Alesis AmpCase Headphone Amplifier Case for iPhone 4 & 4S

The Alesis AmpCase Headphone Amplifier Case for iPhone 4 uses the iPhone's 30-pin dock connector to transmit high quality audio with a wider dynamic range than you would get via the standard headphone jack. The case features a convenient volume control wheel as well as a mini USB jack so you can charge your iPhone without removing it from the AmpCase. Thanks to its slim profile, the AmpCase adds little bulk to your iPhone so you can keep it attached at all times.