The go anywhere Headphone Amp delivers a musical quality and attitude that defines the spirit of Electro-Harmonix. As uniquely musical as it is portable, the ultra-light Electro-Harmonix Portable Headphone Practice Amplifier lets you practice as loud or funky as you want without waking up your neighbors. They are designed specifically for musical instruments. You can now get the character sound of your live instrument with this amplifier. It also handles high gain pedal board input delivering your favorite tone and definition. They are super quiet with a battery included while headphones are not included. You can insert the 1/8-inch stereo plug from your headphones into the output jack. The volume knob sets the output level. You can connect the output of your instrument or effects pedal to its 1/4-inch input jack.