Orgon Systems Mulitmode Filter

[jhaible]

> I, for one, would *love* to see Audio Precision plots of those "7
different
> BP filters". Somehow,
> I doubt that claim!

Theoretically you can get an infinite number of band pass filters from
4 poles just by creating two separate peaks (with the same Q or with
different Q each) by just varying the spread between the two partial
filters.

Whether this is possible with one chain of integrators, one feedback loop,
and the usual 5 weighted coefficients for tapping each node in the chain,
this is another question. I couldn't answer aswer it offhand, but it
doesn't seem impossible. (I'm sure our math experts will know it offhand.)

And then there is another approach that will be able to do this no
doubt: The cascading of two separate state variables. I think some
Roland synths used this topology (JP6 ?), though it offered just the 3
most prominent choices 4pLP, 4pHP, and one of many possible 4pBPs.

I think there were SSM and/or CEM chips that offered that too (besides
the 3350 whith its separate filters). Another way to overcome the Moog
bass loss in LPF / high Q setting.

JH.