Hi Alexandre,
mea culpa, you were right about the modulation index using Phasor! :D
here we are the 2 implementation, one with Phasor and SinOsc sync(1) (in
the previous mail I said sync(2) but I meant sync(1) ), and one without
Phasor but just with 2 SinOsc:
Phasor phasor => Gain g => SinOsc carrier => dac;
SinOsc mod => g;
carrier.sync(1);
phasor.freq(100);
modInd(5,200); //change parameters here and listen the result
while( true ){
second => now;
}
fun void modInd( int i, int fm ){ //arguments: modulation index,
modulation frequency
float am;
i/6.283185307 => am;
mod.freq(fm);
mod.gain(am);
}
////////////////////////////////////////////////////////
////////////////////////////////////////////////////////
// m = mod osc; c = carrier osc;
SinOsc m => Gain g => SinOsc c => dac;
Step cm => g; //cm = carrier freq in Hz
while( true ){
modInd(5, 200); //change parameters here and listen the result
cm.next(100);
second => now;
}
fun void modInd( float i, float f ){ //arg: modInd, freq mod
float am;
i*f => am; //(modInd = Am/Fm), then (Am = modInd*Fm)
m.freq(f);
m.gain(am);
}
On 04/06/17 22:44, Alexandre Torres Porres wrote:
2017-06-04 13:59 GMT-03:00 mario.buoninfante
<mario.buoninfa...@gmail.com <mailto:mario.buoninfa...@gmail.com>>:
Now 2pi is needed only if you deal with a ramp, with a phasor.
Cause Phasor*2pi gives you a sine. If you already have a sine
there is no need to use 2pi.
Hi, let me try to be clearer. Phasor * 2pi going through a sine
function gives you a sine wave. SinOsc can also be drive by a Phasor.
Such as this.
Phasorp => SinOscosc => dac;
440=>p.freq;
1=>osc.sync;
4::second=> now;
In this case, you get a sine wave and you don't need to multiply the
phasor by 2pi, because the input is normalized, from 0-1
What I was trying to say is that if you have a modulating index in
phase modulation, and you want to replicate it in frequency
modulation, you alsop need to multiply it by 2pi.
I'm not challenging the math or equations, just adding an
implementation detail in Chuck code. I know I wasn't clear about it,
sorry. Hope it's clear now.
But my main point was something else. It is true that if you multiply
the index value by the modulation frequency value, such as in your
code, you sort of get a similar behaviour than you'd get with phase
modulation. But there's another detail missing if you're to really
convert it.
One thing about this conversion is that the waveform/function of the
modulation signal needs to also be adjusted. In terms of sine waves,
if you have the phase signal being modulated by a sine wave, you need
to modulate the frequency with a cosine wave.
With other waveforms it gets more complicated. By the way, the rule of
thumb (multiply the index by the frequency) also changes, that is
important to note as well.
My main point is just that it's just best to implement via phase
modulation, if that's the behaviour you want.
cheers
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