Nobsound Tube 6N11/12AU7 HIFI Stereo Buffer Pre-AMP Preamplifier Inspired by Musical Fidelity X-10D circuit; Using classic triode amplifier circuit In Class A station the voice effection is best. All the series audio channel use Wilma coupling capacitance The Output using the deep negative feedback circuit,distortion reach to 0.008%.frequency response reach to 10HZ-100KHZ,Output impedance is dropped to 200ohm. ADD the independent power supply filter,Make the background more quiet, higher signal-to-noise ratio. The tube have 12AU7 or 6N11 two versions. We will send it at random; Input Voltage: AC 110v/50-60Hz; Size: 230mm X 310mm X 90mm