Hi,

I'm working on the digital filters and I've read this paper "Improving the 
Chamberlin Digital State Variable Filter" (https://arxiv.org/abs/2111.05592). 
Digital State Variable Filter is explained in a more modern fashion and authors 
(Lazzarini et Timoney) propose to a very interesting improvement for high 
frequencies and add the Bandreject and the Allpass filters.

My first intention was to use the Csound biquad opcode with the parameters 
calculate from the transfer function. It works well except for the Allpass 
filter. There is no inversion of the phase at the cutoff frequency, phase is 
always at 0 ! I make a mistake certainly.

 From an efficiency view, is it better to use the opcode proposed in the paper 
(opcode Svar3) based on the difference equations or using the biquad csound opcode ?

In a previous thread, I see that statevar opcode implement the state variable 
filter. Is it the old Chamberlin design ? Can we expect a new opcode based on 
the paper ?

Regards.
T. Aimé

Csound mailing list
Csound@listserv.heanet.ie
https://listserv.heanet.ie/cgi-bin/wa?A0=CSOUND
Send bugs reports to
        https://github.com/csound/csound/issues
Discussions of bugs and features can be posted here