analog wavetable?

[Grant Richter]

The Wiard "Waveform City" module is just such a device. The "digital"
waveshaping section is actually an analog module (voltage in, voltage out).
The input voltage is digitized by a high speed analog to digital converter.
The eight bits from this are used to point to any of the 256 steps in the
stored waveform (actually a transfer function).
A four bit analog to digital converter selects one of 16 "waves" under
voltage
control, and another four bit analog to digital converter selects one of 16
"banks" of 16 waves.

If you put a calibrated sawtooth into the unit it will simply "scan" out
all
256 values in sequence (like a counter). You can then use a voltage 
to scan through the wavetable itself. A zero crossing detector prevents
switching to a new waveform, except at a zero crossings, to eliminate
"clicking".

The nice thing about the design is that it behaves in every way exactly
like an analog oscillator, just with 256 waveforms. The same circuit
can be used for control voltage quantization, and as a non-linear synthesis
device like the Serge wave multipliers.

Inexpensive shareware for programming the 27C512 wavetable PROMs
is available at
http://www.wiard.com

----------
> From: Plinio Andres Barraza <pab210 at is8.nyu.edu>
> To: synth-diy at mailhost.bpa.nl
> Subject: analog wavetable?
> Date: Sunday, June 13, 1999 7:48 PM
> 
> 
> 
> I was wondering if anyone on this list knows of, has thought of, or
better
> yet, designed or built an analog oscillator that works like a digital
> wavetable oscillator.  
> 
> I can't imagine how it would work except that one
> could somehow design a complex envelope generator, and figure out a way
to
> make it repeat itself (the hard part) indefinitely.  Of cource, it would
> also be nice if one could controll the time it takes to complete one
> cycle, hence the frequency.
> 
> any ideas?
> 
> Plinio