Actually the high-quality sine circuit is *quite* common. According to my schematic
library, most vintage oscillators used this standard design. For example, my Aries VCOs
produce a pretty good purity sine using this:

http://www.leinermedia.net/aries/AriesSchematics/AR-317s.gif

My guess is modern VCO designs use the cheap low-quality diode circuit instead because:

A - the simple diode circuit requires no calibration where the Hi-Q one has two trim pots
to set (symmetry and purity).

B - According to this thread it appears many analog users are unaware or inexperienced
with quality VCO sines. So there no customer demand.

BTW, nobody is advocating "pure" sines - just ones with no audible harmonic distortion.
That's certainly is easy to design in analog.

--- In Doepfer_a100@yahoogroups.com , Florian Anwander <fanwander@...> wrote:
>
> Hi laryn91
>
> > I don't get it either. All I asked is if anyone knows of any euro VCO that can produce a
sine
> > wave without audible harmonic distortion (Plan-B and ZO so far). To me this a very
useful
> > feature.
> I don't know that there would exist any schematic for this. I never have
> seen a schematic for a pure sine oscillator that is V/Oct voltage
> controlled. I may be wrong, but I think it is not really possible.
>
> Florian
>