[sdiy] Configurable Phase Shift Project

[JH.]

> I'm using the VTL5C3/2 dual element phase shifter and TL074's.  The timing
> cap is 560 pF.

That comes as a big surprise! What's the lowest resonant frequency (feedback
up)
you can get with this? I think in the Compact A is adjusted to 50Hz for the
lowest possible
peak. Your samples definitely have something of the Compact A tone, but I
thought
the A goes lower. And it "dives" lower, with a linear ramp controlling
incandescent
lamps, so the modulation stays longer in the higher range than in the low
range on a
log Hz scale, but it dives down to 50Hz quickly and then rises again.


> I really want to try the Quadra compandor method that you used in the,
well,
> Quadra phase shifter as well as the Storm Tide flanger.

May be worth a try, but it will also change resonant behaviour completely.
Would be interesting to switch it in and out.

> I tried it just a bit with an NE570 yesterday, but my results were
abysmal.
> It was sort of a cursory check, and I think I'll try the 4007 based
> circuitry of the Quadra and Storm Tide.  I'm not sure if this is correct,
> but it looks like controlling the expander with the rectified control
> voltage of the compressor will certainly help.

I think so, too. But you could also do this with the NE570, connecting the
VCAs of both halves to the rectifier of one half.

> As an aside, I notice Dr.
> Moog used the 4007 at least for compression in the Moog Stage Phaser.

The old 12-stage phaser has a highly unusual, very interesting compander.
It's built around two dual Vactrol stages, and it has an envelope detector
with fast attack, fast release, and a sort of "hold" time. Ween the input
level fades away, the CV does a staircase kind of thing, which apparently
causes
less harmonic distortion than just using a release time.

Don't know about 4007 in Moog - is this in the Moogerfooger pedal ?

JH.