I love using piezo contact mics - they're small and cheap, and can do a whole bunch of different things.
Unfortunately, they can sound pretty rubbish. In particular, they don't like long cables - all of the bass disappears, and they get quite "muddy".
I came across Zach Poff's writeup of Alex Rice's piezo preamp here, which is a great solution - phantom powered, low noise, pretty simple and a little bit of gain.
With a lot of help from Matt Venn, I've redesigned the board layout with a view to putting it inside bottle-cap hydrophones: as small as possible, and approaching circular.
The current version is always on GitHub: https://github.com/mo-seph/PiezoPreamp (Creative Commons, as per the originally shared versions)
I've had a batch of 100 boards made - if you want to buy one, email me. They'll be unpopulated (i.e. you have to solder components on it), but cheap (£1-2, probably). If there's enough interest, I'll put together some kits with components in. A Farnell parts list is attached.
Project Blog[edit]
Piezo Preamp Build and Testing
Submitted by dave on
I've just had a batch of piezo preamp circuit boards made by makepcb.com, and given them a first round of testing. Here's the results!
Piezo Boards
Second generation Piezo Preamp boards on their way
Submitted by dave on
Matt put this picture of the next round of Piezo Preamp boards up on his Flickr Stream. I've removed the piezo -ve input, and tied it to ground, which might loose 3dB of gain, but makes figuring out ground planes a lot easier. I couldn't hear the difference when I shorted piezo -ve to ground, and it makes the layout much smaller and easier.
First set of piezo preamp boards
Submitted by dave on
| Attachment | Size |
|---|---|
 PiezoParts.txt | 771 bytes |