The Voltage Controlled Filter contains highpass-, bandpass- and lowpass 24 dB filters to shape your sound. The filters can be combined if needed. The cutoff frequency can be set with the OCTAVES knob. The resonance is set using the Q-knob while the OUT knob sets the overall output level of the signal connected to the bottom output. When a signal (for instance ADSR envelope is connected to the top ENV input, the ENV knob sets the amount of effect that has on the filter. The ENV knob goes from -1 to +1. When set to the center (0) there will be no audible effect. Any signal to be filtered should be input into the right ES input. The input level is set using the ES knob. To modulate the filter connect a signal (for instance LFO) to the TM input and set the desired level using the TM knob. Connect any signal to the EXT input to drive or modulate the filter cutoff frequency in any other desired way.