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Introducing the Wrongamin, wrong sound generator.

The Wrongamin is an easy and cheap to build sound maker that I designed to create a range of wrong sounds. From dusty old record crackles to a deep hungry animal growl heard through several out of tune AM radios. 
 

 
It uses three LDRs (Light dependent resistors) to change the pitch of three very high frequency oscillators. What is interesting about this machine is that in normal operation we don’t hear the oscillators directly as they are tuned far above the highest sound a human can hear. What makes this instrument audible are the interactions between the three oscillators which project downward into the realm of our perception. Some Theramins operate on a similar principle and this is where the Wrongamin gets its name.
 

“A Theramin can sound very wrong in the wrong hands, a Wrongamin sounds wrong in everyones hands!”

I have drawn up a schematic for the Wrongamin (click above for full size version). As you can see this is quite a simple circuit. You can build it using just one integrated circuit (40106B or 74C14) 3 x LDRs, 3 x signal diodes, 4 capacitors, and 2 resistors. If you want to get fancy and have more gain to drive a line level input then add one more IC and a hand full of components. (See Wrongamin Pic above for all parts needed).

NOTE: if you want to leave out the amplifier section: connect A (oscillator out) directly to input of the Output Section – easy. I have not actually tested this configuration but I have no reason to believe it won’t work. I included the amp section because I want to boost the signal a lot to drive my sound-card’s line input.

Here is a video of the Wrongamin’s first test…

Hope you enjoy, Let me know if you make one!

Leafcutter John.

Tags: AM radio, CMOS, leafcutter john, noise maker, Synth, Synthesizer, Theramin, Wrongamin

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