Sonoclast New Instruments for New Music

MIDI to CV/Gate Converter

I built this MIDI to CV/gate converter specifically to add MIDI control to my Moog Werkstatt, but it could be used to add MIDI control to any other 1 volt per octave synthesizer. Design choices that distinguish this converter from others are:

  • It is pretty bare bones. My intent was to make it suitable for wiring into other devices rather than, say, producing a complete standalone unit or Eurorack module.
  • It outputs velocity control voltage for each note. Velocity data is included with every MIDI note, so it makes sense to use it for additional expression.
  • It supports pitchbend as +/- a whole step. Pitchbend is required to play microtonal pitches, as I like to do.
  • It uses a 12-bit DAC. This means that the pitch resolution is (5 octaves / 4096 voltage levels) ~1.46 cents, which is a smaller interval than we can discern.

Other specifications:

  • Powered by ground and +5V lines. Be sure to use a clean source because the tuning depends on it.
  • Accepts as input MIDI notes and pitchbend events from all MIDI channels. MIDI notes 24-84 (3 octaves below middle C and 2 above) are the 5 intended octaves. MIDI notes 0-23 and 85-127 just wrap around, i.e., 0-23 are the same as 60-83, and 85-127 are the same as 25-67. Other MIDI messages are ignored.
  • Outputs 5 octaves of pitch control voltage (0-5V, 1 volt per octave), velocity control voltage (0-5V), and gate (0V off, 5V on).
  • Last note priority for up to 10 held notes. More than 10 notes held results in dropping notes.