Keeley Katana Boost Pedal w/ Power Supply Bundle Includes a Power Supply! Internal Power Supply Boost - turns your 9 volts into 18!!! The power supply's high voltage is what leads to this super clean headroom pre-amp. Sound like rack or studio gear! JFET design - clean tones, tube like when they overdrive or clip. Metal Film Resistors and Caps. Ultra Low Noise Design. Push-Pull Speed Knob. Gain controlled by side mount knob so it can be adjust with your feet. Pull out the Speed Knob for saturated higher gain tones