Martin E1 

The Martin E1 includes controls for Volume (to control overall output of the pickup), Tone (to control the bass and treble response of the pickup), and Phase (to reverse the phase 180 degrees, which can decrease feedback and increase bass response). It also includes a built-in chromatic tuner that does not need an instrument cable to be used. When the chromatic tuner is engaged, all output will be muted for silent tuning.