Headphoneus Supremus
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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1000+ Head-Fier
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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Formerly known as Res-Reviews
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.


100+ Head-Fier
Pros: Small form factor,
Nice Accessory Package,
Great sound Quality,
Good Battery Life,
Low to none hissing
Cons: none for this price
Nexum AQUA+ The 32 bit Wireless Headphone DAC & Amplifier


1. Disclaimer:

First of all, a big thanks to NEXUM for providing me a free sample of the AQUA+for review purposes. I am not affiliated with NEXUM beyond this review and these words reflect my true, unaltered opinions about the product.

2. 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: https://www.nexum-design.com/

Price: $139.00

3. What is the AQUA+:

The AQUA+ is 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.


4. Package and Accessories:

The device comes in small card-box and contains the following items;

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



5. Design and Build Quality:

The NEXUM AQUA + is a small (4.5*4.5*1.2cm), lightweight (25g) and well made device that has a square shape with rounded corners. The AQUA+ has a frame that is made of aluminum, while the top and back covers/caps are made of plastic for a better wireless transmission.


On the sides you can find the power button with a 32 bit marking, the volume wheel that has multiple functions, a led light and the 3.5mm headphone jack.

The NEXUM AQUA+ has three different options for the cover caps; these are midnight black, Sublime Gold and Radiant white. My device is Sublime Gold model.


6. 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

7. Hardware and Operation:

The NEXUM AQUA + has some nice hardware specs like a high quality DAC, Wireless charging etc. that I will now explain for you.

a) DAC Section:

The DAC (Digital to Analog Converter) used in the NEXUM AQUA+ is the CS43130 of the Company Cirrus Logic Inc. that supports sampling rates up to 32bit – 384kHz. According to Cirrus Logic, the CS43130 features a high impedance of 600 Ω and inter channel isolation of >110 dB to minimize pre-echos and ringing artifacts.

The CS43130 is designed with proprietary digital-interpolation filters that support five selectable digital filter responses. Filtering options include low group delay with pseudo-linear phase and a fast or slow roll-off. Volume matching of the analog output levels and channel mixing enable a seamless transition between the DSD and PCM playback paths.


The onboard low noise, ground-centered headphone amplifier provides proprietary AC impedance detection to support headphone fingerprinting to provide a consistent and transparent audio experience for the end user regardless of transducer impedances or frequency responses.


b) AMP Section and Drivability:

The NEXUM AQUA + has an onboard amplifier that is integrated in to the CS43130 SOC (System on a Chip). The amplifier supports earphones & headphones with impedance between 8ohm-300ohm and has an output power rating of 7.5mW@300ohm per channel (1.5Vrms output).

The AQUA+ was able to drive my Audio-Technica ATH M50 to pretty loud volume levels.

According to Cirrus Logic, the onboard headphone amplifier provides proprietary AC impedance detection to support headphone fingerprinting to provide a consistent and transparent audio experience for the end user regardless of transducer impedances or frequency responses.


c) Bluetooth and supported Audio Codecs:

The AQUA+ supports the Bluetooth 4.2 protocol and different types of codecs. This means whenever you pair the AQUA+ with a Bluetooth device it selects the best possible codec that your audio source (DAP, Tablet, Smartphone) supports.

Supported codecs are aptX / aptXLL / AAC and SBC. That means that you no longer hear an FLAC, WAV, MP3, DSD, etc. music file. All audio formats will be decoded by the output device to PCM and then transcoded to aptX, AAC or SBC via Bluetooth audio (in 16bit) to AQUA+. Then AQUA+ leverages its 2 embedded chipsets, high-quality SRC & Hi-Res DAC, to convert it to 32bit.


What do these codes actually mean?


In digital audio data reduction technology, aptX (formerly apt-X) is a family of proprietary audio codec compression algorithms currently owned by Qualcomm.

The aptX audio codec is used for wireless audio applications, notably the real-time streaming of lossy stereo audio over the Bluetooth A2DP connection/pairing between a “source” device such as a Smartphone, Tablet Laptop or a DAP. Products bearing the CSR aptX logo are certified for interoperability with each other. (Ref: Wikipedia)

aptX LL:

aptX LL = Low Latency is intended for video and gaming applications requiring comfortable audio-video synchronization whenever the stereo audio is transmitted over short-range radio to the listener(s) using the Bluetooth A2DP audio profile standard. The technology offers an end-to-end latency of 32 ms over Bluetooth. By comparison, the latency of standard Bluetooth stereo varies greatly depending on the system implementation and buffering. Solutions are available that use standard SBC encoding/decoding that achieve end-to-end latency of less than 40 ms. (Ref: Wikipedia)


Advanced Audio Coding (AAC) is a proprietary audio coding standard for lossy digital audio compression. (Ref: Wikipedia)


SBC, or low-complexity sub-band codec, is an audio sub-band codec specified by the Bluetooth Special Interest Group (SIG) for the Advanced Audio Distribution Profile (A2DP). SBC is a digital audio encoder and decoder used to transfer data to Bluetooth audio output devices like headphones or loudspeakers. It can also be used on the Internet.

It was designed to obtain a reasonably good audio quality at medium bit rates while keeping low computational complexity, having Bluetooth bandwidth limitations and processing power in mind. (Ref: Wikipedia)

How the Bluetooth pairing works:

The Bluetooth pairing of NEXUM AQUA + is quite simple and has an operating range of about 10 meters. You need to press to the 32 bit key until the led flashes in red and blue colors. This operation is needed only for the first time. For the next time you need only to power on the device and enable Bluetooth connection of your source (Smartphone, Tablet, etc.) and a female voice of the NEXUM AQUA + will say “device is connected”.

Please note, that the AQUA+ is designed for headphones with 3.5mm jacks and is unable to support wireless headphones.

d) Wireless Charging:

The Nexum AQUA+ supports the Qi Wireless charging that is an open interface standard that defines wireless power transfer using an inductive charging over distances of up to 4 cm (1.6 inches). Thanks to this feature, the only thing you should do is to but the AQUA+ on the charging pad that is included in the package AQUA+. The charging time takes about 2 hours and has even charge my Samsung Galaxy S8+ that also supports this feature.



e) Battery life:

According to NEXUM, the AQUA+ should be able to play for 8 hours @ 16bits and 5.5 hours @ 32bits on a full charge.

My test have show that the AQUA+ is able top ley for 7.5 – 8 Hours in 16 Bit mode and approx. 5 hours in 32 Bit mode. These values are pretty good for such a small and constantly wireless working device.

f) Background Noise / Hissing:

The NEXUM AQUA + is a very silent working device. There was small to non hissing with some of my sensitive IEM’s like the HiFi BOY OS V3 and Dunu Falcon-C. This is a great capability for a wireless working device.

g) Operation:

The Nexum AQUA+ is easy to handle and has two physical keys/buttons. The first key is the digital volume control wheel of the AQUA+ that supports 64 different volume points and that has also some multiple functions. These functions are Play/Pause (Short Press) /Next Song (Double Short) /Prev. Song (Triple Short).

The second is the 32 Bit key. The 32 Bit key operates as power on/off button and it also activates or deactivates the 32bit/384kHz up-sampling function of the device. The led light changes to a turquoise color when you activate this feature.

h) Microphone:

The headphone mic and wire control will not work while connected, but AQUA+ has a built-in mic and can perform wire control functions with the keys on the device.

8) Equipments used for this review:

  • DAC’s : Nexum AQUA +, Astell&Kern XB10
  • Digital Sources : Ipad Air 2, Samsung Galaxy S8+
    IEM’s : Audeze iSine20, Dunu Flacon-C, TFZ TEQUILA1,
    Earbuds : Penon BS1 Official Version, NiceHCK EBX, HiFi BOY Dream
  • Headphones : Audio-Technica ATH50M

9) Albums & tracks used for this review:

  • Sebastian Ingrosso, Thommy Trash &John M. – Reload (Apple Music)
  • Michael Jackson – Billie Jean (DSD)
  • Casey Abrams – Robot Lovers (Tidal Hi-Fi)
  • Emmanuel Pahud (Claude Debussy) – Syrinx (Flac 16bit/44kHz)
  • Melody Gardot – Who Will Comfort Me (Flac 16bit/44kHz)
  • Aretha Franklin – I Say a Little Prayer (DSF)
  • Diana Krall – So Wonderful (DSF)
  • Otto Liebert & Luna Negra – Up Close “Album” (DSD) – Binaural Recording
  • Alboran Trio’s – Cinque Lunghissimi Minuti (Flac 16bit/44kHz)
  • Megadeth – Sweating Bullets (Flac 16bit/44kHz)
  • Opeth – Damnation (Tidal Hi-Fi)
  • Metallica – The Black Album (Flac 24bit/96Hz)
  • Lorde – Royals (Flac 24bit/48kHz)


10. Sound:

I believe in burn-in and have done that for approx. 100 hours before I wrote this review.

Please note that this is a low budget Bluetooth DAC and all my comments about the sound quality are in consideration of this price range.

Tonality / Bass / Mid / Treble / Soundstage & Imagine:

The AQUA+ is a balanced sounding source with a relative flat frequency response and quite neutral tonality.

The AQUA+ is an energetic sounding device with a well extended and tight bass response. The bass is textured and it sounds pretty transparent. The most impressive part about the bass is the speed; it is pretty fast and accurate for a DAC (especially a Bluetooth one) in this price range.

As mentioned before the AQUA+ is a relative neutral sounding device around the whole sound spectrum. The midrange of this device sounds clear and transparent and has also a good amount of detail retrieval.

After some intensive vocal comparisons I have come to the conclusion that Female vocals like Lorde, Diana Krall or Melody Gardot sounded more natural and emotional then most of the male vocals I have listened during this review.

The instrument presentation sounded pretty natural with some of my IEMs like the HiFi BOY OS V3 and the TFZ TEQUILA1, but the especially the synergy with the AUDEZE iSine20 was very satisfying. The separation and definition of instruments is also pretty good.

The upper midrange of the AQUA+ sounds soft and quite controlled. There is no over sharpness that would be uncomfortable after long listening periods.

The treble range of the NEXUM AQUA + sounds fast, clear and vivid. It is not too bright or too smooth. The detail level is above average and presents a nice amount of shimmer/glimmer.

The soundstage of the AQUA+ is well extended and has a nice sense of space. The soundstage depth is above average but it is pretty wide in staging.


11. Comparison:

Nexum AQUA+ vs Astell&Kern XB10:


The Astell&Kern AK XB10 and the Nexum AQUA+ are one of the best choices if you are looking for a wireless DAC/AMP solution. They are sharing also the same retrial price.

a) Design & Build Quality:

Both devices are well made and very lightweight. The AK XB10 weights only 23g and the AQUA+ 25g.

The Astell&Kern XB10 has an all plastic shell while the AQUA+ has an aluminum frame with plastic caps. Both devices are very small and share the same form factor. The size of the XB10 is 5*5*12.3cm vs 4.5*4.5*1.2cm for the AQUA+.

b) Technical Specifications:

The AK XB10 has to headphone outputs, one for 2.5mm balanced wit a power output of 1.8Vrms and one 3.5mm single ended headphone out with a output power of 0.9Vrms. The AQUA+ has only one 3.5mm single ended output but with a higher output power of 1.5Vrms.

The AQUA+ supports the aptX/aptX LL/AAC/SBC Bluetooth Audio Codec’s, while the SBC, AAC, aptX and aptX HD. The main difference is that the AQUA+ supports aptX LL vs aptX HD for the XB10.

Both devices have a built in microphone that is needed for phone calls.

The AK XB10 has a battery life is around 5 hours while the AQUA+ is able to play up to 7.5 Hours. The AQUA+ has also the Qi Wireless charging option that is a nice extra.

Hi-Fi DAC of both devices is capable of reproducing high-quality sound. The AK XB10 supports sampling rates up to 24-bit/192 kHz, while the AQUA+ is capable to support sampling rates up to 32bit – 384kHz.

c) Sound Comparison:

The AQUA+ has a quite neutral tonality and a relative flat frequency response, while the Astell&Kern XB10 sounds warmer and has a V shaped frequency allocation.

The bass of the AQUA+ sounds faster, tighter and is more natural in presentation, while the AK XB10 has more quantity and depth.

The bass of the AQUA+ sounds cleaner, clearer and has more detail rendering compared to the XB10. The bass of the XB10 is not as tight as the AQUA+ and sounds a little bit loose.

The midrange presentation of the Astell&Kern XB10’s sounds a bit muffled compared the clearer midrange of the AQUA+. The Astell&Kern XB10 sounds better with Male vocals, while the AQUA+ performs better with female vocals.

I think that the AQUA+ has the upper hand in terms of instrument clarity, separation and naturalness.

The upper midrange of XB10 sounds a bit too stiff compared to the softer and more controlled sounding AQUA+.

The treble range of the Astell&Kern XB10 sounds pretty good, but it can not commentate with the performance of the Aqua+, which has the sharper, more extended and faster treble response. Because of these characteristics, the AQUA+ sounds like the better choice if you listen to tracks that need additional speed and control.

Both devices have a good soundstage performance, but the Astell&Kern XB10 has the better depth while the AQUA+ has the better send for soundstage wideness.


12. Conclusion:

The NEXUM AQUA+ is a good performer with its great features, nice build quality and quite detailed sound performance. People who are looking for a wireless DAC/Amp solution should definitely give the AQUA + a try.

13) Pros and Cons:

+ Small form factor
+ Nice Accessory Package
+ Great sound Quality
+ Good Battery Life
+ Low to none hissing

– None for this price

[last edit 08.03.2018]


This review was originally posted on my Review Blog "Moonstar Reviews" :
I can get behind this. I picked one up from their Kickstarter campaign and have been very impressed with its capabilities. It powered my Mitchell & Johnson GL2SE really well, providing a powerful, clear and detailed sound but I mainly use it connected to my amp at home for convenience. The 32 bit upsampling really makes up for the inadequacies of streaming services like Spotify and Amazon Music.
Outstanding review - you're really setting the standard here Moonstar. I also have one of these and I think they're surprisingly excellent.
Thank you very much for your nice words :) Yes I was also very surprised for the first time. Nexum did a really good job with the Aqua+ !