on a laptop or Raspberry Pi to the analog synthesizer, I have made two usb-to-cvgate converters. The first one I designed and implemented was a one channel version that is able to output up to (approximately) 5 Volt. The second one is an improved version with four channels that can be controlled from 0 to 10 Volt.
Using the EAGLE PCB design software, I have drawn the schematics which should allow others to copy them. Also included below is the bill of materials (BOM) with links to component vendors. I have mainly been shopping on Ebay, you can also get it elsewhere of course.
Details of the one-channel USB-to-CV/Gate converter.
Details of the four-channel USB-to-CV/Gate converter.
