ARP phaser - 1st impression

[Joachim Verghese]

On Mon, 26 Feb 1996, Haible_Juergen#Tel2743 wrote:

> There is some amount of distortion all the time. Regardless of the
> input level - guess that's the compander's work.
> Did a first test with various OB-8 sounds - sounded like crap, unless
> the distortion would be an effect that I wanted ...

Really? I've never tried that 4007-based compander myself...I didn't
think it would be that bad.

> I think someone (Joachim?) posted about a similar experience before,
> so I wasn't that surprised. And yes, even at this point where it almost
> clips the signal, there is still a lot of noise.

Hmm...I don't remember much of my experiments with this circuit back
in '88, but I seem to recall that it is somewhat sensitive to the Beta
value of the ladder transistors. High-beta types (BC109C) didn't
work, and even using 3046s instead of the 3086 changed the performance
of the circuit. I never really figured out what the exact reason was.

> Another thing that surprised me: The transistor cascade really doesn't do
> just a phase shift, but affects the amplitude as well. Very weird thing.

Weird, indeed. I don't recall my circuit having that effect.

BTW, did you use the dual FET post-amp, or an op-amp based instrumentation
amp? Not that I think it would make any difference.

-joachim