Cambridge Audio 851C Review

Despite the popularity of digital content, many people (myself included) prefer physical media over the digital download. In fact – where possible, I avoid digital downloads at all cost, and will always choose the CD or vinyl alternative where available. There’s just something about physical media that a collection of 0’s and 1’s stored on a computer can’t match – pride of ownership, the aesthetics, and, in many cases, the sound.

Enter the Cambridge Audio 851C – A CD player/DAC/digital preamp that aims to be the central hub for all of your digital sources. It’s primarily a high quality cd player – but offers a range of digital inputs (including a USB input for your computer) and the ability to serve as a digital preamp for connection directly to a power amplifier such as Cambridge Audio’s own 851W or 651W.


The 851C is designed to play back your digital music collection with the highest possible sound quality. To do this, Cambridge Audio use a blend of clever technology and high-end components.

The DAC (Digital to Analogue Converter)

The DAC section features 2 Analog Devices AD1955 24-bit DACs, coupled with a Blackfin ADSP-BF532 32-Bit DSP (digital signal processor), running Cambridge Audio’s 2nd generation ATF2 technology. Developed in conjunction with Anagram Technologies of Switzerland, ATF (Adaptive Time Filtering) upsamples all incoming audio to 24-Bit, 384KHZ – effectively meaning the DACs have more data to work with, so you hear every tiny detail of your music. It also helps to dramatically reduce jitter, a form of audible interference which affects all digital music – therefore reducing it is a very good thing.

The Filters

The ATF2 technology includes 3 filters to tailor the sound to the listener’s preferences and system setup. Cambridge Audio can explain these better than I can:

The Steep roll-off filter exhibits strong attenuation of aliasing images outside the pass band (i.e. above 22.05kHz) at the expense of a little pre and post-ringing in the time domain. 

The Linear phase filter uniquely features ‘constant group delay’ which delays all audio signals at all frequencies by the same amount meaning all audio is fully time-coherent at the output.

Minimum phase meanwhile does not feature constant group delay but rather the co-efficients have been optimised without feed-forward so that the impulse response exhibits no pre-ringing in the time domain.

The differences between the 3 filters are subtle – you'll have to experiment to see which filter best suits your listening preferences and system setup. You also have the ability to select a different filter for each input – and the 851C will remember your choice.

The Packaging

The 851C is supplied in standard Cambridge Audio packaging – that’s no bad thing, however. Thick foam supports support the product on each end, and polystyrene blocks protect the front and rear. I'd like to see these blocks fashioned from the same foam as the end protectors – as they tend to break up, making a mess. The off-set handles are retained, making the fairly large, substantial box easy to carry.

In the box, you’ll find the standard IEC power cable – in the case of the UK model, both a 3-pin UK cable and a 2-pin European cable are provided. You also get a bag containing documentation, the remote, and 3 triple A batteries.

Initial Impressions.

This is my 3rd 851C. No, I don’t own 3 of them – this is the 3rd one I’ve owned, and the first that worked as expected. The first had an issue with the tray (more on that later) – and the second a slightly miss-aligned casework that caused the player to rock when placed on a level shelf.

Maybe I was just unlucky – or maybe Cambridge Audio have some quality control issues with these machines that need resolving.

I also happened to notice that my second 851C did not have the raised Cambridge Audio logo on the top – whereas the others, including my current one, do. I’m unsure whether Cambridge Audio have updated this player, removing their logo – or perhaps they forgot to stick the logo on. Hopefully Cambridge can shed some light on this also.

Issues aside though, initial impressions are great. Upon lifting the player out of the box, the first thing you’ll notice is the weight. As with all the 851 components, it feels considerably heavier than the quoted weight (10KG for the 851C). This is primarily due to the solid metal casework – the 851C features Cambridge’s acoustically damped all-metal chassis, which makes extensive use of aluminium. The player is built like a tank – everything feels solid, from the connectors on the rear to the thick brushed aluminium front panel.

The vents on the top panel match those found on the other 851 components. Tapping on the top panel yields a dull thump, rather than the ringing exuded by many other similarly priced components. The chassis also features Cambridge’s dual layer damped feet which help to minimize vibrations being transferred to and from the player.

The back

There’s a lot going on on the rear of the 851C. Power is provided by an IEC power connector with dedicated power switch. Next are the control bus, IR in and SR-232C ports – these are used to integrate the player into a full Cambridge Audio system, or for integration into custom installations.

next we have the inputs – 2 pairs of optical and coaxial inputs, as well as an AES-EBU XLR input and the USB input. The USB input has an associated ground lift switch – this disconnects the USB ground from the chassis ground, used to prevent humming or buzzing when using the input. All inputs are 24-bit compatible

And, finally, the outputs – both single-ended RCA and balanced XLR outputs are provided. It is recommended to use the balanced outputs of the 851C with an amplifier or preamplifier with balanced inputs (such as Cambridge Audio's own 851A or 851E). Balanced connections can reject noise and interference in the cable, and offer slightly better sound quality than unbalanced connections

The Front

As is tradition with the other 851 components, the 851C features a simple, neat front panel, featuring only the controls necessary to operate the player. The most noticeable feature is the centralized display – this display is used to show the status of the player, as well as allow you to alter the settings in the configuration menus and access the playback programming options.

Above the display, you’ll find the aluminium-fronted disc tray – this is recessed slightly in the front panel. It would be nice if it lined up perfectly, with a reduced gap around the edge.

TO the left, you have controls for power, menu, mode, filter, and the IR sensor. To the right, you’ll find eject, play, stop, previous and next. If a computer is connected via the USB input, these controls can control the playback – assuming the host playback software supports this function which most do.

It’s a clean, simple layout that closely mimics the design of the other 851 components. The buttons have a nice tactile feel to them when pressed, and the system responds instantly to button presses.

The Remote

The 851C is supplied with an Azur Navigator remote control – the same supplied with the 851A. I love Cambridge Audio's remotes – and this one is no exception. It's perfectly weighted, balancing perfectly in the hand when using the central circle to adjust the volume or skip tracks. Despite being a somewhat lengthy remote, everything is easy to reach, and the clean layout means you don't have to look too hard to find the control you're looking for.

While this is a nice, perfectly usable remote, I would like to see the Azur units updated to include the updated Azur remote that comes included with the 851E – it's a slightly better remote which can also control the Cambridge Audio Stream Magic 6.

The Transport

Let's take a moment to talk about the transport. The transport (sometimes referred to as the 'CD Drive') consists of a few main components – the mechanism, the laser assembly, and the servo. As previously mentioned, Cambridge Audio have done away with the standard off-the-shelf transports found in many cd players. Many of these transports are not CD-only transports – meaning that their electronics are designed to cater for many types of optical media, from CD's, to DVD's, to data discs and everything else in between

Instead, they've developed their own, in-house transport and custom S3 cd servo. This is a cd-only transport – meaning it is optimised for reading cd's, retrieving the maximum amount of detail from your discs, resulting in improved sound quality.

Powered by an Arm7 processor, the s3 servo uses the latest double-sided surface mount technology, and some custom circuits and software to dynamically adjust the focusing, tracking, and output level of the laser in real time. This enables the player to read information from discs that other players will miss, as with many standard transports the laser adjustments are fixed. It also helps to reduce digital jitter, further improving the sound

The mechanism itself is of reasonably high quality – though the tray isn't as smooth as it should be. It appears from the action of the tray that Cambridge are still using a belt to drive the tray in and out – if they were to use a direct-coupled gear mechanism, the tray would be much smoother – and would last longer. The tray feels a bit flimsy in comparison to other players, such as the cheaper Marantz CD-6004, which has an incredibly solid mechanism.

The laser mechanism itself is also somewhat louder than some other players – it's not over-obtrusive, and can't be heard from across the room – and, with the music up, you probably won't notice it anyway. However, some extra dampening, or a quieter spindle motor would be nice to see.


As you'll undoubtedly have gathered, the 851C is more than just a CD player – therefore its usage is somewhat more complex than your average cd player. That being said, a lot of thought has clearly gone into the player's user interface, making the extensive range of features as easy as possible for the end user to understand and use.

One area where Cambridge Audio always excel is their user manuals – and this one is no exception. It clearly outlines every feature of the 851C, giving clear concise instructions for each and every step.

Playing CD's

Of course, the 851C is first and foremost a cd player – and playing cd's couldn't be simpler. On first power-on, the player will be in CD playback mode by default. Pressing the eject button on the front panel or on the remote will open the tray for you to insert a cd. Upon closing the tray, the player will read the table of contents, and display the number of tracks and the total time of the CD. The player also supports cd-text. when a disc is inserted that contains cd-text, the name of the album will scroll once.

Upon inserting my first CD, I was pleasantly surprised at how quickly the 851C read the disc. The disc is read within a couple of seconds – whereas many modern cd players with their generic transports can take anywhere from 5 to 20 seconds to initialise a disc.

Unfortunately, there's a slight delay when skipping tracks – after pressing either the next/prev buttons, there's a slight pause until the laser moves to begin playing the track. I assume this is to allow the user to skip more than 2 tracks in a single laser movement – however skipping through a cd to locate a particular track can become frustrating.

The 851C doesn’t cope at all well with dirty or scratched discs. My copy of Green Day’s ‘21st century breakdown’ has a tiny, barely visible scratch near the outer edge. Many players simply ignore this, and the disc plays just fine – the 851C, however, drowns out the intro to ’21 guns’ with a series of obtrusive, irritating clicking sounds from both the player and the speakers. Clearly, the error correction algorithm used in the S3 servo needs some work.

The usual programming modes are available – repeat track, repeat disc, random playback and program. The player allows you to create a playlist of tracks on the current CD, meaning you can play back the tracks in any order or skip entire tracks.

The USB Input

The 851C supports 2 USB audio protocols – USB Audio 1.0 and 2.0. By default, the player is set to operate in USB 1.0 mode. This will accept audio up to 24-bit, 96KHZ and works natively under Windows, Mac OS X, and most distributions of Linux. If you're running windows and wish to use USB audio 2.0 mode, a free driver must be downloaded from the Cambridge Audio website – Mac OS X and most Linux distributions support this mode natively. This will allow you to play back files at up to 24-bit, 192KHZ.

The player also supports bit-perfect data transfer, using the Cambridge Audio USB 2.0 driver and a supported playback application. For more details on this function, refer to the 851C user manual.

The Digital Inputs

The digital inputs of the 851C allow you to connect devices such as digital tuners, streamers, Docks, games consoles, televisions, and many other devices with digital outputs – bypassing their inferior DAC sections. Setup couldn't be simpler – connect an appropriate cable from the digital output of your device to one of the many inputs on the 851C, select the input using the mode button on the front panel, and begin playback on the device.


The 851C has several configuration parameters that can be adjusted within its onboard configuration menus. These include:

  1. Auto Off – The player will automatically go into standby after a set period of inactivity.
  2.  Auto Play – Begins playback of a cd immediately after closing the CD Tray.
  3.  USB Class (sometimes referred to as protocol) – Allows you to select the aforementioned USB audio Protocol, either USB Audio 1.0 or USB Audio 2.0.
  4.  Input Naming – allows you to rename the digital inputs to correspond to their connected sources. For example, “DVD”, “PS3”, “dock” etc.
  5.  Front IR – allows you to disable the front infrared sensor. This is useful in custom installations, where an external IR receiver is used.
  6.  Digital Vol – allows the 851C to operate as a digital preamplifier, to directly drive a power amplifier (such as the Cambridge Audio 851W or 651W). When this option is enabled, a balance option is available to alter the left/right balance.

In most cases, you’ll find the 851C is setup correctly out of the box – In my system, it’s used as a simple CD player – therefore I had no need to change any settings.

The Sound

Let me start off by saying – if this player didn’t sound so good, I’d have switched to something better when my first unit was returned. The fact that I persevered with 2 further units is testament to the sound quality of the player.

As with the rest of the 851 range, the 851C’s sound is best described as being natural. Stereo images are rendered beautifully, with a large, 3-dimensional sound stage. It’s not ‘in your face’ – more ‘in your room’. The timing is spot on – notes start and stop with precision. There’s none of that ear-bleeding sibilance often exuded by some players with lesser DACs, and, surprisingly, the player is pretty forgiving with poor recordings.

Let’s start off with some test tracks. The first album in the tray was the new one from The Pretty Reckless – Going to Hell. I’m obsessed with this album – in my eyes, this band can do no wrong. And the 851C does it justice.

‘Heaven Knows’ – an upbeat track featuring a large crowd, heavy drum beat (a lot like Queen’s legendary ‘we will rock you’) and Taylor’s stunning, powerful voice is rendered with precision. It accurately shows off the 851C’s ability to convey a 3-dimensional sound stage – with the powerful drum beat appearing to come from behind. The stereo image is wide and expansive, thanks to those dual Analog Devices DACs. It’s a phenomenal performance.

‘Waiting for a friend’, a calmer number, shows that the 851C is no slouch when it comes to kicking back when required. And the vocals… ah, the vocals. The 851C, despite being a natural sounding player, is able to accurately deliver the emotion in a track. Everything from the acoustic guitar, to the human voice. I can’t find words for it; it’s simply stunning.

Next to ‘Aint it Fun’ from Paramore’s latest self-titled album. This track has a particularly tricky bass line which the 851C makes short work of. It demonstrates a sense of timing that few players can match. This is an upbeat track, designed to get you up and out of your seat – the 851C gets stuck in with enthusiasm, delivering an exciting, energetic performance.

‘Ordinary People’ from John Legend’s ‘Get Lifted’ album further demonstrates the 851C’s abilities – the staccato piano displaying the 851C’s sense of timing, and Legend’s powerful, expressive voice filled with emotion.


Summarizing Cambridge’s other 851 series components was easy – buy them. However, this one’s a little harder. With the 851C, Cambridge have created a device that can stream digital music from just about anywhere – while also serving as a CD player. Its digital section is faultless – I’d buy one for the DAC alone.

It’s the transport that lets this player down. If Cambridge were to implement a less flimsy (and quieter) drive, and better error correction, they’d have the perfect CD player. There also appear to be a few quality control issues which need resolving.

However – when you can get one that works, and providing you can live with the transport, it’s a great CD player. Of course, if you don’t require the CD playback functionality, or if you’d prefer to use an external transport, Buy the new Cambridge 851D – which is essentially an 851C stripped of its CD drive, with the addition a few more inputs.

It would be nice to see an updated version of this player with the transport issues fixed. That said, the sound is the most important aspect when buying new hi-fi component – and in this area, the 851C is unparalleled. Pare it with a suitable amp and speakers (such as the Cambridge Audio 851A, or the Cambridge Audio 851E/W, and some decent speakers; sit back, and enjoy the music.

Read More:
Cambridge Audio 851C Upsampling CD Player/DAC/Preamp

By Ashley

I founded Audio Appraisal a few years ago and continue to regularly update it with fresh content. An avid vinyl collector and coffee addict, I can often be found at a workbench tinkering with a faulty electronic device, tweaking a turntable to extract the last bit of detail from those tiny grooves in the plastic stuff, or relaxing in front of the hi-fi with a good album. A musician, occasional producer and sound engineer, other hobbies include software programming, web development, long walks and occasional DIY. Follow @ashleycox2


  1. Hi Ashley! I have a chance to get a inexpensive 851c, now I have the Cxa80 only, is a upgrade using the 851c like dac over the onboard wm8740? Thanks!

    1. The 851C would be an upgrade, whether you can justify the expense depends on the price and your budget. One of our readers recently commented on the 851C over on our CXA80 Review so it’s worth having a read.

  2. Hi Ashley, nice review, thanks.

    I am currently looking for a new DAC and was looking at both the 851C and the new 851D.  Have you heard the 851D, i would be very interested in your impressions of this DAC and if this is a step up from the 851C?

    Kind Regards


    1. Hi Colin,

      While I've not heard the 851D in person, I wouldn't imagine it to be much different from the 851C. It uses the same AD1955 DACS, same DSP, and the same filtering. The only differences are the 851D has more digital inputs, lacks a CD player, and is slightly cheaper. It also has a headphone jack and a built-in volume control, which you’ll use if you’re using it as a digital preamp.

      It really comes down to what you prefer – more inputs, or a CD player. It’s worth noting that if you have a DVD/Blu-Ray player in your system, even a basic one, as long as it has a digital audio output it can be connected to an 851D and used as a CD transport.

      Hope this helps!

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