View source for Using a piezo element as a contact mic

If you want to record or amplify the sound vibraitons from a surface, you can use a piezo element as a contact mic.

[[File:piezo.png|200px]]

However, do not hook them up directly to other audio equipment!
There can be harmful high voltage spikes.

A simple and o.k. preamp to use is [http://makezine.com/2011/12/20/collins-lab-diy-contact-mic/ this one from collins lab]

If both sound quality and equipment safety is not your greatest concern, a very simple solution is [http://www.zachpoff.com/diy-resources/simple-contact-mike/ this one]

If you want to hook it up directly to a speaker:

[[File:Piezo&LM386.jpg]]
The 220 resistor can be varied, for more ore less gain.
The 3.3M can be replaced with a 1M resistor which is easier to find..