[sdiy] 2164 SVF sound/noise?

[David G. Dixon]

> Yesterday I changed the topology of a LM13700 based 4-pole filter from
> "cap to ground + buffer" to "cap in the feedback loop of an op-amp".
> This second configuration is indeed similar to what could have been
> used for a SSM2164 4-pole LP (drop a resistor at the input and add the
> "stability R/C pair" instead). I did not notice anything changed in
> the sound in the change of topology (besides the added stability). So
> the virtual ground requirement looks like a non-issue to me.

It's not a big deal in LPF topologies.  It's more tricky in HPF topologies,
where the cap is connected to something other than ground on the other end.
That's when you need to know what you're doing with VCAs and integrators, at
the transfer-function level.