AJH Synth MiniMod Transistor Ladder VCF (Silver)

The AJH Synth ‘MiniMod VCF’ is a faithful Eurorack module replica of the 24db/octave low pass transistor ladder filter used in the early Moog Model D Synthesizer. The module has a three channel input mixer and a nice large filter cutoff control knob, 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.

AJH Synth has 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. 

Features

• Eurorack Replica of the 24db/octave Low Pass Transistor Ladder Filter used in the early Moog Model D Synthesizer
• 3 Channel Input Mixer
• 1 Filter Signal Output
• 1V/OCT Input: Changes the filter cutoff at the rate of 1V per Octave, or if the filter is in full self-oscillation (Emphasis Control fully CW) it will control the pitch of the resulting sine wave at the rate of 1V/OCT (When compared to the Model D this emulates having “Keyboard Control” switches 1 and 2 “ON”)
• Frequency CV Input
• 1/3 CV Input: Changes the filter cutoff at the rate of 333mV per Octave (When compared to the Model D this is the equivalent of having “Keyboard Control” switch 1 “ON” and switch 2 “OFF”)
• 2/3 CV Input: Changes the filter cutoff at the rate of 666mV per Octave (When compared to the Model D this is the equivalent of having “Keyboard Control” switch 1 “OFF” and switch 2 “ON”)
• Emphasis CV Input: ±5V
• Emphasis CV Input Level Control: 0% to 100% (Manual Emphasis Level Control is still active and acts as an offset control)
• Emphasis Level Control (Resonance Level Control): Self-Oscillates between positions 8 and 10
• Filter Cutoff Control
• Frequency CV Level Control: 0% to 130% (Greater range than the 1V/OCT Input so over-modulation effects are possible)
• Input Level Control for Inputs 1, 2, and 3