Ahh, thanks Vadim! I was getting my "r" term mixed up with "g", when actually g = 1/r.
For those interested this is how you solve the circuit equations, all of which can be written down directly from the diagram I posted earlier http://dl.dropbox.com/u/14219031/Dsp/sem-1a-linear-svf.jpg and a couple of basic circuit rules: vota1 = v0 - k*v1 - v2; vota2 = v1; vc1 = v1 - 0; vc2 = v2 - 0; iota1 = gr * vota1; iota2 = gr * vota2; gc = s*c; gr = g = 1/r; ic1 = gc * vc1; ic2 = gc * vc2; then solve the two equations which is just kirchoff's current law at each node: 0 = -iota1 + ic1 0 = -iota2 + ic2 and then the output responses are just the output divided by the input (setting c = 1 since it doesn't matter in this case): low = v2/v0 = (g^2)/(g^2 + g*k*s + s^2) band = v1/v0 = (g*s)/(g^2 + g*k*s + s^2) high = (v0 - k*v1 - v2)/v0 = (s^2)/(g^2 + g*k*s + s^2) notch = (v0 - k*v1)/v0 = 1 - (g*k*s)/(g^2 + g*k*s + s^2) peak = (v0 - k*v1 - 2*v2) = (-g^2 + s^2)/(g^2 + g*k*s + s^2) Andy -- cytomic - sound music software skype: andrewsimper On 18 May 2011 10:34, Vadim Zavalishin <vadim.zavalis...@native-instruments.de> wrote: >> Vadim, did possibly get the lp and hp gains swapped in your equations? >> With my working is should the s^2 numerator term should be for the low >> pass output, and the cutoff^2 gain for the high pass output. >> >>> H(s) = (gainLP*cutoff^2 + gainBP*cutoff*s + >>> gainHP*s^2)/(cutoff^2+k*cutoff*s+s^2) > > No. s^2 is the HP numerator while cutoff^2 is the LP numerator. Consider the > limit of H(s) when s->inf or s->0. > > Regards, > Vadim > > -- > Vadim Zavalishin > Senior Software Developer | R&D > > Tel +49-30-611035-0 > Fax +49-30-611035-2600 > > NATIVE INSTRUMENTS GmbH > Schlesische Str. 28 > 10997 Berlin, Germany > http://www.native-instruments.com > > Registergericht: Amtsgericht Charlottenburg > Registernummer: HRB 72458 > UST.-ID.-Nr. DE 20 374 7747 > Geschaeftsfuehrung: Daniel Haver (CEO), Mate Galic > > -- > dupswapdrop -- the music-dsp mailing list and website: > subscription info, FAQ, source code archive, list archive, book reviews, dsp > links > http://music.columbia.edu/cmc/music-dsp > http://music.columbia.edu/mailman/listinfo/music-dsp > -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
