The Mastermind GT, LT and PBC can use a variety of expression pedals. Any resistance value from 10k to 250k can be used. Pedal calibration is required for best results, especially for lower resistance pedals.


Expression pedals are available in two polarities, one used by Roland/Boss and one used by Rocktron and Korg. RJM Music products use the latter. Even if a pedal uses the other polarity, it can be corrected by using a TRS cable that swaps the tip and ring on one side. Custom cable companies like Best-tronics can build such a cable for you. Their part number is SI-17-XX. Alphatone Audio also makes a similar cable, be sure to select the "Polarity Reverse" option.


Technical note: the pot wiper should be connected to the jack's ring for proper operation


Compatible Pedals

These pedals are known to be compatible with RJM products, with no need for a special cable:

  • Dunlop Volume X Mini (need to set internal switch to Ring position)
  • Korg XVP-10 and XVP-20
  • Mission Engineering EP1 w/ polarity switch (set switch to Reverse)
  • Mission Engineering EP1-R (reverse polarity)
  • Mission Engineering EP25-PRO Aero (set polarity switch to Reverse)
  • Mission Engineering SP1-RJM (includes toe switch w/ LED, connect two TRS cables to use both the pedal and the toe switch. Out 1 connects to Exp Pedal input, Out 2 connects to Ext Switch input.)
  • Rocktron Hex
  • Source Audio Reflex (set DIP switches to "Passive TRS (Ring Expression)" - see Reflex manual for details.)


Reversed Pedals

These pedals will work if you use a TRS cable that swaps the tip and ring

  • Boss EV-30
  • Boss FV-500H and FV-500L
  • Dunlop DVP3
  • Fractal Audio EV-1 and EV-2
  • Mission Engineering EP1
  • Pigtronix Dual Expression Pedal
  • Roland EV-5


Incompatible Pedals

  • Active volume pedals
  • Pedals designed for Line 6 effects use TS connectors instead of TRS. This, unfortunately, makes them incompatible with RJM Music products (and most other products, too!).


Volume Pedals

You can use a volume pedal connected using an insert cable. Volume pedals use an audio or logarithmic taper, so most of the value change will happen at one end of the pedal. Masterminds now have a taper compensation adjustment, start with setting taper to X=80 and Y=30 and adjust from there.