exponential rising (was Re: definition of Syncing)

[Magnus Danielson]

> > curious question (possibly stupid, but who knows?): what would it sound like
> > if you had an exponentially rising voltage across that same cap? interesting
> > sounding waveform or no?
> > 
> > mitch
> 
> Well the ARP Omni's (here I go again with the Omnis) tone generation
> circuitry uses exponentially decaying sawtooth waves. These are
> obtained by running each square wave from the polyphonic divide-down
> circuitry through its own RC differentiator circuit. The RC circuits
> are crudely tuned to each square wave's frequency (in some cases by
> chopping off part of the ceramic disc cap and covering up the exposed
> electrolyte with fingernail polish!). This produces a waveform like this:
> 
> 
>        |.
>        | ..
> -------|   -------| ..--------
>                   |.
>                   |
> 
> This wave then goes thru a diode clipper circuit with two selectable clip
> points. One selection chops off the entire bottom half of the wave,
> producing the exponentially decaying sawtooth. This is the wave which
> sounds more string-like and which is used on the Omni most of the time when
> you hear it.

This waveforming is also used in the ARP/Solina String Ensemble. Complete with
the negative clipping.

The waveform then becomes

 |.        |.
 | ..      | ..
-|   ------|   ------

For each key is then the the waveform for that octave and the octave above
combined.

Cheers,
Magnus