What are the equations for all those funny knobs?

[Magnus Danielson]

>>>>> "BT" == Brian Towles <gt7276a at prism.gatech.edu> writes:

 BT> As I try to design my first VCF, I'm trying to correlate how
 BT> different filter quality names relate to the frequecny response
 BT> of a filter.  Obviously cutoff is cutoff.  What about resonance?
 BT> Does that have something to do with the Q value?

Yes. Higher resonance, higher Q value. However, things isn't easy, so
one should remember that this is true for the dominant poles, how the
other poles behaves is a different matter.

 BT> Also, people are always talking about 12db/24db rolloff -- has
 BT> anyone ever designed a 36db rolloff filter?  Or is that just
 BT> too crazy !? ;)

36 db/oct rolloff isn't crazy, but it's usefullness in music may not
allways be high. I have worked with 48 db/oct filters (fixed filters)
and they where a little too steep for my taste.

The common synth terminology is a little bit of a mess seen from a
signal processing theoretic perspective. Most things are luckilly
explainable :)

Cheers,
Magnus