[sdiy] SVF: 2-pole to 4-pole ?

[mark s]

two filter sections.....in the case of a SVF that would mean quad FREQ 
pots, which is not feasible for me. what is this Laplace method you mention?

mark



>A true 4-pole state-variable filter is fixed in its response, so you
>cannot just switch it,  Ray is right about having two 2-pole filters
>cascaded, and a switch to choose the filter.
>
>If you want a "true" 4-pole filter, you'll be delving into s-plane/Laplace
>algebra, which isn't too bad for the simple cases, like an audio filter.
>I've been experimenting with a 3-pole filter (mainly 'cos I had 3 gain
>cells to play with :-) and the maths is ok.