The iFi xDSD was sent to me as part of the head-fi review tour so my impressions are limited to 10 days use and I cannot speak to the longevity of the device.
Thank you to Lawrence and iFi Audio for giving me the opportunity to put the xDSD through its paces.
Unboxing
The xDSD arrived in its retail packaging which consists of white slip-cover box with the device, a cloth bag, and the accessories hiding inside. If you have seen pictures of the xDSD, you probably have the wrong impression of its size. I know I expected the device to be larger than it was and much closer to the size of the other ifi products. In ifi speak, you have the Micro, the Nano, and the xDSD can be thought of as the pico. It is about the same thickness as a smartphone in a protective case and roughly ½ the height. Other devices in the same size range are the Mojo and the Fiio Q1.
Accessories
The Accessory kit comes with a selection of cables including a USB-A male to female cable for attaching the xDSD to a computer. A USB-A male to micro USB male to attach to charging port, and two different styles of USB-A female to USB-B female adaptors. A cloth carry bag, and Velcro connectors to attach the xDSD to a phone along with a warrantee card and a quick start guide complete the kit. The only thing you really need to add to the kit is the Iphone connection kit or a USB OTG cable for use with android devices.
Build
The bulk of the case is metal with a polished faceplate and shell in titanium grey. The rear faceplate is a matte black plastic and is about 3 times the thickness of the front plate. Ifi’s documentation says the plastic rear cap was to improve wireless performance and that it performs substantially better than the all metal cases tested. This helps explain a choice that might at first seem an odd aesthetic to some. The faceplates are held in place using two star-head screws mounted on the outer edges. The device has good heft for its small size and feels extremely solid with no wobble or play in any of the connectors. The metal surfaces are very prone to finger prints and smudges so if that bothers you, you might want to have the aluminum case duracoated.
Features
The xDSD crams a lot of features into a small package for sure. At the core, it inherits the Burr Brown Dac of the Black label series and adds a custom op-amp (OV4627) for the output section. This gives the unit a very capable dac with PCM up to 768 and DSD up to 512 support. This alone puts it at the top end of the specs when compared to most portable dac/amps. In addition, the xDSD supports MQA so regardless of your file type choice, the xDSD pretty well has you covered.
In addition to USB or Spdif inputs, the xDSD supports AptX and Bluetooth connectivity both as source and as target so you can attach your cellphone to stream tidal or spotify and attach your Bluetooth headphones so you can listen completely wirelessly. The downside to this arrangement is that battery life on the xDSD gets commensurately shorter with each Bluetooth connection. With both the HTC m9 attached as the source and a set of Mixcder MS301 over-ear Bluetooth headphones attached as the target, battery life on the xDSD was decreased to roughly 5 hours before needing a charge. The xDSD does have a micro-USB charge port so it can be attached to a power bank to increase the usable life between charges, but this kind of defeats the purpose of being completely wireless only to have to have wires for additional batteries.
To adjust the sound, you have the options of 3D+ and Xbass+ as well as the measure or listen options provided by the digital filters. The measure/Listen function exposes the digital filters of the PCM1793a chip itself and lets the end user choose between minimum phase Bezier filter (Listen) or linear phase transient aligned filter (Measure).
In addition to the features you can see from the outside, the xDSD sports ipurifier, and iematch components internally as well as a battery management system that Ifi refers to as Cyberdrive. The xDSD sports an output impedance of less than one ohm (matching the earlier ifi nano BL) but uses the cyberdrive power management instead of its predecessors direct drive system.
Controls
From left to right on the front panel, you have the 3.5 TRRS balanced connector. This connector works for both Single-ended TRS connections or 3.5mm TRRS Balanced connections. With 4.4 and 2.5mm connectors both more common than 3.5 balanced the addition of a 3.5 to 2.5 adaptor would be a welcome addition for those of us with lots of 2.5mm cables an no 3.5mm TRRS options. (I used a Trinity Icarus III to test the 3.5mm balanced since it was the only 3.5mm TRRS connected headphone in my inventory).
Next toward the center is a pair of LEDs The upper is the Khz LED and displays one of seven different colors to let the user know what type of input is being received by the xDSD. The LED immediately below the kHz LED shows the input type and displays a different color or pattern for USB, Spdif, and Bluetooth inputs.
The central volume knob actually serves several purposes. It is the on/off switch, the input mode selector, the volume adjustment, and the volume indicator LED which displays different colors for each decibel range and for Line out functionality.
To the right of the volume knob are two more LEDs that display the status of 3d+ and Xbass+ followed by a button to turn the two features on or off. In addition, pressing and holding the button in puts the xDSD in pairing mode for Bluetooth as well.
On the rear face from left to right, you have the spdif input (note this is not an analog input), followed by a recessed USB-A male connector for USB input. I really like this connector as it is much less prone to damage from stress on the connector but it does limit the size cable that can be used and I did have one USB-Otg cable that I had to shave the hood down slightly to get to fit properly.
Next in line is the digital filter switch for measure/listen. Worth noting is that the function of this switch is slightly different with DSD input when compared with PCM input so a bit of study and A/B testing with your files may be needed to find the best setting for you. DXD and MQA both have fixed filters and you will see no difference based on which position the M/L switch is in.
Finally at the far right is a charging only micro-USB port. This can be used to charge the device while it is playing via spdif or can be used to charge the device when using the BT mode. I found that when both the main USB connection was attached to a device via USB-otg and the micro-USB were hooked up, the current draw was from the micro-usb circuit, but when the Main USB connection was attached directly to a computer or to a device without using an OTG cable, the main USB port became the power source for the device and the micro-USB port was essentially ignored. (This determined using a DRAK ammeter designed specifically for USB).
Bluetooth
Bluetooth on the xDSD is another mixed blessing. It supports AptX but not AptX HD so it may not be future proofed enough for some, but Ifi took the time to use their internal Burr Brown DAC instead of the Qualcomm’s dac which does improve the sound quality when compared to other Bluetooth devices. I found the range of the BT to be about average with 5 yards being a safe distance and the ability to stretch that distance to 10 yards as long as obstructions were kept to a minimum. Using both a phone and a headphone connected by Bluetooth does cause the battery to run down much more rapidly than wired mode and I found that if I wished to use the xDSD for an entire workday, I either had to run it wired or had to plan on recharging it at my lunch break.
Sound
First off, one would expect that the combination of a <1 ohm output impedance and ifi-match technology would lend itself to use with sensitive in-ears. I found that not to be the case. With the Magaosi k5 a hiss was present regardless of settings. With the Eartech Quint a hiss could be heard with the xDSD turned on but no music playing. I instead found that the Campfire Cascade was a good pairing for the xDSD and did most of my tests with either the Cascade or the Sennheiser HD700.
Compared to its predecessor the iDSD BL nano, the xDSD is a bit more aggressive with a bit sharper edges. The BL feels smoothed over and less dynamic by comparison. I didn’t find the xDSD overly bright but did find that the upper mids and lower treble are pushed a bit forward and this can be made even more so by using the 3D+. The 3D+, at times, helps vocals sound a bit more lifelike but comes at the cost of being a bit overly energetic at other times and I found I enjoyed the xDSD more with the 3D+ disabled.
The same held true for the XBass+ which targets enhancing from 100Hz down and had minimal impact with most of the iems and headphones tested. The exception was the Cascade due to its extremely well extended low bass, the difference of XBass on or off was extremely evident. For those of you who know the Cascade, you will also know the last thing it needs is additional bass so again, I left the Xbass+ off for the majority of my listening.
The filter options are more subtle than either the 3D+ or Xbass+ options but do have a detectable impact. I found the measure to be more to my liking as the listen pushed the upper mids and lower treble further forward than I preferred while the measure kept them inline with the lower mids and provided a more uniform signature.
Output Power
The xDSD had no issue driving the HD700 and Cascades but both of those are relatively sensitive and 150 ohm or lower impedance. In order to really push the xDSD, I used a pair of 600ohm Beyer 880s and found the xDSD had more than enough power to push them to levels above what I use for normal listening. The X also had no problem pushing a pair of Fostex T50rp mods so was equally well off with high impedance and low sensitivity cans. I did find that battery life suffered when using the 880s but that has been the case with every portable I have paired with them.
Comparisons
Fiio Q5 vs xDSD
384 PCM / 256 DSD 768 PCM / 512 DSD
More linear more potent
better when paired with IEMS better with power hungry over-ears
(assumes use of AM1 or AM3a) (AM5 comes closer to xDSD power)
No MQA Support
xDSD vs iDSD Nano BL
Has Bluetooth 1/2 the price of xDSD
includes 3D+ and Xbass+ more laidback and warmer presentation
Separate charge Port 384 PCM / 256 DSD with MQA support
Supports Spdif input better matched to sensitive IEMS
Conclusion
The xDSD has a ton of features, but it is its core function that is the real draw. The fact that the xDSD uses its internal dac instead of the Bluetooth chipset for Bluetooth processing means the sound quality comes much closer to parity with its wired counterpart and the sound quality from the wired version is about as good as can be had at its price point. I would put the xDSD on even footing with the Fiio Q5 or the Mojo/Poly combination when taken in total.
The XDSD form factor is more appealing than the Q5 and smaller and lighter than either the Q5 or the Mojo/Poly combination which will appeal to those who carry it full time. The ability to leave the xDSD in a pocket or backpack and control it from a cellphone and Bluetooth headset is also an advantage.
The disadvantages are it has no analog input or optical so if you intend to use it with an external DAP, it must support either USB out or SPDIF out. An analog input so it can be used as an amp alone would be a welcome addition as it would add even more flexibility to this already versatile device.
I found a particularly good synergy between the Cascade and the xDSD when using my laptop as the source. A 14 lbs workstation is a far cry from the envisioned portable devices the designers had in mind, but it works extremely well. For those looking for a DAC/Amp for their small office space (or dorm room) the xDSD offers performance several steps above what the Schiit fulla can offer in about the same footprint with the added benefit of being able to pick it up and take it with you when you travel.
