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

[mark s]

i am a little discouraged by the phase shifter thing...thank you for the 
responses, will look into them to try and understand what dome filters, FIR 
filters are. seems like the most straightforward solution would be to delay 
the sampled (digit at l) circuit.

another, probably easier, question.

although don lancaster refers to it in the active filter cookbook, i can 
not see how to transform a 2-pole state-variable filter (freq, Q and gain 
being tunable) into 4-pole. (i would like to do it with a 
switch.)  .....something about changing the 'a' factor (gain) but i don't 
get it. hints would be appreciated.

thanks
mark