AJH Synth - MiniMod VCF

Faithful clone of the early Minimoog lowpass filter with all transistor pairs selected and matched by hand what was nt the case with the later Minis. The circuitry runs internally with exactly the same operational voltages and the transistors have the same specifications as 45 years ago. AJH Synth added voltage control of reconance and selectable overdrive.

-24dB/octave steep low pass filter with Moog's famous patented transistor cascade; like on early Minimoogs the transistors are entirely hand-selected for the sake of a better sound. The circuitry runs internally on exactly the same supply voltages and the transistors have the same specifications as 45 years ago, not being SMD types like the rest of the parts.
The resonance has been made voltage controllable with to a opto-electronic part, a vactrol. Unlike other vactrols this one can react on very fast voltage changes and allows for audio modulation.
For modulating the cutoff frequency there are not only the 1V/octave input but also sockets with1/3 and 2/3 volt per octave characteristic which simulate the Minimoog's keyboard tracking switches. The controllable exponential CV input is 30% more sensitive than the 1V/octave input and can be over-modulated.

It's nice to see the filter has three audio inputs with level controls which save you a mixer. Using a jumper you can change the behavoiur of the input stage and make it overdrive substantially.