Interesting Paper available on Moog VCF

Erik The ViKing E.G.P.Schuijers at
Sat Sep 21 14:24:13 CEST 1996

> Date: Fri, 20 Sep 1996 12:22:20 +0100 (CET)
> From: "Erik Schuijers" <E.G.P.Schuijers at>
> What technique many companies use these days is called sigma-delta
> conversion.
> I can't see how sigma-delta conversion would help here.

I didn't say it would help.... It's just a sneaky way of getting a high-res
The anti-aliasing filter could be very simple thanks to the high

Note: in the decoding part of a sigma-delta conversion there's a sum of
quantisation errors.

> Date: Fri, 20 Sep 1996 13:15:51 -0400 (EDT)
> From: Eli Brandt <eli at>
> Take the case where we've got harmonic partials and they're all in
> phase.  So the input signal x(t) is a sum of cos(kt) terms, out to K.
> Each term a_k cos(kt) can be expanded, using the Chebychev* T_n, to a
> degree-k polynomial in cos(t).  Waveshaping their sum with a degree-D
> polynomial gives one of degree-KD.  Then translate each cos^n(t) back
> to a sum of cos(kt) terms, k<=n.  So we have a sum of cos(kt) terms,
> k<=KD.

Hmmm, this is a nice method for making samples. But I don't think this would
work in real-time. (Unless you'd want to give up on your P6-200!!!)


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