Simple mod to add external power and CV/Gate-in control input to a Monotron Duo synth.
Unscrew the case and desolder speaker wires to get access to the PCB.
There are two holes need to be drilled in the case. One for the power wire and for CV/Gate-in 3,5 mm stereo jack socket. The only available space for the socket is at the top right corner of the PCB.
Solder CV/Gate-in wires to a “Vrib” and “Gate” empty pads on the PCB, they are easy accessible. Thank’s Korg!
Connect wires form the board to the socket top ring pin of the jack as CV input, middle ring as a Gate, and bottom ring as a Ground.
Use hot glue to firmly attach socket to the board, make sure it is not moving!
Power input is done using old Mini USB cable with stripped power lines (black and red wires) and soldered in to the battery terminals on the Monotron PCB. You can connect it to any 5V USB phone charger. Some chargers will generate audible noise tho.
Secure the cable with an electric tape to the board to make some strain relief.
Screw the case back and that is it. Enjoy!
