Nexum Aqua+

Nexum Aqua+ / Wireless Bluetooth Amplifier

Website: Nexum

Product page: Aqua+


Nexum Aqua+, a new portable wireless Bluetooth receiver with build-in amp/dac. Very small and compact with standard 3.5mm connection to make any headphones into almost ‘wireless’. Supports last BT versions and wireless audio codecs. Two sampling options and 64 digital volume steps through a control wheel and playback control. And more importantly, powerful and good quality sound from a Cirrus Logic DAC chip.

  • Audio Codec: aptX/aptX LL/AAC/SBC
  • Support Impedance: 8ohm-300ohm
  • Output Power: 7.5mW@300ohm per channel (1.5Vrms output), 7.5mW@300ohm per channel (1.5Vrms output)
  • Bluetooth Range: 10m
  • Noise Level: -93dB
  • Dynamic Range: 92.7dB
  • THD+N@1KHz: 0.0067%
  • Stereo Crosstalk: -92.5dB
  • Microphone: MEMS type with high sensitivity
  • Charging time: 2hours
  • Size: 45 x 45 x 12 mm
  • Weight: 25g

Price (MSRP): U$149.
Available in 3 colors, Black, White and Brown.

Hardware and tech

The AQUA+ implements a Cirrus Logic CS43130 DAC and amplifier chipset inside, supposedly a fine model of the company, same one claimed to be used on some of the well praised last smartphones. It supports sample rates up to the 32 bit and advertised as being able to drive up to 300ohm headphones with a 64 steps digital volume control. The Aqua+ also supports the 4.2 Bluetooth version and the different codecs, SBC, AAC, aptX/aptxLL; check around the web for detailed info about the different codecs and the decoding from the standard music file formats (MP3, FLAC, WAV, etc.).

The Aqua+ device arrives in a simple and hassle-free thick cardboard box. The inner box slides down from the outer box revealing the unit itself and the extra accessories beneath. The package includes a micro-USB to USB cable, a leather Qi dock for wireless charging and a small leather holder with a clip attached to it.

The device is really small (45x45x12mm) and very light in weight (only 25g). While the side part is made of strong metal (steel?) the plates are made of plastic, that may not look too sturdy, however, it was designed like this for the better wireless reception that would not have worked well with a metal material. Using the included holder should protect the small device anyway.

At the upper side there’s the cable jacket for normal 3.5mm plugs, a small LED indicator and a volume wheel at the upper-left corner. The wheel is used for volume adjusting that allows up to 64 steps, and also for playback control. A single click for play/pause, double-click for next track and triple for previous. My main concerns are, 1) the clicking must be done quickly, 2) the wheel is not tight enough so on an attempt to navigate through the tracks it may adjust the volume instead, and 3) the volume control is not tight enough and can turn too high by mistake. A dedicated buttons’ array for playback use would have been smarter, even at the expense of a slightly larger device. Moreover, the device returns to a default volume level on each reboot; a good feature if you use more demanding headphones, but for more sensitive IEM sets the starting volume can be too loud.

On the right there is the power button that has various functions as well. Long press for powering on and off, single press for changing the 16 and 32 bit mode, and double press for Bluetooth source device search. The LED indicator changes according to the current function and mode in use.

Pairing the AQUA+ is very easy, once it is recognized by the device it connects automatically, and if the AQUA+ is already on the BT list then it pairs right after it turn on.

The connection range is claimed to be up to 10m. In practice it is a fairly accurate statement, however it is good only if there is not physical interference in the way; one or two walls and the connection easily drops and on some occasions cuts off. The connection is solid and smooth with a couple of phones I tried the AQUA+ with; on the Xiaomi Redmi and Samsung Galaxy there were no issues whatsoever. However, with portable players like the Hidizs AP200 the range is more limited and there’s some delay on the response, and a similar result with a Win 10 based notebook (if a bit better). Moreover, with the AQUA+ watching movies or short video clips makes the playback slower to load and temporarily freezes the video while the audio continues to work.

Sound Impressions

As usual the sound quality will depend on the headphones sets used, but overall the AQUA+ has quite a positive sound quality presentation. For a very small sound source the sounds is powerful and energetic, giving a strong boost on the lower end, with more body on the mid-bass that gives a slightly thicker lower midrange. For a Bluetooth device it keeps a decent degree of dynamics on the whole mids without losing much of the natural texture of the sound. It is a bit smoother and a bit more laid-back on the vocals and instruments. The treble is not missing in sparkle, and while not too softer it has a less natural/more artificial timbre, which is not too unexpected from a BT signal.

The 32 bit mode on does not just raises the volume level, but gives some extra emphasis on the highs region (and a bit on the upper-midrange too), making the sound overall more clear and sparkly. Due the BT conversion the resolution is not at the FLAC/WAV native level, but it still has a clean background despite the extra amplification gain even with more sensitive IEM sets.

Lastly, from the specs the AQUA+ is supposed be able to play up to 300ohm sets. It is capable to drive up to 150ohm earbuds sets without issues, and while it has an acceptable power for a 320ohm VE ZEN 2/Lite earbud, it won’t bring out the best sound level; so a fair claim nonetheless.

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