Thermae Expander

This little device adds some features I missed from the already great Chase Bliss Thermae pedal.

For inquires and orders contact me at


  • Delay time (aprox 200ms – 6s)
  • Mix (useful when ramping is enabled)
  • Toggle slowdown mode
  • Pitch Interval select (all possible combinations in a knob)
  • Advance step from external audio (configurable threshold and retrigger time 0.1 – 0.9s, only for Thermae in step mode)
  • Engage pedal from external audio
  • LED to show tempo (time mode) or audio detection (trigger mode)


  • Mini-USB powered
  • Midi Out (3.5mm stereo minijack) to Thermae (no special cable needed, just 1/4 inch adapter)
  • Audio In (3.5mm minijack). If using a mono source (microphone, piezo…) the signal must be at the tip of the connector.
  • 2 knobs with different functions depending on mode
  • 2 buttons
  • LED to show tempo or audio detection
  • 3D-printed case and knobs

Important Notes:

  • No cables are included.
  • Midi channel cannot be changed, everything will be sent to Thermae’s default midi channel (#2)
  • This device always sends midi clock, so the Tap tempo of Thermae won’t behave normally if pressed with the thermae expander connected.
  • Any mini-USB power adapter capable of giving >100mA should work.
  • To properly use the external audio trigger, it is recommended to use an “isolated” audio source like a piezo or maybe an auxiliar audio output from a mixer, additional synth output, etc. A simple minijack splitter from the audio source may not give good results.
  • Also, to properly use trigger mode, Thermae must be in step mode (dip switch).