Sorry to disagree, Florian, but the most essential aspect of a (musical) VCO is certainly not its "fine tuning" pot. The fine tuning is just a byproduct of its tuning pot. Use a very high value pot and you're set.
No, the most essential part of a VCO is the quality of its exponentiator. Building a decent VCO isn't all that difficult. Building a good VCO which tracks over a wide range is a whole different matter.

FWIW: I have 4 CEM-based VCO's in my Aemit system. They track over 10 octaves, and the "coarse tuning" pot sweeps through the whole range. Still, I can tune the VCO's in perfect unison quite easily. Though I have to add that they have fine tuning pots too, and I used very high quality pots for the tuning...

_g

--- In Doepfer_a100@yahoogroups.com , Florian Anwander <fanwander@...> wrote:
>
> Hi all
>
> Dieter Doepfer schrieb:
> > The A-143-4 was planned as a VCLFO but not as VCO.
> I think we should take in account, that there is an essential aspect
> missing which is necessary for a real VCO:
> There is no fine tune. I assume the Frequ.-knob would cover a range of
> around 5 octaves or more. I doubt that the four oscillators could ever
> be tuned to a real common pitch as it would be required for unisono or
> polyphonic use.
>
> Florian
>