Little Bear B4-X Portable Dual-Mono Vacuum Tube Headphone Amplifier; Mini Balanced Audio Headphone Amp B4 Upgrade Version

Parameters:
Tube: USA RAYTHEON JAN5899 ×2
Op amp: NE5532*2 (can be upgraded )
Lithium Battery: 12V, 1000mA
Charging time: 2-2.5 hours
Working time: 4-4.5 hours
Output power: 450mW
SNR: 105dB
Suggest load impedance: 16-300Ω
Output: 2.5 balanced Jack*1, 3.5mm Jack *1
Size (L*W*D): 115*69*23 mm / 4.5*2.7*0.9 in (without knobs)

Packing List:
1× headphone amplifier
1× power supply
1× 3.5mm audio cable
2× band

Notice:
When using B4-X 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 intefers the tube and cause noise. That's normal. Because there are microphone effect with all tubes. To avoid it, please keep your cellphone far away from B4-X.

Q&A:
Q: Tried different source and headphones, but the right channel still has static.
A: Maybe the tube has a poor contact after long shipping process, open the chasis and adjust the screw near the tube while listening (if you cannot find it, contact us and we will give you a photo with marks to help you). Maybe the tube is broken, you can buy a 5899 tube in local shops. And we will refund you the cost.
Q: It broke just now four loud pops and it's doesn't work now.
A: Mainly because the battery is run out of power. Please charge it. If no help, please contact us.
Q: The Amp has a lot of electronic feedback/interference when a cellphone is nearby. It creates popping in the headphones.
A: Vacuum tubes are easy to be interfered by devices that can transfer siganl like cellphones, routers. Please keep the amp away from them.
Q: It cannot be charged, something is loose inside the charger.
A: Maybe the charger is broken. Contact us to get a new one please.