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 Forum index » Clavia Nord Modular » G2 Building Blocks
Efficient anti-aliased hard sync pulse oscillator
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Tim Kleinert



Joined: Mar 12, 2004
Posts: 1140
Location: Zürich, Switzerland
Audio files: 7
G2 patch files: 236

PostPosted: Fri Jun 09, 2017 7:44 am    Post subject: Efficient anti-aliased hard sync pulse oscillator Reply with quote  Mark this post and the followings unread

Hi,

I don't use/own the G2 anymore, but still use the demo software to expediently try out new techniques I'm studying or developing.

Here's a new approach to the old "G2 hard sync problem" using a novel technique I've invented after studying what in retrospect could be considered the first VA synth: the Roland D-50.

It's an anti-aliased pulse oscillator with hard sync, PWM and brilliance control.

Compared to my previous attempts, it's very efficient: 15.8% cycles, 17.2% memory.

All pertinent controls and modulation inputs are highlighted, and simple demo stuff added to illustrate implementation.

cheers,
t

EDIT: Further experimentation shows that this oscillator responds spectacularly to audio-rate frequency modulation (which makes sense since it doesn't use BLEPs for anti-aliasing) . To do this, mix the FM modulator signal together with the "22" constant module going into the core triangle oscillator FM input. (FM mode has to be "Trk" however.)


DIYSyncPulse__TK.pch2
 Description:
Efficient anti-aliased hard sync pulse oscillator; new approach; only 15.8% cycles, 17.2% memory

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 Filename:  DIYSyncPulse__TK.pch2
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Electromagnetic Wave



Joined: Apr 28, 2013
Posts: 208
Location: Kebek
G2 patch files: 30

PostPosted: Sat Jun 10, 2017 12:03 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi!

I know nothing about the Roland D-50 but WOW (again!) !! Work very well! Thank you!

I have a question about the Pitch module (Osc Master) with this kind of patches. Is it possible to replace this module by another Osc modules (for microtuning purpose with FM Lin input available)?

I know the internal sample rate from the Osc Master module is 24 kHz (blue cable and doesn’t generate any audio signal) and other are 96 kHz (red cables). I'm not sure I can tune the main pitch with fine resolution as I want with blue cable (instead of red cable and Fm Lin input). Am I right ?
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Tim Kleinert



Joined: Mar 12, 2004
Posts: 1140
Location: Zürich, Switzerland
Audio files: 7
G2 patch files: 236

PostPosted: Sat Jun 10, 2017 3:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Electromagnetic Wave wrote:

I have a question about the Pitch module (Osc Master) with this kind of patches. Is it possible to replace this module by another Osc modules (for microtuning purpose with FM Lin input available)?

I know the internal sample rate from the Osc Master module is 24 kHz (blue cable and doesn’t generate any audio signal) and other are 96 kHz (red cables). I'm not sure I can tune the main pitch with fine resolution as I want with blue cable (instead of red cable and Fm Lin input). Am I right ?


I think you have a wrong understanding of what the OscMaster module does. Contrary to the other oscillator modules, this module doesn't output an oscillating audio signal. It only generates pitch control information from its knobs and (switchable) keyboard tracking, and its purpose is to be able to control multiple pitch destinations in a patch from one centralized source. In this case, it controls oscillator pitch and, inversely, oscillator brilliance in order to prevent foldbacks (aliasing). Replacing it with an audio rate signal from a regular oscillator will cause the patch to cease functioning in the intended fashion.

What kind of fine control are you looking for?
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Electromagnetic Wave



Joined: Apr 28, 2013
Posts: 208
Location: Kebek
G2 patch files: 30

PostPosted: Sun Jun 11, 2017 2:40 am    Post subject: Reply with quote  Mark this post and the followings unread

Sorry if I do not express myself correctly Tim. I understand the difference with other oscillator modules. That's why I wrote "blue cable and doesn’t generate any audio signal". It is more a problem related to the use of this module in my own situation for G2 keyboard and microtuning scale. Not sure if it's better to create another topic for this. Well I will try to explain it here and understand if I can adapt this patch for my microtuning patches because you also use the Osc Master module to control the oscillator brilliance and I do not understand exactly how this part will work if I change something else.

My approach to tune the G2 keyboard as I want is based on the scalaG2 generated patches (using many control sequencer modules. every step is assigned to a key on the keyboard).
http://electro-music.com/forum/topic-17192.html

But the pitch input from Osc modules does not provide the necessary resolution I need. To get the finest resolution available for tuning (0.0057Hz) I use the FM Lin input combined with the pitch input from the oscillator modules. Every note on my G2 keyboard is associated to a step in many control sequencer modules and I tune/adjust each one the best as I can with the help of my ears, a spectral analyser and an oscilloscope to compare the phase from 2 audio signals.

Quote:
Actually there are another 32768 subdivisions between two consecutive unit values. Meaning that a half note step is subdivided into 32678 additional sub steps.
-In practice the internal frequency resolution of the G2 is 0.0057 Hz, which is about 4000 intermediate steps between two half notes at the middle of the keyboard.

source : http://rhordijk.home.xs4all.nl/G2Pages/index.htm

I don't think I can obtain this fine tuning (0.0057 Hz > 32768 subdivisions between two consecutive unit values) with the Osc Master module because this one only generates pitch control information and I think it don't use all the resolution range available for tuning with G2 at 96 kHz. The Osc Master don't have a FM Lin input (or a sync input as some other Osc modules). This module doesn't generate an oscillating audio signal as you said too. I don't think I can use it for 'microtuning' scale adapted for keyboard.

Now I search a way to replace the Osc Master in your patch with a building block that have the possibility to adjust the tuning with very fine resolution + the approach I use (scalaG2 patch) for 'microtuning' scale on G2 keyboard.

I have tried a few tricks to help me understand and find ideas to solve it... without success. As exemple, to add a wire from a new Osc B module output to the Osc C in your patch (sync input). I used the FM Lin input from the new Osc B for microtuning. After doing that Osc C is tuned as I want because of the wire from Osc B output to Osc C sync input.. But I have few aliasing after doing this. To test the aliasing manualy I turn off the lfo, adjust EnvADSR2 module parameters and move the SYNC knob to high value. I hope this is easier to understand now.

Have a nice day!
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