[sdiy] VTL5C2 Phase Shifter Sound Files

[Scott Stites]

Thanks Ray!  I'll try get it to schematic, soon!  I'm basically just
chaining  the standard op amp all pass filter configuration using TL08X op
amps, with 10K resistors, 2N7 capacitors, and the VTL5C2 as the variable
resistor (with a 10M resistor in parallel with it).  I used VTL5C2's mainly
because they can be had cheap.  If I had my druthers, I would use VTL5C3's.
But, the VTL5C2's sound just as good, they're just slower.

The Vactrol LED's are all chained in series.  The anode of first LED is
connected to +15V, the cathode of the last LED is connected to the expo
current sink.   I'm pretty much using Rene Schmitz's exp current sink from
his 4069 VCO design to suck the current through the LED's (I'm using two
2N3904's).  You might have to play with the resistor values a bit to fine
tune it for the sensitivity of the Vactrols, but it worked pretty well right
off the bat using a pot as a voltage divider for the CV.

http://www.uni-bonn.de/~uzs159/

The output of the chain goes back to the input mixer for regeneration.

Then it's just a matter of mixing the output of the all pass filters back
with the dry signal.   As an extra for the Phase/Antiphase stuff, I ran the
resonance loop back to the resonance mixer, with one input going to the
non-inverting input of the mixer (first stage), and the other input going
into the inverting input of the mixer (second stage of the mixer).  I have a
switch that will select which stage the resonance signal goes to.  Then, on
the dry/wet mixer, if you turn the dry signal all the way down, and get just
the wet signal, and crank the resonance way up, you can get those funky
formant-like tones out of it.  Switching the resonance to phase or
anti-phase makes a big difference in the timbre.  Beware, though, it doesn't
work well if you're mixing dry signal in, and having it in anti-phase can
actually work against you for 'normal' phase shifter work.  Right now, I
actually have this as a second resonance loop with the switch, so I don't
forget and leave it in anti-phase and then wonder why my phase shifter went
to pot  =0) - I just crank it down when I'm not abusing it in that manner.

This is the core of what I eventually would like to have as a finished, very
cool phase shifter.  One thing I think would make a great module would be to
use 6 VTL5C3/2 Dual Vactrols and configure it a la the Mutron BiPhase - IE
12 stages altogether that could be either run in parallel in 6 stages each
or 12 stages in series.

Nice work on the VCO, BTW!

Cheers
Scott


----- Original Message -----
From: "Ray Wilson" <rayw at csd.net>
To: "Scott Stites" <scottnoanh at peoplepc.com>; <synth-diy at dropmix.xs4all.nl>
Sent: Friday, October 03, 2003 7:29 PM
Subject: RE: [sdiy] VTL5C2 Phase Shifter Sound Files


> EXtremely cool Scott. I gotta build one of these. I look forward to your
> schemo.
>
> Ray
>
> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Scott Stites
> Sent: Monday, September 29, 2003 1:32 AM
> To: synth-diy at dropmix.xs4all.nl
> Subject: [sdiy] VTL5C2 Phase Shifter Sound Files
>
>
> Hi gang,
>
> I've posted some of my 10 stage VTL5C2 phase shifter sound files at this
> address:
>
> http://mypeoplepc.com/members/scottnoanh/slsdiy/id10.html
>
> I'll post a schemo when I have things nailed down a bit more (after I've
> tried all the 'kitchen sink' stuff).
>
> Cheers,
> Scott
>
>