[sdiy] Multiple Identity Filter

[Andrew Simper]

Although it is possible to build different filter responses like this
care must be taken with where the resonance is fed back. For example,
if you want a 4 pole high pass filter you need to send the resonance
to the same place the input is going, just like you do with the 4 pole
low pass, so that would into one side of the first capacitor, and not
to the input of the gain cell as is hard wired in the CEM 3320. You
still get a kind of resonance feeding the input to the wrong place,
but not the classic 4 pole high pass shape being the equivalent but
mirrored shape of the 4 pole low pass shape that cascade and moog
ladder filters share.

All the best,

Andy
--
cytomic - sound music software


On 28 November 2013 07:52, KA4HJH <ka4hjh at gmail.com> wrote:
> All this talk about pole mixing reminded me that my old site is gone and with it the articles I had posted. Here is the pdf I created of Craig Anderton's "Multiple Identity Filter" article, which is based on a CEM 3320 but could be adapted to other cores:
>
> http://www.mediafire.com/view/29es58ky30v7467/MIF%20Ω.pdf
>
>
> Anyone care to lay out a board with analog switches?
>
>
> Terry Bowman, KA4HJH
> "The Mac Doctor"
>
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