[sdiy] FM with two oscillators

[Florian_Anwander]

Hi Christian 

> I was wondering if it would be simply a question of feeding a
> proportion of the output of VCO2 back into the CV input of VCO1, or
> would there be other steps necessary.
In principle yes. But Better is


VCO2 Audioout -> VCA (ac-coupled) -> linear CV-in of VCO1
                  ^
                  |
              Envelope

 
> Also, is FM only possible (or is it best) with sine waves - My VCO's
> currently only output Square with PCM, saw and triangle.
FM of course works with all kinds of waveforms. But you have to keep in
mind that VCO2 modulates always an oscillator which produces one
definite waveform (most times a sawtooth, sometimes a triangle). The
signal you get on the other wavform outs (eg. square) of the VCO1 is,
what the waveform converter produces from the FM'ed sawsignal.

The guitar like sounds, you are looking for, are very DX-typical sounds
with two beating (slightly detuned) modulators.

OPx
    \
     OPz
    /
OPy

where OPx produces a square like sound and OPy a sawtooth like sound.
OPz is a sine osc.

You may become a sine oscillator using a self resonating VCF

Florian
-- 
Florian Anwander                  |ConSol*  HP-Support
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