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#131685
seancostello
Member

A simple way of creating the type of effect described in the Bode patent:

– Sum input signals to mono

– Run through 6 or more 1st order allpass filters in series, with the coefficients set to a pleasant sounding area, usually fairly close to the unit circle.

– The series allpasses feed a phase-differencing based frequency shifter. FIR based frequency shifters can work, but don't have the built-in phase wiggles of the IIR based frequency shifters. The "classic" frequency shifter feedback effects are based around 12th order IIR Hilbert networks, where there is a considerable amount of phase lag.

– One of the outputs of the phase shifter is scaled and fed back into the input of the allpass filters.

– The system is mixed with the original input signal as needed.

If you replace the series allpass filters with a short delay line, you can get a "barberpole flanging" sound.

It seems like it would be fairly easy to wire such a system up in Vsig. I've built similar networks before in Csound, Reaktor, and MAX/MSP, with my latest realization (ValhallaFreqEcho) done in C++.

Sean Costello