Modulus web page

[jbv]

Paul Maddox :

> Dear all,
>
>   On the Modulus web page you will find a 'PPG and Morph' section.
> This has details of what I'm trying to do and a natty little graphing
> showing a sawtooth and a sinfunction and how the morpher works with
> the two under CV control.
>
>   If anyone has any thoguhts they would be appreciated.

At first glance, the first solution that comes to mind for such a
project of morphing between waveforms
is software.
I can imagine 1 (or 2) ADC hooked to a microcontroler or a PIC. A PIC
looks like a good solution :
20 MHz clock rate, includes RAM and EPROM -> it would use less PCB
space. One can also use a
PIC with on-chip multiplexed ADCs (at least for the CV). Of course, a
DAC outputs the morphed
signal. And of course again, every conversion is done at 44.1 or 48 KHz.

The software itself should be pretty simple, and consist in a fast
endless loop :

    - sample input A
    - sample input B
    - sample CV
    - A-B
    - multiplies (A-B) by value of CV
    - adds the result to A
    - send value to DAC

This is quite straightforward, although the use of a programmable chip
allows some more sophisticated
options :

    - morphing could follow more sophisticated functions than a straight
interpolation. On the front panel,
next to the waveform selector, there could be also a "function selector"
that could be set manually or
via CV...
    - the morphed output could be also transmitted in its digital form
(via an opto or SPDIF connector)
for use in a sampler, or HD recording system...
    - why limit morphing to a single CV ? There could be several CV
inputs, and (why not) morphing
between those CV inputs, and using the result for morphing the audio
signals...
    - etc, etc...

Actually, I'm wondering if a DSP wouldn't be more suitable for that kind
of task...



I can already hear purists say "this is not 100% analog !"...

But honnestly, I thought that any module that would accept control
voltage as input was analog...    ;-)

jbv

PS : I didn't check, but I hope that no one is already doing that for
years !