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
