AEQ-2T preamp is specifically-designed to adjust the frequencies of a bass and Treble, and allows operation of the built-in tuner without the instrument being plugged in. Purpleheart produces a rich mid range with a crisp high end. These pins really are an advantage over old-fashioned pins. Advantage™ pins are easier to take out and easier to put in than standard pins. A special bulb-shaped end makes the pin easy to grip and also prevents the pin from being pushed in too far. Best of all, with Advantage™ the pin and string stay put.