[Product Information]

B4 is a tube headphone amplifier， the sound feels warmer than transistor products. It has built-in battery protection circuit. It powers off after is is fully charged automatically， the charger LED turn to GREEN. Can realize the use of human intelligence. Else . When you charging the battery. This B4 amplifier can not turn ON until you pull out charger interface. because we design it work like that， just make battery safe.
Direction for use: 1. .Ipod / Cellphone / MP3: connect to B4 INPUT socket by 3.5 to 3.5 audio cable. 2. .Switch & volume control share the same knob: Please rotate the VOL Knob to the left， then plug in your Headset / earplugs to HEADPHONE socket. 3. .Turn on your media player， and tune VOL knob from left to right till the volume is suitable. 4 .Turn off: When you do not want to listen， please take off the headphone， turn down the volune till the machine is powered off.
Notice: when using B4 with your cellphone， if you heard some "zhi ~ zhi" noise in your headphone.Probably it is the inteference from your cellphone such like WIFI or 4G signal，which intefer the tube，then cause the noise into the sound.That's normal. Because there are microphone effect with all tubes.To avoid the noise，please keep your cellphone as far as possible from the B4.
Reference data for 5899: (A type Amplified state): Heater voltage: 6.3V Heater current: 300mA Anode Voltage: 100V Cathode resistor: 220 Ω power amplification factor: 20 Anode essential resistance: 4000Ω Transconductance: 5000um / s Anode circuit: 8.5mA Grid voltage: -9V
Package include: 1× headphone amplifier 1× power supply 1× 3.5mm audio cable 1× band