Little Bear B4 B4-X

Little Bear B4 Dual Tube HiFi Audiophile Portable Headphone Amplifier

The difference between B4 and B4-X

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.

B4-X adopts 2 groups of independent power supply(+12V and -12V) for 2 op amps, less mutual effects and can drive 300Ω headphones.
The circuit adopts dual op amp parallel output, with higher output power.

B4-X has 3.5mm and 2.5mm 2 kinds of output interface, suitable for most of balanced and standard headphones.

Description

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’t turn ON until you pull out charger interface.  because we design it work like that, just make battery safe. 

Specification

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)

Original nichicon electrolytic capacitor

TOP HiFi Original DALE resistors.

Precision rings resistance.

Battery: Lithium batteries, voltage:12V, 1000mA

Charging time: 2-2.5 hours to charging full the battery

Working time: 4-4.5 hours
Output power:450mW
SNR:99dB
Suggest load impedance :16-200Ω

Size>115*69*23 mm1(Length XWidth X Depth)(The measurement doesn't include the knob size.)
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

B4 headphone amplifier

Charger (work volrage:110~240V, output voltage 12.6V, Dc socket: 3.5/1.35)

2 x straps

3.5 to 3.5 audio cable

Little Bear B4-X Dual-Mono Balanced Tube Headphone Amplifier

Description

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.

Spercification

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)

Package

B4-X Headphone amplifier

Power supply

3.5mm audio cable

2pcs band

Notice: when using B4-X with your cellphone, if you heard some "zhi ~ zhi" noise in your headphone. Probably it is the interference from your cellphone such like WIFI or 4G signal, which interferes 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.