K&K Hot Spot External Sound Transducer 1/4 Inch Input Pick-Up. The K&K Hot Spot is a small, universal, entry-level transducer with a better than entry-level sound. This single-head pickup is only 1/2" in diameter and 1/32" thick, making it perfect for smaller instruments and a wide variety of applications. The Hot Spot comes with double-sided adhesive film and self-adhesive jack mounting clip. Its frequency range is close to perfectly linear and the output signal is very high for a piezo this small.