xDuoo XD-05 Bal

Introduction

As its own website says, Shenzhen xDuoo Technology Co., Ltd. is a professional company specializing in the development, design and sales of high-end audio products, whose ultimate goal is customer satisfaction. They have a unique audio tuning method and have already designed more than 100 models, as well as owning several patented technologies.
When I think of xDuoo, several things come to mind, the legendary DAP X3, a mix of simplicity, power and a very special sound. And since then I have followed its evolution and have been able to enjoy some of its numerous models. During this time the brand has been evolving. From the simplicity of its initial logo, to the current one, much more stylized and iconic. Its image has also changed, but always within a metallic aesthetic, which now combines the colour red to stand out much more.
If there is one thing xDuoo is known for, it is for its large number of DAC/AMP models. It also has dongles, DACs, DAPS and AMPS, but it's much more prodigious in this combination. In addition, they can be stationary as well as portable. And that's where the XD05 series comes in. Its greatest exponent to date is the xDuoo XD05 Bal, a product that will be reviewed in the following article. As I have already mentioned, this is a portable DAC/AMP with 6.3mm SE and 4.4mm BAL audio outputs, 1W of power, support for DSD512, PCM32Bit/768kHz, battery, AES/COAX/OPT I/O and Bluetooth HD. Its circuit is fully balanced and has a small front display. Really, this xDuoo XD05 BAL offers a lot in one device. In the following, I will try to describe its many features and virtues, as well as its sound.



Specifications

• DAC: Dual ES9038Q2M.
• Weight: 290g.
• Dimensions: 130x75x22mm.
• Gain: +6/15dB.
• Battery: 3.8V/5000mAh.
• 0.91" OLED display.
• SE output power: 1W @ 32Ω.
• THD+N SE: 0.0015% @ 1kHz.
• S/N SE: 115dB.
• Crosstalk SE: ≥72dB.
• BAL output power: 1W @ 32Ω.
• THD+N BAL: 0.0009% @ 1kHz.
• S/N BAL: 117dB.
• Crosstalk BAL: ≥100dB.
• Bluetooth formats: AAC, SBC, aptX, aptX LL, aptX HD, LDAC.
• Charging time: About 5 hours (5V/2A).
• Supported operating systems: Win7/8/10, Linux, Mac OS X, IOS, Android System.
• Battery life: USB IN ≥9H, SPDIF IN ≥ 15H, AUX IN ≥ 24H.
• Sampling rates supported: USB: PCM 16-32Bit/44.1-768kHz. DSD: DOP/Native Mode, DSD64-512. AES/COAX/OPT: PCM: 16-24Bit/44.1-192kHz. DSD: DSD64(DOP).
• AUX output level: 2.0Vrms.
• THD+N AUX: 0.0008% @ 1kHz.
• AUX S/N: 120dB.
• Crosstalk AUX: ≥100dB.
• USB/SPDIF frequency response: 20Hz-20kHz (±0.5dB)
• AMP Frequency Response: 10Hz-60kHz (±0.5dB)

Packaging

The xDuoo XD05 BAL comes in a large metallic looking box. Its dimensions are 253x162x52mm. On its top side there is only a metallic blue diagonal line interrupted by the model name and description. On the back is a summary of its main features, in black ink. After opening the box, the DAC/AMP is inside a small white bag, embedded in a foam support covered with black cardboard, occupying the left side of the box. On the right side there is a metal box, with a transparent plastic window, containing two OP AMP 5532DD. Underneath there is an elongated plate with the WEB address of the brand. This is only the first level. On the second level there are three black cardboard cases, with the logo of the brand in white on each of them. Inside are the rest of the accessories, of which there are many. In a nutshell:

• The xDuoo XD05 BAL.
• 2 OP AMP JRC5532DD.
• An elongated metal plate with the WEB address of the brand.
• 1 quick guide on how to replace the OP AMP.
• 1 warranty card.
• 1 user's manual/quick guide.
• 1 BAL mini-XLR to mini-XLR cable.
• 1 Torx screwdriver.
• 5 Torx screws.
• 1 long USB Type C cable.
• 1 3.5mm SE to 6.3mm SE adapter.
• 1 USB Type C female to Type A male adapter.
• 10 clear rectangular rubber bumpers.
• 1 short angled male-to-male USB Type C cable.
• 1 short angled male-to-male USB Type C to Lightning cable.
• 1 cleaning cloth.

The packaging is large, but for all the contents it comes with, it justifies both the price and the size. The only thing missing is a case for the xDuoo. I would also have been happy with a bag to protect it. But it doesn't come with one or the other.



Construction and Design

The xDuoo XD05 BAL is a device with a flat, wide and rather elongated case shape. It weighs 290 grams and measures 130x75x22mm. The entire casing is made of metal, presumably some aluminium alloy, whose surface has a micro-sandblasted treatment. It is dark grey in colour. The sides are rounded. On the upper side, on the back, there is a change in the surface: there is a glazed plate with the brand logo, the name of the model and a small description, in shiny silver. These glazed surfaces are repeated on the sides, at the same height. Near the left rear corner, between the glass plate and the casing, there is a small round metal micro-perforated grille.
On the front side, from left to right, there is a gold-plated 6.3mm SE headphone output, gold-plated BAL 4.4mm headphone output. On the bottom line is the toggle switch for powering up the device, BOOST disable/enable switch/ toggle, low/high GAIN select switch/ toggle. Above these three switches is a 0.91" high-definition OLED display. Its background is black and the text colour is yellow. The display is on a slightly inclined plane. 4 Torx screws connect the faceplate to the case. The same 4 screws are used for the back side. From left to right, on the rear face, there is the 3.5mm gold plated connector dedicated to the AUX IN/OUT. Next to it, at the top, is a switch/ toggle to select battery or external power use. Below that is the USB Type C input, then the XLR AES connector. Again, there is a USB Type C input for power and charging. Finally there is the coaxial/optical port. On the right side face, near the front, there is a large red potentiometer for volume. It is a metal cylinder with vertical (10) and horizontal (3) slots. On the left side face, also near the front, there are three elongated buttons, rounded at the ends. The first and closest to the front (INPUT) is used to select the input. The second one (FILTER) is used to select among the 7 available filters. Finally, the third one is used to activate Bluetooth. On the lower face, almost at the end, there are several logos with the certifications that the device complies with, the WEB address, designed and manufactured in China, the model number and the serial number.
Internally, the XD05 BAL uses a fully balanced circuit. It allows fast switching of OP Amps, thanks to its sockets. It uses imported, professional, Hi-End capacitors from ELNA and NICHICON. It uses two ESS ES9038Q2M DACs. It adopts CPLD for data reshaping, realizes precise clock synchronization and reduces jitter. For Bluetooth, it uses Qualcomm's CSR8675 chip, supporting version 5.0.
Honestly, I think the XD05 BAL is the best designed model of the XD05 series. It is true that I like the front volume potentiometer better, because of its better ergonomics. But the side design makes it more portable. Actually, given the power it has, I would have liked the volume to be digital with a good 120 steps. It is not easy to adjust the volume for IEMS, especially with the balanced output. Both the weight and the size are large, but the competition has very similar devices, so it's not a drawback comparatively speaking. The side buttons mean that it is not a device to put in a pocket. Well, because of its size, I don't think it's the right size. It's a portable device, but it's a device to leave on a surface. Another thing that doesn't convince me are the toggle switches, they are small and I have the feeling that they are fragile, that I can hit them during handling or transport and break them. I know this is a very personal feeling.
I love the fact that there is a clear possibility to change the OP Amps, but the alternative, the JRC5532DDD, is not an improvement over the OPA 1612A from Texas Instruments.



Connectivity

In terms of connectivity, there is little to fault in this device. It can connect to mobiles, tablets, DAPS and PCs via its USB Type C input port. It supports Win7/8/10, Linux, Mac OS X, IOS, Android System. It has ASIO drivers. It has an AES balanced digital input, 3-pin XLR connection. It has coaxial and optical digital inputs. It can be connected to desktop CD, DAPS, digital transports. It also supports external power through a dedicated USB Type C port. In addition, it is also a Bluetooth receiver, supporting AAC, SBC, aptX, aptX LL, aptX HD, LDAC formats. It has 6.3mm SE and 4.4mm BAL headphone output.
Used via USB it supports 16-32Bit PCM/44.1-768kHz and DSD in DOP mode/Native Mode, DSD64-512. Used by AES/Coaxial/Optical supports 16-24Bit/44.1-192kHz PCM and DSD64(DOP).



Operativity

The operation is the usual one. Everything is explained in the manual, which can be downloaded here:

https://drive.google.com/file/d/1xCqTtiXa4sfim6OTbWP07uIMNaa3mXJz/view

Connected to a PC via USB, it can be used as a desktop DAC/AMP. To increase its power, an external USB 5V/2A power supply can be used. It can also be connected to an IOS/Android phone via the same input. To do this, the USB IN input must be selected by pressing the INPUT button.
To connect any device via the Coaxial or Optical input, select the input with this name.
Select INPUT AES to connect a digital transport or a CD that allows connection via the balanced XLR cable.
To use Bluetooth input mode, press INPUT until UNPAIRED appears. Force the pairing mode by pressing the button with the Bluetooth symbol for 3 seconds. Once paired, a short press of this button is used to pause or resume playback.
The device has a button to select between various DAC filters:

• DSD Filter: 47k cut-off filter.
• PCM Filter 1: linear phase fast roll-off.
• PCM Filter 2: linear phase slow roll-off.
• PCM Filter 3: minimum phase fast roll-off.
• PCM Filter 4: minimum phase slow quick roll-off.
• PCM Filter 5: apodizing fast roll-off.
• PCM Filter 6: corrected minimum phase fast roll-off.
• PCM Filter 7: brick wall filter.

It has a Boost switch to change the Op Amp voltage from ±8V to ±13V.
It has a switch to select between low and high gain.
The volume is on the side with a travel from 0 to 9. It is hard enough not to move by accident.
The Input, Filter and Bluetooth buttons are on the left. These buttons are more susceptible to being pressed by accident.



Measures

It is always difficult to meet power specifications. In my experience, xDuoo tends to be a bit exaggerated in this respect. You should also check whether the specified power is RMS or not. My measurements are RMS and you can see it in the screenshots. In any case, this device is a beast capable of delivering a lot of current, especially at low impedances. Something unheard of in a portable device.
The output impedance, both SE and BAL, is always less than 1, something to be celebrated in such a powerful device. Therefore, it is completely safe to use with IEMS, despite the high power it possesses.
For the measurements I have placed the potentiometer in a position where the output measured on the oscilloscope is clean and without visible distortion. It should be borne in mind that these are empirical measurements with a simple device and that distortion is only measured by eye, observing distortion in pure sine waves.
For the measurements I have used external power, but I have also checked these values with battery power. I found no power variations using battery or external load. I have used the Boost mode deactivated.



No Load low gain SE

Maximum voltage without visible distortion and without load is 2.63V. The potentiometer at maximum saturates the signal.



No Load High gain SE

The maximum voltage without visible distortion and without load is 3.31V. The potentiometer at maximum saturates the signal.



15 Ω High gain SE

For a portable device to be able to deliver 2.3V for 15Ω, this means a current of 150mA and a power of 350mW. Values that destroy many other devices. And this is a Single Ended output.



33 Ω High gain SE

The specs say that the power per SE for 32Ω is 1W. Very hard to believe. The values obtained are 2.77V for 1kHz, which means a power of 230mW and a current of 84mA. I’m somewhat disappointed with these measurements, given that the current it is capable of delivering at lower impedances is 150mA. If it could deliver that current at 32Ω the power would rise to 740mW. But it doesn't.



100 Ω High gain SE

3.08V for 1kHz, which implies a power of 95mW. Very close to the maximum voltage.



No Load low gain BAL

4.91V, a barbaric figure.



No Load High gain BAL

6.61V, a very high value.



15 Ω High gain BAL

If the SE power at low impedances was already surprising, now it is even higher. 2.81V means 530mW and an exaggerated current of 190mA. Simply brutal.



33 Ω High gain BAL

5V for 33Ω, here the 150mA that I was missing is delivered. Note, as I use a 33Ω resistor, the power is 760mW. OK, it's not 1W, but it's a great deal.



100 Ω High gain BAL

Almost 6V, 360mW for 100Ω. It should move whatever you throw at it.



Frequency Response

Ultra-flat frequency response from 10Hz to 40khz, without any crosstalk. An exemplary device.



Sound

The xDuoo XD05 BAL uses a dual DAC from Sabre ES9038Q2M. It is perhaps one of the most widely used DACs from ESS and there are many configurations of it. There are products that show that cooler, more analytical character that Sabre is known for. But, on this occasion, this is not the case. The implementation of the xDuoo has a clear neutral tendency, although not without musicality. Its response is completely flat and I can't perceive any colouring in any of the ranges. The sound is quite full, with a good density, it is not impressive in any aspect and that attests to the neutrality I am talking about. And if I say it's not impressive, I don't mean that in a pejorative sense, not at all. While other products aim for a sound that is somehow attention-grabbing, the XD05 BAL is characterised by great precision, but without sounding analytical or bright. It's a sound that feels easy, with a great exposition of detail, big and lush, technically speaking, more for its capabilities, than for presumptuous presentation. There is absolutely no pretension in the sound of this xDuoo and that is a quality that is appreciated as the hours go by and more so, when re-testing an inferior product.
In the low end, it's great to see how good the control is there. The XD05 BAL manages to tighten the bass even more, gaining in speed and agility. In this respect, the LFOs are extremely concise, but without losing fullness or punch. It is able to achieve a lot of depth while maintaining a completely clean sound, with a quick decay and fleeting presence. There is no doubt that the lower range presentation is quite technical, but I still find it neutral and colourless. Texture is on the less explicit side and roughness is average, but I can't complain about the level of information they possess. On the other hand, thanks to his great skill, the area is very descriptive and detailed, the generation of planes is perceptible and precise, as well as the layering of the bass. It is very easy to navigate between the low-frequency layers and this increases the immersion in the sound and the sense of depth.
The exposition of the central range mixes technicalities with the fullness of its perception, generating a rich and highly expressive representation, especially in the section of details and nuances. I want to insist that this is not an analytical sound, but when I describe the richness it possesses, it could give this feeling. However, for a device to be faithful and capable of providing a level of expressiveness and information, as the xDuoo XD05 BAL does, it doesn't have to have that label, but one has to appeal to the musical quality it gives off. And that's what the mids are like, musical, rich and expressive. The detail oozes out and is easy to detect, but without artifice or overexertion. Everything appears natural, as if it had always been there. The small nuances combine with the melody and the clarity of the sound to generate a pleasant, pleasing, complete, full, rich, dense, filled, but airy sound. It is a seamless, explicit, distinguished and very capable of conveying an enormous amount of information.
If I had to choose one word to describe the treble, it would be "realism". The upper range has a natural splendour, which does not stand out because of its presence, but because it is so well done. The high notes shine because they are always there, they do their job, and they are displayed in the sound in the right measure. This is not to say that they are merely a mere sidekick, not at all. The upper range has the same technical attributes as the other ranges: precision, skill, speed, immediacy, but above all, naturalness. The best upper range is the one that can be enjoyed without standing out individually from the other ranges. And so it is here, in the XD05 BAL there is no predominance of one band over another, but there is a pure and musical synergy between them all, which is capable of extolling the naturalness of the whole, its technical capacity and the rest of the abilities, to generate a superior sound, extensive at both ends, but contained and realistic. Pure luxury and pleasure.
Scene-wise, it's not the biggest sound I've ever heard, and that keeps it closer to its more neutral, realistic approach. Nor is it an eminently transparent or crystalline presentation, but there is plenty of separation, space between notes and detail. In this sense, if there is one thing I must emphasise in this section, it is the ability to give body to the instruments and give them three-dimensionality. The XD05 BAL is not only capable of layering, but it is also adept at breathing air and life into voices, filling them from within for a more lifted, realistic and present projection. And when this is combined with the mass that the instruments already possess, it creates a much fuller, more realistic and physical scene, bringing a sense of vibrancy and presence, as well as heightening the scene, but without extending beyond a logical, natural and realistic presentation. In the end, the xDuoo XD05 BAL is a beast, but tamed. An example of neutral sound quality, which surprises by its purity and never by artifice, without misrepresenting the musical information, just interpreting it in a realistic but full way, both technically speaking, as well as by its descriptive level.
Finally, I have tested the filters and the Boost selector, as well as changes to the OpAmps. The changes produced by the filters and Boost selector are minor, at least for me. Whereas playing with OpAmps is always more susceptible to change, although as the changes are not quick, we must rely on our memory to remember their effectiveness, which can always be inaccurate. Still, that the xDuoo XD05 BAL offers this extra tuning variety contributes to elevate its appeal to the listener.



Conclusion

When I think of the xDuoo XD05 BAL, I see it as a complex device. At first, it was difficult for me to review such a complete device, with so many inputs and outputs, so many functionalities and so much power. It has not been easy for me to synthesise all its features without seeming tedious, monotonous or repetitive. We are in front of a superlative audio device, typical of a higher price range, able to compete clearly with more expensive products, but without losing the essence of xDuoo. The brand has thought well about what this gadget should have and has executed it masterfully. The XD05 BAL is a very complete product, it is really very powerful, has a fully balanced circuit, multiple filters, battery, external power supply and all kinds of inputs and outputs. In addition, it supports Bluetooth in all its specifications and the best audio formats. What more could you ask for? Well, that it fulfils all these functions and that it sounds good. So, that's where this xDuoo really stands out. There is no doubt that its musical performance places it among the references of the range and all this offering a totally neutral sound, but very rich and detailed, balanced in all its ranges, very technical but at the same time, very realistic, informative, skilful and natural. A pure sound, which will make us enjoy the music without us even realising it.



Earphones and Sources Used During Analysis

• TRI KAI x HBB
• Letshuoer D13
• Letshuoer S12
• Yanyin Aladdin
• Penon Globe
• Penon Fan
• Rose QT9 MK2s
• BQEYZ Topaz
• Dunu Falcon Pro
• Rose Martini
• Hidizs MD4
• Earbuds Anonymous
• Smabat M4
• TinHiFi P1 MAX Giant Panda

Ratings

• Construction and Design: 90
• Packaging and Accessories: 85
• Connectivity: 95
• Operability: 90
• Sound: 94
• Quality/Price: 95

Purchase Link



You can read the full review in Spanish here

Although xDuoo updated their renowned XD-05 DAC/amp last year, they still didn't provide a balanced output. That gap has now been bridged with the xDuoo XD-05 Bal, which is a completely re-engineered and re-designed product that's smaller as well as more powerful and richer in features.

As a funny aside, "bal" (pronounced more or less like "bahl") means both "ball" and "lie" in Milanese, the language once spoken in and around Milan (forcefully eliminated by the Italian government in the past few decades and now basically extinct). Thankfully enough, though, there's no lie about the XD-05 Bal!

Disclaimer: I received this unit free of charge from Linsoul, who sells it for $429. Additional info is available on xDuoo's website.

This review was originally posted on Soundphile Review.

Packaging & Accessories​

xDuoo really upped their game when it comes to the packaging: the box is shiny and premium-looking and it contains a treasure trove of accessories. The list is quite long: a metal plate with the xDuoo logo (a key chain?), a set of two op-amps, a 1.2 m USB-C to USB-C cable, a USB-C to USB-A adapter, a screwdriver, three 10 cm long cables with a USB-C connector on one side and USB-C, Lightning and micro-USB terminations on the other, a mini-XLR3 to mini-XLR3 cable, a 3.5 mm to 6.3 mm jack adapter, an adhesive patch to attach the DAC to another device, a set of rubber feet, a set of five spare screws, two pins to seal the 3.5 mm jack ports and a manual.



There's also an optional faux leather case, which in my case is blue; it only protects the sides and it is quite thin, but it does offer protection against scuffs and scratches.

Design & Build​

The design of the xDuoo XD-05 Bal is quite similar to that of the XD-05, with a few key differences. The basics are identical: it is a metal parallelepiped with various ports and connectors on the back, as well as a screen on the front, with additional buttons on the side. The main difference is that the device is now a dark grey instead of black and it has red and white accents, while the volume knob that was on the front has been moved to the right hand side. It's a simple, modern design that's almost austere, but it gives you all the things you need to use the device in a clear, accessible way.



The peculiarity of the XD-05 Bal is the presence of three glass inserts in the posterior area of the top and lateral sides. What appears like a concession to mere form is instead a very functional choice, as the presence of these glass inserts allow Bluetooth to work: if those weren't there, the case would act like a Faraday cage and block (or severely limit the strength of) any signal coming from and going to the inside. These inserts also make the device look quite a bit more stylish, so there's also that. There's also a small metallic circle with holes in it, but it's not clear which function it performs as the manual doesn't mention anything related to it.



The size of the xDuoo XD-05 Bal is certainly not that of a device you can keep in your pocket, unless you have very large pockets; it is more of a desktop device that you can carry around and use with a notebook or another portable device, rather than a DAC/amp you can use while out in the streets. Its weight is considerable at 297 grams, but it's still low enough that it won't weigh you down if you carry it in a backpack.



Build quality is quite nice and in line with expectations from xDuoo, which has progressed quite a bit in the past few years in terms of perceived quality of its products. The metal is machined with precision and there are very small seams between the main section and the two lids, held in place by screws, on the front and the back. xDuoo gives you a screwdriver to remove them so that you can replace the op-amps with ones of your choosing - opening up the device is how I discovered about the function of the glass inserts.

The various buttons and switches are located in logical and easy to access places. The front hosts the 6.3 mm jack and the 4.4 mm jack outputs; the power, gain and bass boost switches, and the main OLED screen. On the right hand side there is the volume wheel, of which you only actually see the side, while on the left hand side are the input, filter and Bluetooth buttons. The back hosts 3.5 mm aux input/output jack, a switch to select if power should be drawn from the battery or from the USB port, the USB-C port that makes this possible, a second USB-C port that handles the signal, a micro-XLR3 port to manage AES input and a combo coaxial and optical input through a 3.5 mm jack. All in all it's a very complete input-output section that puts the XD-05 Bal in iFi micro iDSD series territory in terms of flexibility.



The screen has a yellow-orange hue and is visible even under direct sunlight even though it's not extremely bright; conversely, this means it won't blind you if you use the device in the dark. In general, the colour o the text is quite a bit easier on the eyes than the blue of previous models. The screen tells you information on the input, the sampling rate, the filter and the battery level.

There are also LEDs coupled with the USB ports which are meant to tell you if the device is charging and if it receives the signal correctly. My only complaint with them is that they're placed below the ports, so that it's quite difficult to see them. Placing them above the ports would have made much more sense and would have made it possible to, as an example, see at a glance if the device is still charging when a cable is plugged in.



The volume knob has a good feeling when rotating it, with a nice weight that allows you to adjust volume precisely, but the fact that it is embedded makes it difficult to rotate it without directly looking at it and gives you little space to do so. It has an imbalance zone between 0 and 0.75 in which audio is played with the left channel louder than the right one; after that zone the two channels have the same volume.

Specs & Features​

The xDuoo XD-05 Bal offers many ways to connect it to your sources: USB-C, optical, coaxial and even AES in the digital domain, plus aux in/out. This makes it quite versatile and able to be employed in many different use cases. The AES input is basically made to pair it with the xDuoo X10T II, but there's actually quite a large choice of desktop devices that feature that feature the connection as well.

As I mentioned, there's an aux in port which allows you to use the XD-05 Bal plus just as an amplifier, bypassing the digital stage entirely. Selecting aux as the input method actually shuts down the electronics related to the digital portion, allowing you to save battery life. The port actually works as line out as well, though unfortunately this is a real "line out" with no way to adjust the volume.



On top of all these possible connections, the XD-05 Bal features Bluetooth as well: although xDuoo doesn't disclose what version of the standard it uses, they do say which codecs are available and those are SBC, AAC, aptX, aptX LL, aptX HD and LDAC. That means that basically every codec out there with the exception of LHDC is represented. The Bluetooth connection is relatively stable, but it's a bit temperamental and shows some random dropouts that are difficult to ascribe to anything specific, while the range is not quite large: I can walk around my small studio, but as soon as I get out of it the connection stutters and there are interruptions. Bluetooth is therefore best used to connect to a smartphone or other connected device in a convenient manner, but not as a mean to have the source too distant from the DAC/amp.



xDuoo uses the ESS Sabre ES9038Q2M DAC, made specifically for mobile applications. It's not clear why xDuoo chose this in place of a desktop DAC, but it may involve battery life. The XD-05 Bal supplies 1 W of power from both the balanced and the unbalanced connectors, which is quite unusual and defeats the purpose of using the balanced one in the first place - since the main advantage around it is the additional power output. It's not clear how THD can be lower on balanced than on single-ended, too, given that balanced is inherently more distorted than single-ended, so if the data is to be trusted there's a suspicion that the path may not be fully balanced and that amplification could be actually not balanced. It's only a suspicion, though, and I have no proof either way, so take this with a full mine of salt.

I found the xDuoo XD-05 Bal too powerful for in-ear headphones and other sensitive, low-impedance headphones: even at the minimum volume, music is just too loud and I had to either lower the volume via software or use a device like the iFi IEMatch. Unfortunately the latter is not an option if you have a 4.4 mm cable as no IEMatch-like device exists currently as far as I know.

Battery Life​

xDuoo mentions 9 h of battery life when using the XD-05 Bal with USB input and 24 h when using it with aux input. I found the 9 hours figure with USB to be pretty accurate. Charging takes quite a long time and in my experience it can take up to 5 hours to charge the device an that's quite a long time, even for a device with a battery this large - though once again xDuoo is right here with the numbers.

Since the XD-05 has a hardware switch to power it up, it has no automatic sleep or power off function, so if you forget to power it off it's going to drain the battery completely. I quite like the fact that you can actually choose how to power the XD-05 Bal through a switch on the back, even though I would have preferred for a single USB port to be present since the stock cable xDuoo provides also carries power, defeating the purpose of a distinct port.

Sound​

I've tested the xDuoo XD-05 Bal with a HiFiMAN Arya, a Sivga SV021 Robin and a Sennheiser HD 6XX.

With 1 W output, the XD-05 Bal has enough power for basically any headphones out there; even power hungry headphones such as the HE-560 have no issues getting to very high volume. In addition to this, the background is completely devoid of any hum or hiss: you can hear just the music (or the silence, if you press pause).

Soundwise I find the XD-05 Bal to be quite neutral - I can't hear any effect on sound in terms of pure frequency response, as the device gets totally out of the way.

I can hear very little difference when enabling the "boost" feature. I can sense some change, but it's so slight I don't know if it's a product of my imagination (or of the placebo effect). The same goes for the filters: if there is any difference between them, I can't really say I hear it clearly - and that's expected, so there's nothing really new or surprising here.

Final Thoughts​

The xDuoo XD-05 Bal is a very welcome evolution over the previous XD-05 devices as it integrates a few changes that are quite welcome: USB-C is certainly one of them, but so are Bluetooth and the 4.4 mm output. The XD-05 Bal is quite a complete device that offers a ton of functionality in a design that's quite convenient to use and that's built to last. It also offers some quite unusual options, too, such as AES input, as well as an accessory set that is beyond complete.

Overall, the xDuoo XD-05 Bal is quite a great device that trades blows with the de facto rulers of this space, the iFi products, while having a much lower price. And while it's by no means perfect, it's a device that has a lot to offer as a portable desktop DAC/amp. So much so that I can't see any valid reason not to put it in the "Best of" page - it's just so good I can't avoid recommending it.