Synthrotek MST Expressor Lets You Use Expression Pedals With Your Euro Modular

MST_EXPRESSOR_SQUARE-500x500Synthrotek has introduced the MST Expressor – a Eurorack module allows you to use expression pedals with your modular synth

The Expressor has two identical powered expression pedal processing units in one module, allowing you to do things such as:

  • Control volume with your foot
  • Attenuate CV or audio if no expression pedal is plugged in
  • Add positive or negative voltage with the flick of an ankle:
  • Sweep a filter cutoff
  • Transpose CV
  • Pitch bend
  • Direct audio volume control
  • Attenuate and expand external CV
  • LFO rate adjustment
  • Modulation amount control

Here’s the official video overview:


  • Processes audio and DC signals
  • Two discreet expression pedal input channels (1/4? TRS jacks)
  • External signal (audio or CV) input per channel
  • Precise output adjustment: attenuator/scale control per channel
  • 3-position switch select of +5V, -5V or 0V (mute) per channel
  • External input bypasses the switch voltage (the switch voltage and external input are not active at the same time, i.e. the voltage will not offset your input signal.)
  • Red/green LED per channel (red = positive voltage, green = negative voltage)
  • Compatible with passive TRS 1/4? expression pedals, such as the M-Audio EX-P

The MST Expressor is available fully assembled for US $124.99. DIY options are also available.

Leave a Reply