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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
Audio files: 14
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Posted: Sat Mar 24, 2012 3:29 pm Post subject:
Photophonobservotron MK1 Subject description: a photo-theremin and some notes about 4093 oscs and heterodyning |
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This is a really simple device, only using a 4093 chip and some diodes, but it makes a hell of a lot of fun sounds
The key is heterodyning via one of the NAND gates.
Previous sound machines I have seen made with with a 4093 chip use each oscillator to gate the next. This is good for a start however, using that method you miss out on a lot of interesting phasing and timbral effects. For example if a 4093 oscillator is gated with a higher frequency than it is oscillating at, then only the gate frequency gets through to the output. The gate must be less than half the frequency of the oscillator which it is gating in order for it to activate/de-activate the oscillator and still allow it a burst of pulses between off/low periods.
I found that (for me anyways) it's much more interesting to combine two oscillators via one of the other two-input NAND gates on the chip, just listen to the sample! There is much more spacey and rich sound than you get from a chain of oscillators gating each other.
The diodes in the schematic act as an OR gate and the oscillator connected via the switch is an LFO, but it also goes into the audio range. This arrangement is used to gate the signal from the central NAND gate, giving you the bleepy sounds you hear at the very start of the sound sample and intermittently throughout it aswell.
I'll get some photos of the finished device soon, I made it pretty
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The output stage is the pulldown resistor for the diode OR gate, it may be an idea to keep the volume pot below 100k, the resistor above the volume pot is to lower the voltage to optimize it for use with an amplifier expecting a very low voltage- like a g |
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12.31 KB |
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8728 Time(s) |
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Gets really good around half way |
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photophonobservotron MK1.mp3 |
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3.25 MB |
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1174 Time(s) |
_________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
Green Dungeon Alchemist Laboratories |
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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
Audio files: 14
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tjookum
Joined: May 25, 2010 Posts: 360 Location: Netherlands
Audio files: 26
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Posted: Sun Mar 25, 2012 2:25 pm Post subject:
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nice one! Looks great and the sound is really impressive. _________________ There he goes. One of God's own prototypes. A high-powered mutant of some kind never even considered for mass production. Too weird to live, and too rare to die.
Hunter S. Thompson
movies
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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
Audio files: 14
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corex
Joined: Mar 02, 2010 Posts: 114 Location: Las Vegas
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Posted: Mon Mar 26, 2012 10:14 am Post subject:
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Sounds and looks nice, and the schema is simple too!
Are those test tubes? What's the glass over your LDRs? |
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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
Audio files: 14
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Posted: Mon Mar 26, 2012 11:08 am Post subject:
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Yup I cut some test tubes in half with the hot-water bottle cutting method to construct those hyper-proximity field deflectors, preventing damage to the light sensors and looking snazzy too! _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
Green Dungeon Alchemist Laboratories |
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corex
Joined: Mar 02, 2010 Posts: 114 Location: Las Vegas
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JingleJoe
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
Audio files: 14
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Posted: Tue Mar 27, 2012 10:19 am Post subject:
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SCIENCE!
A note on construction of the LDR holders:
As backing I used card painted black and cut larger than the tube diameter, I made two small holes for the LDR leads, then hot glued the LDR in place.
In hindsight I would have liked to crimp the leads to the card with copper wire or staples as when soldering, the hot glue melts. As long as you do one lead at a time, with a delay to allow the glue to set again, then it works okay.
I glued the tubes in place at the back/inside side with a liberal amount of epoxy which allowed the LDRs mounted on card to be affixed by epoxy aswell. _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
Green Dungeon Alchemist Laboratories |
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