Lumin U2x Network Streamer Review

Over the past few years, Lumin has appeared frequently on StereoNET with reviews of the D3, T3, P1, P1 Mini and M1, respectively. To recap quickly, the company was established in 2003 by Pixel Magic Systems of Hong Kong. In an industry where most rely on generic computer boards and add-on modules, this company is unusual for developing its own hardware and software solutions. I reviewed the P1 Mini and was suitably impressed. Hopefully, the U2x will continue the company’s winning streak…

UP CLOSE

Designed to offer the ultimate in digital output performance, the U2x replaces the U1x as Lumin’s flagship streaming transport. The first top-of-the-range model to feature the company’s latest custom-designed System-on-Chip, it packs enough processing power to handle audio streams up to 32-bit/768kHz PCM and DSD512, as well as resampling to DSD256. It comes in two boxes – the streamer and the power supply. Both are CNC-milled from a single billet of aluminium and feel luxurious yet indestructible. The former measures 350x345x60mm and weighs 8kg, the latter is 106x334x60mm and weighs 4kg. Available in black or silver, both boxes are compact enough to be placed together on a hi-fi rack.

Lumin says the power supply has been designed with meticulous care. Twin toroidal transformers provide independent digital and analogue feeds, while low-noise linear regulators and thick aluminium walls minimise electrical and magnetic interference. The supplied locking umbilical cord is 1.5m in length and flexible, giving you plenty of placement options.

The streamer’s curved fascia features a bright monochrome OLED display with basic track information. You won’t get album art or fancy VU displays, but this makes for good legibility. The display can be dimmed or disabled if you so prefer. Around the back are two networking ports, an RJ45 socket and an SFP fibre slot. Both can be used simultaneously, and Lumin suggests using one port to connect to your router and the other to your music library storage. Fibre has the added benefit of isolating the unit’s electrical ground from noise on your network. In my review of the P1 Mini, I found that the fibre port provided a cleaner and more precise sound if you have USB storage that connects to either of the two USB-A ports.

As a dedicated streamer, connections are focused on networking, digital outputs and clocking. The digital outputs comprise an isolated USB output (a new feature for Lumin), TOSLINK, coaxial, BNC and AES/EBU. The USB output handles streams up to 32-bit/768kHz sampling rate for PCM and DSD512. The S/PDIF and AES/EBU outputs are rated up to 24-bit/192kHz and DSD64 (via DoP).

Lumin has now joined the clocking game with 10MHz reference clock input/outputs. The U2x can function as a master clock or be slaved to an external clock. A master clock allows connected units to share a common timing reference, minimising jitter and improving sound quality in theory. Such inputs have begun to appear on high-end DACs, network switches and DDCs, giving rise to plenty of use cases. The Lumin also has Femtosecond accuracy word clocks. When used together, the 10MHz clock signal serves as a reference to the word clock to increase its accuracy. You can toggle the operation of the 10MHz clock in the Lumin App. Lastly, an earthing post lets you experiment with grounding accessories or connect the unit to another grounding point in your system.

After connecting the unit to my home network via a wired LAN cable, the latest firmware was downloaded and installed. The Lumin app needs to be downloaded to access the player’s settings and navigate through your music library. The app can also be used to control other UPnP-compatible streamers. It’s been my control app of choice in recent times, which is testimony to its attractive GUI and ease of use.

The U2x plays all major file formats and is MQA compatible. Streaming services such as Amazon Music, Qobuz Connect, TIDAL, KKBox and Spotify Connect are supported. The Lumin also works with music management software like Roon (as an endpoint), Audirvana and Plex. Because the company believes that Wi-Fi and Bluetooth degrade sound quality, neither is supported here. You do get Apple AirPlay compatibility, though.

The app taps into the U2x’s settings and offers a plethora of features to customise your music navigation experience. The more noteworthy ones are clock selection and resampling. For the latter, you can choose a specific setting (native, up or downsampled) for each sampling rate. This streamer is also compatible with Lumin’s attractive remote control unit, but this is not included in the box, which is surprising considering that this is a flagship product, and the cheaper P1 Mini includes it!

The Lumin can also function as a preamp by applying attenuation to its digital output stream. You can switch between the default software and Leedh Processing, a patented third-party algorithm. The latter was noticeably superior and should be activated if you are using the volume control feature. Most U2x owners would be using a dedicated preamp, but this is still a nice-to-have feature.

I set up my review sample with a wired RJ45, running to my hi-fi room network switch. The digital outputs were then sent to my Totaldac D1-Six DAC. The rest of my reference system comprises a Conrad Johnson GAT S2 preamp and ART 27A power amplifier, and Vivid Audio Giya G4 loudspeakers. My listening notes were made streaming TIDAL, using the BNC S/PDIF output, and with the internal 10MHz reference clock enabled. All files were played without resampling. This is worth mentioning as the sonics change quite significantly depending on how you set it up.

THE LISTENING

This is a strikingly realistic-sounding streamer, one that delivers a holographic portrayal of instruments and voices. Its basic sound is quite analogue–like, in the sense that it doesn’t sound clinical or processed, and it boasts quite a dynamic approach to making music. There’s an enjoyable fluidity to its nature that is musical, non-fatiguing, and yet highly resolving.

You do need to configure it properly, though. Using the U2x as a Roon endpoint yielded a very dynamic and forward sound, a clear departure from the more relaxed Lumin house style. Similarly, I found the BNC and USB outputs to differ – the latter sounded clean, while the former had better dynamics, yet less control and composure. I also preferred having the 10MHz clock enabled, which resulted in better presence and a firmer tone. The plethora of options does mean that you can tune the Lumin to your taste, but it takes some experimentation.

At its best, this is a highly communicative device. Take Merry Christmas, Mr Lawrence by Ryuichi Sakamoto as an example. In his final concert movie before his death, the great man played this piece at a slower tempo, filling it with emotional intensity and poignancy. The piano solo track started with high notes that had crisp attack and textured harmonics that contrasted with the heavy and sustained notes. Throw in the delicate phrasing and you were treated to a performance that charged my listening room with an emotionally riveting and life-like performance. The Lumin showed this in full effect.

Complex recordings like Panorama by Fernando Huergo Big Band were handled impeccably, with precise staging and instrument separation. This recording is not loud or dynamic, but has lots going on. The brass instrument solos breathed with palpable energy in the leading edge and reverb of notes. What impressed me further was the deft retrieval of details in the recording, like the excellent drum work, even in the thick of things. Vocals came across as fluid and detailed. Tony Bennett and Diana Krall’s duet of I’ve Got A Crush On You was rich, mellow and smoky. Suitably laidback and grain-free, the Lumin did not smooth over any detail, and retained the recording’s vocal texture and subtlety.

This streamer had no issue with keeping up with dynamic tracks or delivering punchy basslines. For example, The Robots by Kraftwerk sounded tight and dynamic. Even at higher-than-normal volumes, the Lumin kept a firm hand on timing and tempo, with plenty of reserve bass power on tap. The synthesiser tunes here should have even tired bodies up and about doing their best robot-dance moves.

The U2x does not imbue the music with any particular tonal character of its own, but in the treble, things can sound just a little too polite. At the same time, extended and clean, high frequencies have a silky character to them that tempers the energy of some musical genres – like heavy metal, for instance. This is something I’ve observed in other Lumin products, although this one is the closest to neutral in my experience.

THE VERDICT

The Lumin U2x is an astoundingly good streamer. It has a beguilingly fluid sound that draws you in and keeps you hooked with its natural and realistic reproduction of music. It’s expensive, but worth the coin if you have a set-up capable of doing the Lumin justice. This is digital audio close to its absolute finest.

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