FiiO E1 Portable Headphone Amplifier, Sound Booster With Volume Control - For Apple iPod, Nano, Classic, Video, iTouch And iPhone 3G/4 Designed for iPod-iPhone, (Not For iPod Shuffle), Improves the sound quality with the line out from the dock Built in high quality Texas Instruments's headphone amplifier Integrated Circuit High power output to drive high impedance or low sensitivity headphones or earphones Easy control of the playback of the iPod/iPhone while the player stays securely in your pocket Powered by the iPod/iPhone, built-in clip, you can clip it onto anything,plug and play