Filter Topologies ( was ASM-1 VCF "external" audio input? )

[Brian Towles]

Sean Costello wrote:

> For Aphex Twin sounds, the best bet would be to construct a clone of the
> Korg MS-20 filters. You could get a Sallen-Key topology out of a 3320,
> but you wouldn't have independent cutoff for the highpass and lowpass
> filters, and you certainly wouldn't have the raunchiness of the original
> MS-20 filters.  The MS-20 filters can be constructed using the 13600
> dual OTA, which is available for 80 cents or so from Mouser.  A nice
> schematic can be found at
> http://www.mindspring.com/~vco/maxx2/page_015.html, or check Music
> Machines at Hyperreal for the original schematic.

i read this and began to wonder if anyone has ever done a "controlled" testof
different filter topologies?  for example, one could use a particular ota and
listen to state-variable, sallen-key, etc.  under normal conditions they should

have similar operation, but what about overdriven?  does anyone have
experiences with this?

brian