(Last Updated On: January 15, 2020)

With great power comes great responsibility.

Header image. The xDuoo XD05 Plus spotted in its natural northern habitat.

xDuoo XD05 Plus

"The xDuoo XD05 Plus can easily serve as a desktop device. It can function equally well as a standalone DAC, or as an amp, or as a combo unit. It offers a (perhaps unbeatable) all-in-one mid-range option for someone starting their personal audio journey. Rather than worrying about buying separate amplifiers, DACs and a portable rig, most folks could be easily satisfied with just this little device. Truly impressive."

Pros:

  • »Solid build quality.
  • »Extraordinarily powerful and suitable for both desktop and portable usage.
  • »Supports single or dual OpAmp rolling.
  • »Excellent battery life.
  • »Great format support.
  • »Astounding assortment of included accessories.
  • »Clear, natural and powerful sound.
  • »USB C, Optical and Coax digital connections. Analog input and output.
  • »Impedance switch and three levels of gain.
  • »Terrific value. All the above at a reasonable price point!

Cons:

  • »A black knob on a silver case.
  • »Side buttons oddly positioned and labels are on the bottom of the device.
  • »iOS lightning to USB C cable is not included.
  • »Impedance switch not properly documented and ambiguously labeled “Boost”.
  • »Too much power for sensitive IEMs and an imbalanced volume control at the lowest volume levels.
“What’s in a name? That which we call a rose by any other name would smell as sweet.” – William Shakespeare

In Romeo and Juliet, Shakespeare posed the immortal question that Chi-Fi manufacturers seem to be determined to ignore. These manufacturers appear to go out of their way to make it impossible to differentiate the really great products from the chaff. Almost all the products are named some impenetrable code of letters and numbers.

Consider a company like Chord Electronics that has a memorable and easy to understand product lineup. Mojo. Hugo. Poly. They clearly belong to the same family and yet each is unique and unforgettable. They are all unmistakably Chord.

Schiit Audio has also figured out how to be memorable with naming decisions, albeit made with their tongue firmly placed in cheek.

On the other hand, how many Chi-Fi products have a name consisting of two random letters, plus one or two numbers, and perhaps a hyphen thrown in for good measure? Rhetorical question. All of them? Or at least it seems that way.

The updated xDuoo logo is prominently displayed on the top of the XD05 Plus.
The updated xDuoo logo is prominently displayed on the top of the XD05 Plus.

Enter the xDuoo XD05 Plus, which may well be “sweet”, but appears hopelessly confused as to its own name. I’ve never seen a product or company name written in so many different ways. Shakespeare would be appalled.

Seems like we should start out by determining exactly what we’re discussing today.

Is it xDuoo, XDUOO, Xduoo, or XDuoo?

According to the packaging and emails I have received from the company store (service@xDuoo.net), the correct capitalization is xDuoo. Yet, the website displays both ‘Xduoo’ and ‘xDuoo’ on product descriptions and the sender name for info@xduoo.com is written as ‘Xduoo Official’ on emails I have received from them.

Note the differences in the spelling of 'Xduoo' and 'xDuoo' on side-by-side products. (From xduoo.net)
Note the differences in the spelling of ‘Xduoo’ and ‘xDuoo’ on side-by-side products. (From xduoo.net)

Is it XD05 Plus or XD-05 Plus?

Now, this is equally murky. I’m inclined to believe the writing literally on the device: ‘XD05 Plus’. This is backed up by the user manual. However, the website lists it as: xDuoo XD-05 Plus Headphone Amplifier.

For consistency sake, I’m declaring that it is now officially the “xDuoo XD05 Plus”. Everybody else just needs to follow suit. Pronto!

XDuoo Company Overview

There is not a lot of information available on xDuoo. They are located in Shenzhen China and (according to their website) have served as an ODM for many well-known brands and companies for several years.

“An original design manufacturer (ODM) is a company that designs and manufactures a product, as specified, that is eventually rebranded by another firm for sale.” – Wikipedia.

XDuoo focuses on headphone audio products including portable and desktop DACs, amplifiers, Bluetooth modules, DAPs, and interconnection cables.

The XD05 Plus is an upgraded model of the previous XD05 DAC/amp which is still available for $50 less (the Plus is priced at $259). At this point, I usually pose a question along the lines of “but is the Plus worth the upgrade?” and let the reader decide as they read the article. This time, let’s cut to the chase.

Yes. Yes, it is.

The original (non-Plus) XD05. (From xduoo.net)
The original (non-Plus) XD05. (From xduoo.net)

In a nutshell, although very similar looking, the Plus improves almost everything over the previous model. The USB charge and input ports are now both USB C. Amplifier output power is doubled to 1 Watt at 32 Ohm, with lower distortion and higher signal-to-noise. Battery life is improved with faster charging supported. The USB and DAC chips are both updated. The Plus also supports single and dual OpAmp chip rolling.

So, what’s important to you when choosing a portable DAC/amp?

  • Size and weight?
  • Format support?
  • Variety of digital and analog inputs?
  • Ability to drive a wide range of headphones?
  • Sound quality?
  • Price and value?
  • All of the above?

At first glance, the XD05 Plus appears to tick all the boxes. Is it truly the promised ‘sweet rose’ of portable audio devices, or are there hidden thorns that we will soon discover?

The XD05 Plus tethered to an Android phone.
The XD05 Plus tethered to an Android phone.

Specifications

Compliant operating systems: Windows XP/7/8/10, Mac OS X, IOS, Android

DAC chip: AK4493EQ

USB chipset: XMOS XU208

Output power: 1000mW at 32 ohms

Frequency response (amp): 10~100kHz (±0.5 dB)

Frequency response (USB/SPDIF): 20Hz~20kHz (±0.5 dB)

THD + N (USB/SPDIF in): 0.0016% at 1kHz

THD + N (aux in): 0.0009% at 1kHz

S/N: 117dB

Crosstalk: ≥75dB

Battery: 3.8V / 5000mAh

Battery life: ≥13 hours (USB in), ≥21 hours (SPDIF in), ≥40 hours (aux in)

Sampling Rate Support

USB (PCM): 16–32bit / 44.1–384kHz

DSP: DOP / NATIVE mode, DSD64–256 (1bit / 2.8M–11.2M)

DXD: 24–32bit / 352.8K–384kHz

OPT/COA (PCM): 16–24bit / 44.1–192kHz

DSD: 1bit / 2.82 Mhz (DOP)

The extremely attractive outer box.
The extremely attractive outer box.

XD05 Plus Packaging

The XD05 Plus comes very attractively double-boxed in a white outer cardboard case and an inner embossed black box. The unit itself is securely nestled in black velvet covered foam.

When removed, it allows access to yet another white cardboard box holding all the accessories. The unboxing experience is excellent and really conveys the impression of a premium product.

In the Box

  • The XD05 Plus device.
  • 80 mm USB C – USB C OTG cable.
  • 80 mm USB C – USB Micro OTG cable.
  • 105 cm USB C – USB B 2.0 cable.
  • 1/4” to 1/8” (6.35 mm to 3.5 mm) headphone jack adapter.
  • 10 clear rubber adhesive feet.
  • 5 extra case screws – note the unusual star shaped head pattern.
  • 2 small black-handled, silver metal pegs that appear to function as port covers for the Digital Input and Aux In/Out ports.
  • 40 mm x 70 mm clear silicone (xDuoo branded) spacer pad for portable tethering.
  • Quick Start Guide and warranty card.
  • “Magic Stick – 1pc”? That’s what it says in the Quick Start Guide in the “Package List” section. Perhaps it’s an invisible magic stick?
The impressively generous assortment of accessories in the box.
The impressively generous assortment of accessories in the box.

This is an OUTSTANDING included accessory package. Ten grippy and attractive adhesive feet (when you only need 4)? Five extra screws for the case in case you lose one while doing OpAmp changes? Wowsa. Color me impressed. The only notable missing accessory for me was a USB C – Lightning cable (for iOS) which I ordered from the online store.

Users have reported issues with aftermarket USB C – USB C cables. According to an email I received from xDuoo when I posed them the question, “you can use any USB C with OTG function canble (sic), not only the cable from our company.” That being said, I failed to find a suitable replacement dual USB C cable labeled as ‘OTG’ not from xDuoo.

XD05 Plus Design

As mentioned, the Plus looks much like the former XD05 model. It’s a standard aluminum sleeve design with screw-on matching brushed silver aluminum face and back plates. Measuring approximately 14.5 cm long, 7.5 cm wide and 2.5 cm high, it pushes the size boundaries as a pocketable device, but is still compact enough for portable use.

The front face plate has a small blue OLED screen (centered between the volume/power knob and a full size ¼” headphone jack) which displays sampling rate, input source, battery life and DAC filter. It’s tiny but bright and easy to read.

Unfortunately, the orientation of the Micro USB jack on my Android phone means that they are tethered upside down. A modern phone with USB C would (of course) avoid this issue.
Unfortunately, the orientation of the Micro USB jack on my Android phone means that they are tethered upside down. A modern phone with USB C would (of course) avoid this issue.

Below the screen protrude three tiny black plastic switches. The ‘BOOST’ switch is described in the manual as “increased thrust” to adapt to different impedance headphones. Safe to say that this can be left off unless using headphones above 150 Ohms impedance.

Centered is the ‘BASS’ boost switch that adds 6 dB to the low end. On the right is the 3-position ‘GAIN’ switch that (from the manual) “boost up +3 / +11 dB, for drives (sic) high impedance headphones”.

The GAIN switch is potentially dangerous for your sensitive IEMs and your hearing if you accidentally engage the third position with the volume control halfway up or above. This is a LOUD unit and can drive the vast majority of full-sized headphones in the lowest gain position.

Viewed from the front, there are 3 small silver recessed oval buttons on the left side, which appear unlabeled unless you pick up the device and turn it upside down. (Why the bottom!?! Please write the labels on the side or top where we can see them!).

  1. “INPUT” toggles between USB/coax/optical/aux inputs.
  2. “SRC” only functions with coax and optical inputs and selects upsampling between 48 kHz, 96 kHz and 192 kHz (displayed as SRC48, SRC96 or SRC 192 on the front screen).
  3. The ‘FILTER’ button has different functions whether listening to PCM or DSD files:
DisplayFilterDisplayDSD1DSD2
PCM1Sharp roll-offDSD6439 kHz76 kHz
PCM2Slow roll-offDSD12878 kHz152 kHz
PCM3Short delay – Sharp roll-offDSD256156 kHz304 kHz
PCM 4Short delay – Slow roll-off
Clearly this is a feature-rich device with multiple upsampling and filter options to tailor the sound to your preferences. Don’t let it scare you off. In my experience there isn’t really a ‘bad’ choice that will dramatically negatively impact the sound quality. Audible differences are quite subtle between the options.
The back plate is clear and well organized. Note I have one of the included black plugs in the Digital 3.5 mm jack.
The back plate is clear and well organized. Note I have one of the included black plugs in the Digital 3.5 mm jack.

The back plate has two 3.5 mm jacks on either side. One functions as both digital optical and coax SPDIF input and the other does double duty and an analog input and output. There are 2 USB C ports for charging and for data input. Between these ports are two small LEDs that indicate a digital USB link (solid blue) and charging status (red blinking while charging).

The analog output is a fixed line out (in other words it is not controlled by the volume knob) and functions beautifully to use the XD05 as a dedicated DAC for a full-sized audio system. In fact, it may well take this duty over in my desktop headphone stack.
The Bluetooth add-on modules are unfortunately not color matched for the XD05 Pro. (From en.xduoo.com)
The Bluetooth add-on modules are unfortunately not color matched for the XD05 Pro. (From en.xduoo.com)

The only obvious feature missing is integrated Bluetooth support. xDuoo does offer Bluetooth add-on modules that plug into the rear panel, the 05BL and the 05BL Pro. Both are a bit bulky and add length to the device while covering up the charge and analog output ports. They are definitely a compromise compared to an internal Bluetooth implementation.

XD05 Plus Internals

The internal layout and design of the Plus is quite changed from the original XD05. The Plus features an optimized ultra-low noise LDO voltage regulating circuit to power the decoder, amplifier, and digital receiver chips separately which reduces interference and increases battery life.

A comparison of the internals of the Plus (on the left) and the non-Plus (on the right) of the XD05. (From head-fi.org)
A comparison of the internals of the Plus (on the left) and the non-Plus (on the right) of the XD05. (From head-fi.org)

The new Asahi Kasei AK4493EQ DAC chip supports native DSD, DXD and PCM audio file decoding (but no MQA support). The XMOS XU208 digital receiver chip supports sampling rates up to 32 bit/384 kHz and DSD64 (DOP – DSD over PCM) via the optical/coaxial input. The design also features a dual-chip low phase noise oscillator and CPLD chip to reduce jitter.

Also new is the larger 5000mAH battery, which is capable of 13 hours of playback through USB, 21 hours through the coaxial or optical input, and an impressive 40 hours via the analog aux input.

OpAmp Rolling Support

The included stock OpAmp is a dual Texas Instruments OPA1612. The XD05 Plus can support smaller dual SOIC OpAmps via a socketed SOIC to DIP8 adapter or can be replaced with a pair of single OpAmps in the two DIP8 sockets.

Two OpAmps installed in the XD05 Plus. (From ixbt.com)
Two OpAmps installed in the XD05 Plus. (From ixbt.com)
Reportedly two Burson Audio V6 Vivid OpAmps are too large to fit in the case, however users have reported very good results with a single Burson Audio V5i, Sparkos Labs SS3602 or pair of MUSES03. Unfortunately, I did not currently have these on hand to verify.

XD05 Plus Sound

Ok, ok. We get it. It’s got A LOT of features, but as I’ve said before, the proof is in the pudding. How does all that tech sound?

Good. Really bloody good.

The xDuoo XD05 Plus blurs the line between a very good desktop amplifier and a portable device. Most obvious is the sheer brute power this little monster can provide. 1 full Watt at 32 Ohms is nothing to sneeze at.

1 Watt at 32 Ohms. (From en.xduoo.com)
1 Watt at 32 Ohms. (From en.xduoo.com)

The inclusion of a full sized ¼” headphone jack, three gain positions, and impedance (BOOST) switch really signifies that this little amp is more at home with full-sized headphones than tiny ultra-sensitive IEMs.

In fact, the BOOST switch and (especially the) GAIN switch are intimidating when using the XD05 Plus with sensitive IEMs. I can’t stress enough that damage will be done to both the headphones and your ears if you inadvertently increase the gain and volume.

Frankly, this worries me as the Plus is a pocketable device and these switches protrude (slightly) from the front panel. Accidental adjustments could be catastrophic.
The impressive feature set of the XD05 Plus. (From en.xduoo.com)
The impressive feature set of the XD05 Plus. (From en.xduoo.com)

Other than temporarily playing around with the BASS switch, the vast majority of my listening was done with the bass boost disabled. It appears to boost primarily in the mid-bass range and it added unnecessary thickness to the sound for my tastes. That being said, there are undoubtedly music and headphone combinations that will benefit from this feature.

As is my typical routine, I tested the xDuoo XD05 Plus with a variety of sources, headphones, musical styles and file types. It worked perfectly from my MacBook, iPhone, and old Android phone (something I can’t say for the Chord Mojo).

Headphones were swapped between Symphones Grado clones, Sennheiser HD650, Audeze LCD-2, Meze 99 Classics and KZ ZSX IEMs. This presented a wide variety of sensitivities and impedances.

The xDuoo XD05 Plus does what a good DAC/amp should do. That is, it offers clear and dynamic sound, without unwanted coloration or sonic weaknesses. The Plus is virtually indistinguishable from good desktop amplification. In a portable device that is high-praise indeed.

For the truly golden-eared, there may be more technical devices capable of better micro-dynamics, but for us mere mortals, it’s the impact and clarity of the XD05 Plus that impresses. I detected no irregularities across the audio frequency spectrum and I feel confident that the Plus is delivering what it should.

Keep in mind that all my listening was done with the relatively inexpensive stock OPA1612 OpAmp in place. If you are an OpAmp rolling believer, the XD05 Plus offers an amazingly solid starting place for your rolling journey.
The 1/4
The 1/4″ headphone jack and BOOST and GAIN switches mean the XD05 Plus is more at home with full-sized headphones.

Unfortunately, using the very sensitive KZ ZSX IEMs with the xDuoo XD05 Plus is less than ideal. With this combo, there is almost no usable range on the volume control. The volume knob doubles as the power switch, so by turning it clockwise to power on, the lowest volume level is approximately at 8 o’clock on the dial. After a quiet relay click, the music can be heard very quietly playing in the background.

Between 8:00 and 10:00 on the volume control, channel imbalance is very apparent and doesn’t disappear until the volume is at a relatively normal/loud listening level. 11:00 is LOUD and 12:00 is unlistenable (keep in mind the knob turns until 5:00). And this is all with the GAIN switch at its lowest level.

With gain set on the highest level, anything above 10:00 on the volume control is dangerously loud with sensitive IEMs!

On the positive side, there is little to no background hiss and the noise floor is not noticeable at reasonable listening levels. If you are one to like to listen to your IEMs loud, there is more than ample power on hand to bring out the best in them. Lizzo’s entertaining 2019 album ‘Cuz I Love You’ really grabs your attention and absolutely punches you with this combination.

XD05 Plus Comparisons

There are a number of excellent DAC/amp options currently out there and I’ll only touch on a few that I have experience with. The most obvious comparison is with the original (non-Plus) XD05.

xDuoo XD05 (non-Plus)

We already touched on the differences between the ($50) less expensive XD05 and the Plus version above. To specify these differences:

XD05non-PlusPlus
Input Port (USB)USB AType C
Charging Port (USB)Micro USBType C
Input Choicen/aSwitch Button
USB Receiver ChipXMOS U8XMOS XU208
Coax/Opt Support DSDNoYes DSD 64 (DOP)
FPGANoAltera-EPM240T
DAC ChipAK4490AK4493
OpAmp ChipOPA1612OPA1612 (Supports dual chips)
Output power (32Ω)500mW1000mW
THD+N0.0025%0.0016%
S/N112dB117dB
Battery Capacity3.7V 4000mAh3.8V 5000mAh
Battery Life USB>11H>13H
Battery Life SPDIF>16H>19H
Battery Life AUX> 23H> 40H
Weight270g276g

iFi xDSD

I reviewed the excellent jack-of-all-trades iFi xDSD device and was impressed, but in the end, I didn’t love it. It is physically about ⅓ smaller than the XD05 Plus, can play higher resolution files (768kHz PCM and DSD512), supports MQA playback, and includes Bluetooth out of the box.

The Plus offers better battery life, more amplifier power and in my opinion, a superior interface. Both sound excellent, but the xDSD is about $140 more expensive.

Testing the XD05 Plus against the Chord Mojo in the background.
Testing the XD05 Plus against the Chord Mojo in the background.

Chord Electronics Mojo

I recently reviewed the Mojo and fell for this little device. To be clear, the Mojo is in a different price category at almost twice the cost of the XD05 Plus, although it is about 4 years older. The Mojo supports 32 bit / 768 kHz USB playback but only supports 24 bit / 96 kHz through the SPDIF optical/coaxial connection.

The Mojo works better with sensitive IEMs, but has a bit less power for truly demanding full-sized headphones (not that I have found any that it won’t drive properly).

Design-wise, they almost couldn’t be more different. The Mojo is iconic, esoteric and artistic with its multi-colored rolling ball controls. The Plus is much more straight-forward and utilitarian.

To my ears, the Mojo has the edge in sound quality and general musicality out of the box, but the ability to roll OpAmps in the xDuoo XD05 Plus means that you may be able to tune the Plus more for your tastes.

Conclusion

Shout out to Linsoul Audio for providing this review unit. If you are looking to purchase the XDuoo XD05 Plus, it is available on Amazon.

Earlier I posed a theoretical checklist of important considerations when selecting a portable DAC/amp. The xDuoo XD05 Plus really checks all the boxes. It’s a well-implemented design with excellent format support, a plethora of connection options, outstanding power and very good sound quality. Not to mention that it is an amazing bang-for-the-buck value proposition, especially since the Plus can do double duty as a desktop DAC or amplifier.

I would also be remiss not to mention the included accessory bundle again. I’ve never seen a more complete package. All manufacturers should take note.

Relaxing at home in front of the fire with the XD05 Plus and Audeze LCD-2s plugged in.
Relaxing at home in front of the fire with the XD05 Plus and Audeze LCD-2s plugged in.

The xDuoo XD05 Plus is undoubtedly a great product, but it isn’t quite perfect. According to the Peter Parker principle, “with great power comes great responsibility.” The XD05 Plus delivers power in abundance but does not quite live up to the more subtle aspects of responsibility.

A more delicate gain design is sorely lacking. Currently the ‘loud’, ‘somewhat louder’, and ‘VERY LOUD’ options are too much for sensitive IEMs. The imbalanced volume potentiometer at the lowest volume levels further exacerbates this issue.

Since the Plus is a battery-powered device, in a portable size and shape, it really should deal with portable IEMs better. Too much power, not enough subtlety.

However, paired with full-sized headphones, all that power delivers in spades. The Xduoo XD05 Plus is clear and dynamic and doesn’t overtly color or change the sound. Lots of digital filter options and the ability to swap OpAmps is further icing on the sonic cake.

The xDuoo XD05 Plus can easily serve as a desktop device. It can function equally well as a standalone DAC, or as an amp, or as a combo unit. It offers a (perhaps unbeatable) all-in-one mid-range option for someone starting their personal audio journey. Rather than worrying about buying separate amplifiers, DACs, and a portable rig, most folks could be easily satisfied with just this little device. Truly impressive.

Now let’s hope someone comes up with a better name for it.