The MST MIDI to CV Expander module is a tiny but extremely powerful expansion module for the MST MIDI to CV Converter. The Expander includes an arpeggiator and allows you to have additional CV, gate, velocity, modulation and aftertouch outputs on a separate MIDI channel. You can also set it to the same MIDI channel as the Converter and use one of the three note priority selections, which will allow you to do duophony/pseudo-polyphony. You can daisy-chain Expanders together to add even more channels.

The Expander really shines when it is used with a DAW. Multiple Expanders can be set to different MIDI channels in any sequencer (like Ableton for example), making live performance with your Eurorack simple.

The Expander connects to the MIDI to CV Converter using an I2C cable (included with the the kit and the completed module).


  • Three note priority modes: high note, low note or last note
  • Arpeggiator modes: Forward, Ping-pong, Random, and Order Played (see the manual for more info)
  • Arpeggiator latches when a sustain pedal is held on a MIDI keyboard (once the arpeggio is established)
  • Control the arpeggiator with a modular or MIDI clock
  • Manual MIDI Reset Button
  • Volts-per-octave trimmer accessible from the front panel
  • Velocity, Modulation and Aftertouch CV output jacks function independently but can be used simultaneously
  • Pitch CV and gate outputs
  • Select MIDI channels 1-16 with an internal DIP switch
  • Gate / Note Priority LED indicator
  • Polarity protection


  • Current draw:
    • +12V: 55mA
    • -12V: 15mA
  • Module Depth: 48mm
  • Width: 2HP


Please note: the Expander will not work without the MST MIDI to CV Converter.