[sdiy] OOOOPS!!!! (Top octave CPLDs)

[Tim Parkhurst]

Halloo OT (Other Tim),

I was sort of thinking of summing different squares through resistors to
make a saw wave (the Don Lancaster method). I was also poking around with a
design (on paper) the other day that takes a saw and uses four comparators
to make four independent pulse waves (very simple, I'm sure it's been done
before). If you tweak the duty cycles and mix these together just right, you
can get very close to a saw. 

Perhaps a nice addition might be to allow switching between two or three
different duty cycles. Is that possible with your design? It wouldn't make a
nice smooth transition, but it would add a little versatility.

Tim Servo

************************************
> -----Original Message-----
> From: Tim Ressel [mailto:madhun2001 at yahoo.com]
> Sent: Wednesday, October 30, 2002 5:32 PM
> To: Tim Parkhurst; synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] OOOOPS!!!! (Top octave CPLDs)
> 
> Hey other Tim (and all),
> 
> The TOG project consists of two chips, each one
> handling half an octave. This is because of the way I
> do the generation, and due to size constraints. I use
> a comparator to create the output wave. This allows
> duty cycles other that 50/50. The original MK50240
> came in a 30/70 version; I wanted to keep that option.
> In fact, mine can to any duty cycle. The down side is
> the duty cycle is hard-coded in the chip.
> 
> I will be offering the chip set for sale. Price for
> the two chip set + sockets will be $20 + $5 S&H
> 
> --TR
> 
> As far as summing pulse trains to make saw waves, I'm
> not sure how that would work. I've seen the Don
> Lancaster method of making saw waves by summing 50/50
> square waves with resistors, and I've seen the
> Simonton design making narrow pulses by gating
> together 50/50 square waves. Are you talking about one
> of these? Is there a schematic I can look at?
> 
> --TR
> 



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