I'm a field recordist and thus use a variety of DIY contact microphones and piezo based contact microphones and hydrophones. The mics on the cheaper side don't come with their own impedance adaptor or preamp.
A piezo mic usually has an impedance that is a lot higher than a standard microphone. Without an impedance adaptor, one usually gets thin and weak signal (the impedance mismatch works as a high pass filter).
The Bigamp Piezo solves this by handling 7.5 Mega Ohm at the input side, which is enough for practically all piezo elements out there, and more than many similar impedance adaptors. This way you get a lot more out of your piezo based microphone, and even makes a DIY contact microphone sound full and proper.
Unfortunately, it is not the quietest of impedance adaptors I have tried, but you won't hear it on all but the quietest of sounds. Because it also works as a tiny preamp (which seems to provide more than the stated 3db of amplification), you don't need to deliver as much gain to your microphone, which seriously helps in offsetting additional noise.
As a bonus, the fact that it makes a signal balanced makes that you can handle long cable runs.There also very sturdy. My bigamp piezo's have travelled everywhere with me, from the tundra to the rainforest and they look it (a bit), but they still work great.
The small form factor also makes them very easy to use, even when on the move.
Recommended for all your contact mic (and diy hydrophone) experiments.
