[sdiy] Tracking Generators?

[Microtonal]

I was working on nonlinear waveshapers 15 years ago and just began to revive
it due to some requests on the MOTM mail list.  You're right, diode break
point generators are the basis for these circuits.  They can function for
both control voltages and audio signals, naturally.  Check any old wave
generation or shaping text book for the basic circuitry.

The concept of paralleling many waveshapers and VCAs and controlling them
from a single envelope seems very inefficient.  If you are paralleling
waveshapers, then you're really just creating a more complex waveshaping
function.  It would be much better to create a single, more complex
waveshaper circuit and use a single VCA.

Harmonic results of nonlinear waveshapers are determined by Bessel
functions.  No diode waveshaper will come close to simulating those
functions as the diode breakpoints are too sharp.

John Loffink
microtonal at worldnet.att.net
The Microtonal Synthesis Web Site
http://home.att.net/~microtonal


----- Original Message -----
From: "Grant Richter" <grichter at asapnet.net>
To: <owner-synth-diy at node12b53.a2000.nl>; <synth-diy at node12b53.a2000.nl>
Sent: Sunday, January 28, 2001 11:47 AM
Subject: [sdiy] Tracking Generators?


> Hello All,
>
> Has anybody taken a shot at implementing a "Tracking generator" like in
the
> Oberheim Xpander?
>
> I'm still pursuing the idea of deliberate non-linearity as a control
voltage
> (and maybe audio processor). This is what I have managed to dig out so
far.
>
> 1. Buchla Music Easel / 259 appears to be some kind of non-linear
waveshaper
>
> 2. Most famous is Serge wave multipliers
>
> 3. There was a Moog 900 series module that had independent control of
> positive and negative base clipping and peak clipping
>
> 4. Diode break point generators in the analog computers.
>
> 5. Then there is the Tracking generator in the Oberheim Xpander. I am sure
> this is software though.
>
> 1-3 are audio processors and 4-5 are for control voltages. I am looking
for
> a simple design for versatile non-linear processor.
>
> OK Why? We were talking about harmonic generators, Steve Curtin pointed
out
> that a harmonic generator by itself is practically useless since static
> harmonics are boring. So each harmonic needs a VCA and envelope, which is
a
> lot of circuitry. However, if there was a simple enough non-linear
function
> generator, then a single envelope could be twisted into many envelopes and
> used to control the harmonic VCAs, giving animation to the sound with
about
> half the parts hopefully.
>
>
>