[sdiy] chaotic sound/analog computer

[Derek Holzer]

Hi folks,

I've been reading a great article on "Chaotic Sound Synthesis" (Dan  
Slater, Computer Music Journal Summer 1998--first page can be  
previewed at http://www.jstor.org/pss/3680960 ). In this article, he  
presents a block diagram of the Ueda attractor, "a second-order  
nonlinear differential equation that can be readily solved by an  
analog computer". Slater continues:

"The Ueda attractor is similar to a state variable filter, except that  
the inverting stage has been replaced with an x³ circuit and the  
signal input is connected to the first integrator stage. The Ueda  
attractor is based on a ring-circuit topology that includes a pair of  
integrators and an x³ function. A chaotic system requires both  
feedback and nonlinearity. The feedback is provided by the  
ring-circuit topology, and the nonlinearity is provided by the x³  
circuit. The x³ circuit can be constructed from a pair of analog  
multipliers."

The crucial part of the diagram that I can't work out how to cube the  
signal. What would work for something like that? Something using an  
OTA? Two four-quadrant multipliers? Can anyone point me to a suitable  
circuit for getting the cube?

best!
Derek

-- 
::: derek holzer ::: http://blog.myspace.com/macumbista :::  
http://www.vimeo.com/macumbista :::
---Oblique Strategy # 80:
"Go to an extreme, come part way back"