[sdiy] Ueda Attractor

[Dan Slater]

Hi Matti;

The basic patch of the Ueda Attractor is shown in figure 2 of the article. I
implemented it on a small analog computer (Comdyna GP-6 -- further details on my web
site) pretty much as shown in the article but you could do it quite easily with
conventional opamp circuitry. I don't remember for sure but the input resistors
probably were around 10K and the caps around 0.02 uf. Not shown were a pair of
potentiometers attenuating the input to the two integrators, useful for tuning. Two
multipliers were used to form the X^3 term. The 1st multiplier squared the signal
and the second multiplied that times the input signal.

I did not implement the variable power non-linearity but it could be done in a
number of different ways. One would be to use log antilog circuitry with sign
extention, the other would be to form various integer powers x, x^2, x^3 etc., using
standard analog multipliers and interpolating between the stages under voltage
control. My guess is that the second approach would be more interesting from a
musical standpoint and would avoid crossover / slew rate problems near zero signal.

Good luck;

Dan Slater


Matti wrote:

> I'd have sent this straight to Dan Slater, but I thought that there'd be some
> list members interested, too.
>
> Dan:
> at http://www.nearfield.com/~dan/Music/chaos/Chaosrel.htm, you mention that
> "The similarities in circuit topology between the Ueda Attractor, state variable
> filter and quadrature oscillator suggests a module with
> multiple capabilities"
>
> All right, a bit of a while at google later, and I can't find any schematics for
> a hardware Ueda attractor, just differential equations. You mention also an X^k
> function...could you share whichever schematic you used, or the name of the
> resource that you used?
>
> Many thanks.
>
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