Ben Chapoteau-Katz requested a passive ribbon controller for use with his Prophet 6 synthesizer. I’ve been curious about Velostat for some time - a semi conductive woven plastic fabric material - and figured it would an interesting challenge. Existing ribbon controllers on the market are expensive and require external power in exchange for an included CV convertor for direct connection to modular synths. Many modern synths like the Prophet have built in expression inputs that are assignable to any number of controls.

The initial experiments were performed with a strip of copper tape (I had leftover from a guitar cavity isolation project) stuck to a 3-ring binder. I discovered the Velostat has an inherent resistance of ~10kohms per 5” or thereabouts. I used this figure to determine the correct voltage divider values so that at minimum and maximum the synth’s expression pedal input would give a satisfactory range of control.

The ribbon controller is constructed out of copper bar, copper tape, 3M double stick tape, masking tape, velostat, nylon and cherry wood. It’s terminated to a standard TRS connector with a bourns trimpot across the tip and shield for adjusting the voltage divider ratio.