[sdiy] 1 V/Oct Chaos

[Ian Fritz]

Hi all --

The VC Chaos generator I described a couple of weeks ago has four 
OTAs:  two are used for integrators, one for a LP filter (leaky integrator) 
and one for the loop gain.  I have found that driving the first three with 
the same control current and using a second control current for the gain 
circuit provides the same range of phase space orbits as observed with four 
independent currents, at least as far as I have been able to observe.

With the two-current setup, the first control varies the overall speed of 
the orbits and the second controls the orbital pattern.  These controls are 
nearly independent, although not exactly so, probably due to circuit 
non-idealities, offsets, etc.  I have verified that the speed control has a 
linear response over at least six octaves, which means that if the three 
integrator OTAs are driven from a standard expo converter source (as in a 
typical VCF), the result will be chaotic orbits with a 1 V/Oct rate response.

The pictures of the orbits I put up before are still up, if anyone who is 
interested missed them.

   Ian

    http://home.earthlink.net/~ijfritz/xfer.htm