[sdiy] Low Cost Comb Filter Methods

Neil Johnson neil.johnson71 at gmail.com
Thu Jun 14 18:26:33 CEST 2018


Andy wrote:
>> If anyone is interested in the linear case then here are the equations to solve the circuit:
>> https://cytomic.com/files/dsp/comb-filter-resonator-equations.pdf
>> and here is an implementation in python generator by my circuit solver:
>> https://cytomic.com/files/dsp/comb-filter-resonator.py
>> and a plot of the filtering of a sawtooth given one set of component values:
>> https://cytomic.com/files/dsp/comb-filter-resonator.png

Brian wrote:
> There’s one error in your reproduction of the schematic, though. rp is not supposed to be grounded, but should be connected to the +V supply. How much does that change the equations? It should reverse the current through the resistor, at the very least.

And also note that the op-amp used is a Norton op-amp, so it draws
current on its inputs.  That will change the equations.


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