[PD] filtering: a lowpass resonant filter

martin brinkmann mnb at martin-brinkmann.de
Mon Aug 25 21:01:20 CEST 2008

Damian Stewart wrote:

> to answer my own question:
> use [biquad~] with coefficients taken from the [lowpass] external.

i while ago i have tried to build a resonant lp with biquad~, but had
problems with clicks, when the coefficient were changed (even with quite
slow changes). only very slow changes did not produce clicks, which is a
little strange, since biquad-filters in my vst-plugins do not produce
any clicks (and i compute the coefficients only every 96 samples or
so (iirr), i use "the other" biquad form though.

i had better luck with the cpole/zero~ objects, the result sounded
at least like a resonant lp, good enough for a little "squelchy
bassline synth". though i still have not found out how to
calculate the a0 (volume level scaling) coefficient right (and i could
not get hold of the book that was reccomended on the list yet)

bis denn!

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