MiniMod Transistor Ladder Filter

Minimoog VCF with hand-matched transistors

The stuff of legends, the Moog transistor ladder filter changed the face of the musical landscape forever. The MiniMod VCF is a faithful replica of the filter used in the early Model D synthesiser.

There is a three channel input mixer and a nice large filter cutoff control, along with “1/3” and “2/3” CV inputs to emulate the action of the original VCF keyboard switches, apply 1v/oct to either of these inputs and the VCF keyboard tracking will be the same as the original with Keyboard 1 (1/3) or 2 (2/3) engaged, or use the 1v/oct input to emulate both switches selected. There is a variable Exponential CV input which is about 30% more sensitive than the 1v/oct input, this allows some nice over modulation effects.

We have added Voltage Controlled Resonance (Emphasis) in addition to manual Emphasis control. This uses a vactrol as the control element. The fast vactrol used allows modulation speeds up into the audio range. The filter will of course self resonate and act as a sine wave oscillator too.

There is also an overdrive facility which can be selected with an onboard jumper. This allows the input to the filter core to be substantially overdriven, great for adding a bit of extra dirt to the sound.

Module Width: 14hp

Current Usage: 70ma