Hungry Robot Modular VCF

The Hungry Robot VCF is an all analog, 4-pole low pass filter with a self-oscillating resonance control.  It is a close replication of the filter circuit found on the famous Prophet 5.  It uses a HM2040 which is a high quality, faithful replication of the original SSM2040 chip.  This resonant filter has a beautiful tonal quality.  The over-sized knobs provide a satisfying tactile response.  The cutoff frequency can be controlled by external control voltage.  It has a built-in attenuator and invert switch for the incoming CV.  CV input does not track at 1V/Oct, but is scaled to act as a VCA when a 5V signal is applied to CV input.  As with all Hungry Robot "Modular Boxes" the VCF can be powered by a simple 9V DC, Negative Center power supply.