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All-Pass Circuits

Posted: Tue May 05, 2020 1:12 pm
by mediatechnology
All-Pass Filters

The Elliptic Equalizer uses an All-Pass Lead Filter in the Mid channel to compensate the phase error of the Side HP Filter. Jung provides an excellent discussion of All-Pass filters that some of you may find useful.

All-Pass Filters from the 3rd edition of the "Audio IC Op-Amp Cookbook" https://proaudiodesignforum.com/images/ ... g_1987.pdf

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Re: All-Pass Circuits

Posted: Thu May 28, 2020 10:22 pm
by AnalogJoe
There is a great treatment by Kugelstadt in TI's "Opamps for Everyone" chapter on All-Pass filters, including higher order All-pass. I had to design and build high order all-pass filters to implement analog delays for my PhD project, I wrote an optimization routine in MATLAB to find the optimum time constants of each filter to achieve a specific time delay, the book was of great help.

Check page 325 of this free book https://web.mit.edu/6.101/www/reference ... eryone.pdf

Re: All-Pass Circuits

Posted: Fri May 29, 2020 9:10 am
by JR.
Back last century, all pass filters were used inside premium analog loudspeaker crossovers to generate time alignment delay.

JR

Re: All-Pass Circuits

Posted: Fri May 29, 2020 10:43 am
by AnalogJoe
JR. wrote:
Fri May 29, 2020 9:10 am
Back last century, all pass filters were used inside premium analog loudspeaker crossovers to generate time alignment delay.

JR
They are still used today!, Douglas Self talks about their application in his Active Crossover Design book. Although most are replaced by DSP these days.

Re: All-Pass Circuits

Posted: Sun May 31, 2020 7:31 am
by JR.
I was still selling cheap analog crossovers at last century, but Peavey was already making digital crossovers back then. Now the cost of putting DSP crossovers and more (like sophisticated protection circuitry) inside powered speakers has gotten even cheaper.

JR