[sdiy] Smith's Evolver Desktop's spikey VCO waveforms

[rburnett at richieburnett.co.uk]

> Looks like preringing, check all bypass capacitors. Also check voltage
> rail buffer caps for high ESR with the Peak ESR meter.

I can't view the picture here (the server gives me a 403 Forbidden),  
however if you are seeing pre-ringing in the waveform then that implies 
the system is not causal.  In which case its more likely the glitch 
you're stressing about is either an artifact of a soundcard's anti-alias 
filtering, or a digital oscilloscope's reconstruction filter, depending 
on which method you used to capture the waveforms.  It may not actually 
be present in the original waveform!  Both the soundcard and the digital 
storage 'scope are apt to display waveforms with pre/post-ringing under 
circumstances where they have limited bandwidth and are hit with sudden 
discontinuities in the input signal.  Look up Gibbs phenomenon.

-Richie,