[sdiy] VCO vote?

[jhaible at debitel.net]

> Read this with some humor, but the background is really serious.

I try to answer in the same way. (;->)

> Every now and then some people tell us that this or the other
> VCO sounds so much better then some other VCO.

And often they don't tell us if they really mean the VCO, or
the sound of a certain synth with filters wide open. 
In the latter case, what is attributed to the VCO, might also
come from the signal path after the VCO (slightly ringing 
circuits, limited bandwidth, nonlinear stuff), from the
CV path that controls the VCO (noisy opamps that just provide
the right kind of noise for pleasant drift), or even from
the power supply (noise to unlock otherwise badly syncing VCOs,
or unwanted coupling to soft-sync otherwise well-designed
VCOs). And, not to forget, *sometimes* the difference may
actually lie withing the VCO core (opamps whose noise gets
shaped within a expo converter feedback loop, offset currents
that introduce low frequency mistracking, finite capacitor
discharge times that alter the waveforms; even ringing from
a rapid cap discharge and some inductive components).
Well, some of the ringing that is shown sometimes may just 
be introduced by the scope probe, so it may or may not be present
in normal operation. Some waveshape distortion that is
often quoted simply comes from AC coupling of the "wide open"
signal path after the VCO.

JH.

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