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furious contact microphone assembly

There are too many posts on alt.noise concerning how to build contact microphones, and to myknowledge, nobody ever posted a page like this in response. Plenty of bad advice out there...

Hopefully this page is a little more useful than some of the responses I have seen over theyears. If you actually follow these directions, please e-mail me and let me know where they'reflawed/lacking.

This is one way to put together a contact microphone. It is not the best way, but the end resultis pretty satisfying. And it doesn't cost much (once you have a soldering iron).

Here are a couple ofinteresting ideas on improving this design that were sent to me.Radio Schlock parts list:

Piezo Transducer 273-073ATwo conductor inline 1/4" PhoneJack 274-340A24AWG "audio cable" 2conductors plus shield part no.278-514Heat shrink tubing

The functional element - a piezo electrictransducer is commonly used as a speaker.Different models come in different plasticpackaging, each more annoying to excise thanthe other. Do not buy the 12VDC versions -they cost more, and you'll end up throwingaway the drive electronics anyway.

Start by breaking off the two plastictabs on the sides of the casing with apair of pliers.

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Next, take pliers and 'crunch' the back panelaround the circumference. Do not 'crunch' theinput leads. Do not 'crunch' hard enough tomash the PZT.

Use a thin edge (screw driver, xactoblade etc.) to gently pry the backplate off of the packaging. Careful

not to bend the visible brass PZT disc

The back is off. Now, take the pliers and gripthe 1/8" top edge of the plastic cylinder. Bendradially outwards. Repeat all the way around

the housing cylinder. This should free up thePZT. Gently pry it out of the casing.

There it is, your very own $1.50contact microphone. It needs to be

connected to something...

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Cut off about a 3 foot length of wire and stripthe ends. The ground wire needs to be twistedtogether (far left of the three).

Twist one of the wires together withthe ground wire, and tin the ends ofthe wire with solder. Do this on oneend only. On the other end of thecable, cut off the ground wire so that

only the two insulated wires areexposed.

Your cable ends should look something likethis:

Unscrew the housing from a 1/4"jack. Solder the ground wire to thelarge contact, and the 'signal' wire(white) to the contact point (seebelow). Careful not to melt the

cheapo connector. Also, be carefulto make sure your solder wycks onthe surface of the contacts, meaningthat you have a good solder joint.

Clip off any excess wire that protrudes from the

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contact points (the white wire goes through thea hole, cut off the excess once it is solderedinto place).

Tin both wires on the other end of thecable. Put two short pieces of heat-shrink tubing on the PZT leads.Solder wires together. I prefer to dothis by lining up two tinned leads side

by side. Some people prefer to twistthe wires together before tinning andsoldering.

Pull the heat shrink tubing back over the solderjoints. Use a hair dryer to shrink the tubingover the joints. You're done. Go stick your

contact mic on something, and call it art.

Mounting the microphone is easy - I use doublesided tape to affix the element to whatever Iwish to probe. It is a VERY good idea to tapethe grey cable down to the object for strainrelief. If you don't do this then one good tugand you'll be e-mailing me asking about

soldering to the element itself. This is a pain inthe ass, but can be done - usually with someminor damage to the element.

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