Robust Cajon Pickup/Preamp Wide range tone control High quality signal output. The MEINL Cajon Preamp is a robust cajon pickup/preamp that can be tuned to the particular sound characteristics of any cajon. A tone control with a wide range allows you to find your perfect mix of bass and treble. Use the phase switch to change the overall timbre. Placing the tranducer on the inside top panel of your cajon near the playing surface results in the best sound.