Fishman PRO-EQ II Acoustic Instrument Preamp..... Compact outboard preamp for any acoustical instrument including bass, cello, viola, violin and guitar. This perennial favorite now features a tough new injection molded case featuring an easy access battery compartment, input trim control and advanced new electronics which provide longer battery life. Other features include:* Volume, bass, middle, treble, and brilliance sliders * AC adapter jack * Phase switch and sub-bass trim control Requires (and can be used with) any type of piezo or magnetic pickup and 9-volt battery. (Not included)