Phasers - if you don't have enough already

[Martin Czech]

> With all this talk about the SSM 2024 and the SSM2164 im coming back
> to an all pass stage that I've proposed a long time ago on synth-diy.
> 
> You're all familiar with the OTA all pass stage as found in the EH Small
> Stone,
> Moog 12 Stage, and probably many other phase shifters. All these circuits
> work
> fine with 3080-type OTAs which allow a large output voltage swing, but they
> fail to work with the above mentioned SSM VCAs that need a virtual GND node
> at their outputs.
> 
Maybe I didn't get the magic of your proposal, but it sounds pretty like
state variable filter. Why not using some state var sections?  They can
give all kind of responses and you could use them in parallel or serial,
each with it's own frequency control. I think you need to sum the hp and 
lp output, and you don't even waste gm stages, because it is a 
second order ap (I think). Using the other outputs makes a formant filter e.g.

m.c.