[sdiy] VCO reference voltages

[David G. Dixon]

> Didn't know I was such an authority...

Don't sell yourself short!

> Ehm well. Fixing the tuning pots is possible, but be aware that you want
> your +15 V (or what ever) mirrored to -15 V (see Oberheim SEM) rather
> than individually controlled. Also, it comes to no great use unless your
> sources also has stability treatment. It becomes an endless hunt for
> precision. Consider the good enought argument.

Yes.  I've read the arguments in favor of regulating the rails, and I would
probably do this had I not already laid out and built some new VCOs without
it.  Changing it now would be a major hassle, as it would completely change
my board layout, and would require adding another IC (to invert the existing
reference).  Once I found that I was in pretty good company among DIYers,
and even among makers of some fairly expensive commercial VCO modules which
are advertised as being very precise and stable, I figured that it was OK to
leave it as is for now.

Maybe I'll address it in my upcoming 2164 Expo Tricore VCO design (which
will also have through-zero capability).

> Maybe isolation of noise-makers is needed. Star-feed/ground or even
> separate supplies.