The Dyna Comp is a compressor that allows you to set a maximum output level and the sensitivity at which it triggers. This device can produce that punchy, clicky sound on a clean guitar that you've heard on so many pop hits. It can also equalize the volume of sustained sounds for lead work, Power: Single 9 volt battery or Dunlop ECB-003 AC adapter - Controls: Footswitch toggles the effect on/bypass (red LED on) Level Output The sensitivity knob adjusts the compression ratio (the highest sensitivity is maximum compression).