[sdiy] Configurable Phase Shift Project

[scottnoanh at peoplepc.com]

Hi JH,

Thanks!  You don't know how many times I've refrained from bugging you with
questions the last couple of days =-D.

I'm using the VTL5C3/2 dual element phase shifter and TL074's.  The timing
cap is 560 pF.  I started out with the template I'd used long ago when
working with VTL5C2's, which used 2n7 caps (and this was still a bit
fiddly), but I just couldn't get a decent sweep out of that value with the
5C3/2's.  The sweep seemed to be bunched up around the lower frequencies.  I
then tried 1n caps, which was an improvement, and then I went down to 560 pF
(the only other value I had a fair quantity of).  This seemed to really
improve the sweep tremendously, as small as that value is.  I'm not sure if
it's the optimal value, but it's working for me right now.  As an aside, um,
the caps are disk caps (yuck), but I had a bunch of them.  The last four
stages I threw on today were some polystyrene that I found while looking for
my germanium diodes (can you see where this is leading?).  Anyway, just
testing the four stages of polystyrene certainly demonstrated the value of
using them (next order from Mouser).

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.  With this phaser,
my ears don't notice much amplitude variation with added regen, but it sure
makes getting a decent recording level without compression tricky.  I'd like
to get the amplitude a bit more uniform, and the effect of a balanced
signal/regen signal you describe certainly sounds attractive.

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

All of those extra peaks and notches, when modulated very slowly, sound
really good through the Dim C, so I can imagine they'd really sound great
through the Dimension D clone.

Take care,
Scott

----- Original Message -----
From: "JH." <jhaible at debitel.net>
To: <scottnoanh at peoplepc.com>; <synth-diy at dropmix.xs4all.nl>
Sent: Wednesday, February 22, 2006 5:35 PM
Subject: Re: [sdiy] Configurable Phase Shift Project


> Sounds beautiful.
>
> Are these all equal stages? VTL5C3? what capacitor value?
>
> JH.
>
>
> ----- Original Message -----
> From: <scottnoanh at peoplepc.com>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Wednesday, February 22, 2006 10:34 PM
> Subject: [sdiy] Configurable Phase Shift Project
>
>
> > I've returned to a project I started last summer, a multi-stage phase
> > shifter I call, surprisingly, the MultiPhase.
> >
> > The intended product is a phase shifter with two independently
controlled
> 12
> > stage chains that can be operated in series or parallel.  Like the Moog
> > Stage Phaser, the resonance and output taps will be selectable for each
> > section.  Having two 12 stage chains will allow up to 24 stages in
series,
> > with the ability to configure the structure to emulate the phase shift
> > structures (but obviously not the sounds exactly) of many different
phase
> > shifters.
> >
> > One thing I've played with, for example, is the structure of the Schulte
> > Compact A - eight phase shift stages with the resonance, inverted and
low
> > pass filtered, between the first two stages.  I have no idea if it
sounds
> > anything like a Compact A, but it still renders a very nice sound.
> >
> > The new page is here:
> >
> > http://mypeoplepc.com/members/scottnoanh/birthofasynth/id18.html
> >
> > Not much there yet, but a couple of samples - the big one has a section
> > using the 'Compact A' structure, plus 16 stage phase shift with no
> resonance
> > and 16 stage with resonance.
> >
> > There's a short white noise sample of 20 stages.
> >
> > I'll add more to it as time goes by.....
> >
> > What?  Oh, Vactrols.
> >
> > Cheerio,
> > Scott
> >
> >
>