[sdiy] op amp integrators

[Thom Ash]

hi everyone.

you might remember a while ago i posted about a module i made that
generates a Lorenz attractor [www.aovt59.dsl.pipex.com/chaos.html for
more info/mp3s]. anyway i've been thinking it would be cool to add a
speed control to it and... well, i need some help :/ 

the speed of the circuit is determined by the size of the three caps;
each of these works with an op-amp to form a integrator like this
['scuse the ascii]...


      +----||---+
      |         |
      |   |\    |
dx    | G-|+\___|__ x
dt ---+---|-/
          |/


i've been told that for a tuned circuit, the time constant is determined
by a capacitor and a resistor... where would i put a pot to alter the
speed?

also, the fact that there are three seperate integrations that would
ideally be controlled by one pot is confusing [to me anyway...] would
this basically require it to be voltage-controlled and have the pot just
generate a cv? if so, could someone point me in the right direction?

thanks!

thom