Pre-distortion Diodes for Moog Ladder Filter

[Michael B. Irwin]

I tried the following experiment. Fed a sine wave into an SSM2045
lowpass VCF and fed part of the output  back into the control voltage
input with a potentiometer, with the cutoff set to around 2 KHz. With
increasing audio-C.V. feedback, the sine is joined by a strong 3rd (
2nd?) harmonic and then becomes distinctly buzzy-sounding. The
distortion is less pronounced as the cutoff freq is increased.  It
sounds a bit like the Moog distortion ( but a real A/B test will have to
wait... )