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 Forum index » Clavia Nord Modular » G2 Patches - Experimental
Brutish
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ian-s



Joined: Apr 01, 2004
Posts: 2585
Location: Auckland, New Zealand
Audio files: 42
G2 patch files: 612

PostPosted: Wed Feb 01, 2012 12:27 am    Post subject: Brutish
Subject description: High Quality Sine/Cosine with wave shapers.
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I got inspired this afternoon. Varice posted his excellent multiwave block and I got to lamenting the poor aliasing performance of my own DIY wave shaping on the G2. I did some experiments a while ago using a quadrature sine DIY block but the pitch tracking/sine quality was not the best. I wished there was a good quadrature oscillator on the G2, then it occurred that I could borrow Varice's sync trick to lock two regular sine oscillators at startup. Given a known start frequency, I just calculated a 1/4 cycle length pulse and synced the oscillators off the rising and falling edges, Another Delay/Value Switch ensure that the pitch stays at the known frequency for the first cycle, see Yellow Block.

The other waves are all derived from the core. If we sum the full wave rectified top and bottom of the sine and cosine, we get a triangle wave of 2x Frequency (Cyan block)

Take the XOR of the sin/cos and use it to invert every downward slope of the triangle and we get a 4x Sawtooth. (Green Block)

Phase shift the sawtooth and sum with the inverted saw and we get a variable width pulse (Purple Block)

If we now assume the 4x waves are the fundamental, we have a -1 oct triangle and a -2 octave sine. The Blue Block sine frequency doubler adds a -1 octave Sine.

The sub sines reminded me of the excellent minibrute synth (wish I had one) so I threw in a metalizer (wave wrapper) on the -1 triangle wave.

It is important that the two oscillators stay close to 90deg out of phase, sometimes adding or deleting modules to the patch screws this up but all should be well on the next patch load. Smile


Brutish.pch2
 Description:
High Quality Sine/Cosine with wave shapers.

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 Filename:  Brutish.pch2
 Filesize:  2.61 KB
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ian-s



Joined: Apr 01, 2004
Posts: 2585
Location: Auckland, New Zealand
Audio files: 42
G2 patch files: 612

PostPosted: Wed Feb 01, 2012 1:50 am    Post subject: Reply with quote  Mark this post and the followings unread

lol

Thinking a bit more about the sync, it occurred that adding an offset pre-sync might be an easier way to get the phase offset.

Seems to work and uses less mem/dsp

cheers


Brutish2.pch2
 Description:

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 Filename:  Brutish2.pch2
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Last edited by ian-s on Wed Feb 01, 2012 2:03 am; edited 1 time in total
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iPassenger



Joined: Jan 27, 2007
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PostPosted: Wed Feb 01, 2012 1:55 am    Post subject: Reply with quote  Mark this post and the followings unread

I think the sync needs to be -63?

Great idea by the way and i love the waveshaping.. very interesting.

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ian-s



Joined: Apr 01, 2004
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PostPosted: Wed Feb 01, 2012 2:05 am    Post subject: Reply with quote  Mark this post and the followings unread

iPassenger wrote:
I think the sync needs to be -63?

Great idea by the way and i love the waveshaping.. very interesting.


Thanks, just spotted that Embarassed
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iPassenger



Joined: Jan 27, 2007
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PostPosted: Wed Feb 01, 2012 2:30 am    Post subject: Reply with quote  Mark this post and the followings unread

ian-s wrote:
iPassenger wrote:
I think the sync needs to be -63?

Great idea by the way and i love the waveshaping.. very interesting.


Thanks, just spotted that Embarassed


It worked right on -64 for me at first and then as I was messing with it I noticed it was moving around and I figured that couldn't be right.

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varice



Joined: Dec 29, 2004
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PostPosted: Wed Feb 01, 2012 8:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey, thanks Ian for the compliment on my CEM Style VCO patch. I’m glad that you like it and that it inspired you to work on this Brutish patch. And wow! - this is very nice work!

I hope that you don't mind, but I took the liberty of tweaking your patch a little bit though. Wink

First, I noticed that the saw and pulse waves are 180 degrees out of phase, so I swapped the inversion settings on the inputs of the final mix in the pulse section. Now the sawtooth and pulse waves mix together better.

I changed the level convertor in the 2xSin section from a bipolar input type to a positive. Now this section produces a bipolar -64 to +64 output like the other sections.

I noticed that the derived triangle and sawtooth waveforms are not symmetrical. This is caused by the two sine oscillators not being exactly 90 degrees out of phase. The -63 offset setting of the sync signal into the second sine oscillator along with the rounded off peak of the first sine oscillator produces this problem. The -63 offset value is used because the ideal -64 value pushes the sync signal below the zero-plus level threshold of where the second oscillator can detect it. I added a mixer module with a feedback loop to create a “Unity + a smidge” amplifier before the phase offset module. With the feedback exp mix value set to 1, there is just enough signal boost to get the second sine oscillator to sync with the first with the phase offset value set to the ideal value of -64. Now the second oscillator is closer to a 90 degree phase shift and the derived triangle and sawtooth waveforms are more symmetrical.

I added a 4xTriangle section.

Variation 8 is set to reproduce the original sound of the Brutish2 patch for comparison.


Brutish3.pch2
 Description:
A tweak of Brutish2

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 Filename:  Brutish3.pch2
 Filesize:  2.76 KB
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varice
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ian-s



Joined: Apr 01, 2004
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PostPosted: Wed Feb 01, 2012 9:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

I don't mind at all, nice tweaks (and error corrections).

Great solution to the -64 problem, saves another constant module.
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varice



Joined: Dec 29, 2004
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PostPosted: Thu Feb 02, 2012 1:07 am    Post subject: Reply with quote  Mark this post and the followings unread

ian-s wrote:
I don't mind at all, nice tweaks...

Cheers Exclamation

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iPassenger



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PostPosted: Thu Feb 02, 2012 3:59 am    Post subject: Reply with quote  Mark this post and the followings unread

varice wrote:

I added a mixer module..


I thought about doing this but wasn't sure how much to add and wasn't sure if it would upset something else.

Nicely done dude. Smile

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Tim Kleinert



Joined: Mar 12, 2004
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PostPosted: Mon Mar 26, 2012 1:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

If anyone is interested, here's my solution to quadrature oscillators:
http://electro-music.com/forum/post-357372.html#357372
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