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INTRODUCTION
Piezo sensors are quite incredible little things. They can be used to detect the slightest variation in
pressure, force, or strain and convert that energy into a voltage. Over the past several decades they've
been used in numerous applications in several fields including the audio industry. Unfortunately, they've
developed a bad reputation for sounding "harsh" and "brittle" when used as contact microphones
in acoustic instruments. This is due to improper impedance matching and the inadequate driving
circuits that are usually used with these sensors in audio applications. Piezo sensors in themselves are
capable of a very wide bandwidth, and when used properly, can achieve excellent results. So with the
intention of getting the most out of a piezo sensor, we here at Zeppelin Design Labs have developed
The Cortado -- a balanced piezo contact microphone. This mic contains a phantom powered circuit
that properly matches the piezo sensor input impedance and drives the signal via a balanced output,
which allows for wide bandwidth (~20Hz-20kHz), low signal losses, and high signal to noise ratio.
The Cortado's circuit was originally designed by Alex Rice
alex-rice-piezo-preamplifier/) for use in his contact mic hydrophone, but it can be used in countless
other applications with excellent results. In the recording studio or on stage the Cortado can be used
on pianos, percussion, guitars or other stringed instruments. It can be used for a variety of mic and
sensor applications such as a plate reverb pickup or wooden stomp box mic. We even created a tin
can vocal microphone out of stuff we found in the trash (as pictured on this manual's cover). This is
the perfect accessory for a lofi geek or a field recording enthusiast. Let your imagination run wild...
discover what the pipes in your apartment building sound like, what bridge suspension cables sound
like, even what melting ice sounds like. Anything that vibrates or resonates with an audible frequency
can be captured by The Cortado contact mic. Several field recording enthusiasts around the web use
this circuit (or something similar) to record some pretty cool stuff. Just do a Google or Youtube search
for "contact mic field recording."
The assembled Cortado kit can take several forms, suitable for many different applications.
• Standard Contact Mic. The circuit board is shielded in a metal box and the piezo disc and cable
are also shielded.
• Tin Can Mic. Use this configuration whenever the entire Cortado will be installed inside a shielding
container, such as a tin can, garbage pail, grounded metal sculpture, etc. The piezo is attached
with a fine wire; the piezo and circuit board remain unshielded.
• Instrument Pickup. Similar to the Standard Contact Mic, but the circuit is shielded not with a metal
box but with copper tape, to reduce size.
STANDARD CONTACT MIC
(http://www.zachpoff.com/diy-resources/
TIN CAN MIC
3
INSTRUMENT PICKUP
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