PAiA Moog Ladder VCF Module

The customer wanted a Moog Ladder filter.  I chose to use the YUSynth MiniMoog VCF PCB as the size would fit behind a double wide PAiA panel and I could adapt it to run on the +/-9V power supply.  I made the panel using 1.5mm anodized aluminum with the print graphics feature from FrontPanelExpress.  I added a attenuators for the input and CVs and modeled the graphics similar to the 4730 Multi-Modal filter.  A real Moog 904A listed for $250.00 in 1967 and ~$500.00 in 1973.

 

The YUSynth PCB is a perfect width for a 2wide PAiA panel.

Resistor changes for +/-9V operation

R10 150K 75K
R24, R27 270K 158K
R26 1K2 845R

 

Resistor changes for PAiA levels

R3, R4 120K 100K
R5 56K 120K
R32 120K 39K

 

I made brackets similar to the PAiA and mounted the PCB to the panel.  I added a 2.2 F output capacitor with 100K bleed resistor for operation with the 2720-1 VCA since those inputs must be AC coupled.

 

 

Operation

I adjusted the output level so self-oscillation was 1V pk-pk.

 

I then adjusted the input level so with some resonance the output was just a bit over 1V pk-pk.

 

A bit more resonance drops the output level just a bit to under 1V pk-pk.

 

Maximum resonance is quite wild.

 

With no resonance the output level is hot at 2V pk-pk.

 

Adjusting the input attenuator to 50% results in a 1V pk-pk output.

 

 

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