Hello to everyone!

I want to realize a PD patch which can simulate the typical scheme of the "Phase Shifter", or rather with a 3 notch filters bank with their variable center frequency. How can I implement a notch filter?

Thanks in advance.

@TJ88 A notch can be done with [biquad~] but setting the coefficients is not easy.
In extended the "ggee" library had a [notch] object that achieved that and had inputs for centre frequency and bandwidth.
If the library is available through Deken (Help, Find Externals) it might still be in the library.
Or you can compile it from here.......... https://github.com/pd-externals/ggee

Otherwise you could use the fourier transform like this....... notch.zip
It will be possible to modify the [expr] for a triple notch.

You could also look at H15.Phaser.pd in the Pd doc/audio.examples folder, which might well be closer to what you are looking for.
David.

Thank you, David for your precious support.
My target patch is to simulate a "Phase Shifter" like the guitar Boss pedal for my personal use. It is a Delay-Line effect, so it could be more complex.
Anyway, I want to realize the delay line with 3 different notch filter in series but I want to design it with with only one, initially. I will try to increment them after. My idea is as follows: the single notch filter is controlled by an LFO with 4 parameters: the center frequency, the bandwidth (Q Factor) and the amplitude (Resonance). The 4th one is the Stage, but I will develop it in a second time . The input of the patch will be a keyboard MIDI control.
Refferrals:

Can you help me?
Thanks in advance.

@TJ88 I am out the rest of the day, but here are a few things to look at, download, and try out......
https://forum.pdpatchrepo.info/topic/9942/phaser-chorus-flanger

https://forum.pdpatchrepo.info/topic/11021/stepping-phase-shifter

https://forum.pdpatchrepo.info/topic/2962/phase-shifter

https://guitarextended.wordpress.com/2011/12/28/phaserchorus-effect-with-pure-data/

.... and I am sure there are others.
David.

Hello to everyone! Thanks to David for the suggests.
I'm working at the patch using the [notch] element by ggee external library for design the filter.
How can I put in series 2 or 3 notch elements in series to create the bank of filters?

Thanks in advance.
Here my patch.
main.pd

@TJ88 I just modded a patch by @katjav to sweep notches and work in vanilla.
You might like it...... like.zip
Left hand side works..... and then change the sweep speed, width and peaks.
It could be made to sweep down as well.
Right hand side not working yet in vanilla, but anyway it will not sweep properly.... lower latency and no time to adjust except in jumps.
David.

Thanks @David for your tireless answers! I have seen @katjav patch but it doesn't respect my requirments and targets.