FiiO A3 (E11K E11) Kilimanjaro 2 Portable Headphone Amplifier with Extreme Audio 3.5mm Stereo to RCA Cable FiiO E11K (A3) Portable Headphone Amplifier is designed for mobile Hi-Fi listening applications and is compatible with a wide range of headphones, earphones, and other in-ear-monitoring systems. utilizes an OPA1642 as the voltage pre-amplifier and an AD8397 power amplifier to deliver a maximum power output of 450 mW at 16 (270 mW at 32 ) with a frequency response of 20 to 20,000 Hz, a signal-to-noise ratio of equal to or greater than 108 dB, and a T.H.D. of less than 0.004% into loads between 16 and 150. For controls, the amplifier includes a low-high gain toggle switch, a rotary volume control, and a fully discrete bass boost circuit that can be bypassed to decrease interference and lower the overall noise floor Frequency Response: 20 to 20,000 Hz Headphone Impedance: 16 to 150