[sdiy] small VCO core

[Tony Clark]

> Why sawtooth? My recent experiments show that it is much easier to shape
> other waveforms from a triangle core.
> Also, a triangle VCO doesn't have the problem with the sawtooth reset time.
> Mine stays in tune to over 20kHz, without any HF compensation whatsoever.

   Hi all,

   I originally did some LFOs this way, but of course I discovered that 
the glitch point in the sawtooth conversion basically made the waveform 
useless (unless you like that sort of thing!).
   I much prefer to use a sawtooth VCO core and then waveshape.  While 
the waveforms may not be as stable in higher frequencies, the VCO is 
_excellent_ in sub-audio modulation.
   As for sawtooth reset time, you can improve upon it using a variety of 
tricks such as a smaller integrating cap, plus speeding up the reset 
circuitry.  Using appropriately sized caps in strategic areas of the 
circuitry can reduce the reset glitches pretty well for audio-range 
applications.

   Tony

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