Ifi ZEN Stream Network Bridge Reviewed

I recently found myself looking into replacements for my current streamer of choice, to take better advantage of my new Topping D90LE DAC. I’ve been using a Cambridge CXN V2 since late 2019, feeding the Musical Fidelity M6S DAC via coax. But that setup didn’t give me the ability to stream PCM at maximum possible resolution, nor DSD, and the new Stream Magic control app has some accessibility issues that make it quite frustrating to use. And the D90LE only has 1 coax input, which I wanted to use in preference to an optical connection for the Cambridge CXC CD transport which I will retain.

It seemed a streaming transport, sometimes known as a ‘network bridge’ would be the logical choice. Such a device has no DAC of its own, instead outputting to a DAC of choice usually via the USB interface, which supports audio of a greater resolution than any of the other common digital inputs besides I2S. There are a few network bridges on the market that range from sensibly affordable (relatively speaking of course) to laughably overpriced. ‘Sensible’ options include the Pro-Ject StreamBox S2 Ultra, the recently announced Musical Fidelity MX Stream (review Here) and this, the Ifi ZEN Stream.

Intended to be paired with the ZEN DAC, but at home in any system with a USB or coaxial input, the ZEN Stream (the ZEN hereafter) is a tiny, curvaceous unibody stuffed with clever tech to clean up the digital signal, output by a powerful 64-bit computer running a heavily customised version of the open-source Volumio operating system. It supports AirPlay, Tidal Connect, Spotify Connect, DLNA / PUNP and NAA and is Roon ready. Ifi make a big deal of their ‘Active Noise Cancellation II’ and ‘iPurifier’ technologies on the USB and coax outputs respectively. And ‘exclusive’ modes are said to improve sound quality by enabling only the required software and services for a given streaming task, reducing what Ifi calls ‘software jitter’. Bold claims indeed, so I reached out to Ifi who kindly loaned a sample unit to test.

The ZEN is small but deceptively heavy. The front branding is rather unsubtle, made mores by the lack of physical controls bar the power and hotspot activation buttons. You can’t change the function of the hotspot button to something more useful day-to-day (play / pause for example), nor is there a front-mounted USB port which would have been nice. You can’t doubt the build quality though, and the design is distinctive and not something that deserves to be hidden away, even if the front branding is rather unsubtle.

Spec wise the ZEN is powered by a 64-bit, quad-core ARM SOC (system on a chip) running at 1.4gHz, essentially the same device as you’d find in most streamers and popular single-board computers like the Raspberry Pi. It has 1GB of RAM, of which roughly 700MB is free when the system is idling in its ‘all-in-1 mode with all services enabled. For reasons of power efficiency the CPU can down clock to a minimum of 408mHz when its full power is not required. The ZEN has 8GB of internal memory, of which roughly 5GB remains free on a standard installation.

A femto-precision GMT clock claims to eradicate jitter. The aforementioned Active Noise Cancellation II claims to “remove distortion from the audio signal” – not a technically sound claim if one were being pedantic, as the signal is digital, not strictly an analogue audio signal. Digital signals can, however, suffer from so-called ‘transmission impairment’ of which distortion is a form as well as noise and attenuation. Ultimately the cleaner the signal the better whether analogue or digital, even if error correction makes any subjective advantage moot.

Active Noise Cancellation II (ANC hereafter for brevity) is a method of power supply conditioning developed by Ifi primarily for use in USB-powered devices. USB Power from common USB ports is very noisy, often tens if not 100s of millivolts. This noise can be caused by a huge number of factors including noise picked up on the data or power bus, ground noise, faulty or poorly designed power supplies causing interference etc. Normally, power supply regulation is required to remove this noise. Common regulators are wired in series with the powerline and require at least several 100mV or more above the desired regulated output voltage to function.

In a USB-powered device where we’re adding regulation to a rail that is already nominally at 5V, this loss is unacceptable for stable performance with maximum output voltage. ANC is a circuit that regulates the power supply voltage, without any voltage drop, whilst also claiming better noise rejection than typical regulators. it generates a signal identical to that of the incoming electrical noise but in the opposite phase, actively cancelling it out. ANC is highly effective at removing low- and mid-frequency noise, while passive insulating filters deal with higher frequency interference. This combination is measurably more effective at eradicating noise corrupting the USB signal than devices relying solely on passive filtering.

The ZEN is packaged with a 9V ‘wall-wart’ switch-mode power supply, an ethernet cable and a small plastic tool to adjust the ‘exclusive mode’ setting. When powering it up for the first time it will appear as a WiFi hotspot, a mode that is disabled after a short period of inactivity. Hotspot mode can be re-enabled by pressing the hotspot button on the front of the unit. Connecting to the hotspot via a smartphone or computer gives you access to the web interface at ifi.local, where you can enter wireless network information. You can also use the Streamifi app for iOS and Android, which gives you instructions to guide you through getting the ZEN up and running. If you connect via ethernet, the ZEN will appear on your network after boot up and there is no further network configuration required. However you choose to set it up, it’s straight-forward and efficient, and I encountered no issues.

When you have the ZEN on your network, you’ll want to check for OTA (over the air) updates via the web interface. There was an update available for my sample unit which brought with it a number of notable improvements, including fixes to the USB DAC hot plug support. It also added MQA authenticator, added system Auto Update switch, optimised ssl verification of internet radio and changed the Format/Freq LED colours so as to be compliant with MQA’s UI indication: Yellow (44/48kHz PCM), White (88/96/176/192/352/384kHz PCM), Cyan (DSD64/128), Red (DSD256), Green (MQA), Blue (MQA Studio) and Magenta (Original Sample Rate(OFS)).

The ZEN immediately connected to my Topping D90LE DAC via USB without complaint and I proceeded to change a few settings. I recommend enabling the ‘full settings mode’ to give you access to everything, and disabling the mixer unless you need the ZEN to provide a volume control. I disabled Roon and Tidal as playback sources as I use neither, and disabled Bluetooth as my DAC provides Bluetooth already to a much higher standard than the ZEN does.

The user interface is pretty standard for an OEM Volumio installation. One of my major gripes with Volumio is their subscription-based features and their necessity to register an account to access the plugin repositories in a standard installation. Neither are issues here, though there is sadly no access to the plugin repository. You do get a few of the premium features though including Tidal Connect.

By accessing the ZENs development interface you can enable SSH and manually install plugins if you know your way around the linux command line. The login credentials are the same as the default credentials for the Volumio open-source images. Volumio runs on a Debian base, so you can install any other packages you choose and make use of the ZEN’s computing power for other tasks – though doing so will be outside of the remit of Ifi’s warranty and support. It’s nice to have the option if you’re DIY-minded, though. You could for example configure multiple hard drives in a software RAID for more redundant media storage, setup SAMBA shares to connected drives to directly transfer media, access content remotely via SFTP, install and configure CD ripping packages, implement infrared remote or custom installation control support and anything else your heart desires. You can’t achieve any of this through the interface itself.

The lack of a default plugin repository in particular is a shame as there are several great plugins for Volumio including internet radio directories (much better than the default radio implementation) and plugins for equalisation, room correction, control, integration and even CD playback and ripping. The latter is also provided as a premium feature in a Volumio streaming plan and also by default integrated into streamers from Pro-Ject and Musical Fidelity. It would be nice to see the CD ripping and playback features available via the ZEN perhaps with a few added features; automatic ripping on disc insertion, selectable codecs and configurable codec options, default storage locations and configurable file / folder naming and tagging.

These are features that need to be added in OEM editions of Volumio as a whole, though Ifi are one of the brands with the influence to see these improvements come to fruition. You can manually install the abcde ripping package on the ZEN along with its dependencies, and configure a USB CD rom drive with a udev rule for automatic ripping. But I’d wager that most ZEN buyers aren’t tinkerers, and even if they were the lure of a device like the ZEN is its pre-configured, out of the box functionality.

Returning to the ZEN itself and I was pleased to note that AirPlay, an essential function of any streamer in my opinion, is persistent. That is unlike other streamers which disable the AirPlay service claiming better sound quality (nonsense) and require that it be re-enabled each time the unit is restarted. However try as I might I couldn’t get AirPlay to work at all on the ZEN.

I figured it may be due to having lossless streaming enabled in the Apple Music app, so I disabled it with no joy. I then tried connecting the ZEN via ethernet and disabling the wifi. – but again, no dice. I factory reset the ZEN restoring the software that it shipped with and tried again without success. I tested AirPlay using a MacBook Pro and an iPhone, both on the same network and neither could connect and stream to the ZEN. Both had no trouble connecting to the MX Stream (also Volumio-based) or the Cambridge CXN on the same network. I note that none of the other reviews I found for the ZEN stream mentioned AirPlay, so assume it isn’t widely tested.

I did get web radio to work, however. The inbuilt directory does have a few gaps in its station list, at least in the United Kingdom. Almost the entirety of the BBC’s output, for example, is absent. Fortunately Ifi have added their own station list, which does contain the major BBC stations as well as stations from Absolute Radio and audiophile streams from Linn, Naim and Radio Paradise. Any of these stations, along with others in the directory, can be saved to your favourites for quick recall later. There’s a search function and artwork, stations logos, artist and track names are displayed in the player interface.

The ZEN can provide sufficient current to power a single portable hard drive, a USB CD ROM drive or the matching ZEN DAC from its USB ports. It’s also possible to use a powered USB hub to run more than 1 hard drive from the system, or connect up keyboards, mice and other accessories. The music library feature maintains a database of content across connected external drives, connected network shares (all common protocols are supported) and the internal memory. There is no option to change the storage location of the database and it’s unclear how big of a library you’d need before the database filled the remaining space on the ZEN itself.

There’s not much to report sound wise. The ZEN is a network bridge that takes digital audio and offers it up to a DAC of your choice. It shouldn’t impart any sonic character of its own, and it doesn’t. I tried the DLNA exclusive mode to see if I could validate the claims made in preference of using the ZEN in its ‘all-in-one’ mode, but I couldn’t. Even running the ZEN digitally into a Focusrite Clarette+ 8Pre interface, recording the output and comparing it against an original high-resolution PCM audio file, there was absolutely no difference what-so-ever. The Claret is renowned for being extremely flat, with conversion as close to a straight-wire approach as it gets and the equal of digital converters at any price. I don’t have an audio analyser to measure the ZEN Stream, but if I were a betting man I’d say the exclusive modes cannot be objectively validated.

However pure transparency is the essence of true high-fidelity. I firmly believe it is the case that most audiophiles prefer a tonally coloured sound, which they perceive as neutrality. But that is not hi-fi. The objective of hi-fi is to reproduce the source as accurately as possible, and that is pure transparency. That’s what the ZEN stream offers. If you want to stream content from drives, servers or over the internet, and you already have a DAC you like, the ZEN Stream from Ifi will do it as well as anything else. It is my hope that Ifi will fix the AirPlay implementation, and bring a few more premium features to the ZEN including Volumio’s plugin repository and CD ripping support. As it is the ZEN stream covers most user’s needs for a simple, compact streaming device, and earns my recommendation.