Massdrop O2 Objective 2 Headphones Amplifier Description: Condition: New Opened BoxContents:Massdrop O2 AC Adapter 120VInput: RCA Output: 6.35 mm Power: AC adapter (included, select 120V)Gain: 2.5x and 6.5x / 1.0x and 3.3x (select your configuration)Volume potentiometer taper: Alps 15A or 3BFrequency response: +/-0.1 dB (20 Hz–20 kHz)THD at 1 kHz, 150 ohms: 0.0016%IMD CCIF at 15 ohms: 0.001%IMD SMPTE: 0.002%Noise (ref 400 mV): -105 dBMax output (33 ohms): 613 mWMax output (150 ohms): 355 mWMax output (600 ohms): 88 mWOutput impedance: 0.54 ohms