Genz Benz Shuttle Series 900 Watt Bass Amplifier (STL9.0) Ultra Lightweight 4 lb Design 500W/8 ohms; 900W/4 ohms Analog 12AX7 Tube Preamp Digital SMPS (Switch Mode Power Supply) High Current Class D Amplifier Patent Pending P.H.A.T topology Active EQ w/Parametric Mids 3-Band Signal Shape Circuit (Footswitchable) Signal Mute Switch (Footswitchable) Extended Range Input Gain Structure for Active/Passive Sensitivity Q1BZ1