Audio notch filter with variable Q and frequency needed

neazoi · Mar 29, 2013

Audio notch filter with variable Q and frequency needed, to knock out interference in a natural radio receiver.
Any schematic available?
I have seen these twin-T filters compared with opamps are good enough

FvM · Mar 29, 2013

Twin T-filters aren't well suited for frequency tuning, there's a number of better filter topologies, they are periodically discussed at edaboard.

The intended frequency range is an important criterion. There are single resistor tuned filters with f0 ~ 1/√R and dual resistor tuned filters that achieve f0 ~ 1/R. The latter can be also Q tuned with a single resistor and are usually implemented as a dual integrator structure.

neazoi · Mar 29, 2013

FvM said:
Twin T-filters aren't well suited for frequency tuning, there's a number of better filter topologies, they are periodically discussed at edaboard.

The intended frequency range is an important criterion. There are single resistor tuned filters with f0 ~ 1/√R and dual resistor tuned filters that achieve f0 ~ 1/R. The latter can be also Q tuned with a single resistor and are usually implemented as a dual integrator structure.

The frequency range of the receiver is 20Hz-15KHz max, but most of the knock-out job has to be done in the region of 50Hz to 3-4KHz.

Have you got any example of the proposed solution, or any other suitable schematics?
I have seen some in the web but I do not know which one to build.

I am thinking of a single filter and then maybe cascade some of them to make a multi-notch filter, to cnock-out more than one interference signals.
Any thoughts would be appreciated.

Audio notch filter with variable Q and frequency needed

neazoi

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Audio notch filter with variable Q and frequency needed

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