Steve Howell and a simple footpedal controller for the Roland SH101. Plus a solution to The Case of the Missing Theremin Parts List.
A simple and inexpensive footpedal controller for the Roland SH101.
This modification was originally designed for a pupil of mine who has a slight disability in that he doesn't have the full use of his right hand: he couldn't use the pitch-bender on the left-hand side of the SH101's keyboard effectively as most of his playing is done with his left hand. We toyed with the idea of modifying the optional 'poser's' grip controller and attaching it to the right of the synthesiser, but that proved to be fruitless, so instead we came up with the idea of a footpedal controller.
The design is simple. A nine-volt battery is routed via a potentiometer, the 'swing' being controlled by a variable footpedal normally used for wah-wah purposes. As the footpedal is moved, so varying degrees of DC voltage are applied to the VCO or VCF via the two pitch-bend sliders located above the bender lever. The footpedal plugs into the 3.5mm mini-jack socket that normally inputs the grip control, and the result is either pitch-bend (up or down with this design) or filter sweep the amount of which is regulated by the two sliders.
Construction is also simple. A Colour-sound Swell pedal was used for the prototype and rewired to accommodate the circuit in Figure 1. The value of the potentiometer is not critical, but a linear type must be used to ensure a really smooth sweep. Pressing the pedal down gives an upward pitch bend, but the circuit can be modified to produce downward sweeps. The jack socket is wired to turn the battery off when the lead is unplugged and not in use.
A second modification you might consider is to use a footswitch to introduce the LFO sinewave modulation normally obtained by pushing the bender forward. Any simple push-to-make footswitch will suffice (these are obtainable from many electronic stores) and the 2.5mm mini-jack socket is used to plug it into the SH101. Alternatively, you could use another rocker-type footpedal to fade the vibrato effect in, and the circuit for this is given in Figure 2.
It must be pointed out that when these two pedals are connected, you still have use of the bender lever and vibrato facility, so there's no reason why they shouldn't become a permanent part of the SH101. The extra flexibility they offer effectively gives you another hand to play either the controls or another keyboard. Together, the two pedals shouldn't cost more than £20, so it's actually cheaper than Roland's own grip controller and, to my mind, well worth the investment. The pedals could also be used with other synthesisers for similar purposes, as most synths have the facility to control the filter cutoff frequency with an external controller, but pitch-bending may require some modification to the synthesiser itself as not all synths have this facility.
Because of the simplicity of the circuit, it should be quite easy to come up with variations on the theme to provide other facilities (such as pitch-bend up and down), so don't be afraid to experiment.
If you've got a design of your own that you feet would be suitable for this column, send it to Short Circuit, E&MM, (Contact Details).
Gear in this article:
Feature by Steve Howell
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