Variable ramp generator

[mbartkow at ET.PUT.Poznan.PL]

Steven Cook <steve at babcom.u-net.com> wrote:

> I've been following this with interest as I've recently created a variable
> ramp generator in Csound (i.e. cheating!). My method is similar to Don
> Tillman's, but arrived at independently.
> 
> 1) Start with a positive sawtooth and a CV, both with the same range, say 0 to 1.
> 
> 2) Send the sawtooth into a VCA whose gain is controlled by the CV. Gain
> should equal 1 / CV.
> 
> 3) Send the output of the VCA into a limiter/clipper (precision rectifier?)
> set to 1 (the sawtooth's peak). The output from this should be a variable ramp
> from 0 to 1 followed by a DC level of 1.
> 
> 4) Send the sawtooth also into a 2nd limiter/clipper set to limit downward
> excursions to the level of the CV. Subtract the CV from the output of this.
> Send into a 2nd VCA whose gain is equal to 1 / (1 - CV). The output from this
> should be a DC level 0f 0 followed by a variable ramp from 0 to 1.
> 
> 5) Subtract the second ramp from the first ramp.
> 
> 6) Go to the pub :-)

Steven,

Cheating is what you do all the time :-)
I think it is basically the same as Don's method, and when implemented "as is"
it leads to a very similar circuit structure. The only difference I see is that
"saturator" is used instead of "select minimum" circuit. In fact, both may be
achieved using diodes and an OA. Both methods are equally practical, imho.

regards,

mb


--

Maciej Bartkowiak, PhD
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