Brian,
I don't know if you have found what you were looking for as yet but there are other methods to digitally modulate a devices output. Both methods use bit rate modulation.the first is akin to frequency modulation but isn't strictly because the pulse width is constant and the number of bits per period are varied by a digital to freq converter.
The second method which I have developed uses binary rate multipliers to control the number of fixed pulse width pulses per period.This technique can take the DMX channel data to directly control bit rate.simple ist order filtering will yeald a variable voltage or current output.