SV: Re: [sdiy] Nonlinearities in IR3109 filters

[Magnus Danielson]

From: karl dalen <dalenkarl at yahoo.se>
Subject: SV: Re: [sdiy] Nonlinearities in IR3109 filters
Date: Wed, 2 Aug 2006 22:23:35 +0200 (CEST)
Message-ID: <20060802202335.28575.qmail at web27612.mail.ukl.yahoo.com>

> >Antti's analysis of a hypothetical SSM 2040 seems to indicate that an
> > OTA based cascaded 4-pole with feedback will have higher self-oscillation
> > amplitude than a Moog ladder, unless some sort of feedback limiting is
> > included. Very interesting.
> 
> No filter has higher reso levels then the other per se, wheter hypotetical
> or not *any* level can be adjusted, no matter if its a SSM2040 or a ladder
> or a SVF. Original moog ladder has an inbuilt defect (design error) i dont know
> if that counts as a parameter to judge from regarding the resonance levels.
> it shure declines if freq decreases. 

I tend to look at it as a design flaw, not a design error. Then again, this
form of non-perfect aspects of designs seems to make them "popular" for their
"character".

> For instance many folks says (2pole SVF type ) SEM filter cant resonate
> in sinus, ofcourse it can.

I agree. It is designed not to normally, with intention. Just look at a normal
cos/sin oscillator core, it is nothing but a normal state-variable filter in a
particular setup.

> Besides is the SSM2040 really an OTA filter?

The SSM2040 is indeed a bunch of simple OTAs.

> I tought people here had dissected that filter as a laying ladder?! 

No, that's the SSM2044. It's all in the SSM2044 patent.

Well, well, time for me to shut up again.

Cheers,
Magnus