SMSL SH-9 Balanced Headphone AmplifierSMSL SH 9 Balanced Headphone Amplifier Innovated designed with all discrete output stage circuit, which has ultra low distortion, as low as 0. 001%, and the output current for amplification. A fully balanced circuit design from inputs to outputs. Use electronic volume control to ensure the volume level are the same for left and right channel. Audio grade component and HIFI coupling capacitors. Protection with mute circuit and protection circuit, for