Hardware Reviews

Innuos Zen MkII


Every streaming system needs a library, not the sort that furnishes a room but typically a hard drive where all your music is stored. You can get by on streaming services like Qobuz and Tidal if you want more music but there’s a monthly fee and a quality compromise. Most digital music libraries are stored on a NAS or network attached server, a hard disk drive with a small computer running software that ‘serves’ the required music to the streamer when asked. NAS drives come in various shapes and prices and while more expensive than USB drives, cost rather less than most dedicated audio servers. That’s because they are produced in volume and don’t need to worry about being electrically quiet, they also have switched mode power supplies (SMPS) which are a major source of interference and to be avoided if you want great sound. Network audio systems also require a switch so that the NAS, router and streamer can work together and these are another source of noise, noise that’s added to the signal and fed back into the mains via another SMPS.

So you can see that the potential for undermining sound quality with streaming systems is quite high. One way to improve matter is so use linear power supplies with the peripherals and optical connections that provide a degree of isolation, another is to find a company that makes dedicated audio servers which have been built with sound quality in mind.

Innuos designs a range of streaming products for both audio and video in the UK an builds them in Portugal, a range that contains three Zen models of audio server with a built in disc drive. The Zen MkII is the middle model between the half width Mini Zen at £699 with a 1TB drive and the 1TB SSD equipped Zenith MkII at £2,299, there’s also a bigger Zenith XXL with 4TB of SSD for £4,599. I reviewed the Zenith last year and was impressed why what I heard, there is more to these stealthy servers than mere styling. Feature wise they offer both USB and network outputs, so you can use a USB DAC or a network streamer, more importantly you can also bypass a network switch because there are two Ethernet connections on the Zen, one for the network and one that’s dedicated to a streamer. The latter not only removes a source of noise from the signal path but also filters incoming noise.


Innuos ZEN Mk2 rear


A medical grade mains filter and linear power supply goes some way to keeping gremlins at bay, it has a quad core Intel CPU with 4GB of RAM and offers 2 GB of memory playback which means that any electrical noise generated by the spinning discs is kept under control. The Zen servers run InnuOS software which comprises a Linux system created specifically for audio purposes. The UI and music library software uses Squeezebox software which means you can use control apps created for that well established system. I used something called iPeng 9, an inexpensive and well thought out app for iOS that is a lot better than any other third party app I’ve tried. It allows access to internet radio and streaming services like Tidal if you have a subscription. Android users can drive it with Squeeze Commander.

Operation is slightly different to other servers that I’ve tried. When you want to put new albums on the library via the desktop of your computer, they need to go in the auto-import folder first. Then you go to the my.innuos.com page on a web browser that finds your server on the network and offers a variety of different settings including back-up, library (below) and quarantine, the latter containing problem titles, in my case these were mostly duplicates but also included a ‘damaged CD’ that I had ripped. Settings include ripping mode and speed, configuration for a Sonos library, how to play DSD and a variety of other options. You can choose between two ripping formats, WAV or full fat FLAC, that is totally uncompressed FLAC which most seem to agree is the best option from a sound and metadata perspective. To get your album files into the library, go to the import page and choose ‘from auto-import’, the Zen then looks at the metadata for the new albums and sorts them into files for standard and high resolution titles. Sometimes inevitably it can’t find them, in which case they go into the unsorted folder, these titles can usually be found with the app but are not as well filed, ending up in the unknown artist folder for instance. The web browser approach makes up for the absence of a screen on the server and associated navigation buttons, and in truth is a far easier and more comprehensive method for managing the device.


innuos library


In the system the Zen performed very well via both USB and Ethernet connections, delivering a relaxed, open and well focused result with a range of different music. Timing is also good for the price, this is one area where digital sources regularly fall down and while I have heard better from a server, I haven’t done so at this price. What you want from a server is a quiet, reliable and easy to use source of data that your DAC or streamer can turn into an analogue signal. With a reasonably revealing system the differences between servers can be surprisingly large, the more affordable examples tend to sound more digital in the old fashioned sense of having a slight graininess, a distortion that’s more obvious in the treble but which pervades the entire spectrum. The Zen MkII does not have this quality, it is as clean and smooth as you like, which means that the music it supplies has a freedom from artifice, a naturalness in fact, that is hard to beat with other digital sources.

There is plenty of detail on offer which ensures pieces have all the vivacity, space and pace that they require to inspire you. This result was found with a lot of different tracks but Haydn’s String Quartets from the Norwegian 2L label made a very good case for both the Innuos and the Primare DAC30 I used with it. It delivered the music in full scale with full dynamics and excellent image depth yet in a relaxed, effortless fashion. It delivers shades of tone and three dimensionality that others near the price cannot match.


zen red 3 4


I also enjoyed the fact that the iPeng app lets you search internet radio stations even if it can’t guarantee a steady feed from all of them, very little can in practise. But it’s a well thought out app that offers a variety of ways to look at your library.

With the Zen I got better results via Ethernet than USB when using a Lindemann Musicbook:25 DSD as a streamer and DAC. I don’t have the same cable type for both links but both are high end examples, Vertere HB-USB and Chord Co Sarum Super ARAY network cable. Ethernet seems to have an advantage in terms of timing in every instance that I’ve been able to make this comparison so this finding is not specific to the Innuos, but it does make a good case for using the streaming route.

All in all the Innuos Zen MkII makes a very good case for using a dedicated audio server rather than a NAS drive and network switch, it sounds considerably better for one, making even a high end NAS seem distinctly crude by comparison. It also gives excellent results with both USB and Ethernet connections thanks to the efforts that the company has put into creating a quiet power supply and well isolated outputs. The onboard drive makes it easy to back up your disc collection and the styling is pretty cool, did I mention you can also change the colour of the LED?


Type: Music server with HDD storage and CD ripper
Storage: 2TB WD Red hard drive
Network connection: RJ45 Ethernet
Digital Outputs: RJ45 Ethernet direct, USB 2.0
Back up connection: USB
Formats supported: WAV, AIFF, FLAC, DSD, ALAC, OGG Vorbis, AAC, MP3
Sample rates: 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4KHz. 192kHz, 352.8KHz, 384KHz , DSD64, DSD128, DSD256
Bit depths: 1bit, 16bit, 24bit, 32bit
CD rip format: FLAC (zero compression)
Streaming services supported: Qobuz, Tidal, Spotify Premium
User Interface: Web browser, third party control applications
Other Features: UPnP server, DLNA device compatible
Dimensions (HxWxD): 70 x 420 x 320mm
Weight: 9kg

Price when tested:
Manufacturer Details:
T +44(0) 1793 384048

network server


Jason Kennedy

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