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Author Topic: Am I supposed to hear the noise when I use noise as a modulation source?  (Read 1803 times)

Tausendberg

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So, I think both Modular V and Prophet V's noise modulation might be bugged.

On Prophet V when I use the little LFO/Noise knob or in Modular V when I connect Pink Noise or White Noise to a modulation input (FM for an oscillator for example), I will start to get the desired detuning of the oscillator but I will also always get what sounds as if the audio signal of the noise generator itself was mixed into the audio output.

Is this supposed to happen or is it a bug?

FYI, for some sounds I like to use a bit of noise generator driven frequency modulation because it gives the oscillator a "broken" or "shorted out" effect.

Tausendberg

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Perhaps I am mistaken about what frequency modulation entails...

I was experimenting just now by taking a sine wave, connecting it to a VCA, taking another sine wave and connecting it to the first oscillator's frequency modulation input and I was expecting that it would alter the pitch of the first oscillator based off of the intensity of the volume, but instead I'm seeing it generate all sorts of harmonics and I don't know what to make of that...

Karamba

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Perhaps I am mistaken about what frequency modulation entails...

I was experimenting just now by taking a sine wave, connecting it to a VCA, taking another sine wave and connecting it to the first oscillator's frequency modulation input and I was expecting that it would alter the pitch of the first oscillator based off of the intensity of the volume, but instead I'm seeing it generate all sorts of harmonics and I don't know what to make of that...

It does alter the pitch but has nothing to do with volume intensity. If you want the Frequency modulation to be affected by the velocity then patch a cable from the "vel" jack to the FM jack of the driver being used by your sine wave connected to the VCA, turn the fm jack screw all the way to the right or left, then the frequency will change accordingly to the velocity of the keyboard.

For the noise, I'm not sure if it's normal to hear it when being used for FM but I can confirm I hear it too (or sounds similar at least).

Maybe attach a screenshot to make sure I understand what you mean?

LBH

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Regarding Noise as a modulator i would say that kind of behavior is a bug.
When using noise as a modulator you are not supposed to hear noise unless it's a part of the modulations result.
I can confirm In Modular V and Prophet there seems to be a bug. You hear noise from the moise generator even if it's only used as a modulator.
Do this apply to other applications?
EDIT: Thinking some more about it, i'm actually not sure that hearing the noise is wrong. If the noise modulation is strong enough, then i think hearing the noise is normal. But i would like to not hear the noise if it's actually not a part of a effect of the modulation. I would like Arturia to have a look at it to judge. EDIT END


Regarding Sine modulation.
You somehow describe FM systhesis.
And the effect also depend on volume/ or amount of the modulator.
If you for instance
1. take a sine from OSC 1 to be used as the carrier to be modulated, and then
2. take a sine from OSC 4 and connect it thru the mixer to be used as the modulator to modulate the frequence of the carrier (OSC 1), then you can hear the differences when you change the volume/ amount of the modulator (OSC 4) in the mixer.
That's normal behavior i would say.

« Last Edit: July 16, 2016, 08:43:48 pm by LBH »

Tausendberg

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I really think that it's a bug that we can hear the noise generator as audio when it's used only as a modulation source.

At first I thought it was just some kind of odd quirk related only to frequency modulation but I'm testing the noise generator as a modulation source for pulse width modulation and amplitude modulation while looking at the output through an audio spectrogram and I can see the noise generator's audio appearing in the output even though the modulated variables in question shouldn't have anything to directly do with, you know, the frequencies associated with the noise signal.

It seems like it's a bug.

Tausendberg

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Also just check Prophet V2...

Same issue with noise input into frequency modulation, pulse width modulation, and filter cutoff modulation. The audio signal of the noise generator keeps apparently intruding into the audio output.

I'm going to check if any music equipment stores near me have any Prophet 6s on display to compare if that's really how it's supposed to behave.

Edit: Nevermind, apparently the Prophet 6s that they sell now don't do the lfo to noise thing anymore. Hmm... so where I could test a real prophet 5. Hmm.
« Last Edit: July 17, 2016, 01:01:45 am by Tausendberg »

Tausendberg

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Alright, well, in case anyone is wondering, using CableGuys Midishaper I was able to generate noise generator driven CCs and consequently get a completely clean sounding noise based modulation source.

Arturia, I hope you don't mind me mentioning that I use another brand's product to supplement the functionality of the Modular V, Midishaper is not a competitor with any of Arturia's products though it is useful for bringing in some features that Modular V doesn't have (another use is that you can use it to replace the Modular V's LFOs because MidiShaper has LFO retrigger but Modular V doesn't.)

Tausendberg

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Regarding Sine modulation.
You somehow describe FM systhesis.


HAHAHAHA! Gosh, here I am just experimenting with different things expecting very simple and predictable results and instead I chance upon one of the fundamental forms of sound synthesis. I love modular audio production.

FM synthesis is still something I don't totally understand but I feel like I will have to in time... I've even watched youtube videos that tried to explain it to me but I'm still not totally comprehending it...

jeffbart

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Regarding using noise as modulation source. I think (and I hope!) what we are hearing is the resulting action or effect of the noise on the e.g. osc pitch, not the original noise itself.
I experimented at low levels of pitch mod using noise, and got small, rapid pitch changes, and as the level of mod is increased, the pitch changes got more and more wide until it resembled the noise that was modulating it.
Same with filter cutoff mod using noise. On Modular and 2600...

Perhaps noise being what it is will make anything it modulates, at a strong enough level, resemble noise??

Or perhaps I'm wrong... maybe Arturia's method of using noise as a mod source is not what we think?
Maybe Arturia could check if indeed the noise used for modulation is being added to the audio out.

Cheers Jeff

« Last Edit: July 23, 2016, 09:05:25 am by jeffbart »
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Tausendberg

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For the Prophet, I also tried the cutoff modulation and I also watched some videos of the Prophet 5 in use and from what I can tell, the noise modulation is supposed to be nice and clean sounding and not like what the noise itself sounds like, especially for something like filter cut off where you can clearly hear the filter's cut off being modulated while also the noise audio intrudes into the output.

Tausendberg

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Re: Am I supposed to hear the noise when I use noise as a modulation source?
« Reply #10 on: September 18, 2016, 03:09:50 am »
AH! I figured out a practical way, in Modular V, of how to use noise as a modulation source without actually having the perception of noise mixed into the audio output.

You connect the noise output to a sample and hold module input, and then use the sample and hold output as the modulation source and dial the clock rate to the desired amount.

While reading the manual for the Microkorg, I saw that Korg refers to the 'random' setting for the LFO as 'S&H' and that's when I realized a 'random' lfo is just a noise generator routed through a sample and hold module.

In the case of the modular v, routing a noise generator through a Sample and hold module is actually preferable than using a 'random' output from the VC LFO modules because the VC LFO modules, for whatever reason, don't output 'negative' values while the routing I'm describing in this post does!

Synthesizers are fascinating.

 

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