Pole Mixing Filter module, 100x200 mm, with six knobs and six jacks

This is a multimode VCF based on a design by Electric Druid (ED). It uses pole mixing to achieve multiple filter behaviors.

Changes from ED design include

  • Resistor value changes
  • Added AC coupling capacitor on input signal to resonance compensation mixer.
  • Added op amp buffers and pulldown resistors on LP1–4 after AC coupling capacitors.
  • Added second inverting stage on input. Reduced first stage gain to 0.51 and increased output stage gain by the same factor.
  • Changed BP resistors for unity gain at peak.
  • Changed 7th mix to {1, 2, 2, 0, 0} notch.
  • 7th and 8th mix have enough resistor footprints to implement any desired mix.
  • Multiplexer replaced with rotary switch.
  • Added header for expansion.

Git repo