fosi audio n2 headphone amplifier 3.5mm portable amp gain & bass switch audio hi-fi earphone headset powered dual-output with lithium battery for iphone, ipod, ipad, mp3 and computers fosi audio audio input: 3.5mm headphone port headphone output: 3.5mm headphone port charging port: type-c volume adjustment mode: high precision volume knob power supply: dc 5v 1a internal voltage:±9.5v op amp: opa1642 current amp: 1w triode to tube battery capacity: 2200mah battery life: about 12h magnification (av): gain=l:3 gain=h:6.8 low-frequency gain(bass=on): +6db frequency response: 10hz-25khz snr: >100db thd+n: 0.005% headphone output impedance: 16ohm-600ohm headphone output power: 16ohm/330mw 32ohm/320mw 64ohm/298mw 300ohm/100mw dimensions: 4.17 x 2.64 x 0.55 inches (106x67x14mm) product weight: 126g