What's the main difference between the previous B-2?
Narrower bandwidth (2Mb only) provides better anti-interference ability.
Lower power consumption, longer battery time. (7hrs working per charge.)
Auto Off: The TX will turn off automatically since there is no input signal for 10 minutes, then the RX will also turn off after another 10 minutes.

NUX B-2 PLUS
The NUX B-2 PLUS is a pocket-size 2.4GHz wireless system that offers guitar players an easy solution to go wireless. Step on the latest NUX wireless transmission algorithm, B-2 PLUS secures a better connection in a noisy RF environment. With the newly-added auto-off function, you'll never have to worry about leaving the system on and draining out the batteries.

HD audio quality,ultra-low latency & comparable operating range
NUX B-2 PLUS offers 24bit/44.1KHz high definition audio quality and has a comparable operating range of 60 feet(line-of-site) with less than 5ms of latency.
You can hardly find anything better within the same price range.

Improved connection stability
Products utilizing the 2.4GHz frequency band is everywhere nowadays: it's critical to find a way that can avoid most unwanted interference. Instead of increase the transmit power, we decided to narrow down the bandwidth to 2Mb so that B-2 PLUS can find the most available band. It's like driving a Motorcycle through a crowded highway.

Plug-and-play operation, 4 optional channels
Plug the transmitter into your guitar, plug the receiver into your amplifier or effect pedal: turn on both the transmitter and the receiver, and you're good to go. You can also take advantage of its four optional channels when gigging with your friends.
Up to four B-2 PLUS can be used at the same time in one space.

Guitar friendly, smart design
Plug the transmitter into your guitar, plug the receiver into your amplifier or effect pedal: turn on both the transmitter and the receiver, and you're good to go. You can also take advantage of its four optional channels when gigging with your friends. Up to four B-2 PLUS can be used at the same time in one space.

Buckle design, easy to take and keep
Tongue-and-groove buckle clasp design to help avoiding losing the transmitter / receiver. Just buckle them together when you are not playing the guitar.

Specifications:

operating frequency band: 2.4 GHz
audio quality: 24-bit / 44.1 kHz
operation range: Up to 15 meters / 60 feet line-of-sight (environment-dependent)
frequency response: 20 Hz – 20 kHz
latency: less than 5ms
THD+ noise: less than 0.05% 1kHz @-10dbFS
auto-sleep mode: after 10 minutes without operation
built-in battery capacity: 3.7V/750mA (transmitter & receiver)
battery life: up to 7 hours of playing time
dimensions: 73(L) x 40(W) x 55(H) mm
weight: 57g