Cambridge Audio Azur 851N: Network player, DAC and preamplifier combined

Cambridge Audio Azur 851N
Cambridge Audio Azur 851N

Although Cambridge Audio describes the Azur 851N as a network audio player, it is also a DAC, equipped with USB and S/PDIF digital inputs, and a preamplifier that connects directly to a power amplifier via a variety of outputs. There’s also a wired Ethernet connection, and Wi-Fi works in conjunction with the included USB antenna. The device supports Apple’s AirPlay feature for direct connection to iOS devices and computers running iTunes, and can be paired with a separately purchased Bluetooth adapter that is compatible with the aptX codec, allowing connection to a wider range of computers and Android devices.


Digital inputs come in the form of two coaxial RCA phono jacks, one AES/EBU input (which, like Ethernet/Wi-Fi streaming, supports file formats up to 192 kHz/24-bit) and two optical. There is also an asynchronous USB 2.0 Type B input, allowing you to play DSD64 files from a connected computer. Three Type A USB ports on the rear panel can be used to connect external media (one also allows you to charge a connected smartphone or laptop), and there is another USB port on the front panel. Add Internet radio and Spotify Connect to all of the above and you have comprehensive digital functionality for any system; and all these features are for once realized not at the expense of ease of use.

Thanks to the large display with clear indication – the interface visualization of the new streaming module with the in-house name Zander, which controls the proprietary StreamMagic software stack – the device can be controlled either from the front panel by conventional scrolling and “clicks”, or remotely, without the use of additional equipment.

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The unit comes with an impeccably equipped remote control, but for the best experience, it’s best to use an Android or iOS tablet or smartphone running Cambridge’s updated Connect app, which can be downloaded for free from Google Play or iTunes. It’s one of the most well-designed network player management apps I’ve come across; Intuitive and flexible to use, it works perfectly in conjunction with this display, displaying both the content being played, as well as album art or radio station artwork.

One of the interesting aspects of this application’s design is the way it interacts with the Cambridge Audio 851N and music stored on the user’s network. Typically, in such systems, the application simply controls the player, which browses online music stores, but not here. Dominic Baker from Cambridge Audio explains: “Although the Zander is one of the fastest modules available today, when it comes to web browsing, it is nowhere near the level of modern smartphones. Therefore, now we use the capabilities of the smartphone to perform all browsing operations, selecting tracks, etc. The application points the device to the desired file only when you press the play button. This makes control faster and more optimal.”


The internal “filling” contains a digital circuit solution already familiar from the flagships of the model range – the Cambridge Audio Azur 851C CD player : two Analog Devices AD1955 DACs are used in double differential mode – one per channel.

Before D/A conversion, ATF2 type upsampling is performed, also used in the Cambridge Audio Azur 851C: second generation Adaptive Time Filtering provides flexible up-conversion to 384 kHz / 24 bits before the digital data reaches the DAC and is used as to reduce jitter and to remove digital noise far beyond the audible range.


In addition, there is a choice of digital filter settings, as in the player and DAC mentioned above. Linear phase filter, minimum phase filter and high slope filter are available; All of these options are selected using a button on the front panel, which also performs full phase reversal when pressed and held for about two seconds. Cambridge recommends a ‘you never know until you try’ approach, where there is no one ‘correct’ setting, only one that best suits the signal source, specific audio system and personal preference. The player stores the settings selected for each input in memory, so different filters can be used depending on the source being used, internal or external.


The ball is ruled by a 32-bit SHARC processor, which is responsible not only for oversampling, but also for the volume level if the Azur 851N is directly connected to a power amplifier. The processor is designed to maintain full digital resolution even at lower volumes by resampling the signal at each level change stage, rather than the life-saving bit reduction used in some digital preamps.

Other 851 series digital devices use the Blackfin processor, but here the more powerful SHARC has been chosen to support DSD64 file transfer via USB using DoP (DSD over PCM) technology. Baker explains that the choice of DoP and, by extension, SHARC, was prosaic: “At the time we were developing the Cambridge Audio 851N, we could not find any DACs that, while supporting DSD by default, would outperform the AD1955.”


Not only does the Cambridge Audio Azur 851N use a SHARC DSP to increase the resolution of all content decoded by the device to 384 kHz/24 bit and process DSD64 data streams coming via the USB port, but it also has significant additional resources that made it possible to implement three different digital filter algorithms before the Analog Devices DACs (the latter replacing the 192 kHz Wolfson DACs used in earlier USB DACs and players). The Linear Phase Filter provides a constant group delay, producing a time-coherent output with limited pre/post echo, and is the listener’s preferred option when streaming 44.1 kHz or 48 kHz content. The minimum-phase option works more like an apodizing filter, responding to the impulse effect of any unnatural, unobservable pre-echo, but increasing the energy of the post-echo and initiating a non-linear group delay. Finally, the high-slope filter option is a classic “brick wall” approach that weakly attenuates any pre/post echo but provides a linear-phase output with excellent attenuation of any digital artifacts just outside the audio range. Additionally (probably due to higher upsampling rates), the Cambridge Audio Azur 851N delivers a wider and flatter frequency response than its predecessors.


Combining solid design, flexible, intuitive controls and superb sound that fully copes with aggressive rock and brings out the full scope of classical music, this unit perfectly complements the flagship Azur range. Streaming DSD network content would make it ideal, but as a source or core component of a complete system, the Cambridge Audio Azur 851N offers excellent value for money.

Specifications Cambridge Audio Azur 851N 

DAC 2 x Analog Devices AD1955
Digital filter ATF2 second generation, upscaling 24 bit / 384 kHz
Filter operating modes Linear Phase, Minimum Phase, Steep
USB USB Type B, 4 x USB Media (one on the front panel)
File system FAT32, NTFS
Inputs AES/EBU, 2 coaxial, 2 optical
Outputs coaxial, optical, unbalanced, balanced
Inputs coaxial, optical
Optional Ethernet, Wi-Fi (WEP, WPA, WPA2), Bluetooth (via optional USB module), RS232, IR In, Control Bus (input and output)
Bitrate support up to 24 bit / 192 kHz
DSD support DSD64 (when receiving a signal from PC)
Dimensions (WxHxD) 430 x 115 x 360 mm
Weight 8.1 kg

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