Closer Examination

The xDuoo XD05T is completely green, which makes it easy to spot on your desk or inside a backpack. This also makes it divisive for those who prefer something that won't be as eye-grabbing. There's also the part where the XD05T is 17 x 8 x 2.2 cm and weighing ~400 g, making this more of a transportable device than a pocketable one. It's not as massive as the xDuoo XD05 Pro when it comes to portable DAC/amps—I don't think anything is that big—yet I feel the XD05T is going to be more a device you have on a desk than always on the move with you. You can easily one-hand it though, since the width isn't that different from a modern phone. Helping further is the part where the relevant buttons are all placed near the bottom, including a textured volume control wheel on the right in red—you will feel the rotation easily with 99 volume steps on offer—as well as three small buttons on the left for Bluetooth pairing, DAC filter selection (FIR 1-8 PCM only + FIR9 for DSD), and changing the input mode. The chassis is aluminium given a green anodized finish that is non-slippery and dust/fingerprint resistant yet smooth to the touch, with an acrylic inlay on the front that has the brand logo and product name in yellow/gold lettering. There are also vents on the side, with a similar set on the back—where we also see the serial number and certification logos—aiding in passive cooling of the vacuum tubes underneath while also providing a look at the glowing tubes when in use.


The top side is where the inputs are located, which makes sense since you will have these cables away from you normally. This is also where the XD05T really starts to distinguish itself from smaller, more portable sources that have far simpler I/O. As mentioned before, there is an optional DC power supply sold by xDuoo and that's where the barrel connector on the top left comes in. I suspect most people will simply use the Type-C port below to charge the internal battery and run the device directly off external power though—DC 12 V/3 A or 5 V/3 A (or higher current) allows for fast charging (3.5-4 hours), compared to the ~10-11 hours taken if you use a slower charger. This is also where the 3-way toggle switch alongside comes in, allowing you to choose whether to charge the battery or run off the battery itself, as well as run off external power. Some audiophiles believe AC mains can be "dirty" and will go to great lengths to clean up power sources too. DC power supplies, and of course any power circuitry designs in sources, are usually more than capable of handling such issues. If there remain audible issues, then you probably have bigger problems with your electrical wiring anyway. Regardless, you can bypass power supplies entirely by using the built-in battery—although the ~4-5 hours of use per charge cycle is meager at best. There's an indicator light to help visualize the battery status during charge/discharge. The XD05T offers USB in via Type-C, which is separate from the Type-C power input to again decouple the two. This is in addition to coax/optical in as well as 3.5 mm single-ended and 4.4 mm balanced line inputs if you wish to use this purely as an amplifier. Those latter two ports also work as line outs, if you wish to in turn use this purely as a DAC, allowing for very good compatibility with a variety of other items similar to what a desktop-class source offers.


The other outputs are seen on the bottom side closer to you, and again this is where you will have headphones/IEMs connected. The volume pot control wheel and the other three buttons are alongside, making the various functions you will use more often readily accessible to you despite the size of the unit. Did you expect to see a full 6.35 mm single-ended headphones output on a portable device? Now you have, and it comes alongside a 4.4 mm balanced headphones output too. Note that you can't use the XD05T with headsets (TRRRS for audio + mic-in) or remote-controlled pro-audio devices, or mono headphones either. Not really a big deal for most people reading this review though as stereo headphones and line out to 2-channel speakers are far more common. A power switch is next up, with markers above to show the off (left) and on (right) positions. Then we see a 3-way switch for Turbo, which is a gain level selector going between low/medium/high levels with each step raising the volume by 3 dB as measured off the 4.4 mm output. There's also a Bass switch which we will get to later, although I imagine it's self-explanatory in what it does when turned on. Above these switches is an OLED screen with yellow color pixels to further help control the device, allowing you to see the input/output/gain modes etc., while also working as a playback indicator. The screen is inset slightly into the body so it doesn't get damaged if you accidentally drop the XD05T on this side.


After all testing was finished, I did take the time to disassemble the XD05T since it's held in place via four Torx screws on the top and bottom. I heavily discourage doing this though, since not only will you likely void warranty but it's also not trivial to do so and put it back together. There are some tiny tricks involved, and the acrylic section having glue on the inside that gets the ribbon cable connecting the primary PCB to the daughter board with the screen to stick incessantly to it doesn't help. Either way, we see the XD05T is not your typical op-amp based DAC/amp, and there's a LOT going on here. For example, that 6000 mAh battery runs nearly the length of the device, and it's needed here given there is no non-tube amplification mode available. This means the XD05T very likely uses Class A amplification which is more power hungry since it runs at full-blast all the time. This also explains the low battery life on offer, and is something you should be aware of as a potential dealbreaker. I found the battery level visible in the screen to help here, with 0/25/50/75/100% steps seen similar to a phone battery level.


The underside of the PCB is busier and also where we see some of the primary components used, including an XMOS XU316 USB bridge for desktop users. The XD05T saves on some component cost by not going with flagship ESS Sabre ES9039PRO 8-channel DACs, instead opting for two ES9039Q2M 2-channel DACs that have basically all the features you'd like for even a desktop stereo setup, let alone a portable one. Continuing down the money savings route, we also see a discontinued but still obviously effective Cirrus Logic CS8422 24-bit stereo sample rate converter as well as a set of SG Micro SGM4806 power supply audio click-pop noise eliminators that have since been replaced by the newer SGM4808. More relevant to users will be the Nisshinbo NJW1195A high-precision 4-channel resistor ladder electronic volume controller, in case you were worried about channel imbalance from the analog volume potentiometer used. The basic functionality of the XD05T, including the screen, is handled using a GigaDevice GD32F350 32-bit Arm Cortex-M4 microcontroller.


The other side has a Qualcomm QCC5125 low-power Bluetooth 5.1 SoC, typically seen in TWS IEMs. Then we get to the star of the show in the form of the two vacuum tubes used for the output power amplification. The xDuoo XD05T doesn't go with more typical and modern Korg Nutubes or even the larger Raytheon JAN-series pentode tubes, instead opting for literal 1960s Soviet-era 6N16B dual triode micro tubes. These are enclosed in a glass bulb as usual, and under vacuum to prevent the eight leads from burning out. Notice how they are soldered onto riser boards though, making them hard to replace if they go bad. This is fairly typical of micro/miniature tubes, and I am not really worried about the tubes going bad anytime soon given these should be running at a relatively low bias voltage and xDuoo has also carefully sorted and matched the pair in use here. I also did not notice any tube-associated pinging noises either, unless you knock against the chassis or are rough with the cables. Replacement tubes are easily found and not very expensive at least, but suffice to say that tube rolling isn't really a key feature here. These are paired alongside high-performance and fully modern capacitors, including in the output section, and a close-up of the daughter board that has the screen and the volume pot helps round off this section.