phasers

[Joachim Verghese]

Hi!

> So the fixed stages are in the same chain as the variable stages ?

That's right.

> Then it's different to this other idea where a fixed line works
> "against" a variable line fpr creating the notches ...

Yes, it's a single cascade. Does any of the other well-known
commercial designs use a separate cascade of fixed stages?

> but waitaminute: do the fixed stages shift in the same direction 
> as the variable ones?

I guess so, as they are very similar:

Fixed stages (standard op-amp all-pass):

* 10k resistor into inverting input of op-amp
* 10k feedback (op-amp output to inverting input)
* 10nF/20k HP RC-network into non-inverting input

Variable stages are like the fixed, except that the RC values
are 6.8nF/100k, and there's an opto-coupler element in parallel
with the 100k resistor.

More details later!

Best,

-joachim