chaotic function generator: Chua's circuit

[Kimmo Koli]

On Fri, 8 Nov 1996, Ray Peck wrote:
> 
> Has anyone here tried "Chua's circuit", which is a chaotic function
> generator?  See
> http://www.ccsr.uiuc.edu:80/People/gmk/Projects/ChuaSoundMusic/
> 
I heard couple year ago Leon Chua's presentation on his chaotic circuit
and there was a Mac demo of chatic sound generation. The software had 8
sliders you could control with a mouse. Sometimes the result was white 
noise and sometimes it sounded like randomly plucked guitar strings etc.
Anyway, all produced sounds were interesting and useful for music
synthesis.

The problem with this circuit is the controllability of the frequency.
Some people have tried it but the resulted circuitry was more or less
idiotic (well, they were not analog circuit designers in the first place).

There is, however, an other way to make a chaotic oscillator. It is a delay
circuit (two T/H-amplifiers with non-overlapping clock) and a nonlinear 
feedback. The frequency can be controlled with an external VCO or a simple
one opamp LFO so it is either a sub-oscillator or a weird LFO.

I'm actually building a test circuit like that very soon (actually, I 
intended to design the PCB this weekend, but unfortunately other thing 
came up...). The circuit has an envelope controlled nonlinearity. The 
envelope controll gradually turns the circuit off (=amplitude control with
some added dynamics). Could be useful for making a chaotic precussion 
module.  Works beautifully in Matlab, but still the circuit is missing...

Anyway, I'll try to make the PCB next weekend and if the circuit works I'll 
put it in my web-page after that.

> Seems like it would be a winning control module.  They have simulation
> source in 100k+ of BASIC (including fancy plotting stuff).  It would
> probably be worthwhile writing the core in Csound to check it out.
> 
By the way, the author of the CAS-1-article and the simulation program
has a three-hour seminar on chatic signal coding here in our University
today at two o'clock. Why: our laboratory is working with his laboratory
in the same joint project founded by EU. So hopefully I'll learn something
new on chaos today or later...  

That all this time,
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  Kimmo Koli      			     kimmo at ecdl.hut.fi 
  Helsinki University of Technology          http://www.ecdl.hut.fi/~kimmo
  Electronic Circuit Design Laboratory
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  FIN-02150 Espoo     			     Tel:  +358 0 451 2273
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