[sdiy] Dual/quad opamp bleed-through

[David G. Dixon]

> MS-20; yes. Soft sync is evident on many units I have seen. But only
> when you try to set the pitches very close to one another.

Yes, I saw this in my circuit.  When the two oscillator frequencies were
brought very close together, they would lock onto each other.  Also, the
hard sync seemed to snap to various resonant frequency combinations rather
than scanning smoothly through the frequencies.  I didn't realize this was
an artifact of the circuit layout, and it was kinda cool, but further
confirms the foolhardiness of my original approach.

I'm starting to think that the whole idea of a "dual" VCO is faulty.  Better
just to build two identical VCOs!  It bears noting, however, that the
modulation possibilities between two VCOs are very rich, and not often
discussed.  For example, VCO cross-modulation can give some very strange
waveforms.  Having the two circuits on the same breadboard inspired many
connections which I might not have thought of otherwise.