Wavetables, wavetables

[List, Christopher]

> -----Original Message-----
> From:	Don Tillman [SMTP:don at till.com]
> Sent:	Friday, October 30, 1998 2:02 PM
> To:	rsowa at WizjaTV.pl; synth-diy at mailhost.bpa.nl
> Subject:	Wavetables, wavetables
> 
	<SNIP>

> So I'm thinking if you want a wavetable VCO, it would only be worth it
> if you had some hooks to do something interesting with it.  For
> instance... 
> 
> Memory is cheap, perhaps a three or four dimensional table loaded with
> waveforms that morph to each other.  Or a second table that provides a
> parameter to modulate the pitch of the oscillator.  
> 
	Yes, the Digisound D-VCO that came as a kit. (I got one from
Kevin Lightner 2 years ago and STILL haven't built it - just because I
dread wiring up all the LEDs) It used a CEM3340 running at high
frequency (extra small cap) to drive a counter and RAM lookup - with a
741 opamp on the output to smooth the waveforms! The ram is not only
addressed by the VCO-driven counter, but also by two other counters that
let you pick one of 4 "groups" and each group has 8 "variations" of the
waveform. These other two counters could be set via a front panel
switch, or scrolled via incoming clock (cough audio frequency - cough
cough)... Come to think of it, I should be ashamed of myself for not at
least getting the PCB together and playing with it, though I think it
had some odd power supply requirements - nothing a couple of regulators
couldn't take care of though. The schem is online here (thanks Kevin!!);
	http://www.synthfool.com/vcdoschm.jpg

	you can see sample front panels and PCB layouts by linking
through here;
	http://www.synthfool.com/schm.html


> Or a "sliding waveform", where starting point of the waveform can be
> modulated and the waveform is designed to do something interesting
> with that sort of change.
> 
> I'm unfamiliar with wavetable VCOs in commercially available synths;
> are there any cool manipulation or modulation features?
> 
	  -- Don

	The uWave has both the sliding start point as well as the
ability to slide through the wavetables - controllable by all the
various modulation sources. I also think each wavetable is 2-dimensional
(multiple wave variations / wave) - but because I have a strange old
photocopied manual that lacks diagrams, I've never been too clear on
that :). Unfortunately, modulation of one Osc's wavetable by the other
is not paossible...

	- CList