Zeppelin Design Labs offers the Cortado, a piezo contact mic (or pickup) with a balanced output signal, properly impedance-matched to your mixing console or recording device. The piezo runs into a little phantom-powered circuit that makes for much wider bandwidth, flatter frequency response and superior cable-driving capacity compared to your usual unbalanced piezo pickup. It's available as a highly-adaptable DIY kit, or ready-to-use configured as a contact surface mic.