FiiO X series music players X1, X3II, X5II, X7 and the DAC/amp E17K utilize a 11-pin micro USB port and may realize exclusive docking expansion functions such as amplification and charging. Utilizing TI's TPA6120A2 current feedback headphone driver, the K5 utilizes exclusive technology to lower its output impedance to a transparent <1? and increase its maximum output power to up to 1.5W@32?. Utilizing an extra current amplification stage and comprising an internal high efficiency, low noise power supply, the K5 has high current output, satisfying highly dynamic program material, and has three gain settings suitable for headphones of different sensitivities. Compared to the last-generation E-series products, the K5 has made breakthrough strides in exterior design and craft, with lower tolerances for all joints and seams, more high-quality sanded surface finish and an indented front bezel assembly for a further upgrade in appearance. When the K5 powers on/off, the docked X1, X3II, X5II, X7 or E17K will power on/off in sync, a great convenience for users and a sign of complete integration of the docked devices. Besides docking function, the K5 also has standard line inputs for other source components, and secondary dock input and USB pass through input. The K5 realizes further amplification of X3II/X5II/X7/E17K's DAC signal by directly connecting them to USB source through USB IN port and receiving the decoded line signal through the dock for amplification.(USB DAC driver installations for X3II/X5II/X7/E17K required where applicable). Besides regular RCA line output, the K5 also possesses balanced line output function when docked to the X5II or X7, and can be connected to other professional amplifier components for even better sound effect.