Subject: Re: [linux-audio-dev] Moog VCF in SpiralSynthModular
From: Dr. Matthias Nagorni (mana_AT_suse.de)
Date: Thu May 23 2002 - 19:51:22 EEST
On Wed, 22 May 2002, Paul Kellett wrote:
> One of the variations is mine :) It's an interesting filter structure as
SSM seems to use this one. Today I implemented all three variants I found
at http://musicdsp.org. I like variation 1 (by Paul Kellett) and variation 2
(by Timo Tossavainen) most. However I was not able to tune any of these
filters. Moog invented this kind of filter because he wanted to be able to
play music with it. If you e.g. connect a VCO and the Moog VCF to one CV
source, they should oscillate at the same frequency.
Some weeks ago I implemented all filters I found at
http://www.harmony-central.com/Computer/Programming/Audio-EQ-Cookbook.txt
and the peakingEQ is perfectly tuned. I also implemented the simple
resonant lowpass filter proposed by Paul Kellett (used e.g. in terminatorX)
and I was able to tune this as well.
Any hint on how I can tune the Moog VCFs ?
> it is so simple (4 first order lowpasses with overall feedback) but there
> are so many things you can play around with. I expect everyone who implements
> it does it slightly differently!
Yes, but is it not easy to lose the special properties of the Moog filter
by using wrong combinations of the parameters ?
BTW I added the example example_vcf.ams for VCF tuning verification in
ftp://ftp.suse.com/pub/people/mana/kalsatools-current/ams-1.2.0pre3.tar.bz2
Pitchbend on MIDI channel 0 crossfades between VCO and VCF (with peaking EQ).
Matthias
-- Dr. Matthias Nagorni SuSE GmbH Deutschherrnstr. 15-19 phone: +49 911 74053375 D - 90429 Nuernberg fax : +49 911 74053483
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