[sdiy] Additive VCO

[M.A. Koot]

Thanks everyone for the kind feedback.

I'm still just a student doing electronics/mechatronics, so I'm pretty
unexperienced and of coarse: it's just an idea I had. 
I like a lot of the other ideas here, it's a good thing the harmonics may be
drifting a little bit, saves a lot of trouble.
As I see, it seems to be pretty utopic to try and create a signal from
analog Sine's, but since I have even less experience in programming DSP's, I'd
still like to try it analog.
I'll look at the triangle-splitters, it sounds really interesting! But
Theo's Pulse-devider is interesting also, although I dont' know if indeed the
harmonics would get too static.
I guess I'll have to trial and error to find out the best way.

Another feature I might like to add is single VCA's for every hamonic.
That'd be a lot of work, but it would be very nice I think if you would be able to
change every single harmonic amplitude over time using envelopes etc. That's
something I could look at after the actual sine production of coarse..

best regards,
Michiel

> My initial thouht is - there's no way it could work. But if you do it
> precisely, it may be interesting. Harmonics don't have to be exactly 2,3,4
etc.
> times the frequency of fundamental to make the sound interesting. Better
> yet, if they are slightly detuned, like 2.001, 3.001, 3.999, the sound
will
> evolve and not be so boring static like, say Kawai K3.
> 
> I had an idea like this some time ago. I wanted to make several VCOs that
> are kept in tune by means of soft-sync. It may be hard to achieve for
> harmonics greater than, say, 20.
> 
> Another solution is to use waveshapers on fundamental triangle OSC. Split
> the slopes by 2,3,4,5, etc and make them wrap on split points. Easy to
say,
> but circuitry may be complicated.
> 
> And if you can achieve pure sinewave of fundamental frequency, you can use
> Tschebyshev polynominals to make hundreds (yeah, tell me I'm crazy) of
> harmonics. That'll require one multiplier like AD633 and other minor stuff
> like opamp for each harmonic.
> 
> One last thought - if you want real harmonics, and want them all to stay
> in tune, use DSP and do it all digital.
> 
> Roman
> 
> ---- Wiadomo¶æ Oryginalna ----
> Od: "M.A. Koot" <makoot at gmx.net>
> Do: synth-diy at dropmix.xs4all.nl
> Data: Mon, 8 Mar 2004 00:25:18 +0100 (MET)
> Temat: [sdiy] Additive VCO
> 
> >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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> >
> 

-- 
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