[sdiy] Additive VCO

[Ken Stone]

Maybe start with a triangle oscillator, then rectify, and amplify to get the
second, do again for the fourth etc. Feed the triangles into triangle to
sine converters, and you have a number of your waves already nicely phase
locked.
Of course for third, fifth etc, you'd need to get creative.

Ken

>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
>
>-- 
>+++ NEU bei GMX und erstmalig in Deutschland: TÜV-geprüfter Virenschutz +++
>100% Virenerkennung nach Wildlist. Infos: http://www.gmx.net/virenschutz
>
>
_______________________________________________________________________
Ken Stone   sasami at hotkey.net.au or ken at cgs.synth.net
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>