Nexum AQUA+

General Information

AQUA+ | 32bit Wireless Headphone Amplifier


About NEXUM:

NEXUM comes from Taiwan and is established in 2013 with focusing on wireless audio technology design. Over the years, NEXUM launched several products into the market like the MEMO, AQUA, TuneBox2 and LINKA. They are care about design to bring more value to our lives.

NEXUM Official Web Page:

Price: $139.00

The AQUA+ :

The AQUA+ is a small (4.5*4.5*1.2cm) and lightweight (12g) Wireless operating DAC with a built in amplifier that supports Hi-Res music files with sampling rates up to 32bit 384K and is compatible with multiple operating systems like Windows, Mac, Android or IOS etc.


Technical Specifications:

Audio Codec : aptX/aptX LL/AAC/SBC
Support Impedance : 8ohm-300ohm
Output Power : 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
Certifications : BQB/FCC/CE/NCC
Size : 4.5*4.5*1.2cm
Weight : 25g


Package Contents:

1 x AQUA+
1 x Charging Pad
1 x Leather Clip
1 x microUSB cable
1 x User Manual


Latest reviews

Pros: Small and lightweight design
Easy BT pairing / BT codecs support
2 sound modes
Cons: Plastic plates (though, for technical reasons)
Volume knob is too sensitive and lacks accuracy for playback control
Fix volume level on startup is too loud
Nexum Aqua+ / Wireless Bluetooth Amplifier

Aqua + (4).JPG

: 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.

aqua - design.png

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.).

Aqua + (2).JPG

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.

Aqua + (3).JPG

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.

Aqua + (1).JPG

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.

Aqua + (4).JPG

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;
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Pros: Small and light. Nicely made. Very good sound quality. Wireless charging capability. Good power output. Low noise floor. Fine volume controls.
Cons: Bluetooth range isn't very good (although it's designed to be kept close to your phone when in use).
In recent months I have really started to appreciate the benefits of wireless headphones and have had the opportunity to try out many of the more popular ones out there - both full sized and earbud/iem types. Obviously like with all things, some were better than others.


The Aqua+ is a tiny portable Bluetooth receiver and headphone amplifier in one. Designed to be used only wirelessly, the unit only has an headphone output socket - no word input at all. The unit comes supplied with its own USB powered wireless charging dock (which is a really nice touch and greatly adds to the value of the device (everything battery powered should feature this technology in my opinion), the usual fairly short USB cable and a really neat tight fitting leather case which features a really tight metal belt clip. This gives you confidence that you won't lose the unit when you're out and about. All in all a really satisfying package.


The unit is designed to allow wired headphones to be used wirelessly with your devices and features 32-bit output. It's very small and lightweight device features a nice analogue style volume control which offers fine control. A voice prompt informs you when the unit is powered on and connected to your device. One nice touch is that the voice is nicely quiet and has a distinctive English accent. Another nice touch is that the unit always starts with a fairly low volume so you won't get any sudden surprises.


Equipment used:


Sennheiser 598SR
Ultimate Ears Triple Fi 10's
1More Triple Driver IEM's
Magaosi triple driver IEM's


Google Nexus 7 2013
LG v20

Sound Quality:

The first thing that surprised me was the volume. When driving iem’s it can go far louder than I'm comfortable with and it even drives my full sized Sennheiser headphones without any problems. In fact it goes a little louder than my V20 in low impedance mode. I really like the volume dial as it offers a reasonably close approximation to an analogue control and also offers fairly fine control which is always welcome and often missing from many Bluetooth headphones. The volume control can also be pressed for Play/Pause and activating Siri/Google Assistant. I think the ideal scenario for the Aqua is to have the unit clipped to your belt and bring it up to your mouth when you are making a phone call. When used this way callers had no problems hearing me at all but I don't think the microphone is sensitive enough to pick up your voice whilst the unit is still attached to your belt.

The sound quality is superb. Really deep bass, sweet, not harsh top end and clearly defined mids. Using the APtX codec from my LG V20, there was no discernable noise floor above that of the recordings themselves. There's plenty of volume in reserve so there's some really nice dynamics going on. I found the sound quality to be perfectly acceptable for long, analytical listening sessions - I can’t really give the unit higher praise than that.

The Aqua offers selectable upsampling to 32 bits and this definitely offers an improvement in the sound - allowing a little more detail to the higher frequencies - apparently this is at the expense of battery life though. Whilst in the subject of battery life I've not had the unit run out on me yet - the power management on the unit will shut off power after a period of inactivity and the wireless charging really makes it easy to ensure the Aqua is airways ready when you need it.


For me I can't see this device replacing my excellent Sony WH1000XM2 headphones or even the Apple Airpods but this is primarily because I like to be completely wireless whenever possible. However this device does allow me to use my better wired iem's wirelessly when I'm out and about and it's good enough for me to appreciate the benefits these better headphones can offer. Another advantage for me is that I can listen to music in bed quite loud using the same IEM's without disturbing my wife - that's something I definitely can't do with the Apple Airpods.
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Pros: Stylish, very small, QI WIRELESS CHARGING, very good amplification, supports every major Bluetooth codec, great accessories
Cons: Small flex in the build.
Nexum Aqua+ Review: APTx, Up-sampling, and Qi Charging, Oh My!
Nexum is a audio tech company based in Taiwan. They specialize in building high-quality source and wireless interconnect devices. Ranging from mobile DACs to WiFi adapters from your sound system, Nexum has quite the interesting lineup. Today we’ll be taking a look at their mobile Bluetooth DAC, the Aqua+.

You can find the Aqua+ available here for $150.


Build Quality

The Aqua+ is made from a brush-textured outer shell and plastic plates for the large faces. The assembly itself is quite well put together, but the plastic plates on the top and bottom have enough flex to be noticeable when you press on it a little. While its not in danger of breaking, it isn’t something I want to see from a $150 product. I’d like to see the plastic replaced with aluminum or at the very least reinforced for a more solid feeling. I understand that this may not be possible given the nature of wireless technologies, so instead glass would be a great substitute look-and-feel wise, if not a durable one.

Volume is controlled by a 32-step wheel located at the corner of the device. It is corrugated for additional grip. The wheel sits firmly in the frame and doesn’t jiggle around at all. It’s got a subtle, but satisfying, click feeling when turned and feels very precise while adjusting volume.

The side wall of the device houses an up-sampling toggle button and the headphone jack. The jack is well-placed within the frame and is lined with metal. It is the only port on the entire construction of the Aqua+.

On the bottom of the Aqua+ you’ll spot a curious lightning symbol. This symbol denotes the most unique and convenient feature of the Aqua+: its wireless charging. Compatible with all Qi charging pads, the Aqua+ is the only wireless DAC I’ve seen to make use to date. It works very well too, and the included wireless charging does its job flawlessly.

Nexum went with CS43130 for the DAC inside the Aqua+ CS43130; a low power chipset. It is capable of up-sampling Bluetooth’s native 16-bit depth to a 32-bit depth. While the perceptibility of improvements from going beyond 16-bit audio is still under debate, the fact that the Aqua+ offers the feature at all is a plus to many audiophiles. It uses Bluetooth 4.0 and supports aptX, aptX LL, AAC, and SBC audio codecs, a wide variety to sau the least. It would be nice to see it support aptXHD and LDAC though.

Performance/Battery Life
Nexum claims that the Aqua+ can drive earphones and headphones up to 300 Ohms. While I haven’t been able to get my hands on anything quite that hard to drive, I found that the Aqua+ didn’t struggle to drive anything that I threw at it.

As far as sound signature goes, the Aqua+ didn’t have any coloring or tonal flavors to speak of. It was completely transparent, aside from the compression that it would naturally have from Bluetooth, though as per usual, that was near negligible too.

As far as battery life goes, at a medium volume, I averaged 6 hours and 31 minutes of use per day over the course of two weeks on reasonably efficient IEMs with my max use-time being 8 hours and 9 minutes and with the minimum being 5 hours and 44 minutes. Nexum lists the Aqua+ as having between 5–8 hours of battery life per charge, so these results are completely consistent with their claims.


Inside the box you’ll find:

  • 1x Nexum-branded Qi charging pad
  • 1x Micro-USB cable
  • 1x carrying clip

The charging pad and carrying case are made from a leathery material. I can’t tell if its genuine or a substitute, but I’m leaning towards the latter. The stitching on it is accurate and free from flaws. The carrying case fits the Aqua+ exceptionally well has a nice velvety interior to keep it from scratching. It’s easy to clip onto your pants and is not obtrusive.

The Nexum+ is one of the most advanced and convenient Bluetooth DAC’s I’ve seen to date. Featuring the latest in Bluetooth technology and support a slew of audio codecs, the Aqua+ is sure to work with all of your devices to provide you with a high-quality experience. It even features wireless charging, a blessing in today’s dongle-filled world. The Aqua+ isn’t perfect though. It is stylish and well designed but still feels a little flimsy, and doesn't cover studio-quality codecs like AptxHD and LDAC. So if you're willing to ignore the small amount of flex it gives you and want to hear what it has to offer, definitely check out the Aqua+. You get a ton of technology in a very tiny package.
If you are interested in finding out more about the current hell-hole that is developing high-end BT audio devices, I think there were some good articles on Head-Fi or some other tech website. The one, in particular, I'm thinking about was related to CES, but I can't say for sure. I read it a while ago.

Thanks for reading!
Every major codec* except the modern ones, AptX HD and LDAC. You should check out the Radsone Earstudio. Smaller, dual DAC, modern codecs (which Android O devices support) balanced 2.5mm port, and only $99!
Wow, you're right! I'll make an edit. Thanks for the heads up.

To be fair though, the Radsone Earstudio does have less amplification available. That's a different story though :)

And BTW, an Android 0 device is only required to support those if it shipped with it, not if it was updated to it (similar to Treble). So, for example, cheap Redmi devices that get updated to O might not support AptX HD.


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