These are simply metal contacts -- drawer knobs, threaded brass light
fixture balls, etc. -- that are wired to the pair of circuit-bending points.
Each of the two circuit points goes to its own body-contact. Nothing is
wired between them at all... no switches, potentiometers, sensors... nothing.
These contacts, when mounted on the instrument's case, are meant to be
bridged by the player's body. This placing of human flesh amidst the circuitry,
now conducting electricity as surely as any other component on the board,
turns the body into a potentiometer of sorts. A variable human resistor.
Body-contact circuitry points are discovered
in the exact same way as the circuit-bending pairs... with a test lead
system. However, instead of the alligator clip test lead grasping a small
jeweler's screwdriver at each end, you do. You simply hold a screwdriver
in each hand. The search process is the same as before. The circuit makes
its usual sounds while you listen to the changes that might occur due
to the electricity now flowing into one screwdriver, through you, and
out the other screwdriver back into the circuit. If good points are discovered
they are wired, as mentioned before, each to a metallic body-contact mounted
on the instrument's case. These can then be touched by the player thereby
creating the same body-circuit as discovered with a screwdriver in each
Rarely is this electricity ever felt by
the player. In a certain 9 volt amplifier, my first circuit-bent instrument,
the body-contact system did deliver small shocks. But nothing like the
static shocks of wintertime carpet-strolling or, worse, the dangerous
shocks that befall most musicians now and again from improperly grounded
The important note here,
however, mentioned before and worth repeating endlessly, is to try these
ONLY ON BATTERY-POWERED AUDIO DEVICES OPERATING
ON AN ONBOARD BATTERY POWER SUPPLY OF 9 VOLTS OR LESS.
Trying to circuit-bend anything plugged into the "house-current" of your
AC wall outlet, directly or through an AC adapter (power supply, power
converter, "wall wart", etc.) is OUT OF THE QUESTION!!!
NEVER TRY TO CIRCUIT-BEND ANYTHING PLUGGED INTO A WALL OUTLET. Never.
Circuit-bending, in its anti-theory universe, creates electronic realities
that at times are too bizarre for its own electronics to handle. The circuit
crashes. Turning it off and back on might reset it, but it might not.
Interrupting power from the battery supply may be the only way to reset
the circuit. The batteries can be removed, of course, and put back in.
But more conveniently (and safer, since
some crashes represent the possibility of circuit damage and resetting
should be done quickly), wiring a push-button switch in the middle of
one of the two wires connecting the battery compartment to the circuit
board will give you instant access to power interruption.
Push-button switches come in two types: "normally
open" (or "N.O.", this MAKES the connection when pressed), and "normally
closed" (or "N.C.", this BREAKS the connection when pressed. You want
the "normally closed" version to break the connection between the batteries
and circuit. Mount this switch on the instrument's case where it's out
of the way and not likely to be hit by accident.
"Line" outputs, the electronic audio signals usually fed to a mixer or
amplifier, can be derived from the wires going to the speaker of the unit
you're working on. Simply solder two more wires to the speaker terminals
and solder the other ends of these wires to an output socket of some type
(1/4" "guitar" jack outlet, "RCA" phono jack, etc.) mounted on the instrument's
case. A standard cable can then be used to make the connection between
the new instrument and the other equipment. BUT...
Use a test amp first! This can be an inexpensive,
low-watt amp, bought 2nd-hand and driving a small non-critical speaker.
Such a system can be found for $20 at Goodwill & Salvation Army outlets,
yard sales, pawn shops, the classifieds, etc. As long as the unit has
a standard line input to plug into ("tape", "tuner" or "accessory" phono
jacks, usually), it will serve the purpose.
The idea here is that unknown signal levels
will be sent into the amp during various circuit-bending experiments.
This might risk the well-being of the amp or speaker if certain precautions
are not followed. So, an expendable amp/speaker is best.
Be sure to have the amp turned all the way
down when first determining if the speaker-derived line output will work.
Connect the extended speaker wires to the amp's line input. This can be
done by clipping one end plug from an input cable (like a standard phono
cord) and stripping the insulation off to expose the two wires within.
Connect these two wires to the wires you soldered onto the speaker terminals.
With the other end plugged into the amp's line input and the new instrument
making its sounds, slowly turn up the amp.
If the sound from the amp is louder than
the usual line-input signal from a standard source (tape deck, guitar,
synth, etc.), the new instrument's output level, coming from the speaker
wires, may be too high or "hot". To tame this output a resistor of the
correct value can be soldered between one of the instrument's speaker
terminals and then to the wire that leads to the amp. Better yet, a miniature
potentiometer, called a "trimmer", can be soldered in place of the aforementioned
resistor. The trimmer can then be adjusted to set the instrument's output
level precisely. Experiment with trimmer values around 5k, but have higher
& lower values at hand as well.
Creating line outputs is very important in
circuit-bending. The small speakers that most of the circuit-bendable
devices come supplied with cannot come near to reproducing the frequencies
that the electronics are creating, even before circuit-bending. And after
circuit-bending, frequency response can be mind-boggling since clocking
speeds are commonly altered. This results in ranges of frequencies that
can surpass human hearing at both the high and low ends. A hi-fi reproduction
system can illustrate the power of the circuit-bent instrument's voice
in wonderful ways. Also, line outputs open the circuit-bent instrument's
voices to signal processing; reverb and EQ, namely. These standards of
the electronic music studio can expand and sharpen the circuit-bent instrument's
voice, as with the voice of any electronic instrument. These signal-processing
systems are the counterpart of the acoustic instrument designer's adjustments
of body shape for tone and resonance refinement.
Along with creating new circuit
paths, as discussed, replacing components with others of a different style
or value will also bend circuits in wonderful ways.
For example, a standard resistor on a circuit
board can often be replaced by a potentiometer or photo cell (both are
variable resistors). If this is a resistor that had set the pitch of a
voice (very common), that voice now becomes tunable, changing frequency
with the turn of a dial or the shifting of light. As would follow, a potentiometer
can be replaced with a photo cell as well (i.e., the pitch dial/potentiometer
of an oscillator could be replaced with a photo cell providing theremin-like,
hands-in-space frequency control).
Motion sensors such as mercury, boxed ball,
and "tilt" switches can be wired into small devices for dance or gesture-driven
Two solutions are at hand in the instance
of limited space for the mounting of new controls, a predicament the circuit-bender
will eventually run into. Circuitry can be completely removed from its
original housing and installed in any number of new enclosures. Or, a
remote control panel containing the new switches and dials can be constructed
and run into the original housing by means of braided or ribbon cable,
a type of self-contained color-coded multi-conductor wire.
In the instance of limited space to solder
to, as in short component leads, IC pins, etc., study the circuit to see
if the area you wish to solder to is connected to an easy-to-get-to trace
on the board. This is often the case. A hard-to-get-to resistor lead,
for example, within the circuit might connect with a printed-circuit trace
that emerges, with full access, on the other side of the board. Soldering
to a trace that connects to the desired component elsewhere is the same
as soldering to the component lead itself. This technique can be a real