The Radiopool Thereglyph: a poor man's Theremin made from a talking dinosaur game
Ever since a chance encounter with the new soundscape produced by a short-circuited toy amplifier in the 1960s, Reed Ghazala has been randomly exploring audio generation in compromised electronic devices such as talking games and toys. He has written a book on the subject, teaches others to bend circuits, and has created experimental instruments for many well-known artists including Tom Waits and Peter Gabriel. His latest work started life as an educational dinosaur game – which was broken apart, rewired and rebuilt, and then introduced to a plasma globe to become the Radiopool Thereglyph.
Many of the instruments created by Ghazala began as surplus or secondhand electronic toys, games or keyboards, which were then opened up to reveal the circuitry and subjected to random audio short-circuiting to create new experimental audio generators. The technique is called circuit bending and can be undertaken by just about anyone, with or without experience in electronics.
Ghazala says that, for reasons which will become clear shortly, only battery-powered devices should be used for circuit bending experiments – anything over 6 volts may prove too hot to handle. He does state, however, that in over 40 years of circuit exploration, there has only been one incidence of a component flying across the room, and that was due solely to the accidental application of high voltage to the circuit. Using any device that requires connection to a mains outlet is actively discouraged.
The circuit bender's basic weapons arsenal is likely to contain a soldering iron, a hobby drill, some miniature wrenches, wire clippers and strippers, test leads, and some metal jeweler's screwdrivers. The more adventurous tinkerer may also have an assortment of resistors, capacitors, potentiometers, sensors, switches, LEDs and the like, to add some interesting new voices to the audio output.
The very nature of the art means that the device chosen for experimental sacrifice may become unusable, so the source device is often a cheap toy or game – those with interesting audio effects of voices are particular favorites, such as those which electronically imitate human or animal sounds.
The technique involves using a probe to discover notable sounds produced by connecting different points on the device's exposed circuitry (note: refer to the earlier warning against using mains-connected devices). The points are marked for reference and the process repeated until a library of new sound circuit locations is obtained.
Directly connecting the two points via a switch or potentiometer allows the new sounds to be turned on or off, or up and down, and the various controls can then be mounted somewhere on the front of the compromised device. Incorporating light, humidity, motion or body contact sensors into the new circuitry adds further dimensions.
For his latest audio experiment, Ghazala added some spatial sonic shaping into the build process. "I extended radio-sensitive circuit points (usually there are many) via antennae," he told Gizmag. "I placed a small plasma globe near the instrument. The globe emits radio energy, affecting the instrument's functions. Interrupting or disturbing this energy changes the instrument's voice, similar to a traditional Theremin."
Unlike a Theremin, the Radiopool Thereglyph cost just a few dollars to make and in common with all bent instruments, Ghazala began by exposing the circuitry. The shapes on printed on the circuit haven't been added, they were hidden away behind the dinosaur graphics on the original game. He then sought to create an unstable audio circuit and looked for the potentiometer setting that brought the circuit to the very edge of collapse. This made the circuit susceptible to interference, and a strong, but dirty, RF generator in the shape of a small plasma ball was introduced.
Ghazala says that moving the RF source around the former children's game and placing his hand between the circuit and the globe allowed him to locate and extend "sensitive circuit points to antenna and the metal plate (points that might change the sound of the instrument when touched or connected together)." All of the bends were discovered by accident or investigative play.
Like a Theremin, pitch and volume can be altered depending on the proximity of an object (such as a hand) to the antenna and radio plate, without actually touching the surface of the instrument. To the left of the Radiopool Thereglyph, Ghazala has placed two body contacts and a blue envelope pilot. A red logic pilot, antenna, RF "Filter For PI" plate , and speaker switch are positioned on the right.
The Filter for PI plate has also been wired to a sensitive circuit point, resulting in a variety of sounds when touched or approached by a hand interfering with the RF bombardment.
To the top of the Thereglyph are the grain, oscillation and frequency controls – the golden wheel between the grain and frequency dials controls the oscillation and was ripped from the remains of an old television set.
"The Radiopool Thereglyph might be considered the poor man's Theremin, this build cost maybe US$10," Ghazala told us. "Or it might be the contemporary Theremin, since the search for a wider, original sound palette in music is on-going. Clearly, the radiopool instrument concept will spawn a new field of played-in-the-air instruments."