Pre-distortion Diodes for Moog Ladder Filter

[Tony Allgood]

BJ said:
What seems to bee an gained parameter in theory is in reality drovned in
noise!!Thats the problem with the Moog filter, "its noisy" as hell and
as son as levels are shifted you add noise.

Tony says: On this I will disgaree. In my tests on various filters last
year, I found the Moog to be the quietest I tested. The LM13700 or
3080/FET arrangements were noisier, both in audio band hiss and CV
breakthrough. Only by trimming every stage in the two part SVF could you
hope to get rid of the CV breakthrough. In the end I abandoned using a
SVF with OTAs because of noise. A ladder made from well matched top and
bottom pairs, and a decent diff amp is far quieter to my ears. And it
doesn't sound horrible (get ready to duck) when you overdrive it. As a
audio processor the Moog filter is better. However, there are better
OTAs around. Perhaps by using THAT DBX vcas and op-amps, you would get a
better VCF as a SVF, but the cost is prohibitive.

Regards,

Tony Allgood, Cumbria, UK

e-mail: oakley at techrepairs.freeserve.co.uk

Rack mounted Moog VCF module. Details to be found at...

http://aupe.phys.andrews.edu/diy_archive/schematics/effects/filter.html