Hardware Hacking 29Amp/Driver/Contact Mike assembly into your mixer just as you would a reverb
or effect processor: connect a send bus output to your driver-amplifier input, and
bring the contact mike back to any console input to amplify and mix in the
“reverb” with the dry signal. Often flexing or dampening the object can affect the
character of its filtering of the original sound. Try this process with loose guitar
strings, Slinkies, balloons, plastic bags, vinyl records, drumheads, oil drums,
buckets of water, bowls of jello. Whether as a reverb substitute in a mixdown
situation or as part of a live performance setup, this is a cheap, easy, fun route to
unusual signal processing.
With all due respect to the First Law of the Avant Garde, this transformer
assembly does not do a very effective job of increasing the gain of a Piezo disk
used as a contact mike – its use is effectively limited to boosting the efficiency of
a Piezo driver. But don’t take my word -- try it for yourself.
You can create feedback by plugging a contact mike into the amp input and a
Piezo driver into the output, and attaching the two to the same object. Flexing or
dampening the object can affect the feedback pitch, and turn a piece of garbage
(such as the plastic bubbly packaging from toys) into a playable instrument -- an
electronic musical saw. You can configure several channels of amps, drivers and
contact mikes to send audio signals through a series of objects for multi-stage
processing; using Y-cords you can branch off and mix after each resonator-object.
Get together with your buddies and form a Piezo Band. (See Chapter 27 for more
information on matrix processing.)
Whereas size does not greatly affect the loudness of a contact mike made from a
Piezo disk, it makes a big difference when you are making a driver. If you have a
choice, get the largest possible disk and you get a bigger sound out of whatever
you are driving.
By the way, if you place your finger across an un-Dipped, bare Piezo disk while
it is being run as a driver you may experience a mild, not entirely unpleasant
electric shock. This demonstrates how high the voltage gets when jacked-up by
the transformer. To reduce distracting stimulation and protect the driver from
damage or shorting you should Dip it as you did the contact mike.
Another Kind of Driver
In addition to Piezo disks, small motors can be adapted as drivers. They are
most effective for lower frequencies, and can complement the rather tinny
quality of the Piezo. Connect the two wires of any small DC motor (one that
runs off batteries) directly to the output of your mini-amplifier. It should twitch
in response to your sound source. Sometimes coupling the body of the motor
directly to an object will be sufficient to transmit the vibration; sometimes you’ll
need to get clever with a cam on the motor shaft. Some motors work better than
others (vibrators from pagers and cell phones tend to be good) -- experiment.