korg monotron Duo for eurorack with cv control

korg monotron duo in 6hp eurorack

There are plenty of korg monotron projects around for eurorack and controlling the filter with CV, but I wanted to make it so that the Duo fits nicely into a small rack configuration, and doesn’t blow my HP budget. So, with a sleight of hand, turning the pots on their sides, we can get all the controls on a small front plate with added 3.5mm jacks for inputs. Why hasn’t this been done already?

CAUTION – this can destroy your lovely Duo

Here is a sound demo on youtube: https://www.youtube.com/watch?v=FdYjuxtOjE8

6hp-ish, in the rack

So, the trick was to unsolder the pot fixing lugs and then extremely gently bend the pots on to their sides. being very careful with the soldering iron, I just about got away with it

here is the view of the underside of the lugs desoldered, with the CV input wires. I had terrible trouble getting the pitch to work, and in the end found that it needed to go to Vrib. DISCLAIMER – i don’t know anything about why or if this will fry the Duo.

so, the next thing was make a breakout board to ft all the jacks, additional pots, and the odd resistor and cap.

this slots in behind the pots, with lots of insulation tape to stop shorting, frying, blue smoke, dragons escaping etc, etc, etc

Then, cut down the faceplate plastic, brutal, but needed.

And lastly, make some little ears for it to sit in the rack, as the montron casing fit perfectly between the rails on the rack, but we need it to sit on top of the rails on the rack, so, I ran out of energy for some nice mounting brackets, and went with the thermoplastic option. you can see in the image below the problem with the speaker grill plastic. its too thick to leave in place, so had to be cut, and then moved out then refit.

you can find the schematics for the cv connections and values of resistors and pot across the web.

The problems: – you need tiny little fingers to do the small controls, but these can be set, mostly, and then cv tweaked, – i could never really get pitch to align with other modules, but that doesn’t matter if playing it a single voice, and the biggest issue, the grill over the speaker means that the faceplate in the eurorack is not very solid across the grill part, so i have to reinforce it.