WOLO Power Play is a complete amplifier and speaker system designed to boost the sound of any iPod, MP3, CD, or other audio device. It's compact with all solid-state amplifier circuitry built into the weather-resistant case. Connecting an audio player to Power Play is super simple. Just insert the included wired jack into the audio player's headphone outlet, then turn on the audio player. Use the player's volume control to increase sound output up to 40 watts! The state-of-the-art amplifier turns on automatically when the audio player (or compatible horn) sends an audio signal. When the signal stops, Power Play's smart technology turns off the amplifier. Comes with both 12-volt DC and 110-volt AC power adapters. Speaker measures 6.25"L x 5.25"W x 5.25"H.