In case anyone is interested, I have completed my minimoog filter project. Its a 24db lowpass resonant voltage controlled filter. I used the circuit detailed in the service manual along with this circuit for the power supply (adapted slightly):
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There are also simple op-amp amplifiers on the input and output to give buffering and suitable signal levels. I can use it as an in-line effect unit or as a mixer insert effect. The smaller controls adjust input and output levels, the unit can be made to overdrive if desired.
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Its all kept to the original design, I did decide to use polyester coupling capacitors though, they seemed to sound clearer without really altering the tone.
I have a short mp3 demo of some effects, with resonance, without, overdriven etc if anyone wants to hear it in action.