Most DIY enthusiasts who are interested in audio gear are familiar with the standard “tin can mic” (or variations thereof), in which a piezo disc is taped onto the bottom of a tin can and then plugged into a high impedance voltage amplifier, like a guitar amp. These types of microphones are nice because they are so easy to make, but they are quite limited in most other areas, including bandwidth, microphonics, signal to noise ratio, impedance matching, and cable driving. These issues usually result in a very noisy and brittle sounding microphone. So out of frustration with these limitations, we created the “New and Improved Tin Can Mic” -- the standard tin can mic taken to the next level! Using common household items along with a simple circuit, this mic has a tonality similar to the original tin can mic (for all you Tom Waits fans), but improves upon nearly every other feature. The heart of the mic is the Cortado contact microphone which consists of a tiny phantom powered circuit which creates a balanced output from a piezo disc. This circuit provides a high impedance to the piezo disc, but also provides a low output impedance to match a mixing console input. By properly matching the input and output impedances we achieve a much wider bandwidth than the original tin can mic. The fact that the output is balanced provides a very high signal to noise ratio, and it allows for a long microphone cable to be used without signal degradation.
Another improvement we've made to the standard can mic is that we've added a styrofoam cup as a mechanical resonator. The cup floats inside of the tin can via rubber bands, which helps keep microphonics and feedback (in live performance situations) manageable. Another benefit of using a floating mechanical resonator is that it's easy to mod the mic to change its tonality. We can easily alter the resonant frequency of the mic by changing the mass of the cup, or we can emphasize a higher resonant harmonic by adding a vibration node to the cup.
The Cortado contact mic in itself is capable of a very wide, flat bandwidth which is suitable for use as a contact mic in lots of recording situations, on anything from a piano soundboard to a plate reverb. The circuit is fairly simple and can be built from common parts using the schematic given in this Instructable. As a service to the DIYer, the Cortado is offered as a kit from Zeppelin Design Labs. The kit includes the circuit board as well as all the other parts (including matched FETs) to make the Cortado into a variety of configurations for different applications. For this instructable, we will document the construction of the Cortado kit for its application in the “New and Improved Tin Can Mic.”
Every track in this song was recorded with only the Cortado contact mic. The vocals were recorded using the Cortado configured as the "New and Improved Tin Can Mic" described in this Instructable. For those interested, the band in this recording is Ami Moss and the Unfortunate. Recording notes and more info can be found here.
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