[sdiy] Additive VCO

[M.A. Koot]

Hi everyone,

I'm trying to design an additive-VCO, there aren't too many around, and
that's why I would like to at least try it myself.
My initial idea is by having one expo-converter, having the output devided
over several Opamp-adders (to create the harmonic-offset). Those Opamp-adders
have 2 inputs each then, one with the CVin, and one with the offset voltage.
Each of those opamp outputs then go to seperate Sine-VCO's, one sine for
each opamp-output.
Then finaly mixing all the signals together, and that should be it.
The things I'm troubling with though, is how many harmonics (i.e.
Sine-VCO's) should I have at least to create a decent Additive VCO? I was thinking of
about 16 Sine-VCO's. 
Another thing that popped up is: How "correct" do they have to be?
I can assume that if you want to create fairly true additive waves, with
Fourier in mind, they have to be pretty accurate, increasingly with the
harmonic-number probably.. But I wouldn't know how this would be in "real life". 
I hope anybody could help me, does anybody maby already have some experience
in this?.

Thanks, cheers,
Michiel

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