Korg Monopoly VCA Mix Mod

About Korg Monopoly VCA Mix Mod

Korg Monopoly has four VCOs. Every VCO has its own Level pot (=potentiometer). These potentiometers always produce scratch noise when regulating VCO’s level. Even precisely cleaned and greased potentiometer will scratch. This is very annoying when playing the synth. The solution is to buy a new original pot, which are really rare. Or to buy some modern pot and fit it to the PCB. This can be a very time consuming task. And again, you never know when the new potentiometer will start scratch again!

Another solution is to low-pass the pot’s noise and apply the filtered control voltage from the pot to a VCA. This is exactly the principle of this mod. Now it is not the potentiometer which actively attenuates the signal, but a VCA with smoothed controlled voltage. The VCA is a V2164 with four independent channels. When Level is set to MAX, the attenuation is 0dB. When Level is set to MIN, the attenuation is -60dB.
The signal level on IC18-pin1 is the same as in original schematic. So the mod will not influence your Monopoly.

Korg Monopoly VCA Mix Mod Kit

1x fully populated and tested PCB
1x cable (4 wires, 40cm)
2x distance sleeve
7x resistors: 0207 9k1, 0207 2k4, 0207 27k, 4x SMD1206 3k9 (use resistor code table to identify resistor values)
1x M3 screw and 1x M3 nut

Installation

The Mod is a non destructive mod. No trace cutting is necessary. You only have to make a 3mm hole to the Mod PCB to the Monopoly’s VCO board.
You make the installation on your own risk. We are not responsible for damages on the device or injuries that can be caused by missing knowledge, bad installation, ignoring safety rules or missing technical skills.
This tutorial is just a suggestion. The wiring in this connection was tested and is fully working.

This schematic shows every electrical step to install the mod.

Remove all red marked parts. These are R139, R140, R146, R151, J200, R144, R148
Solder 27k resistor into R144.
Solder SMD resistors 3k9 as on the photo.