[PD] more |vcf~| things

[Roman Haefeli]

hi

wow, thanx for this post. this doesn't sound like crap at all...:-)

roman

----- Original Message -----
From: "matthew jones" <mj at isvr.soton.ac.uk>
To: "PD-List" <pd-list at iem.kug.ac.at>; "Roman Haefeli"
<reduzierer at yahoo.de>
Sent: Wednesday, March 09, 2005 2:31 PM
Subject: Re: [PD] more |vcf~| things


> > filters tend to
> > get an unlinear behaviour somehow, the closer the cutoff-freq gets
to
> > the nyquist-frequency.
> > maybe someone else has a more 'academic' explanation for that
behaviour.
> yeah, here goes:
>
> considering the filter in the z-plane, the poles (associated with the
peak
> of the filter) occur in pairs: one is the conjugate of the other.
This
> means that as you move the pole around from zero to pi, another pole
mimics
> this, whose position is the same but reflected in the real axis.  As
you
> approach zero or pi, the peaks begin to merge into one, so there is a
less
> rapid fall-off rate.
> Also the overall gain tends to increase for these regions, if fed
white
> noise.  This is simply to do with the superposition of the two
responses
> (+ve and -ve freqs).  The picture attached shows the response with a
single
> pole at radius 0.6, first at pi/2 (black) and second at 4pi/5 (red).
>
> Than again, if I'm talking crap please correct me!
>
> Matt
>
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