adding notch to SV filter

[Byron G. Jacquot]

>i'm building a standard state variable filter and i would like to have a notch
>output in addition to the HP, LP and BP. is it acceptable to obtain it by
>subtracting the BP from the input signal? or is there some less simple but
>more correct way of doing this?

I think it might be more commonly done by summing the highpass and lowpass
outputs.  You might check the ASM-1 schems as a reference on this.

Byron Jacquot