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 Forum index » Clavia Nord Modular » Nord Modular G2 Discussion
NMG2 OscShpA
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an2netto



Joined: Apr 23, 2017
Posts: 1
Location: Ukraine

PostPosted: Sat Apr 29, 2017 2:29 am    Post subject: NMG2 OscShpA
Subject description: waveshaping algorithm
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I'm trying to figure out what transfer functions are applied behind NMG2 OscShpA oscillator. In the manual the Sine3 is described as follows:

At 50% Shape setting, the signal is a perfect sine wave and at 99% a lot of even harmonics have been added.

I recorded a scope of the waveform:
https://youtu.be/Tz4nzEbgdY8

Could anyone give a hint on the algorithm being used here?
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Electromagnetic Wave



Joined: Apr 28, 2013
Posts: 208
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PostPosted: Sat Apr 29, 2017 5:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi!

I don't know what is the exact algorithm but this is usefull (from the doc/OscShpA too) :

"by gradually transforming the signal, adding more overtones and creating a more complex and rich signal"

I'm curious to reproduce it with a 'wave table patch' + morphing to pass from waveform A > waveform B.
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Blue Hell
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PostPosted: Sun Apr 30, 2017 12:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

I think .. it might be phase distortion synthesis.

For a normal osc you would make a saw shaped signal and use that to look up or calculate the wave to be played.

In phase distortion synthesis you would change the shape of the driving saw ... in this case an S shaped curve might have been used.

To change the harmonic contents you would fade between the saw and the warped saw.

Some more on that : https://en.wikipedia.org/wiki/Phase_distortion_synthesis

On the G2 you can do a sine lookup by setting a sine oscillator to zero Hz and then use the Phase Modulation input to do the lookup - with a saw as an input you would get the sine, with a distorted saw you would get .. something else.

Ideally you would want the saw to be aliassed for this, but audio oscillators are anti-aliassed .. you could try an LFO instead.

I did not test anything of the above BTW .. just guessing.

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Tim Kleinert



Joined: Mar 12, 2004
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PostPosted: Mon May 01, 2017 1:59 am    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
Ideally you would want the saw to be aliassed for this, but audio oscillators are anti-aliassed .. you could try an LFO instead.

LFOs are unusable for this purpose because of the low sample rate. I used to use a klutzy (i.e. wasteful) inter-/extrapolation scheme to upsample a sawtooth LFO from control to audiorate for use as a phasor -that was, until I figured out this: doh

arrow http://electro-music.com/forum/topic-67855.html
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Electromagnetic Wave



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PostPosted: Sat May 06, 2017 2:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sorry for my ignorance... I like to learn from others people questions. Is a sine from a resonant filter (self oscilating) is antialiasing ? If not, can we use these sines to create (additive synthesis) a saw usable for what Blue Hell suggest?

And is the square from the invert module at 48kHz is antialiasing too ? If not is it possible to turn this one in a saw (aliased) with any technics ?
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