MOTM

You know what this crowd needs? A Shepard generator (aka quadrature 
oscilator). It's four LFOs that are 90 degrees out of phase with each 
other (0, 90, 180, 270). When driving four VCOs, the effect is said to 
be an acoustic illusion analogous to the "barber pole" optical 
illusion. I've never heard one but I see the evil "D" brand includes 
one with their MIDI-CV converter, an odd choice, I thought. I also have 
an old Paia experimenter's kit but I can't find the chips or the docs. 
Come to think of it, this sounds kind of like the LFO section of a 
'410.

That's it, any takers? (Stooges, start your engines ;)

Chuck

The Doepfer version also requires additional modules: a "minimum" of 4 extra
VCAs and VCO / VCF / VCP (?)s, according to the website.  It also only uses
saws and triangle waves.  Square would be useless, but sine would be nice.
I'd like a MOTM version to be a little more "complete", even if it meant
that it only had 4 phases.

Hmm, I'm not feeling coherent.  Did that make sence?  Or even better, is it
remotely reasonable to get 4, 6, or 8 VCAs, VCFs, and LFOs in one package,
with varying LFO shape...?

--PBr

> -----Original Message-----
> From:	doctorq@... [SMTP:doctorq@...]
> Sent:	Friday, November 17, 2000 4:30 PM
> To:	motm@egroups.com
> Subject:	[motm] more module ideas
> 
> You know what this crowd needs? A Shepard generator (aka quadrature 
> oscilator). It's four LFOs that are 90 degrees out of phase with each 
> other (0, 90, 180, 270). When driving four VCOs, the effect is said to 
> be an acoustic illusion analogous to the "barber pole" optical 
> illusion. I've never heard one but I see the evil "D" brand includes 
> one with their MIDI-CV converter, an odd choice, I thought. I also have 
> an old Paia experimenter's kit but I can't find the chips or the docs. 
> Come to think of it, this sounds kind of like the LFO section of a 
> '410.
> 
> That's it, any takers? (Stooges, start your engines ;)
>

A Shepard Function Generator is like two quadrature oscillators interleaved
45 degrees out of phase (for an 8-stage, the minimum for a decent effect I
think).

Sine waves would be best, with triangle a second for the purest barberpole
effect.

I have heard the effect demonstrated and it can be quite unusual. Very
interesting sonic illusions can be generated. Also some really wild phase
shifting effcts that never cycle back (the basis of the 'barberpole
phaser').

John S. "Paia" Simonton wrote an article for the February 1983 'Polyphony
Magazine' (later 'Electronic Musician') showing how to do this cheaply. It
was the basis for the Paia EK-9 experimenter's kit. I have always meant to
build it but haven't yet.

For VCAs they had some kind of really cheap 'Hex VCA' board as well at the
time.

-----Original Message-----
From: doctorq@...
To: motm@egroups.com
Sent: 11/17/2000 7:30 PM
Subject: [motm] more module ideas

You know what this crowd needs? A Shepard generator (aka quadrature 
oscilator). It's four LFOs that are 90 degrees out of phase with each 
other (0, 90, 180, 270). When driving four VCOs, the effect is said to 
be an acoustic illusion analogous to the "barber pole" optical 
illusion. I've never heard one but I see the evil "D" brand includes 
one with their MIDI-CV converter, an odd choice, I thought. I also have 
an old Paia experimenter's kit but I can't find the chips or the docs. 
Come to think of it, this sounds kind of like the LFO section of a 
'410.

That's it, any takers? (Stooges, start your engines ;)

Chuck

In a message dated 00-11-17 20:07:57 EST, you write:

<<  It
 was the basis for the Paia EK-9 experimenter's kit. I have always meant to
 build it but haven't yet. >>


ken,
fwiw, i had one of these way back when from paia and built it into the old 
serge system. if you can find the parts to build it, it worked very well and 
was fairly inexpensive.
best,
dave