AW: Re: REQ: Phase Shifter Schematics

[Haible_Juergen#Tel2743]

> of the ElectroHarmonics SmallStone Phaser which is a quite nice guitar ph=
> aser.
> It should be a quite simple task to make this thing CV controlable.
>
> There is 4 1-pole allpass filters which are built around the CA3094 chip.=
>
> Note that the control input of the CA3094's is a current inputs. The data=

These are surely intended to be current inputs, but in that special 
application
they are connected to the buffer output of another 3094 over a 100 Ohm
resistor. So I guess that they actually *voltage*-control the phase shifter
stages, taking advantage of the exponential relation between V and I
on a current mirror.
Just a guess - not sure about this at all, but it would make sense.
(And there's a question remaining: The inputs are all tied to the same
control node in parallel, but each OTA is on a different chip, so
the current distribution should be interesting!)

JH.