While being used as an oscillator, the RK4 is controlled via its pitch CV input (Hz / v). For tuning adjustments, there is a potentiometer. The resonance knob can be employed to morph the waveform from sine to square. Another potentiometer edits the output volume.
For utilizing the RK4 as a bandpass filter, an audio input with level control was implemented in the module. Its tuning potentiometer sets the cutoff frequency, the pitch CV input can be used for modulations.
Audio input and output
Pitch CV input
3U Eurorack module, 8 HP wide
Current draw 400 mA at +12 V and 10 mA at -12 V. - Attention! While heating up, the module needs about three times more power.