From ross healy Sent Sat, Oct 21st 2006, 00:02
From ross healy Sent Sat, Oct 21st 2006, 00:02
Doepfer 101-3 Magnus Danielson wrote: > From: Jason Proctor <xxxxx@xxxxxxx.xxx> > Subject: Re: [AH] all pass filter? > Date: Fri, 20 Oct 2006 16:02:34 -0700 > Message-ID: <a062007aec15f05dd1fe7@[10.0.1.201]> > > >> the CGS steiner synthacon filter as an all-pass input - verr nice >> >> so the "cutoff frequency" is the frequency at which the phase >> shifting starts? i'm not sure i get the concept as such. >> > > Actually, that's where the phase-shift is in the steepest change. If you look > at a single-pole lowpass, it shifts 180 degrees with 90 degrees at the cutoff. > In an single-pole allpass, it shifts 360 degrees with 180 degrees at the > cutoff, just as if you would have put two single-pole lowpass filters in > series, but withouth the change in gain as the frequency shifts. > The rate of phase-change is greaters at the "cut-off" which is apparent for > geometrical reasons if you would plot the poles and zeros, but that would > involve alot of armwaving, as if we haven't done enought of that here. :P > > Cheers, > Magnus > > > > >