MXR M 81 Bass Preamp, Combination of Preamp and DI Box for Electric Bass, Separate controls for input and output, Parametric mids, Pre / Post switch determines whether the EQ will take effect before or after the Direct Out, Controls for Output, Mid Freq., Input, Bass, Mid and Treble, Pressure switch for ground lift, 2 Internal switches control the use of the Direct Out and a True Bypass can be switched, Status LED, 6.3 mm Jack inputs and output, XLR output, Operates on 9V battery or optional AC adapter (article nr #409939#, not included)