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stefanv
Joined: May 09, 2009 Posts: 17 Location: Moorefield, Ontario, Canada
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Posted: Wed Dec 23, 2015 7:43 pm Post subject:
PAiA 3790 Stereo Chord EGG Remake |
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I recently became interested in the PAiA Chord EGG, a random flowing chord generator based on a 1970s top-octave generator chip. My application was a source of music in an alarm clock, but of course neither the kit nor the TOG chip are available any more.
I decided to undertake a redesign of the Chord EGG, using only off-the-shelf commodity ICs (such as quad op-amps). I stuck to the original architecture wherever possible, but started from scratch in other areas. The end-result is a Chord EGG sound-alike. It uses the same number of chips as the original (5), but they're all the same (TL074 quad op-amps).
I built it on a 7.7" x 3.2" piece of stripboard. If anyone's interested in building their own, there should be enough detail in this article I wrote:
Chord EGG 2015: Remaking a PAiA Classic
There's an audio sample at the end of the article too. _________________ Stefan Vorkoetter
http://www.stefanv.com |
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varice
Joined: Dec 29, 2004 Posts: 961 Location: Northeastern shore of Toledo Bend
Audio files: 29
G2 patch files: 54
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Posted: Wed Dec 23, 2015 9:45 pm Post subject:
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I built a PAiA Chord EGG kit (and many other PAiA kits) back in the 70’s. I still have it Oh, such fond memories... It is good to see that you are reviving this classic in analog hardware
For those with a Clavia Nord Modular G2 or the free G2 Demo software, check this out:
http://electro-music.com/forum/topic-22930
And this topic:
http://electro-music.com/forum/topic-22782.html _________________ varice |
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DES
Joined: Feb 28, 2003 Posts: 794 Location: New Jersey
Audio files: 8
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Posted: Thu Dec 24, 2015 11:08 pm Post subject:
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I believe the original used the Mostek Top Octive chips, right? I still have 4 or 5 of those lying around....might be fun to cobble a chord egg together...
Can you select the key or is it totally random? _________________ Dave
www.davesneed.com |
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stefanv
Joined: May 09, 2009 Posts: 17 Location: Moorefield, Ontario, Canada
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Posted: Fri Dec 25, 2015 10:16 am Post subject:
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Yes, the original used Mostek (or equivalent chips). I'd hang on to those as a retirement fund.
In the original EGG, the chip is driven by an RC oscillator. I would be easy to make it tunable to let you select the key. But the circuit itself just cycles between the I, IV, and V chords (two inversions of the first) of whatever key it's tuned to.
Of course, you could have a bank of jumpers connecting the TOG to the rest of the circuit, letting you, for example, rewire it for a minor key.
In my remake, the oscillators are individually tuned, so of course it would be possible to retune to a minor key. _________________ Stefan Vorkoetter
http://www.stefanv.com |
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