Flickinger Petal Pusher Buffer and Boost Pedal - White  From Flickinger

The Flickinger Tone Boxes Petal Pusher is a line buffer, line driver, and boost pedal all in one compact enclosure. 

KNOB:
This controls the overall output volume of your Petal Pusher. Be aware, this device is capable of a very large volume boost to your signal. Make sure not to overload other effects or your amplifier! At full counter-clockwise position, your Petal Pusher acts as a unity gain line buffer to help negate impedance mismatches within your signal chain. Put the effect at the beginning or end of your signal path for this purpose. As you turn the control clockwise, you get a subtle transparent boost to your signal. This is great for eliminating signal loss due to long cable runs or having many true-bypass pedals. At full clockwise, the Petal Pusher can force other pedals or your amp into greater saturation and sustain. Or you can use it as a lead boost! 

9V:
Your Petal Pusher uses a 2.1mm (BOSS type) 9V AC adapter. Make sure the center pin is negative. Using the wrong polarity will not harm the pedal, however it will not function.