[sdiy] filter resonance

[john mahoney]

----- Original Message ----- 
From: "harrybissell" <harrybissell at prodigy.net>


> Bzzzt.  (wrong)
>
> Some filters have resonant feedback as you suggest... but most do
not.
> The State Variable filter has feedback from a circuit point that is
not
> always accessible (the BPF output) and the Moog ladder has feedback
to
> the other side of the input differential pair, normally never
accessible.
> The Sallen-Key (MS-20 et al) have a very different resonance control
> (basically the gain of the amplifier)
>
> Filters with cascaded integrator stages (like the CEM3320) could use
the
> technique you describe.
>
> Bear in mind that you might use linearized photocell methods to do
the
> resonant control (see National Semi AN-20 "analog multiplier")

Thank you for the clarification, Harry. Always a fount of good
information.
--
john