Modular Synth Panels

The main idea of "waveform animation" is to impart dynamism to the sound 
that is independent of pitch.  The MPWA accomplishes this by sawtooth 
phase shifting, which sounds something like pulse width modulation but 
different because the harmonic series is different for sawtooths.  (I 
also built a complex pulse modulator from Electronotes, all those years 
ago.)  Here is an MP3 I just made, a 2-minute excerpt from a very 
ancient recording over 20 years ago on cassette tape.  The recording 
quality leaves much to be desired, but it will serve to get the idea 
across.  This was done with one VCO, droning on the same pitch 
throughout -- yes I was a rabid minimalist and the piece is 30 minutes 
long -- and driving the Multiphase Waveform Animator (Lester Ludwig 
design) with its sawtooth.  The MPWA contained eight LFOs and eight 
sawtooth phase shifters.  It had one input and one output and had no 
controls.  The output was a mix of the original plus all eight phase 
shifts.  In this patch result was processed through a Low Pass VCF with 
a moderate Q setting. There is some modulation of the stereo field.  I 
can't remember all the details.  Most of the richess of the sound comes 
from the animation.

The MPWA would track any frequency changes of the VCO, but the LFO 
frequencies were fixed.  Read Mark Barton's discussion about the MPWA on

http://www.cyndustries.com/

A problem with the MPWA was that it worked best with low frequencies, 
such as in my example MP3.  Cynthia's Sawtooth Animator's LFOs can track 
the incoming frequency.  "Low input frequencies mean slower LFOs and 
high frequencies mean faster LFOs - all of them."  And the LFO 
frequencies can be voltage controlled.  Other features include LFO 
outputs (nice for making correlated filter patches), and a pulse 
output.  All intriguing features, to be sure!.

One question I have is about the input level being 5V p-p, which I 
gather is Modcan standard for audio signals.  No doubt it will not be 
difficult to modify the input for 10V p-p MOTM sawtooths.  Likewise I 
wonder if the output level needs boosting as well.  I am very interested 
to see how Dave Wright's conversion goes.

-Richard Brewster


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>  Description : Electronotes MPWA Circa 1980 
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