My new Studiologic keyboard is a great compact stage piano and synth, but it’s missing 1 key feature: fixed filter frequency control! I performed a quick circuit bend to make the joystick/modwheel mounted filter input more fine-adjustable with a simple rotary control.
Both of the spring-loaded joysticks are fitted to an auxiliary PCB, and they are 2-axis dual potentiometer models from C&K. By reverse-engineering the PCB layout and following the signal, ground, and power traces I was able to insert my own switch and potentiometer circuit between the microcontroller and auxiliary PCB, creating a bypass and secondary control for the filter frequency.
This project received coverage in and MatrixSynth.