modified / circuit bent KORG POLY800

via this auction

"The mods we have installed on this synth consist of 3 main sections, Filter mods, FM mods and Audio mods.

FILTER MODS:

Cutoff & Resonance Knobs: The new resonance knob can take the resonance well into self oscillation and far beyond what is normally programmable from the front panel. This can produce the kind of screaming tweeter eating top end and subsonic bass that gives these machines a whole new range of sonic possibilities. The filter cutoff knob allows you to perform long filter sweeps for those squidgy burbling analogue lines that you could never actually perform on a Poly800 before now. Both parameters are still also controlled by the normal programming methods which can set the range of the knobs control.

12dB / 24dB Filter Response Switch: Somewhat mysteriously the filter chip used in these machines has both 12dB/Oct and 24dB/Oct outputs but only the 24dB one is actually used. This mod adds a switch to select either a 24dB or less drastic 12dB filter response

VCF CV input: This socket round the back of the machine adds an external 0 to 5v control voltage input that controls the filter cutoff. The new filter cutoff control knob is disabled when a jack is plugged into the socket.

FM MOD'S:

These consist of a source selection knob and an FM (frequency modulation) amount knob. Essentially VCF FM allows you to modulate the filter cutoff at audio frequencies to create all kinds of clanging cross modulation and bizarre alien splatters & sweeps. This effect works best with the resonance cranked up into self oscillation which is where the new resonance knob mod comes into its own. The source selection knob allows you to select one of four sources for the FM signal. These are DCO1, DCO2, Noise and audio input. The audio input takes its signal from before the input level knob so you can use the audio to modulate the filter cutoff but remove the actual audio signal from the mix. The source knob also has an off setting.

This Poly800 still produces all the normal sounds possible with this unit when the new controls are not in use. It runs from either 6 x C size batteries or an external 9v power supply.

Listen to the soundcloud demos below to hear the kind of extra sounds that can be produced using the new mods."

Modified Korg Poly800 demos by circuitbenders.co.uk