Idea for an envelope generator

[gstopp at fibermux.com]

     Wow it's beginning to sound like a lot just to get around the 
     traditional ADSR shape... hey! Here's an idea. Build a couple panel's 
     worth of stuff like a two-row ten-step sequencer and a VC slew limiter 
     and a ring modulator and a window comparator and some other stuff 
     maybe, and patch it together until it works! Now you get a) the fun of 
     messing with it till it works, and b) a couple of real cool modular 
     synth panels :-)
     
     Careful doing analog division by zero - it may result in an output of 
     infinity volts! Watch out for lightning bolts.
     
     Pursue the d*g*t*l approach at your own risk.
     
     - Gene
     gstopp at fibermux.com


______________________________ Reply Separator _________________________________
Subject: Re: Idea for an envelope generator
Author:  Christopher List <Christopher_List at sonymusic.com> at ccrelayout
Date:    2/9/96 7:21 AM
     .
     .
     .
OK, so, more thinking... New Idea. You've got two rows. Row A is voltages with 
n pots, Row B is times, with n+ 2 pots. As has already been discussed in 
another thread, we can set the time for each step by using B to set the 
discharge time of a cap and creating a gate signal from that. So, using just 
this, we've got a self-stepping evelope generator, but it "steps" from voltage 
to voltage. 
     
Now, the big trick! By running the output through a CV slew limiter, we can set 
a slope from step to step, using a voltage, right? We just need the right 
voltage at each step to get the slope we want...
how about this... 
Slope = dY/dX. dY = (Row A voltage at sequencer step N) - (Row A voltage at 
step N - 1). dX = Time = voltage that sets gate time for step N = output of row 
B for step N. Now, you can use some analog multipliers to do voltage division, 
right? - I wish I had brought my AD734 data sheets in today. So, you just do a 
little trimming to get these two voltages scaled correctly (dY and dX) - divide 
them, then use that as the CV for the slope of the slew limiter! The only 
problem might be if you had a time of 0, I don't know how the divider would 
handle it - but that doesn't matter! - Even if the divider is off by a little 
bit, that just means you'd have little flat spots or tiny jumps in the curve 
around the the step points...
     
Ideas? Flaws? Time to give it up and start thing about a digital approach?