The xDSD uses four, small, variably colored LEDs on its front panel to indicate its current operating states. If you are color-blind, this could be an issue. The centrally located volume control also uses a colored center section to indicate your volume level. White means a line-level output of two volts; no light signals a muted output; a blue light is -95 to -76dB down in level; a magenta color is -75 to -58dB down; cyan is -57 to -40dB down; green is -39 to -22dB down; yellow/green is -21 to -4dB down; and red indicates that you’re at -3 to +6dB, which tops out the xDSD’s potential output level. Along with these four LEDs the front panel has two LEDs on the right side. When the top button is lit, the iFi’s 3D+ circuit is engaged; when the bottom LED is lit, the X-Bass function is active. When both are lit, both are activated. Your selection is made via a small soft-rubber button on the extreme right side of the front panel that also serves as the Bluetooth “linking” button.
The xDSD supports multiple input options. Sources include USB, SPDIF coaxial, TosLink, and Bluetooth. The Bluetooth connection supports both aptX and ACC. The xDSD’s clocking system is derived from parent company AMR’s DP-777 DAC in conjunction with a memory buffer. This circuit reportedly reduces source jitter, which for Bluetooth, can be as high as several thousand picoseconds. The custom Bluetooth system includes the aptX codec that reportedly delivers “near CD-quality” sound from Android and Apple devices.
On the output side, the xDSD has one option—a mini-stereo output on its front panel. Given the DAC’s projected use and lack of front-panel real estate, the mini-stereo plug connection, rather than the studio-standard ¼" headphone jack, makes perfect sense. But if you have headphones that have only a ¼" stereo jack, you will need an adapter to reduce that ¼" stereo to a mini-stereo jack. The two adapters I had around were almost 2"-long metal columns that when combined with the stereo jack (such as the Furutech) made for a weighty 5"-long metal pole sticking out from the front of the xDSD. Even using the Grado adapter (which has a short flexible cable between its input and output connectors) made for a rather ungainly package.
Most audio devices that I know of are not left- or right-handed (unlike baseball gloves), but the xDSD is an exception. To see all the controls clearly you need to place the xDSD on the left side of your desktop. Why? Because that adapter combo I mentioned, and even a good percentage of mini-stereo-terminated cables, will obscure the control LEDs when the xDSD is on your right side. For easier usage, I installed two 2" by 2" squares of high-density foam, one under the xDSD and the other supporting the converter jack, beneath the xDSD to raise it off the desktop. This way I could use the xDSD when it was on my desktop’s right side (which is where the rest of my computer electronics are located). Also, elevating the xDSD slightly off the desktop makes it far easier to turn the volume knob.
Linking to a Bluetooth source was as simple as holding down the BT button while putting your smartphone into pairing mode via the settings menu. My iPhone SE linked with no issues, as did my HiDiz AP-60 II portable player. Since this was the same weekend as the Telluride Music Festival, which is broadcast live over KOTO, Telluride’s community radio station, I spent a good deal of time tethered to the iPhone/xDSD combo while working out and doing household errands.
The xDSD proved to be a remarkably agnostic headphone interface. It had enough juice to drive the HiFiMan HE1000 V2 headphones to satisfying levels, with 21dB of additional gain to spare. Conversely, with the sensitive 121dB/1mW Earsonics S-EM9 there was no background hiss whatsoever. I used a wide variety of earphones with the xDSD including AKG-7xx, Meze Classic 99, Sennheiser HD 700, Sony MDR-Z1R, MrSpeakers Ether, Astell&Kern Billie Jean, and Ultimate Ears Reference Remastered CIEMs. In every case the xDSD introduced no noticeable alterations in the intrinsic harmonic balance of the headphones attached to it.
One of the primary intended functions of the xDSD is portable use. Its shape and design add to its “pocketability.” The knurled volume knob is easy to locate blind while the xDSD is in your pocket. The other pushbutton on the front panel is set into the body of the DAC, so it can’t easily be activated accidentally. Pushing the volume button inwards puts the xDSD into mute mode—this was also easy to do while the unit was still in my pocket.
My optimum desktop-performance signal chain employed the HiFiMan HE1000 V2 headphones tethered to the xDSD. The xDSD was fed from the iFi iUSB 3.0 USB which was connected via USB 3.0 to a Mac Pro 2013 Titanium Trashcan running Roon. In portable mode, my favorite combination was the new Earsonics EM10 CIEM paired with the xDSD. I was impressed by how close the EM10’s came to recreating the HE1000 V2’s detailed and complex soundstage, as well as that puff-of-air bottom end that I heard through the xDSD/HiFiMan HE1000 V2 combo.