Archive of the former Yahoo!Groups mailing list: MOTM

previous by date index next by date
  topic list next in topic

Subject: VCO Triangle/Sine glitches

From: "Paul Schreiber" <synth1@...
Date: 1999-03-27

After 4-5 hours of basic research, I have ∗minimized∗ the glitch on the top
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