MOTM

After 4-5 hours of basic research, I have *minimized* the glitch on the top
portion
of the triangle wave (which of course shows up on the sine as well).

This glitch is an artifact of the full-wave rectifier action due to:

a) finite switching times of the diodes
b) diode capacitance
c) finite switching time of the comparator that discharges the main
integration cap

DC offsets in the sawtooth are trimmed out by using a 'scope.

Now, the glitch itself is 1-2uS wide. That's right, *microseconds*. You can
see it on a 'scope.
You can't hear it, or hear another problem when the VCO is used as a LFO.
The width of
the glitch is constant up to about 12Khz.

Also, if you pass the triangle through a LPF, it goes away.

So, I just thought I'd toss this out beforehand.

If it makes you feel better, the glitch is about 1/2 the one on a Moog
modular. And, our triangle
symmetry is 10X better above 4Khz than Moog's.

Paul Schreiber
"Basic research is what I'm doing when I don't know what I'm doing." W.Von
Braumm

Guess what? Emu modulars have this glitch as well, along with enough sine
distortion that you can just barely actually hear it.

SSM VCOs have a nice notch in their triangles also.

Dave Bradley
Principal Software Engineer
Engineering Animation, Inc.
daveb@...

>
> If it makes you feel better, the glitch is about 1/2 the one on a Moog
> modular. And, our triangle
> symmetry is 10X better above 4Khz than Moog's.
>