⌈ In 2013, LUMÏN stormed the market and joined the pantheon of world-class audio file players by offering DSD playback. Its first player, simply called Lumïn, was a challenge to the competition. We are testing the company's most expensive file transport, the U2x model. ⌋

U2X IS THE LATEST, flagship audio file transport from Hong Kong-based Lumin. According to the manufacturer, it has been designed “to deliver the highest quality digital signal without compromise.” And further:

The device is completely free of analog components – it focuses solely on delivering a perfectly clean digital signal to an external DAC or streamer. The solid, CNC-milled housing and external linear power supply based on a dual toroidal transformer emphasize the premium class of this solution, while the latest clock circuits and isolated USB port ensure minimal jitter and network interference.

Such a statement, which expresses a conviction about the uniqueness of a product, is nothing special. It would be really strange if a manufacturer said something else, such as: “We have a new transport, it's pretty good, although there are probably devices on the market that are better in some respects.” So, press releases are full of superlatives. But among all this empty rhetoric, there are products that convey a sense of special, genuine pride – pride in the results and in the used solutions, usually seen for the first time from a given manufacturer. U2x is no different.

▌ U2x

AUDIO FILE TRANSPORTS AND PLAYERS are specialized computers whose operating system has been stripped of all functions except those related to audio. Each manufacturer does this in their own way, including the design of the microprocessor they use and the software they develop for it. The more skilled they are in this field, the better the results they achieve.

Let me remind you: a file player is a complete device that we connect to a LAN or a USB drive on one side, and output an audio signal on the other. File transports, on the other hand, require an external digital-to-analog converter and only output a digital signal. Files are delivered to them in the same way as to a player, but if an SSD or HDD is installed inside, the device can also operate as a server.

LOOKS • Developed for the Lumin model in 2013, the external design formula for this company's devices still looks fresh and appealing. It is defined by a slanted, semi-circular front panel, a low profile, and a top panel expanding beyond the rear of the device thus ‘covering’ the connected cables, modeled to some extent on the Scottish company Linn's players of the time, and now found in parts of other companies' products, such as the French Devialet (profile and rear panel).

The housing is made of milled aluminum block, to which two plates are screwed – the bottom and rear ones. The electronics are mounted on the upper wall of the company's products. At the front, there is a small display showing the artist, song title, file type, and a bar graph with a circle showing the progress of the song. The time is displayed in the center.

You can also change the settings in the menu, and the volume will then be displayed. The device uses an advanced algorithm called Leedh Processing, which adjusts the volume in the digital domain. The manufacturer, , calls it “lossless.” It is a circuit that converts the input signal into 32-bit words and regulates their amplitude in this resolution. It has been available in Lumin devices since mid-2020, when the company released software version v13. It is worth remembering that if you use this option, the DSD signal is converted to PCM, then adjusted and converted back to DSD before the converter.

The power supply utilizes a separate housing. It is a linear power supply. Initially standard, this solution has become an exception at Lumin – most of its products now feature switching power supplies housed in the main device enclosures. The U2x power supply housing is also milled from a single block of aluminum. Inside, there are two large transformers and three separate voltage stabilizing circuits. The power supply is connected to the main device by a thick cable terminated with a multi-pin plug.

FEATURES • In the case of Lumin, subsequent generations of its devices receive more powerful and faster main processors, known as SoCs. An SoC is a single integrated circuit that contains all the essential components of a computer system, such as a processor, memory, graphics, communication, and sensors.

As the manufacturer declares in press materials, he used its more powerful version in U2x which is supposed to help it achieve a “significant increase” in computing power compared to its predecessor (U1x), thanks to the use of the most advanced, fast System-on-Chip processor, which was introduced to the market in 2022.

This is not apparent on paper. The device supports the same files as its predecessor, i.e. the highest values used in recording studios, Native DSD512 and PCM768. It can also function as a simple LAN switch, with one RJ45 input and an optical SFP (Small Form-Factor Pluggable). The manufacturer calls this feature Dual-Network, as it allows other devices in the digital system to be isolated from LAN noise. The transport also has a newly developed, isolated USB output for audio signals.

However, something else seems to be the focal point – options related to the master clock. I have the impression that this is one of the major changes that will result in new product versions with the clock implemented and, most likely, a separate clock. Here and now, however, the device uses a special 10M chip, i.e. with a frequency of 10 MHz. In the menu, you can enable it or leave the previous Femto clock. The U2x has two clock signal outputs that can be connected, for example, to a D/A converter and a LAN switch. This way, the Lumin becomes the center of your streaming system.

As it is standard for this manufacturer, we can upsample, downsample and transcode any digital signal to any other format and resolution, up to DSD256 and PCM384, up to 24 bits. This allows you to play, for example, PCM files and send them outside to a D/A converter via a USB cable, or convert DSD files to PCM and send them outside to a DAC via a digital RCA, BNC or AES/EBU cable. This is important because the USB connection is highly imperfect, and many music lovers and audiophiles still use “old” solutions. Let's take a closer look at this option.

Regardless of your choice, only the USB output allows you to send all available audio file types to an external device. With this in mind, the manufacturer has dedicated one output specifically for audio signals and galvanically isolated it from the rest of the circuit. The other two sockets are used to connect USB drives or flash drives. And there is also a grounding terminal, characteristic of Lumin, to which you can connect an artificial ground – which is what I did.

This manufacturer's transports and file players do not allow music to be played using physical buttons. Although they offer a display, it is small. Control and operation will therefore be carried out via an app. Lumin has its own stable and fast app for both iOS – which is preferred – and Android devices; iOS version 11.0 and above, Android 4.0 or later. For those who want more, the manufacturer also offers a very cool remote control, available at an additional cost.

▌ SOUND

HOW WE LISTENED • The Lumin U2x audio file transport was tested in the HIGH FIDELITY reference system. Its outputs – USB and RCA (S/PDIF) – were connected to the digital inputs of the Ayon Audio CD-35 HF Edition SACD player. This system was compared to the three-box Sforzato DSP-05EX & PMC-05EX file player and to CDs and SACDs.

The Lumin stood on the top shelf of the Finite Elemente Master Reference Pagode Edition Mk II rack on its feet next to the power supply. To prevent it from slipping, its feet were placed on Acoustic Revive RKI-5005 pads. It was powered by a Harmonix X-DC350M2R Improved-Version cable, and its ground terminal was connected to a Nordost QKore artificial ground.

The files were played using the system described in the article on routing in the HIGH FIDELITY reference system (more → HERE ˻PL˺).

» ALBUS USED IN THE TEST ⸜ a selection

⸜ CHET BAKER, A Grand Selection Of His Beloved Songs (Restored Edition ’25) Mouton Recordings/Tidal, FLAC 24/96 ⸜ 2025.
⸜ DORIS DAY, A Grand Selection Of His Beloved Songs (Restored Edition ’25) Mouton Recordings/Tidal, FLAC 24/96 ⸜ 2025.
⸜ FRANK SINATRA, Witchcraft (Restored Edition '25), Mouton Recordings/Tidal, FLAC 24/96 ⸜ 2025.
⸜ PORTUGAL. THE MAN feat. LUCUIS, uLu Selects Vol. 2, KNIK/Tidal, FLAC 24/48 ⸜ 2025.
⸜ THE FAVORS, Finnenas, Ashe, The Dream, Darkroom Records/Tidal, SP, FLAC 24/48 ⸜ 2025.
⸜ ERIC CLAPTON, Slowhand, RSO/Universal International Music B.V/Tidal, FLAC 24/96 ⸜ 1977/?.
⸜ UFO, Phenomneon. Deluxe Edition, Chrysalis Records/Tidal, FLAC 16/44,1 ⸜ 1974/2019.
⸜ ERYKAH BADU, THE ALCHEMIST, Next To You, Contro Freaq Records/Tidal, SP, FLAC 24/44,1 ⸜ 2025.

» The recordings featured in the test can be found on the HIGH FIDELITY playlist on TIDAL → HERE

»«

THE NUMBER OF FEATURES CAN BE INTIMIDATING. This applies to any product, not just audio. In extreme cases, it can even be a reason to reject a device. It doesn't even have to be extreme – we need peace of mind and certainty, not constant uncertainty about “what if...”. Extensive functionality that only serves to emphasize the manufacturer's “potential” is simply harmful. It's as if manufacturers are shifting decisions and choices onto us.

OUTPUT • However, some features are useful and allow us to fit the device into the audio setup. In this case, the first step should be to select the digital output. By default, the signal is sent via the USB output, which is the “widest”. However, there are many indications that the resolution of modern digital devices has once again allowed us to discover the advantages of S/PDIF outputs and highlight the disadvantages of USB.

Therefore, when using Lumin U2x, I would recommend using a non-USB output. I used RCA, but in your case it could be BNC or AES/EBU. They provide a heavier, more articulate sound. It is better organized internally, but above all, it is more resolving, meaning it provides more information about the music. You will experience much greater intimacy when you play tracks from CHAT BAKER, DORIS DAY, or FRANK SINATRA's new remasters.

All of them have been remastered using AI-assisted mastering systems, and in most cases this has yielded really good results (the series is called “Restored Edition”). First and foremost, the sound sources are more tangible. With Lumin, the vocals were incredibly smooth and full. But when I used the USB output, they became a bit dull and the perspective from which we saw them flattened out.

This was particularly evident in Baker's My Funny Valentine and Sinatra's In The Wee Small Hours. Switching to the RCA output was like slightly moving the microphone closer to the singer while pushing the orchestra further back on stage. And moving the microphone closer does not simply mean a louder sound, but a sound with greater scale, deeper and more tangible. This was the case here. Equally interesting was the effect of moving the background away. Its volume was not reduced, nor was its density. It still had a lot of energy, better plasticity than from the USB and more momentum.

MASTER CLOCK • At first glance, I heard much smaller but equally valuable changes when switching between two types of clocking – Femto and 10M. Starting with a digital signal from the RCA output, for example, we can achieve almost everything this device is capable of. But switching the clock to the “10M” position will give you even slightly higher resolution and a slightly more selective sound. It's as if the new clock cleans the sound of the “soot” that previously impaired the clarity.

In the “Femto” position, the sound is also perfect – Lumin's new transport is excellent, let's not have any doubts about that. What's more, it shapes the sound in a way that I like and that I find appropriate (i.e., the best). And yet... Every time I switched to this setting from the 10M clock, it seemed to extinguish something in the sound. It wasn't even about the high frequencies, although there may have been some of the energy in that range missing. It was more about the “presence”, that is, the instant certainty about the type of sound I had with the 10M clock, which was not so clear with the Femto.

However, this difference alone would be negligible if it weren't for a kind of “collapse” of the Femto's sound. With the new clock, it is more selective on the one hand, and warmer on the other. Because that is also how the sound of this device is: warm, endearing, deep. Very pastel, but also perfectly plastic, not carved with an axe, being squeezed out, but rather with the sounds remaining connected to each other, passing gently and smoothly into one another, similar to layers of the stage.

ALL THE REST • I have to tell you something: it’s not that I like all Lumin devices equally. It's not because some are better and others are worse, but because of my taste – different approaches to music have been chosen for them. This is similar to the recent change at SPEC, another Japanese company that I value and respect greatly. It's about balancing between a sound that tends towards fullness and a sound that is more focused on selectivity and clear attack.

Each of these ‘schools’ is legitimate, and each has its supporters. Once upon a time, the choice between them was easier, because the first option was associated with a clear warming and dampening of energy, while the second was associated with sharpening and brightening. Music listeners could therefore choose, but they chose not only the type of sound, but also the entire philosophy and taste behind it. Recently, this has changed and now the differences are not so black and white.

This is because digital signal reproduction today is at an exceptionally high level. What manufacturers have achieved, whether in CD (SACD) players or with files, deserves enormous respect. The minimization of digital noise, both external (EMI, RFI, mechanical vibrations) and internal, including that related to clocking and processing, has resulted in sound that can enchant at every price level.

But even with all that, we still have to make a choice. What Lumin showed in U2x is closer to my heart than the second option. That's because the music is both energetic and dynamic with it – it's no longer just warming – but it's much more internally structured. And it's not just about music from the 1950s, but also contemporary stuff like Silver Spoons, the result of a collaboration between PORTUGAL. THE MAN and LUCUIS, which is going to sound really well.

Similarly, when it gets more intimate, more “Beatlesque,” as in the single The Dream from the album by THE FAVORS, a band founded by Finneas and Ashe (Finneas O'Connell is Billie Eilish's brother and is responsible for the sound of her albums). In both cases, the sound was internally complex and multidimensional, and it also offered an excellent stereo imaging. It was also a sound organized around the main idea of the recording – at least as I could imagine it.

On the other hand, when I listened to tracks with much less compression, such as ERIC CLAPTON's Cocaine from the album Slowhand, when I turned up the volume, I didn't have to worry that something would sound too bright or too aggressive. But it didn't sink into the background either – these are recordings with heavily muted upper midrange. It was similar with UFO's Doctor Doctor in the 2019 remaster of the album Phenomneon. The lead vocals are pushed far back in the mix, yet they were still selective, with a short reverb layered on top.

When the recording was brighter, such as KANSAS's Carry on Wayward Son, a track from the album Leftoverture, the treble opened up, there was no fading, and yet I still remained on what I consider to be the good side of the tonal balance. It was as if the exceptional resolution of this transport allowed for the differentiation of recordings without bringing out their weaker aspects.

Interestingly, although it sounds similar to the XACT S1 Evo, it only takes a moment to know which one is for us and which one is not. The Polish device saturates the bass more and also goes lower in the low midrange. The Lumin, on the other hand, sounds more expressive, although it is still not too expressive to be irritating. The Hong Kong device also widens the panorama more, as in Next To You, where ERYKAH BADU joined forces with producer THE ALCHEMIST.

There are excellent vocals and a contemporary, sampled recording with very low bass frequencies. Lumin will play this type of music in a more exciting way, while XACT will sound more “gutsy”, deeper, with still excellent dynamics. When we listen to MUSE's Unraveling, we know that the Lumin transport is at its best with recordings where everything is in its place, where compression does not kill the expression, where there are clear layers and not a wall of sound.

▌ Summary

THE BEST RESULTS ARE ACHIEVED by playing music from Lumin through RCA, BNC or AES/EBU outputs (i.e. not USB) and using a 10M clock. It will result in highly resolving sound that is also selective. But it is also well-organized and deep. It has both attack and fullness. The device does not overemphasize the sound, focusing more on the density and saturation of the basic building blocks of sound.

The device is also dynamic and expressive. But, again, it does not do this by brightening the high frequencies or the midrange, or by hardening the attack. It is still a sound that is, in a sense, an extension of what this manufacturer is showing in its new generation of devices, such as the T3x player. There is no deliberate warming or deepening of the sound, yet that is the impression we get. There is a great inner calm and tangibility to the sound, as well as a very wide soundstage. Everything is in its place.

▌ DESIGN

LUMIN DEVICES are an example of solid, precise workmanship of chassis and electronics. These devices are manufactured in China, although the bottom panel distinguishes between “design”, which refers to the company's headquarters in Hong Kong, and “manufacturing,” which takes place in mainland China. This is a clear reference to the past, when these two territories were separate political entities and the British-run city was synonymous with technological superiority.

Today, everything looks different, and the “One Country, Two Systems” project (國兩制) has turned out to be a fiction, and Hong Kong is effectively an indivisible part of China. What is more, China's technological development is comparable to that of the world's greatest powers. In some areas, they are still catching up, but in many others, they are at the absolute forefront. However, as we can see, this distinction is still important to the people of Hong Kong.

FRONT AND REAR • The device is extremely robust, as the chassis is made of milled aluminum. The display on the front panel is blue, with a slightly different shade than the LED on the power supply. As usual, the sockets on the rear panel have been carefully selected. The RCA digital output is gold-plated and screw-locked, although it is a stock Neutrik socket. The BNC sockets are also gold-plated, but the XLR looks like it is rhodium-plated. Important – the clock sockets work with 50-ohm cables, not the 75-ohm cables commonly used in audio!

The device stands on four aluminum feet with felt pads.

INSIDE • The electronics are assembled on a single large printed circuit board, to which a smaller board with the main microprocessor is plugged. A heat sink has been attached to the chip, but next to it, on the main board, you can see the Altera Cyclone IV DSP chip. It contains the Leedh volume control algorithms, sample rate converters, and digital signal type converters (PCM, DSD). All components are surface-mounted.

Several interesting solutions are worth noting. All digital outputs are equipped with impedance matching transformers. This will help eliminate, to some extent, jitter associated with cable and connector mismatches. In front of them, also separately for each output, Cirrus Logic CS8406 chips have been placed. This is a digital audio signal transmitter with a cut-off frequency of 192 kHz. Historically, it was designed for various audio applications, including DVD-Audio players, digital A/V receivers, and mixing consoles. The CS8406 supports both consumer and professional audio equipment. Their separation was intended, I assume, to isolate the outputs from each other.

And there is a large 10M master clock box. It is an OCXO device. An Oven Controlled Crystal Oscillator is a type of quartz oscillator that uses a temperature-controlled heating element (called an “oven”) to maintain a constant temperature around the crystal, ensuring high frequency stability and accuracy. This method minimizes frequency fluctuations that can occur due to temperature changes in the surrounding environment. The circuit in the Lumin has been equipped with additional electronics, as indicated by the size of the box shielding the entire unit.

POWER SUPPLY • Let's add that each circuit features separate voltage stabilizers, and the USB audio output, which is isolated from the entire circuit, features a DC converter that seems to power only this component. This is because power supply is an extremely important design element for Lumin. That is why in the U2x, the power supply has been separated into a separate enclosure that is just as robust as the main unit.

The transformers are bolted to aluminum flat bars, which are then bolted to the chassis. The bottom panel provides additional shielding for the entire unit. This is a linear power supply with two large transformers from the Norwegian company Noratel; these particular units were manufactured in Canada. Behind them, you can see three large rectifier bridges and five integrated voltage stabilizers LT 3086 and LT 3015 – this is how many DC lines are sent outside through a multi-pin, solid socket. Next to them, you can see nice capacitors from the Japanese company Nichicon. ●

▌ Technical specifications (according to the manufacturer)

Supported files: up to DSD512 & up to 768 kHz, 16–32 bits | MQA
Supported file types:
• DSD: DSF (DSD), DIFF (DSD), DoP (DSD)
• PCM: FLAC, Apple Lossless (ALAC), WAV, AIFF
• Lossy: MP3, AAC (M4A)
• MQA
Upsampling: up to DSD256 or up to PCM 384 kHz
Digital inputs: USB:
• USB: DoP 128| PCM 44.1–384 kHz, 16–32 bits
• optical, RCA: PCM 44.1 kHz–192 kHz, 16–24 bits | DSD64 (DoP64)
• HDMI: PCM 2.0 Audio, 4K Video Passthrough
Digital outputs
• USB: Native DSD512 | PCM 44.1–384 kHz, 16–32 bits
• BNC S/PDIF: PCM 44.1 kHz–192 kHz, 16–24 bits | DSD64 (DoP64)
• HDMI x1 (HDMI Passthrough & ARC): PCM 2.0 Audio, 4K Video Passthrough
LAN inputs: SFP | 1000Base-T Gigabit Ethernet, RJ45
Dimensions (W x H x D): 400 x 77 x 314 mm
Weight: 7 kg

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THIS TEST HAS BEEN DESIGNED ACCORDING TO THE GUIDELINES adopted by the Association of International Audiophile Publications, an international audio press association concerned with ethical and professional standards in our industry, of which HIGH FIDELITY is a founding member. More about the association and its constituent titles → HERE.

→ www.AIAP-online.org