[sdiy] Harmonic content of the "sigmoid" half-sine wave

[David G. Dixon]

Aaron,

One could get very close to the waveforms in that patent simply by doing
what I mentioned in my last post; namely, putting a PW modified triangle
through a sine shaper.  If, for example, one were to take Ray Wilson's sine
shaper from his VCO, and replace the trimmers with panel pots, one would
have panel control over the symmetry, round-ness, and amplitude of the
"sinoid".  By driving the symmetry far from the centre and running the
amplitude to clipping, one would achieve the last waveform in the patent.

You might not have control over the entire range of waveforms that you would
have with the patent circuit, but you could come darn close with a circuit I
could throw together from spare parts in the next half hour (but I'm not
going to, because I'm about to stuff the custom dual Wilson ADSR board (with
added inverse output and trigger repeat mode) I've just spent the last two
hours printing, etching and drilling).

David G. Dixon
Professor
Department of Materials Engineering
University of British Columbia
309-6350 Stores Road
Vancouver, B.C. V6T 1Z4
Canada
 
Tel 1-604-822-3679
Fax 1-604-822-3619
 
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> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> bounces at dropmix.xs4all.nl] On Behalf Of Aaron Lanterman
> Sent: Wednesday, June 03, 2009 2:12 PM
> To: Tom Wiltshire
> Cc: sdiy DIY
> Subject: Re: [sdiy] Harmonic content of the "sigmoid" half-sine wave
> 
> 
> On Jun 3, 2009, at 2:05 PM, Tom Wiltshire wrote:
> 
> > Golly! I think you've just reinvented Casio's Phase Distortion
> > synthesis! Only this time it's analog!
> 
> Wanna have some fun?
> 
> Put 4,658,691 into pat2pdf. I think most of what's there could be done
> in analog by clever folks.
> 
> - Aaron
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