[PD] bandpass makeup gain formula?

Dario Sanfilippo sanfilippo.dario at gmail.com
Wed Mar 11 18:01:15 CET 2020


Hi, Peter.

If useful, Zavalishin has a normalised BP in a 2p2z state-variable filter
based on the bilinear transform integrator (zero-delay feedback) and the
output seems to be consistent. See 4.4:
https://www.native-instruments.com/fileadmin/ni_media/downloads/pdf/VAFilterDesign_2.0.0a.pdf
.

Attached here you'll find the Faust code for the filter; you can paste that
on https://faust.grame.fr/ide/ and export a PD external. Unfortunately, you
can't give options to the compiler in the web app so it will be
single-precision, but it should still work without extreme settings.

Inputs are CF, Q, K (shelving boost, linear amp), input signal. Outputs are LP,
HP, BP, BP (normalised), LShelf, HS, BS, notch, peak AP.

Dario


On Wed, 4 Mar 2020 at 12:21, Peter P. <peterparker at fastmail.com> wrote:

> Hi list,
>
> I am trying to calculate a makeup gain factor for white noise sent into
> [bp~] and [vcf~] bandpass objects depending on the center frequency and
> the Q (width) so that it measures the same in dBRMS before and after the
> filter. I am currently measuring it but am wondering if
> a.) this has been done before
> and
> b.) if there is an analytical solution to it already
>
> Thanks!
> P
>
>
>
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