[sdiy] Diagnosis Help Please

[Mark Melvin]

Hi all-

First of all, let me say that I'm still new at this
stuff... so be patient with my ignorance. 

I'm almost finished with my first synth project and
almost everything is working... and what isn't working
I believe I can fix.
HOWEVER, I have this annoying feature that I hadn't
planned on incuding.  Perhaps if I describe what I am
hearing someone could make a guess as to what is
happening.

What I am experiencing is best bescribed as "beating"
in the VCO.  To me it seems like there is a signal
that has bled into the VCO.  It seems to be constant. 
If I sweep the VCO over it's frequency range I will
hear the beating (two frequencies sounding together)
changing and then disappearing at a few given points
across the range of the VCO.  I believe these points
are one octave apart.

This goes away completely when power the VCO alone. 
However, when I add one or more additional modules
from my PSU the beating returns and becomes worse with
each additional module.

Any ideas about what this could be?  Thank you in
advance for any help!

-Mark

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