ARP phaser - 1st impression

Haible_Juergen#Tel2743 HJ2743 at
Wed Feb 28 21:35:00 CET 1996

Joachim, thanks for Your answer.

>> 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.

No, the compander itself does a great job. What I wanted to say is that I
haven't got much influence on the level at which the delay line is driven,
because the compander provides a rather fixed level.

>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.

I used 3086's.

>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.

I used an instrumentation amp, built with a TL072 and an LF356.
Because I was too lazy to calculate the exact gain of the original
amp, I made the gain variable (trimpot). Now this might cause
a mismatcht for compressor and expander - but then again, with
the phased (comb filtered) signal I would get some mismatch anyway.
So I don't think it should make much difference.

Another difference to the original: of course I have added a "Manual"
pot as well. Maybe in the Quadra the minimum (first) resonance
frequency is rather high. - I found that I had most of the distortion
when I had peaks at low frequencies. Unfortunately I haven't got
a Quadra to cross check ...


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