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Nobsound B4-X Portable Dual-Mono Vacuum Tube Headphone Amplifier Balanced BLK

Mini size and unique design: built-in tube makes you have a tube amplifier which can be held by one hand, convenient to carry and can enjoy HiFi music everywhere.
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The difference between B4 and B4-X

1. B4-X is a dual-mono balanced version. Its left and right channel are amplified by independent components, and power supply, tubes, and op amp are all independent and symmetric. So the degree of sound separation is higher than B4.
2. B4-X adopts 2 groups of independent power supply(+12V and -12V) for 2 op amps, less mutual effects and can drive 300Ω headphones.
3. The circuit adopts dual op amp parallel output, with higher output power.
4. B4-X has 3.5mm and 2.5mm 2 kinds of output interface, suitable for most of balanced and standard headphones. 


Mini size and unique design: built-in tube makes you have a tube amplifier which can be held by one hand, convenient to carry and can enjoy HiFi music everywhere.
With built-in battery protection circuit: battery lets your listening feast without time limitation. It can't be turned on during charging and will power off automatically after fully charged, and charger LED will turn to green.
Full, delicate and soft sound: warmer than transistors, independent op amp and power supply inhance the SNR and degree of separation, less interplay and higher sound quality.
High-end making material and craft: using gold-plated socket, original nichicon electrolytic capacitor, original DALE resistors and precision ring resistance.

  • 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: 115 * 69 * 23 mm (L*W*D) (does not include the knob)

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: 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.
Average rating: 5.0 based on 1 reviews
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