[sdiy] A question about phasers/notch filters

[Richie Burnett]

Hi Tom,

I don't know if this is the effect you are looking for, but I've uploaded a 
couple of examples of "infinite phasing" I knocked up here.

Orignal audio file: http://www.richieburnett.co.uk/temp/orig.mp3
Slowly falling notches: http://www.richieburnett.co.uk/temp/phased1.mp3
Faster rising notches: http://www.richieburnett.co.uk/temp/phased2.mp3

These examples were made using a digital implementation of a frequency 
shifter and then mixing the output with the original dry audio to introduce 
notches.
I used two lines of six cascaded digital allpass filters, pinching the "dome 
filter" time constants from what Jurgen Haible used here for his hardware 
implementation:

http://www.jhaible.de/fs1a/fs1a.html

-Richie,