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Nobsound Little Bear B4 Portable Vacuum and Valve Tube Headphone Amplifier Stereo Hi-Fi Amp built-in battery (Silver)
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 charg 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 power amplification factor: 20 Anode essential resistance: 4000 Transconductance: 5000um / s Anode circuit: 8.5mA Grid voltage: -9VPackage include: 1 headphone amplifier 1 power supply 1 3.5mm audio cable 1 band
Performance parameters:
Frequency response range: 0-100K-0.1dB
Gold-plated input / output socket
NE5532 OP chip (you can upgrade it to a other better brand OP chip. Like BB or Muse)
Orial nichicon electrolytic capacitor
TOP HiFi Orial DALE resistors.
Precision rings resistance.
Battery: Lithium batteries, voltage: 12V, 1000mA
Charg time: 2-2.5 hours to charg full the battery
Working time: 4-4.5 hours
Output power: 450mW
SNR: 99dB
Suggest load impedance: 16-400Ω
Size: 115 * 69 * 23 mm1 (Length XWidth X Depth) (The measurement does not include the knob size.)
Q&A
Q: Right channel has static. Tried different source and headphones. No help.
A: If there is static noise in one channel, normally it is caused by the tube of that channel. Maybe it has a poor contact after the long shipping process. You can open the chasis and adjust the screw near the tube while listening(contact us and we will give you a photo with marks to help you find it). Also, there is a small possibility that the tube is broken. You can buy a 5899 tube in local shops, which is very normal to see. And we will refund you the cost.
Q: It broke just now four loud pops and it’s dead. Very disappointed.
A: Mainly because the battery is run out of power. Please charge it. If not help, please contact us.
Q: The Amp has a lot of electronic feedback/interference when a cellphone is hooked up to it or nearby. It creates popping in the headphones.
A: Vacuum tubes are easy to be interfered by devices that can trandfer siganl like cellphones, routers. Please keep the amp away from them.
Q: Won’t hold a charge, sounds like something is loose inside.
A: The charger is broken. Please contact us to get a new one.
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Category: Sound and Vision:Home Audio and HiFi Separates:Amplifiers and Pre-Amps
Location: London