Donner Compressor Pedal Ultimate Comp Guitar Effect Pedal 1.TLevel ,Comp,Tone knobs allow you to dial in your desired sound.Two modes:Normal and Treble compression 2.Our circuit has been optimized according to the characteristics of the electric guitar andperforms outstandingly over the spectrumofdifferentplayingstyles 3.The compressed tone is round and smooth,full of musicality, andperfectly retains the original guitar tone 4.Whole Aluminium-alloy classic, stable and strong.True bypass provide transparent tone. 5.DC 9V Adapter power supply(not include). Working Current: 12mA Power Supply9V DC (Negative in the center). Two Modals: Normal and Treble. Level KnobControl the sound volume with effect. Tone KnobControl the tone of sound. Comp KnobAdjust the intensity of compression. Input &amp; Output JackAnalogy though 1/4 mono audio jack. LED LightLED indicator shows the working state. Full metal shellAluminum-alloy classic, stable and strong. True BypassTrue bypass for zero tone coloration.