[sdiy] Filter Musings

[Ian Smith]

> Excepting the trivial case of two identical filters, you will get a more complex behaviour than with a single filter.
> Two 4-pole LPFs in parallel form an 8-pole filter indeed. But you also get zeroes, so there will be no 48dB/Oct slope.
>
> Serial connection of two 4pole LPFs without zeroes means *multiplication* of the transfer functions -> poles only -> 48dB/Oct slope
>
> Parallel connection of two 4pole LPFs without zeroes means *addition* of the transfer functions -> finding the common denominator to
> perform the addition means you get "jw"-terms into the numerator -> zeroes are created.
>
> JH.

So say I take a transistor ladder core and put it in parallel with a diode ladder core... is that enough of a difference so that they're not identical? Or should it be, for example, two TB-303 cores but with differing values of caps?

I'm really intrigued by this now.

-Ian 
 		 	   		  
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