Interesting Paper available on Moog VCF

[Don Tillman]

   Date: Tue, 17 Sep 1996 12:06:10 +0200
   From: thierry.rochebois at ief-paris-sud.fr (Thierry Rochebois)

   >I do find it strange that all of this work has been put into making a very
   >powerful DSP system emulate a circuit that can be built with about $2 in
   >parts. Oh well, I guess they have to use those NeXT cubes for something. :)

   Well, when you know that the Clavia NordLead uses a Motorola 56002 DSP and
   that this machine is polyphonic... and is very expensive when you compare
   its price to the price of the DSP (about $30-$40). As far as I
   know, the price for a DSP56002 evaluation board is about $200... If
   you can implement good simulations of Moog Filters and others, it
   is not as stupid as it seems at first sight.

You seem to be suggesting that this algorithm is used in the Nord
Lead, that the Nord Lead has a good simulation of the Moog filter, and
that a digital simulation of a filter is a good thing because a DSP
evaluation board costs $200 (huh?).

Please note that Stilson & Smith's paper is very recent original
research; this is *not* the algorithm used in the Nord Lead.

The interesting thing about this paper is the tremendous amount of
work necessary to just position the poles of a digital filter close to
the poles of a very simple analog VCF.  There is no attempt made to
deal with nonlinearities or other interesting behavior responsible for
the characteristic sound of the filter.

  -- Don