[sdiy] Good 24db/oct HP-LP-BP-Notch filter Schematics ??

Neil Johnson neil.johnson71 at gmail.com
Thu Mar 6 16:11:01 CET 2014

Mattias Rickardsson wrote:
> I see. Perhaps you'd want to check out the non-broken link on this page as well:
> http://modularsynthesis.com/njohnson/3psv/3psv.htm

Ah yes, I'd forgotten about Dave's page.  Just goes to show that once
you put a schematic online you can never take it down.  Hope it proves

>> But yes, a 3-pole SVF extends the 2-pole form, adding a third pole
>> which sits on the real axis.  Adding a fourth integrator adds one more
>> pole, so giving two conjugate pole-pairs.  It is the damping that gets
>> "interesting".
> I remember now that I've seen those 4th order SVFs in the past.

Its quite interesting.  The majority of text books discuss 2nd order
in detail, then simply wave their hands at anything higher.  Some
justify it by saying no-one is really interested in higher-order
functions, and anyway handling higher-order polynomials is difficult
so don't bother ok?  Which seems like a bit of a cop-out. Thankfully
with programs like maxima it is relatively easy to juggle the terms
around without making tedious mistakes...


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