envelope generators

[Ray Peck]

"Matthew S. Padden" writes:
>Get hold of the schematics for Digisound's VCES module (can't remember the 
>number right now). It's a four stage (ADSR) generator, but each stage has 
>voltage control of the rate.

This brings up something I've been thinking about for a while.
If/when I build a modular (which I've wanted to do for about 15 years,
and I'm not that old), I'd like it to have two important features:

1. user settable presets, and
2. computer control of all patches and parameters.


The way I envision this working is as follows.

First, all parameters have to be voltage controlled.  Build 10 or
12-bit DACs for each of the parameters.  The manual knobs on the front
would simply bump the values going into the DACs up and down (one
would likely want coarse and fine knobs).  No pots, just something to
drive a digital counter, but they would *look* like pots.

Each module would have some addressable number of parameters, so that
the inputs to the DACs could be bussed together (with sample/hold
registers on each) and addressed from the computer.  The computer
would know through software configuration that module 1 was your adsr,
and that parameter 0 through 3 were inputs to the attack portion, 4-7
were inputs to the decay portion, etc.

Each module would also have a maximum fixed number of input and
outputs.  These i/o's could either be analogue, going through an
addressible crossbar switch, or could be bussed, digital control
"signals".  I would think 12 bits would be enough for the latter.
For the crossbar, think of the VCS3 pin matrix, but with the pins
being under software control.

Instead of having one master physical square of patch switches like
the VCS3, one could have momentary switches on the modules, each with
an alphanumeric LED.  If you want to connect the audio mixed output of
OCS 1 to the input of the ring modulator, you would touch one of the
unused "output buttons" on OSC1, hold it, and touch the relevant
"input button" on the ring modulator.  The control software would
conenct the two together either logically (by routing digital
signals), or physically (by manipulating a software-controlled
crossbar switch).  The LEDs near the switches would light up to show
that "patchcord f" was connecting these two ports.

A quick tap on a switch would make all the ports that are "patched
together" flash, while holding down the button would let you set a
patch.


This sort of system would give you lots of benefits:

o	you'd still have knobs to twiddle, which is totally winning

o	you could still have all analogue, wobbly modules

o	you could memorize and quickly recreate patches

o	you could have purely digital modules interacting with purely
	analogue ones (e.g., run a control voltage to your S/PDIF
	module, out to your Mac where you run it through a room
	simulator and looper digitally, and then back into the
	analogue domain).

o	you could use your computer to prototype or implement any sort
	of processing you wanted, and use it like any other module in
	the rack.





What say?