“So little distortion, it’s barely measureable”… “The best sounding amplifier Cambridge Audio has ever made” – That’s what Cambridge Audio say about their new 851E Preamplifier and 851W Power amplifier combination. Bold claims indeed, especially given the success Cambridge Audio have enjoyed with their recent flagship offerings.
It all started with the 840 series – the 840C upsampling CD player, and the 840A Class XD integrated amplifier that was, literally, in a class of its own. Then came the 840E/W – a pre and power amplifier that brought all the features of the 840A integrated, along with a few adaptations such as Cambridge Audio’s ‘terrapin’ impedance buffering modules and a refined version of the Class XD technology, and set the standard for a flexible, versatile, truly high-end hi-fi separates package.
Now it’s the turn of the new 851 series. The 851A integrated amplifier, the subject of a previous review, impressed me with its huge range of features, excellent build quality, and, most importantly, stunning sound quality. Now it’s the turn of the new 851E and 851W pre/power combination to take Centre stage.
Ordinarily, I’d give each component a separate review – however, in this case, I’ve decided to review the 851E/W (hereafter referred to as the ‘E/W’ to save the wear on my keyboard) as 1. Chances are, by the end of the review, you’ll have already bought them. (Spoiler alert – Yes, they really are that good).
The packaging is fairly standard for Cambridge Audio products – Both products are supplied in strong boxes (complete with corner protectors), with thick foam supports on either end of the product, and foam blocks protecting the front and rear. The off-set handles on either side of the box are present – this is a nice touch, and makes carrying these fairly weighty boxes much easier.
Inside each box, you’ll find 2 power cables (at least for the UK models) – a UK 3-pin cable and a European 2-pin cable. The 851W uses a special, high current power cable, while the 851E uses a standard IEC kettle lead.
In each box, you also get documentation, a control bus cable (more on that later), and, in the case of the 851E, the new Azur remote.
If I were to cover every feature of these components in this review, it would quickly become an audiophile ‘remaster’ of War and Peace. That being said, here are a few of the features on offer:
The 851W Power Amplifier
The first thing you’ll notice when lifting the 851W out of its box is the weight – to say its heavy is an understatement. It feels considerably heavier than the quoted 19KG – this is certainly not an amp you’re going to be moving unless absolutely necessary.
Take a look at the 851W’s feature list, though, and it’s not hard to see why. Not 1, but 2 toroidal transformers supply power to the unit – 1 substantial transformer drives the power amplifier stage, while another provides power for the input and other circuitry.
The 851W features 12 output transistors per channel, and, when using 1 851W in stereo mode, can output a total of 200W per channel (8O) or 350W per channel (4O). You can, however, configure the 851W amplifier to run as a monoblock power amplifier – allowing you to have 2 or more 851W’s in your system. When used in this way, the output power rises to 500W per channel (8O), or a massive 800W per channel (4O).
Cambridge’s ‘class XD amplifier circuit, designed to eliminate crossover distortion and combine the benefits of a class A amp with the efficiency of a class AB design, is the key to the 851w’s incredible sound quality. This clever technology takes a traditional class AB design, and adds voltage to shift distortion to a point where it is not audible to the human ear, effectively displacing it – hence the name ‘crossover displacement’.
CAP5, or ‘Cambridge Audio Protection 5, is a 5-way protection system that guards your amplifier and other equipment against electrical faults as well as operator error. It constantly monitors the internal components of the amplifier, to keep them working inside their safe operating zones. The 851W will automatically enter protection mode if:
- Positive DC voltage is detected at the speaker outputs, caused either by an internal fault or by hard clipping of the amplifier.
- Over-Temperature Detection – Monitors the temperature of the output devices, and keeps the temperature of the within the limits specified by the output device manufacturer.
- Overcurrent Protection – Stops you driving the amplifier too hard, or with speakers of 2 low an impedance.
- Short-circuit Protection – Checks that the speaker terminals are not shorted together. This can be due to loose wires, or spade connectors that are too large for the terminals.
- Intelligent Clipping Detection – Detects when the amplifier is clipping or overdriving its output.
CAP5 insures your system is guarded against any internal fault, or case of ‘operator error’, that may occur – with the price of these components, this is invaluable. Catching these faults can save you a lot of money in the long run.
The 851E Preamplifier
Where do we start – Firstly, the specs. The 851E preamplifier boasts THD figures of <0.0045% THD and a signal to noise ratio of <90 DBU – as Cambridge Audio rightly say, “In preamplifiers, that’s a very good thing!”
The 851E features no less than 8 inputs – the first 3 of which being switchable between balanced and unbalanced, and the 8th a recording monitor loop – for use with 3 head analogue cassette decks, open reel machines or computer sound cards.
Single-ended RCA and balanced XLR preamp outputs are provided, as well as a mono subwoofer output with optional 200HZ low-pass filter.
A solid state volume control offers precise linear volume adjustment reserving the purity of the audio signal, and retains perfect channel balance even at low levels – something that is often difficult to achieve with standard analogue potentiometers.
Bypassable tone controls are fitted, allowing you to tailor the sound to your preferences, to compensate for deficiencies in your room acoustics or your speakers. For those audiophiles who dislike tone controls, it’s possible to disable them with the press of a button – they’re switched in and out with a relay, so when disabled will have no effect on the sound. The 851E also remembers whether or not the tone controls are enabled for each input – meaning you can have them automatically enable for the tuner, but not the CD player – this is a nice touch.
Both units also feature control bus connections, allowing them to control, and be controlled by, other Cambridge Audio equipment. Trigger inputs and outputs are provided, and the 851E also has an RS-232C port for use in custom installations.
Both components feature Cambridge’s acoustically damped, all metal chassis. These solid, well-damped chassis not only look good, but provide a solid platform for the sensitive electronic components which are susceptible to vibration, as well as RF and electro-magnetic interference. They both feature thick, brushed aluminium front panels, and have matching grilles on the top.
Both units feel extremely solid and well put together – there’s no flex in the casings when you lift them, and they’re reassuringly heavy. Tapping on the top of each unit yields a dull ‘thump’, unlike the metallic ringing made by other, less well build components. The sides of the 851w do have a resonating ring to them however – this is hardly surprising, as there’s very little space on the side due to the numerous holes for ventilation that cover the sides, top, and bottom for airflow. These are required as due to the nature of the class XD technology, the unit becomes hot in operation. It is essential that these components be installed in a location with plenty of airflow – such as an open rack. They may become too hot if installed in a cabinet – and why would you want to hide them anyway?
As you would expect with a pre/power combo, the initial setup is somewhat more involved than with a standard integrated amplifier. Fortunately though, Cambridge include a handy quick-start guide to help you get things up and running. It’s fairly simple though – and if you do connect something in the wrong place, Cambridge’s ‘CAP5’ protection system will kick in and save the units before any damage occurs.
851W: The front
The front of the 851W is refreshingly simple – a single power button, and a number of status lights, are all that adorn the thick, brushed aluminium facade. The lights are used to show the status of the amplifier, as well as allow you to access the hidden configuration menu. It’s clean and simple, as you would expect.
851W: The back
Here’s where things get interesting – the back of the 851W features a multitude of input/output connections and switches, allowing you to tailor it to your needs. Balanced XLR and unbalanced RCA inputs are provided for each channel, as well as loop outputs for both to connect further 851W’s if you wish to use more than 1.
Switches to switch between stereo and mono, balanced or unbalanced, and bridge mono/bi-amp are provided, as well as a massive, solid power switch and the AC power connection.
The unit features solid speaker terminals that can accept bare wire, or, by removing the caps in the ends, banana plugs. Rounding out the connections are the control bus and trigger in and out connections.
851E: the front
As you would expect, there’s a lot more going on on the front of the 851E preamplifier – despite this, however, Cambridge Audio have kept the clean, simple layout that is consistent across all of their devices. Positioned vertically either side of the central display are the input selection buttons – it’s nice to see direct access buttons for each input rather than a click wheel. Inputs are switched by relays – meaning there’s little, if any, crosstalk between inputs as is common with cheaper, chip-based input switching devices.
On the left, you’ll find power, the headphone jack, and the mode button used to turn the volume to a balance control, and to access the main configuration menu. On the right, you’ll find the tone controls (which, when pressed, protrude from the front allowing you to turn them – a further press hides them). There’s the direct button for those audiophiles who think tone controls are the root of all evil, and the volume control.
The volume control feels slightly cheap and wobbly – this is probably due to the digital encoder pot Cambridge Audio used – It would’ve been nice to see a better, higher quality encoder used in the 851E. Also, the gap between the knob and the front panel isn’t equal all the way round – again, a better quality encoder would probably solve this. The control however, turns very smoothly, gliding along as the volume is gently raised or lowered.
851e: the back
The back panel of the 851e can seem daunting at first – there’s a lot going on here. Firstly, we have the IEC power connection along with a power switch. Balanced XLR, and unbalanced RCA preamp outputs are provided, as well as the mono subwoofer pre-out.
Next we have the inputs; 8 of them in total, 3 with both balanced XLR and unbalanced RCA connections, the remaining 5 RCA only. Input number 8 is a recording monitor loop – and, as such, is accompanied by a line level output. It would’ve been nice to see 2 recording loops, for those of us who wish to connect, for example, both a sound card and a cassette deck.
Finally; there’s 2 3.5MM trigger input/outputs, an RS-232C port and the Cambridge Audio Control Bus connections.
The terminals and connectors on both units are solid and individually supported with screws – so there’s no chance of breaking them with a tight plug. The XLR terminals on the units aren’t too happy accepting my Audioquest Red River cables – they’re very tight, and the latches don’t work properly. However, these use non-standard XLR plugs – so other cables would probably work fine.
As long time readers will know, I love the Cambridge Audio remotes – and this one is no exception. The remote supplied with the Azur 851E can control all of the 851 components, as well as the stream magic 6.
It feels nice in the hand – it has just the right amount of weight, and balances perfectly when you’re changing the volume or using the central navigation circle. The central circle of buttons, including the volume, skip and navigation control, produce a gentle click when pressed which is a very nice touch. The buttons are slightly raised where necessary, making key controls such as volume and skip easy to find, even when you’re lost in the music.
I purchased an 851C CD player along with these components, and was somewhat disappointed to find it is still being supplied with the old Azur remote. I like having a spare remote – therefore it would be nice to see the entire Azur 851 line shipping with the new remote – for consistency, if nothing else.
The E/W components have several features designed to enable you to integrate them into everything from a simple home AV setup, to an advanced custom installation environment. Trigger in/outputs allow you to control the components from any other device with the appropriate trigger connections, such as an AV receiver, media centre PC, and even some remote controlled power strips.
The Azur remote control can be used to generate commands such as power on/off and mute, for use with learning remotes. Holding down the respective buttons for 12 seconds generates an IR code that can be used to program other remotes. If you choose to use the RS-232C port, there’s a set of remote control codes available from Cambridge Audio’s website.
Both units also feature the Cambridge Audio control bus, allowing you to integrate them into a full Cambridge Audio system. The control bus allows you to, for example, power sync components, or control the volume on your 851E preamp from your phone/tablet using the Stream Magic 6.
Connecting one of the supplied control bus cables between the E and W components allows the 851W to be brought in and out of standby along with the 851E preamp. It would be nice if, when connecting headphones, the amp was automatically powered off – and if headphones were connected from the start, it were not powered on. This would save causing unnecessary wear on the components of the amp – there’s little reason to have the amp powered on when using headphones. There doesn’t appear to be an option for this, though I’m sure it could be addressed in a software update.
There’s not much info on the control bus – the diagrams and instructions provided in the user manuals are vague and don’t go into enough detail – making it hard to get the system working the way the user wants. It would be nice to see a detailed control bus guide that clearly outlines all its functions and how to use them. I’ve written to Cambridge customer care regarding this, and will update this article when I receive their response.
Both the 851E and 851W have on-board configuration menus – the 851E’s is accessed using the front panel display, while the 851W’s uses the status lights to relay information to the user. As you would expect, the 851W has very few settings that can be changed – many of its settings are changed using the switches on the rear of the unit.
The 851E preamp, however, has several settings that can be altered. These include settings for the control bus and the various trigger outputs, the auto power down (APD) which causes the 851 components to enter standby after a period of inactivity, and the ability to change the volume display from DB to arbitrary volume units (0-90).
You also have the ability to name each input individually – enabling you to change the input names to correspond to the connected devices. For example, “CD Player”, “Streamer”, “Tuner” etc.
The 851E’s menu system is easy to use – however, there’s an extremely short delay that makes using the system frustrating. Upon calling up the menu by holding either the mode button or 1 of the input select buttons, after a few seconds of no interaction, the unit will return to its normal display mode. This is extremely annoying, as it gives you hardly any time to alter the settings; especially if you’re referring to the manual for directions.
Usage is as simple as it gets – with the E/W connected together with a control bus cable, powering up the 851E will cause the 851W to power up also – after a series of rhythmic relay clicks from both components, they’re ready for use. I have a soft spot for any component that clatters to life with a series of relays – and these components are certainly no exception.
Selecting your source is as simple as pressing the desired input select button on the front panel or the remote. The 8th source is a recording monitor loop – pressing input number 8 will activate that input, pressing it again will return you to the input you were listening to previously. This is useful if you have a 3 head analogue cassette deck, or are recording using your computer’s sound card.
Most importantly, how do they sound? Well… Musical, powerful… stunning.
The first thing that’s immediately apparent when you first listen to the E/W combination is the lack of noise. Not musical noise, but the noise floor that is so apparent with many other systems. It’s like removing the protective film from a components display; or the difference in sound between a full range speaker and a 2-way design with a crossover, the elements of the track being brought to the forefront of the sound stage with precision and startling realism.
The 851W has an unparalleled ability to convey the musical nuances in a performance. It’s got power in reserve to cater for those hard-hitting, chest-pounding drum kits or orchestral swings. But, at the same time, it has a softer, warmer, more emotional nature that makes music, well, music. The weeping lament of a violin or woodwind instrument. The subtle nuances of the piano. And, of course, the expressiveness of the human voice. All the elements of music that stir the human soul, beautifully rendered and presented to the listener like an intricate piece of art.
Of course, some credit must be given to the 851E – which shares many of the 851w’s characteristics; mainly The low signal to noise ratio and THD figures that result in a noise floor that is, to the human ear, virtually non-existent. The result? An incredibly clear, natural sound.
A system is only as good as the source components connected to it – therefore, it is essential you choose source components with characteristics that match those of the 851E/W – Cambridge’s own 851C and 851D, in particular, being the obvious choices. In my system, I use an 851C and a stream magic 6 – with everything connected together using balanced XLR connections. 1 851W was used – due to budget constraints; I was unable to obtain a second for my system. This is certainly a plan for the future – the audiophile in me is begging to hear these in a dual mono configuration.
The first thing I immediately noticed was how good these components sounded out of the box. Usually, especially with higher end components, they require a week or so to break in – allowing the properties of the electronics inside to settle down and reach optimum performance. Sure, given time these components get better (the optimal break-in time is around a week) – but never before has a component sounded so good in its first hours on my kit rack. A positive start – and it gets better.
We start with some Nirvana – and the ‘MTV Unplugged in New York’ album. ‘Where Did You Sleep Last Night?’, a favourite among some reviewers, sounds every bit as good as I was hoping. The track starts with a hard-hitting guitar intro – it’s not overdriven, rather the classic ‘American Clean’ sound. The track builds from what is otherwise a gentle start to a powerful screaming crescendo, full to bursting with emotion.
This is a track that brings most lesser systems crashing to their knees in a puddle of distortion, bright highs and musical mess. The 851, however, rises to the challenge, presenting a beautiful wide-open sound stage, with each element of the song meticulously arranged – all amassing to an incredible performance.
There’s no hint of brightness or harshness in Cobain’s powerful vocal – and there’s no lack of punch either, the music slamming into your chest at full force.
In fact, the entire album sounds phenomenal – the E/W accurately not only accurately conveyed the music, but also the room acoustics – this is, of course, in part due to the quality of the recording – but it’s impressive none the less.
Next to something softer, and another favourite amongst reviewers. Norah Jones’s ‘come away with me’ is as gentle and enveloping as you could hope for. The bass line is spot on, the 851W showing its ability to grab hold and keep control of those bass drivers. Again, the sound stage is wide open – and the performance is brimming with detail.
Many systems compromise ultimate detail retrieval with power or smoothness – however, with the E/W (and with most other Cambridge Audio equipment for that matter) this is simply not the case. In fact, you’ll be amazed just how much detail these components can bring to your attention. It’s not that the details didn’t previously exist – the 851 adds nothing to the music that wasn’t there already. It’s just bringing them to the forefront, and separating things out – so rather than blurring into one another they get their own space to breathe. This is particular evident in orchestral music – or songs that have orchestral parts.
Play ‘Whisper’ by Evanescence – a piece from the metal genre, but with stunning production and a sublime orchestral ending. Every instrument stands out – not in an obtrusive way (they still blend), but you can hear, and focus on, every single one. It’s the same with the vocalists – The feeling that they’re standing in front of you, within an arm’s reach is simply beautiful to behold.
It’s not just the amount of detail these components retrieve – it’s ability to convey subtle nuances is equally impressive. The velocity with which a drum is hit… the resonance of a tom, or size of a snare drum. The movement of a vocalist’s mouth, or the slightly deadened sound caused by a misplaced finger on a guitar string. All are startling realistic – just as they would be in real life.
Linkin Park’s ‘Hands Held High’ from the minutes to midnight album further demonstrates the virtues of the 851 components – it’s a simple rap/spoken word track, with an underlying bass line and simple snare/hi-hat rhythm throughout. It demonstrates the 851’s timing/rhythmic abilities, and its ability to keep control of the those bass drivers – with each note starting and stopping perfectly in time. It’s not lacking in rhythm or excitement – instead, its sense of rhythm is more refined, making the urge to reach for the volume and start the party even more irresistible.
You can add an excellent headphone stage to the merits of the 851E preamp too – while it’s obviously not going to compete with high-end dedicated headphone amps, it sounds much better than it has any right too at this price.
In fact, I’d happily put it up against many mid-range headphone amps. It’s got plenty of power, driving every headphone I tested with ease – and it takes nothing away from the sound of the 851E. In fact, using headphones proves just how low the 851E’s noise floor really is; yes it may be possible to measure it, but I challenge any human to hear it
The final test tracks are taken from the newly released ‘Going to Hell’ album by The Pretty Reckless. ‘Sweet things (Acoustic’, an acoustic version of ‘sweet things’ found on the deluxe pre-order edition of this album,, is a perfect example of what a talented band can create when computers, special effects, and Auto Tune are taken out of the equation. Of course, the 851 E/W renders this track perfectly (did you expect any different?), but it’s particularly impressive using headphones.
Again, reverb (and perhaps room acoustics) are fairly prominent, and the single acoustic guitar has tons of attack. It’s played hard too – especially in the choruses.
The detail, both in Taylor and Ben’s vocals and the 16th note accents on the hi-hat during the verses, is all present and accounted for – the system simply does nothing wrong; and that’s all you can possibly ask for.
Finally, to ‘heaven knows’ – a fun, upbeat track with a backbeat similar to queen’s legendary ‘we will rock you’. The first thing you’ll undoubtedly notice is the triple knock after the first couple bars – it jumps out at you, just as it should. After all – it’s designed to silence the crowd, who join Taylor Momsen in the choruses. The 851 series keeps it together, even when things become more complicated – it’s one of those songs that demonstrates the 851’s ’bring it on’ approach to music.
I normally struggle to summarize reviews – however, in the case of the 851E/W, it’s simple. Buy it, and thank me later. Chances are you’re already raising a phone to your ear and calling your local dealer for a demo – if that’s the case, this review has served its purpose. If not, I suggest you do so now… if anything, you owe it to your music collection.
The performance of this system is truly staggering. The potential for an 851 system with more than 1 851W is equally staggering – if you can afford it, do it.
Is there anything you would add?
Yes, a couple things. Firstly, a second (or even 3rd) recording loop – it would be nice to be able to hook up a cassette deck or 2, as well as my computer’s audio interface. I’d also like to see the digital volume encoder upgraded to match the build quality of the rest of the preamp.
That annoyingly short delay in the 851E’s menu system needs to be dealt with, and I’d like to see the ability to prevent the 851W automatically powering up if I have headphones connected. And finally; I’d like to see a better, more in-depth control bus manual.
But compared to the extensive list of pros (stunning sound, tons of features, amazing build quality, excellent headphone stage, and – did I mention – stunning sound), these are very minor things that could be altered with a software update, or minor hardware changes.
In summary; another stunning set of components from Cambridge Audio. Pair the 851E/W with an 851C or 851D and some decent speakers, and I’ll see you in musical heaven.