MXR Micro Amp (M-133)This device adds a preset amount of gain,using a single control. With a guitar,this lets you boost your signal for leadwork, adjust between two different guitarswith unmatched output (i.e., humbucker tosingle coils), or it can supply apermanent boost in a long effects chainwhere signal drop off is a problem.Power:Single 9 volt battery or Dunlop ECB-003 ACadapterControls:Footswitch toggles amp on/bypass (red LEDindicates on) Gain knob adjusts totaloutput volume when micro amp Is engaged