Schematics / Bi-N-Tic Filter By Ken Stone
Bi-N-Tic Filter by Ken Stone http://www.cgs.synth.net/ from there : This is a strange mixture of a VCO and a switched capacitor filter based on the filter presented by Jan Hall in Electronotes. If you are after something different, this fits the bill. After all, how many filters have a sync input?
This filter is based on the original idea by Jan Hall, as presented in Electronotes EN92 P14-15, which was in turn based on an idea in a 1974 issue of Electronic Design on a Biquart (twice the order) filter.
A VCO drives a pair of analog switches, switching two banks of eight 0.047uF (47nF) capacitors across op-amps (effectively creating multiple integrators), and this a multi-passband or comb filter is created at f0, f1, f2 etc.. The overall filter configuration itself should be easily recognized. Two controls are provided within the structure of the filter - damping and bandwidth. Not all combinations of these two are actually valid, some resulting in silence, but none the less, quite an array of variations is possible.
for more detailed information on this Filter/Oscillator visit : http://www.cgs.synth.net/modules/cgs57_bintic.html