[sdiy] Steiner VCF as allpass?

[Cornutt, David K]

From: Nils Pipenbrinck [mailto:np at inverse-entertainment.de]
> Does it do allpass if I inject the same signal into low, high 
> and band?

What you want to do is insert the signal into low and high.
Skip the bandpass, because the slopes of the low and high
pass are such that when they are added, it "fills in the hole"
and the response comes out more or less flat; if you add
the bandpass in too, it will have a peak at the crossover
point.  

On Cynthia's implementation, there is an "all pass" input
that actually feeds all three of the other inputs.  This
allows you to tailor any filter response you want by
using the input mix controls for low, band, and high.
To get a conventional all pass, you turn low and high
all the way up, and band all the way down.

The Steiner is a wicked filter -- ballsy and capable of 
some nasty sounds, but very different in behavior from
a Moog ladder filter (which is what most people think of
when you say a filter is "ballsy").