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This Pedal Board is a custom integration of the following components...

  1. Roland GR-55 Guitar Synth
  2. Roland US-20 GK A/B Switcher (CLONE)
  3. Roland EV-5 Expression Pedal... modified to control the synth volume via the US-20
  4. Custom Two-Button footswitch to simulate GK S1/S2 Functionality via the US-20
  5. RMC-Pickup GR-55 Subsonic Filter


The Roland US-20 is an A/B switcher that allows the performer to switch his/her GK equipped guitar to two GK synths (one, the other or both synths at the same time). This US-20 Clone was designed by Roland enthusiast Harald Milz of Germany. I purchased the PCB from him and sourced all of the parts locally to put it together in my own custom packaging.


I did do some modifications as follows...

My US-20 Clone allows a buffered SEND/ RETURN before the GR-55 as well as allowing me to connect a Normal Guitar to the GR-55 in the absence of a 1/4" Guitar in on the GR-55...


GUITAR OUT - allows you to SEND the MAG signal from your Normal pickups using your 1/4" guitar cable to externally conneted effects

GUITAR IN - allows you to RETURN the output of your externally connected effects to the GR-55 OR to connect your normal guitar to the GR-55 and use the GR-55 FX.

(When using the GK Pickup, and there is nothing plugged into either the GTR IN or the GTR OUT jacks, the signal is Normalized and the MAG signal is continuous from the US-20 GK IN to the GK A and B OUTS as normal.)

The S1/S2 and GK Volume break-out of the US-20, to two external footswitches and an EV-5, allows foot control of those functions. These mimic the GK pick-up S1/S2 and Synth Volume, so, that in a Guitar with a Graphtech Hexpander circuit board, the extra holes for these functions did not need to be drilled.


If the user does have a guitar with a Roland GK-pick-up, the small RED toggle switch on the US-20 clone allows the use of a standard GK Pickup for GK Volume or the external EV-5 for GK Volume.





This pedal was modified with a 50k Ohm Audio potentiometer to mimic the GK pickup synth-volume control



RMC-Pickup GR-55 Subsonic Filter

Up until the GR-55, all Roland Guitar synths incorporated a low pass filter to cutoff any low frequency information that is un-needed for the pitch detection circuitry. This previous filtering allowed the use of the Roland GK-pickups and aftermarket piezo-pickups developed by other companies like Graphtech and RMC. The exclusion of that filter on the GR-55 meant that the use of piezo pickups to drive the synthesizer would result in subsonic frequencies and piezo-to-piezo crosstalk that would in turn result in mis-triggering of the GR-55.

RMC pick-up founder Richard McClish produced a solution. His G5-SF-001 Subsonic Filter was designed to install internally in the GR-55; between the 13-pin Input Jack and the Input circuit board.

I rehoused the circuit board with a short section of 13-conductor GK cable into a die-cast aluminum box that was easy to mount on the pedalboard. I did this because I wanted the filter board at the input of the US-20 GK A/B Switch so that any guitar synth downstream would benefit from the subsonic filtering.


  1. The Sub-sonic filter is not my circuit board; it is made by RMC pickups. (I just re-housed it)
  2. The Sub-sonic filter is not required if you are using Roland's GK-3 Hex Pickup
  3. The Sub-sonic filter helps tracking when your guitar has GraphTech or RMC piezo saddles

To get Richard's filter you wil have to contact contact Richard McLish @ RMC PICKUPS

or Primova Sound makes a filter as well @ PRIMOVA SOUND