The STEFFCORP VCF-12 is a voltage-controlled fully discrete filter, based on the 4012 filter used in the ARP 2600.

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.

More about the Slope circuitry:
•  The Slope CV input expects an 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 and limiting circuit is used on the CV input to ensure the crossfade behaves predictably, even if the CV exceeds the selected range.
•  The signal path of the crossfade circuit is based on an 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.

See the Operation Manual for more detailed info. (Coming…)

•  Power protection
•  Buffered inputs & outputs
•  Tracking well over at least 5 octaves during self-oscillation
•  Frequency control 10Hz – 10KHz
•  Power 64mA +12V / 49mA -12V
•  Width 14HP
•  Depth about 40mm

Additional information

Weight 0.35 kg

Assembled, DIY