MOTM

> To do "true" Chowning Frequency Modulation Synthesis (ala Yamaha DX-7) you
> need a VCO where the FM can send the oscillator 'through zero.' In an
analog
> VCO this is tricky.
>
> Someone please correct me if I'm wrong.

The DX-7 uses Phase Modulation (or so I'm plausibly told - I never
checked myself), which is even more tricky to implement in Analogue.
But rather easy in Digital.

Now yes, Thru Zero FM in Analogue is tricky enough, especially when
you want it free of artefacts during the zero crossing. (I have a
CEM3340-based
thru zero FM VCO on my homepage, but this does have such artefacts.)

Who is designing this VCO ?
What method is used ? Sign/Magnitude with reverible triangle core?
Or a BFO ? Or something entirely different ?

JH.