Our friend Scott is a children's entertainer and balloon artist. He asked us to electrify his banjolele, so we fitted it with a Cortado balanced piezo contact pickup from Zeppelin Design Labs. This is the same device featured in our popular Instructable, "New and Improved Tin Can Microphone." That Instructable includes detailed instructions and schematics for building your own mic from scratch, or from our kit.
The Cortado produces a balanced, buffered output signal that provides broader bandwidth, flatter frequency response, quieter signal and superior cable-driving capacity compared to typical, unbalanced piezo pickups. The XLR output from the pickup runs straight into his mixer. Phantom power from the mixer energizes the circuit. He is now independent from a microphone and free to carouse among his little fans. Here's how we did it.
What you will need:
Step 1: Build a Cortado Piezo Contact Pickup
Get yourself a Cortado balanced piezo pickup kit from Zeppelin Design Labs and follow the assembly instructions to configure it as an instrument pickup (as opposed to a contact microphone or vocal microphone). You can make it from scratch yourself too; see our Instructable "New and Improved Tin Can Microphone" for parts list and schematic. Either way, the result is a neat little circuit shielded in copper tape, with a piezo disc at one end and an XLR male connector at the other.
Step 2: Mount the Piezo and Circuit Inside the Body
Remove the sound board. With the industrial sticky tape provided with the Cortado, carefully attach the piezo to the underside of the banjo head just behind the bridge, and a little off-center toward the low strings, as shown. Use a bit of industrial Velcro to attach the shielded circuit to the inside of the body.
Step 3: Complete the Installation
Replace the sound board. In this case, the output cable slipped easily through the gap between the body and the sound board. Some instruments may require a small divot in the body to permit the cable to pass out.
The last task is to apply another little bit of industrial Velcro to the outside of the body to hold the XLR jack in place. And that's it! Scott now uses any standard mic cable to patch in his banjolele.