[sdiy] Additive VCO

[Mike Peake]

At 12:25 AM +0100 3/8/04, M.A. Koot wrote:
>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

The harmonic series doesn't happen to be perfect
math, and shifts in acoustic instruments when
played forte etc.

Sixteen sines would be very nice, if you could
individually set the harmonic number for each.

The Synergy/GDI used FM, IIRC, to generate lots
of harmonics from one of the sines in order to
simulate the upper-range "fur". Pure sines will
be too clean for very complex sounds.

Good concept!

Easier,
-- 
Mike Peake, Your Postwar Administrator

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