CEM3396 & waveforms

[Paul Schreiber]

If you are lucky enough to have a synth that uses the CEM3396 chips, that part has voltage controlled waveshapers in it that makes about 20 DIFFERENT waveforms. I will have the datasheet for this part by Friday on the site:

www.why.net/users/paults

Paul Schreiber
Synthesis Technology

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From: 	Martin Czech[SMTP:martin.czech at itt-sc.de]
Sent: 	Tuesday, March 11, 1997 10:01 AM
To: 	synth-diy at horus.sara.nl
Subject: 	waveforms

Kyle wrote.....


>other than square, triangle, & sawtooth, are their any other waveforms
>that are commonly used in synthesizers?  I'm trying to come up with a
>couple single cycle waveforms to use in a digital synth design.  A 
>frequency modulated sine, perhaps?
>

Well, sometimes synths have a /2 divider (called sub osc),
so you can add a square with half freq.
One could play this game on and on :
Rectifying a tri gives a tri with doubled frequency 
(pll or sync also will work),
and this can be done several times (fast opamps and schottky-diodes).
The "doubled" tri waves are not that perfect, but give strong overtones
if added to the fundamental. Tri waves can be converted into saw and
pulse again, so at the end you have an osc with at least
tri  saw  pulse
tri2 saw2 pulse2
tri4 saw4 pulse4
I've seen that in a DIY synth 15 years ago, cool sound,
and the guy who build it could mix those waveforms volt.
controlled. 
One of the oldest existing machines (Sala's "Mixturtrautonium",
design started in 1925 or so) uses dividers.
so we take the tri4 (or even tri8 if it works) and divide by
3,5,6,7,9 (cheap CMOS programable divider, CD40XX, can't remember).
How does it sound with 8/7 and 8/5 together ? Strange !
Today the "Technosaurus" machine (Switzerland)  has a divider feature.

What about the idea to have the waveform converters input externally
available ? Feed a tri2sin converter with more complex mixtures,...
fun. 
If I follow that thought, the most radical design would be
an osc with only the primary waveform (that is saw in most cases)
and lots of external waveform converters.

Ok, this is more for the analog guys, because you can't do the 8/7
etc. in a short wavetable.

What Kyle wanted is going more or less into a wavetable design, isn't it ?
If you take a look at PPG and microwave and wave you'll find
lots of FM tables, synced saw tables, waveshaped tables (tri2sin converter),
and some FFT tables out of natural samples. 
I have only the microwave, so I wrote a prg for the atari computer,
to generate wavetables (61 waves, each 2*64 Byte long) out of
short samples (1-3 seconds). Now the microwave can speak
to me in chords ! 

m.c.