A discrete ladder-filter, based on the ARP 2600 4012 filter

The VCF-12 features:
•  Two Keyboard CV inputs. (calibrated to track 1V/Oct)
•  Two FM inputs with attenuators. The first FM input allows inversion of the FM CV, as well as attenuation.
•  Two Audio inputs with attenuators.
•  Capable of self-oscillation. (watch your levels though!)
•  Two Low-Pass outputs. (2-pole and the original 4-pole response)
•  In addition, the VCF-12 has a “Slope” output, which can crossfade between 1-pole and 4-pole Low-Pass responses via a Band-Pass response in the centre of the crossfade.
•  The Slope crossfade is controlled by a manual knob and a CV input with an attenuator that also allows inversion. A pair of LED's give visual feedback on the position of the crossfade.

The Slope CV input expects a input voltage in the range of either 10VPP or 5VPP (selectable via jumper on the PCB) to fully crossfade from 1-pole to 4-pole Low-Pass responses. Using the manual knob to offset the crossfade position, it is possible to use either bipolar or unipolar CVs to modulate the crossfade.
A precision reference voltage is used to make sure the incoming signal behave like expected, should you use another voltage-range.
The crossfade circuit is based on an old ARP 2500 circuit, and is fully discrete.

Parts are carefully selected after a lot of testing and comparison, and values are recalculated for eurorack levels to match the original behavior and sound.


  • 64 mA +12V
  • 49 mA -12V
  • 0 mA 5V
  • 40 mm deep

This Module is currently available.

$306 Price in € submitted Nov 23rd 2018, 09:36 by steffensen | last Change Nov 23rd 2018, 12:44 by steffensen
Specs are approved by the manufacturer

6 Users are observing this