FiiO E17K (E17) Alpen 2 Portable Headphone Amplifier USB DAC with Extreme Audio 3.5mm Stereo to RCA Cable The FiiO E17K is a compact portable USB and coaxial digital to analog converter as well as an analog headphone amplifier for driving your favorite headphones. SA9027 USB receiver chip, the device can be used as an external sound card for computers with support for up to 96 kHz 32 bit files and DSD decoding (with ASIO driver and SACD plug-in). For I/O the unit features a Micro-USB socket for charging, data exchange, and the option of docking with future desktop products. It also features a coaxial digital input with support up to 192 kHz/24-bit PCM input (via the included 3.5mm to coaxial converter plug), as well as a dual-function line in / line out for maximum convenience. Frequency Response: 20 to 20,000 Hz Headphone Impedance: 16 to 150 ohms