Auvio Headphone Amplifier Boosts the volume and improves the sound quality of any portable audio device 3 equalizer settings give you the ability to customize the sound output Built-in rechargeable battery operates up to 11 hours per charge Ultra slim design with detachable clothing clip Gain: 8.5dB, Frequency response: 10-40,000kHz, Output Power: 150mW (16 ohms Loaded), Input Impedance: 4.7 Kohms