Saga of the uP developer

[Jim Patchell]

    Darn....There are no original idea's.  I have something like this on my
drawing board.  Thought I was being cleaver.

Paul Maddox wrote:

> Colin,
>
> >
> > The CPU sends two voltages to an expo slew circuit, with a comparator
> input
> > back to the CPU to tell it when the peak value is reached (end of the
> attack
> > phase).
>
> nice trick..
> but how do you get the rate to change?
>

    You need two voltages.  One controls the time constant, the other controls
the voltage that you ramp to.  The one advantage I saw to doing EG's this way
was that you can have as many segments as you want to the contour.  Also, you
can have the time constant circuit do either linear or exponential ramps
without too much trouble.

>
> > The different rate and target voltages for the slew circuit are output by
> > the CPU based on the patch settings, gate and comparator signals.
> > This has a couple of advantages over a fully software ADSR - true expo
> > curves, and a tiny processor load so you could use one CPU for multiple
> EGs
> > (or indeed all the other functions of the synth CPU as in the Source).
>
> Yeah, nice trick..
>
> > Add a window comparator and you could easily do multi-stage rate/target
> type
> > envelopes.
> > Another entry on my rainy day list...
> >
>
> Ahh, so you've not done it, damn I was gonna ask for some more info..
> Have you got any on the moog source? and how it did it?
>
> Im wanting to do a poly synth now and I dont fancy doing 4 Egs for each of
> the 8 voices
> in discrete components..
>
> Paul Maddox

    -Jim