(Last Updated On: September 18, 2020)

Flexibility is the key with this affordable pocket performer.

xDuoo has just released a new device, the XP-2Pro, to fit into the niche of portable Bluetooth DAC/Amp. The $140 Pro is (unsurprisingly) the revised version of the previous XP-2 model. While the internal DAC chip remains the same, the new Pro version adds more power output, advanced codec support, higher bitrate playback, and a more elegant design.

The xDuoo XP-2Pro looks amazing!

xDuoo XP-2Pro

"I’m sure future revisions will continue to reduce in size and increase in power, but for now, the XP-2Pro has fit itself into a sweet spot of affordable, high-quality portable audio. Those looking to try an external DAC/Amp for either their phone or desktop can now have one that will properly drive most headphones, and support a wide variety of connection methods."

Pros:

  • »Flexible connection options: AUX, USB, and Bluetooth.
  • »Premium fit and finish.
  • »Very attractive.
  • »High-quality codec support.
  • »The internal battery preserves the source battery.
  • »Enough power for the majority of headphones.
  • »Clean and clear sound.

Cons:

  • »Very limited volume range with efficient IEMs due to potentiometer causing channel imbalance and more gain than needed on Low.
  • »The Bluetooth range is not as great as I expect.
  • »While not large, this sort of device should be as small as possible.
  • »No way to change audio tracks from the device.
  • »Glass sides are undeniably attractive but are potentially fragile, fingerprint magnets.

To be perfectly honest with you, I didn’t quite grasp the appeal of having Bluetooth in a portable DAC/Amp. On one hand, I thought that if you want Bluetooth, then the freedom of TWS earbuds or a Bluetooth cable adapter would provide the best solution since a device like the XP-2Pro still requires a cable running from your headphones to your pocket.

On the other hand, if you were going to have your phone and a portable DAC/Amp in your pocket, then why not tether them together via a cable (and guarantee the highest sound quality). Alternatively, you could just go with a separate DAP.

The Headphone Audio Facebook Group was quick to point out what was missing in my thinking. The first obvious answer is that if you are looking to buy a portable DAC/Amp then why limit yourself and get one without Bluetooth? A feature is a feature after all.

Another major component I was missing from my thinking was usability. It turns out that using your phone, for any other purpose while listening to music, is far better if it isn’t tethered via elastic bands to a heavy DAC/Amp beneath it.

Finally, since most of us are going to carry a phone anyways, why add a potentially expensive DAP as well to your pockets? While basic DAPs are fairly inexpensive, adding support for streaming services (something that is baked into just about every smartphone these days) means a more feature-rich and pricey DAP purchase is required. And there’s only so much room in our pockets after all.

Of course, all the traditional reasons for adding a DAC/Amp to your portable setup still apply. Support for higher quality file playback, a better sounding conversion from the digital to the analog domain, and having power on hand to properly drive difficult headphones. Missing headphone jacks from the current batch of phones have also necessitated the use of an intermediate device, so why not have a good one?

xDuoo has established itself by producing a variety of high-quality personal audio devices including the powerhouse portable DAC/Amp the XD05-Plus (available in Basic, Standard, and Plus versions). The XP-2 products are a smaller, more portable size and add Bluetooth to the mix, at the expense of a display, op-amp rolling, and power output.

Let’s see if the xDuoo XP-2 Pro can open my eyes as to the benefits of Bluetooth in a portable DAC/Amp.

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XDuoo Company Overview

There is not a lot of information available on the Shenzhen xDuoo Technology Co., Ltd. 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. They claim that “the total number of products designed is more than 100 models, and we have a number of patented technologies that can meet the needs of users.”

“The company’s aim is: customer satisfaction is our driving force!” – xDuoo

XP-2Pro Specifications

  • USB Input Support: Windows 7,8,10, Apple OSX, iOS, Android
  • USB Chip: XMOS XU208
  • Bluetooth Chip: Qualcomm CSR8675
  • Bluetooth Version: 5.0
  • Near Field Pairing (NFC) Support: Yes
  • DAC Chip: AK4452
  • Output Power: 300mW @32Ohms
  • Frequency Response: USB/Bluetooth: 20Hz-20kHz (+/- 0.5 dB), Aux 10Hz-100kHz (+/- 0.5dB)
  • Sampling Rate: USB PCM 16-32 Bit / 44.1kHz – 384kHz, DXD: 24-32 Bit / 352.8-384kHz. DSD: DOP/Native Mode, DSD 64-256
  • Bluetooth: 16-32bit / 44.1-96kHz
  • Bluetooth Codec Support: SBC, AAC, aptX, aptX LL, aptX HD, LDAC
  • Gain: + 3/9dB
  • S/N: 115dB
  • Crosstalk: >= 75dB
  • THD+N: USB 0.001% @1kHz, Aux In 0.0009% @1kHz, Bluetooth 0.002% @1kHz
  • Battery: 3.7v/1800 mAh
  • Charge Time: 3 hours
  • Run Time: Aux 22 hours, Bluetooth 15 hours, USB 8 hours
  • Size: 105x55x15.6mm
  • Weight: 142g
  • Warranty: 12 months
The xDuoo packaging is typically top-notch.
The xDuoo packaging is typically top-notch.

XP-2Pro Packaging

xDuoo knows how to attractively package a product. The outer light-grey cardboard sleeve is covered in pictures and specifications. The internal black box is embossed with the xDuoo shiny black logo. Inside the box, the XP-Pro2 is nestled in a felt-topped foam insert. Underneath is a lift-off cardboard cover for the cables and the manual.

The xDuoo XP-2Pro is a gorgeous bit of gear.
The xDuoo XP-2Pro is a gorgeous bit of gear.

In the box

  • Dual 3.5mm analog audio cable (15 cm)
  • USB-C to USB-C OTG cable (8.5 cm)
  • USB-A to C charging cable (102 cm)
  • Manual
  • Warranty Card
The included accessories include a short dual 3.5mm audio cable for the AUX input, a short dual USB-C cable for tethering to a compatible phone or DAP, and a long USB-A to USB-C cable for charging or for connecting to a computer.
The included accessories include a short dual 3.5mm audio cable for the AUX input, a short dual USB-C cable for tethering to a compatible phone or DAP, and a long USB-A to USB-C cable for charging or for connecting to a computer.

There’s no storage bag nor rubber bands to tether the XP-2Pro to a phone, which can be forgiven as I assume this is intended primarily as a Bluetooth device. However, the lack of an Apple Lightning to USB-C cable is frustrating for us iOS users. I had to purchase this cable for the XD-05 Plus from xDuoo, and thankfully it works fine with the XP-2Pro as well.

As is the norm, a 5V 1A charger is required but not included.

XP-2Pro Design

The entirety of the main body of the XP-2Pro appears to be sculpted from a single piece of grey anodized aluminum alloy. The top section, which contains the volume control and 3.5mm analog input and output sockets, has a seam (but no visible screws) and is made of matching aluminum material.

The top of the XP-2Pro houses the volume/power knob, status LED, AUX input, and headphone output. The red knob is a nice touch.
The top of the XP-2Pro houses the volume/power knob, status LED, AUX input, and headphone output. The red knob is a nice touch.
I’m not a fan of the mismatched black volume knob on the silver bodied XD-05 Plus, but the red knurled aluminum knob looks fantastic as a contrast with the dark grey body of the XP-2Pro. xDuoo says “…the red volume button is matched with deep grey body to show personality in calmness.”

The two large sides of the body are covered in what xDuoo calls “…high-hard 2.5D tempered glass…”. The glass looks terrific. That is, it looks terrific before you touch it. Once you pick up the XP-2Pro, it’s immediately covered in fingerprints. As the glass adheres to the top and bottom surfaces, it protrudes beyond any metal edge, so it’s likely going to be prone to breakage if dropped.

Do not touch the glass on the XP-2Pro if you plan on committing crimes. I've seen Law and Order, fingerprints will totally hold up in court.
Do not touch the glass on the XP-2Pro if you plan on committing crimes. I’ve seen Law and Order, fingerprints will totally hold up in court.

It should be mentioned that 2.5D glass is only a naming convention to describe contoured glass that has a slight curvature towards its edges. So, 2.5D glass can be any brand of glass, strengthened or not, as long as its edges are slightly curved and thinner than the middle of the glass sheet.

2.5D glass does not indicate the quality of breakage resistance or clarity.

The red volume knob functions as a power switch by turning it past the minimum position (and it rewards you with a satisfying-feeling click). On one side, there is a button for cycling through the inputs and another for Play/Pause/Bluetooth Pairing. Between the two buttons is a High-Low Gain switch. The controls are all nice, solid, and tactile.

The microphone, Play/Pause/Bluetooth Pairing button, Gain switch, and Input button are all located on one side.
The microphone, Play/Pause/Bluetooth Pairing button, Gain switch, and Input button are all located on one side.
Short press the Play/Pause/Bluetooth Pairing button to play or pause music. Long press to enter Bluetooth pairing state. While you can play and pause, there is no way to change tracks from the XP-2. The Play/Pause button does not function when connected via USB.

While there is no screen on the XP-2Pro, a single large LED indicator located on the device’s top (between the analog headphone output / AUX input and the volume knob) does change color to reflect the current mode and playback condition.

The single LED on the top of the XP-2Pro changes color to indicate bit-rate, codec, and battery charge status. (From xDuoo.net)
The single LED on the top of the XP-2Pro changes color to indicate bit-rate, codec, and battery charge status. (From xDuoo.net)

Playback LED indicator colors

ColorBluetooth Mode – Indicates the CodecUSB Mode – Indicates the Sampling Rate
BlueSBCn/a
CyanAAC88.2 / 96K
PurpleaptX, aptX LL, aptX HD176.4 - 384K
WhiteLDACDSD64 - 256
Redn/a44.1 / 48K
Green – Indicates AUX moden/an/a

Battery LED indicator colors

Color Battery State
OrangeBattery < 20%
RedCharging
GreenBattery Full

A microphone, used only for Bluetooth calls, is located on the same side as the buttons. The bottom edge has two USB-C ports for a USB data connection and for charging.

You can charge and playback using the USB connection simultaneously, however, xDuoo warns that it will take longer to complete a charge than the typical 3 hours.

Comfort

The XP-2Pro is similar in size to a standard pack of cards. It’s the same thickness, and about a cm longer but a little less than that narrower. This means it fits pretty easily in a pants pocket, but at 140g of solid aluminum, it’s too heavy for a shirt pocket.

The XP-2Pro is sized much like a standard pack of cards.
The XP-2Pro is sized much like a standard pack of cards.
Priced at $140 and weighing in at 140 grams, I appreciate that xDuoo appears to have adopted a $1/gram pricing structure. I kid… I kid… but it would simplify things wouldn’t it?

XP-2Pro Internals

Battery

The battery run time makes a compelling argument to use Bluetooth rather than the USB connection. USB is rated for 8 hours, while Bluetooth is 15 hours and AUX is 22 hours. In my testing, those estimates may be a tad optimistic, but came fairly close, and all lasted for a full day’s worth of listening.

There are two USB-C ports on the bottom of the XP-2Pro
There are two USB-C ports on the bottom of the XP-2Pro

There are two USB-C ports on the bottom of the device and you can charge the device while using it, however, it does take longer to complete a full charge cycle. If you are going to use the XP-2Pro connected to a computer as a wired DAC, it will require another (not included) USB-A to USB-C cable to charge it simultaneously. Of course, connecting via Bluetooth allows you to use the included cable to charge the device.

Charge time is right around 3 hours from low. xDuoo recommends charging the XP-2Pro at least every 6 months.

There are no visible screws, so when the battery needs replacement, you’ll need to contact xDuoo.
The AK4452 DAC chip is used inside the XP-2Pro. (From xDuoo.net)
The AK4452 DAC chip is used inside the XP-2Pro. (From xDuoo.net)

DAC/Amp

The XP-2Pro functions as a wired amplifier, a wired DAC, or a Bluetooth DAC. At the heart of the digital conversion is the Asahi Kasei AKM AK4452 DAC chip. The AK4452 DAC chip was introduced in 2015 and it’s the same chip as was used in the original XP-2. It’s a decent chip, but it is getting a little long in the tooth for 2020.

xDuoo describes the power amplifier circuit as “different from the traditional integrated amplifying circuit, XP-2Pro applies the brand-new OP+BUF circuit structure, bring more thrust. The amplifier output power is enhanced to 300mW.” I’m interpreting this to mean it is a current-buffering Op-Amp circuit.

The OP+BUF amplifier circuit used in the XP-2Pro generates 300mW @ 32Ohms. (From xDuoo.net)
The OP+BUF amplifier circuit used in the XP-2Pro generates 300mW @ 32Ohms. (From xDuoo.net)

The original XP-2 put out 245mW@ 32Ohms. Power output has been boosted to 300mW, so the XP-2Pro should be able to power most any IEMS, or the majority of full-sized headphones (depending on sensitivity).

In fact, the XP-2Pro did fine with my Sennheiser HD650 and Audeze LCD-2 which are currently the most power demanding headphones on hand.

Bluetooth

Bluetooth duties are handled by the Qualcomm CSR8675 Bluetooth chip. It’s Bluetooth 5.0 and can support stereo playback at 192 kHz, although the XP-2Pro is only rated for 16-32bit / 44.1 – 96kHz via Bluetooth.

The Qualcomm CSR8675 Bluetooth chip inside the XP-2Pro. (From xDuoo.net)
The Qualcomm CSR8675 Bluetooth chip inside the XP-2Pro. (From xDuoo.net)
The XP-2Pro will enter the Bluetooth matching mode automatically when powered on and it will automatically connect to the last paired Bluetooth device. You must long-press the pairing button to connect to a different device.

I was a bit disappointed when I tested the range with my typical not-so-scientific approach. I leave my iPhone in the middle of the house and I wander to the corners listening as I go. Dropouts occurred upstairs (behind walls) and before I reached the farther parts of my not-so-big house.

This was a bit less range than I experienced with the Shure RMCE-BT2 and Shanling MW200 Bluetooth adapter cables, which surprised me. It may be due to the all-metal body construction of the XP-2Pro interfering with the reception. I ran into no issues with usage in the same room.

Codec support

I seem to be writing a lot lately about Bluetooth devices, so I’ll say many of the same things again about codec support (forgive me).

The XP-2Pro supports multiple codecs including Qualcomm aptX audio, aptX HD, aptX Low Latency (LL), LDAC, AAC, and SBC.

I’m pretty firmly entrenched in the Apple ecosystem, and unfortunately, Apple decided that for iOS devices (such as my iPhone X), there is no aptX support, so I’m stuck with AAC. aptX does work on my trusty old 2012 MacBook Pro though.

AAC and aptX are virtually audibly indistinguishable, and both are an improvement over SBC. All Bluetooth codecs are inherently noisier than a wired connection, but this typically is only audible at high volumes (greater than 80dB) and/or at high frequencies. As such, AAC, SBC, and aptX codecs roll-off sharply after about 16kHz to minimize this issue.

While 16 kHz is still technically in the audible frequency spectrum, there is very little musical content at that extreme, and after about age 25 we usually lose the ability to hear frequencies that high.

Newer codecs, such as LDAC roll-off at significantly higher frequencies and are less impacted by Bluetooth’s inherent limitations.

XP-2Pro Sound

While I’m a fan of the tactile nature of the volume knob, I’m far less enamored with the potentiometer it’s mated to. Much like with the XD-05 Plus, at very low volumes there is obvious channel imbalance. This is only noticeable when using efficient IEMs, but since this is a portable device, it is likely that users will attempt this sort of pairing.

The following notes were taken using the Thieaudio Voyager 3 IEMs (14 Ohms, 113 dB@1kHz), with the Gain switch on the XP-2Pro set to Low and while connected via a Bluetooth AAC to my iPhone. Note that volume cannot be controlled on the phone when paired by Bluetooth. The time designates the volume switch position as if on an analog clock.

Volume Control PositionAudio Level
8:00Power Off.
9:00Power On. Sound can be heard faintly in both ears.
10:00The left channel becomes louder.
10:05The right channel increases to match the left channel.
11:00Fairly loud listening level.
12:00Much too loud.
1:00Audible hiss with nothing playing.
2:00-6:00Unnecessary headroom.

The usable volume range is very small on the knob (between 10:00 and 11:00). Not quite so bad as with the 1000mW @32 Ohms of the ultra-powerful (for a portable device) XD-05 Plus. Still, the tradeoff between ‘enough power to drive inefficient headphones’, and the ‘ability to use efficient IEMs’ is seriously compromised by the use of a mediocre volume potentiometer.

The volume knob sure is pretty. I wish I could say the same for the potentiometer it is connected to.
The volume knob sure is pretty. I wish I could say the same for the potentiometer it is connected to.

Once again, we run into an xDuoo device that does better with medium efficiency headphones and struggles to find the delicacy needed to pair with efficient IEMs.

The noise floor is very good, however, as it remains entirely undetectable until the volume is far past a normal listening level even with the Thieaudio Voyager 3 IEMs.

Listening was done using my iPhone X (Bluetooth AAC Codec) and MacBook Pro (aptX Codec) with a variety of music, audiobooks, and podcasts.

Swapping back and forth between the USB input and the Bluetooth inputs, the audible differences were very minor and I’m hard-pressed to tell them apart. This is likely a result of the same DAC chip and amplifier circuit handling the audio.

Believe it or not, there are 3 lines on the graph. One for Bluetooth (blue), one for USB (orange), and one for the AUX input (green). Bluetooth is just slightly rolled off after 16kHz but other than that they are identical.
Believe it or not, there are 3 lines on the graph. One for Bluetooth (blue), one for USB (orange), and one for the AUX input (green). Bluetooth is just slightly rolled off after 16kHz but other than that they are identical.

If you take a close look at the measurements (taken with the miniDSP EARS and my MacBook Pro) USB, Bluetooth and AUX measurements were essentially identical for Sennheiser HD650 headphones. Note that these measurements utilized the aptX codec for Bluetooth and the MacBook’s built-in headphone output to connect to AUX.

Overall, I find the sound slightly more bright and flat than I’m used to when compared with the Chord Electronics Mojo. In fact, the XP-2Pro sounds a lot like the xDuoo XD05-Plus. I’m such a tube-amp sound fan, that anything that is more neutral seems to come across this way to me. Regardless, the XP-2Pro sound appears uncolored, if a tad more sterile than my typical daily listens.

The XP-2Pro looks quite diminutive atop the XD-05 Plus.
The XP-2Pro looks quite diminutive atop the XD-05 Plus.

The gain switch works well with providing enough juice for headphones like the Sennheiser HD650, and the result is clean, clear, and relatively transparent. Paired with warmer or more bass-inclined headphones like the Meze 99 Classics, the XP-2Pro seems to yield the best sound to my ears.

If you have a clean source with a decent internal DAC, the wired amplifier section seems to work well without unduly changing the sound or signature of what is coming through. The 300mW@ 32Ohms is enough to give a boost for some underpowered devices. That being said, I imagine bypassing the competent internal DAC will be the least common usage of the XP-2Pro

The original XP-2 is very similar, however the Pro model is a notable refinement in both features and aesthetics. (From head-fi.org)
The original XP-2 is very similar, however the Pro model is a notable refinement in both features and aesthetics. (From head-fi.org)

XP-2 and XP-2 Pro Comparison

 XP-2XP-2 Pro
DACAKM AK4452AKM AK4452
Bluetooth versionBluetooth 5.0, support AAC, SBC, aptXBluetooth 5.0, support AAC, SBC, aptX, aptX LL, aptX HD, LDAC
Output power245mW @ 32 Ohm300mW @ 32 Ohm
Recommend output impedance16 - 300 Ohm16 - 300 Ohm
Supported sampling rate24bit/192kHzUSB PCM: 16-32bit/44.1k-384KHZ DSD64-256
THD+N0.008%@1kHzUSB: 0.001%@1kHz
Adjustable gain+ 3 dB / +9 dB+ 3 dB / +9 dB
Frequency response10Hz - 100kHz (+/-0.5dB)USB/Bluetooth: 20Hz - 100kHz (+/- 0.5dB)
Battery capacity3.7V 1800mAh3.7V 1800mAh
Battery lifeAUX input: 15HAUX input: 15H

Conclusion

Thanks to Linsoul who sent the XP-2Pro along for evaluation. If you’d like one, you can order directly from them or from Amazon.

What’s in a word? Well, if the word is ‘flexibility’, then that’s the word that best describes this new iteration of portable DAC/Amps, like the XP-2Pro. Finally, with the advent of high-quality codecs and proper Bluetooth functionality, wireless high-fidelity is becoming a reality.

I’m sure future revisions will continue to reduce in size and increase in power, but for now, the XP-2Pro has fit itself into a sweet spot of affordable, high-quality portable audio. Those looking to try an external DAC/Amp for either their phone or desktop can now have one that will properly drive most headphones, and support a wide variety of connection methods.

The glass on the front and back surfaces looks so nice when it's free of fingerprints.
The glass on the front and back surfaces looks so nice when it’s free of fingerprints.

I truly wish that excellent mechanical potentiometers would find their way into low-cost products, as the low-volume channel imbalance and not-low-enough gain settings make the XP-2Pro marginally suitable for easy to drive IEMs. The noise floor is excellent (inaudibly low), but again I wish for a lower output power mode to allow for much finer volume control for efficient loads.

However, since flexibility is the name of the game, the XP-2Pro succeeds as far more than simply being a ‘good enough’ solution for most needs. Behold the duct tape of the portable audio world! That is if duct tape had flawless build construction, clear and transparent sound, and worked great in almost any situation you use it for.