[sdiy] linearize OTA for VCF?

[Ian Fritz]

----- Original Message -----
From: "Terry Michaels" <104065.2340 at compuserve.com>
To: "Ian Fritz" <ijfritz at earthlink.net>; "synth"
<synth-diy at dropmix.xs4all.nl>
Sent: Sunday, September 09, 2001 7:46 AM
Subject: [sdiy] linearize OTA for VCF?


>
> Consider this:  Non-linearity in a low pass filter isn't necessarily all
> that bad, the filter cutoff will usually attenuate many of the harmonics
> created by the non-linearity, especially the higher harmonics, which are
> harsher.  OTOH, if I was designing a high pass filter, I would make that
as
> linear as possible, that's a case where the harmonics created by
> non-linearity are more objectionable and noticeable.
>

Good point. The design I'm working on now is actually a high-order VC Bessel
all-pass. I'm going to try using it for the delay-time part of a
physical-modeling oscillator (non-linear excitation coupled to time delay).
The response to a narrow pulse should be a smeared out delayed pulse (just
as in actual acoustic instruments).

  Ian