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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Filter White Noise to get Pink Noise
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roglok



Joined: Aug 28, 2010
Posts: 202
Location: uptown

PostPosted: Mon Jan 02, 2012 10:59 am    Post subject: Filter White Noise to get Pink Noise Reply with quote  Mark this post and the followings unread

Hi all,

After lurking around for years I finally got around to writing my first post - and of course it's a question Smile

Although I'm no electronics expert, I have started to build a +/-12V modular synth and already finished a few modules. I am planning to build Ken Stone's Real Ring Modulator and want to add a really simple noise source to fill up the remaining panel space.

Ray Wilson's simple transistor based circuit caught my eye, but I would like to add an additional noise colour (preferably pink). How complex is it to derive pink from white noise? I have considered a simple RC low pass filter to create brown noise, too...

Here's the original schematic:
Posted Image, might have been reduced in size. Click Image to view fullscreen.

Any suggestions and, if possible, schematics are appreciated!
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roglok



Joined: Aug 28, 2010
Posts: 202
Location: uptown

PostPosted: Mon Jan 02, 2012 1:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

I found something. According to this article, pink noise is produced by applying a -3dB filter to a white noise source:
http://www.decodesystems.com/pink-noise.html

Would it work to tap pin 7 of the op-amp in Ray's schematics and simply add this circuit?

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blue hell
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Joined: Apr 03, 2004
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PostPosted: Mon Jan 02, 2012 1:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

roglok wrote:
Would it work to tap pin 7 of the op-amp in Ray's schematics and simply add this circuit?


It should, yes.

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Jan
also .. could someone please turn down the thermostat a bit.
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Captain Biscuits



Joined: Jun 11, 2010
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Location: Northampton, UK

PostPosted: Mon Jan 02, 2012 2:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

The schematic for Ray's Noise Cornucopia is probably worth a look. It uses pretty much the same noise source and then uses that noise (the output of pin 7 as you say) to create several different noises. He describes his Low Pass White Noise as "pinkish" so it might depend on just how pink you want your noise to be Smile
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roglok



Joined: Aug 28, 2010
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PostPosted: Mon Jan 02, 2012 3:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks guys!

Quote:
it might depend on just how pink you want your noise to be


Pinkish sounds alright to me Smile Although it requires another IC, I'll probably go for the Noise Cornucopia filter since it throws in some extra high pass noise..
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fluxmonkey



Joined: Jun 24, 2005
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Location: cleve

PostPosted: Tue Jan 03, 2012 2:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

noise cornucopia is my fave analog noise source, well worth the build. but if you want simpler, there's an even older MFOS design buried in The Cave:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

i've built it, i like it. home-etchable PCB layout is there, too

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roglok



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PostPosted: Tue Jan 03, 2012 4:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

ah, now i see... the filter network should be in the feedback path of the amp.

anyway, i have already created a stripboard design for the first part of noise cornucopia (white, lp + hp noise), so i'll probably stick with that. the analog noise is planned as an addition to the cgs digital noise generator, which already features random gates, so the only thing a full build of noise cornucopia would add is grainy noise.
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