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Cambridge Audio Azur 840E Preamplifier & 840W Monoblock Amplifiers Review

Doug Schroeder reveals how the Cambridge Azur 840E and 840W amplification system fared in today's landscape

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In the ever understated way of the British, Matthew informs, “the 840W runs slightly warmer than a conventional class B/AB amplifier and the ventilation slots on the top of the unit must not be obstructed.” This is absolutely true. In the tradition of owners who fail to read first, during burn-in I stacked the two amps with the preamp on top, and fired them up. I gave a thought to running them all night, but experience has taught me to be paranoid and check everything. I am so happy I returned to the room to assess, as the amps were cooking like a hibachi. I immediately shut them down and separated them. No ill effects came from the “scorched amp” test, but I was reminded again to read first, and never, ever leave a new component running without thorough familiarization of its operating temperature!

Even though these are solid-state amps their design makes them run really hot; now I refer not to their thermal nature, but rather their sonic nature. I will state this in the most forward manner: If these amps did not sound so good I would nod a polite “Howdy-Do” to them and send them on their way, writing a “they’re fine” summary. But they are not fine, they are sizzling, nay, searing in performance! If they raise the room’s temperature, they most certainly raise my desire to hear them. Their sound is commensurate to the thermal energy they produce. As the heat of the sun draws us outside to bask in its rays, the hot performance of the 840W’s draws me to them.

The big deal is the proprietary “Class X-D Technology” which is said to, “eliminate crossover distortion at low signal levels. Cambridge Audio explains that the crossover point is “actively displaced”, which, “creates a region of pure Class-A operation where the crossover zone would otherwise be before moving into an enhanced form of Class B at higher levels.” If I guess correctly, the Azur 840W creates its own nano-black hole for crossovers, which explains the phenomenal energy output.

To explain the Nano-Black Hole Amp concept (or Class XDNBH), I asked Matthew to clarify. I was only mildly disappointed to learn that the amp does not produce a Black Hole. It does something nearly as wondrous: it makes the crossover point disappear! In reality it gets displaced; it is only gone if you look for it in the wrong place. Displacement of the crossover point has been a method tried for years in amplifier design in order to eek out more operation in Class A and less in Class B. The key here is a transition at much higher levels and less abrupt than conventional Class A/B designs. One of the tricks (Cambridge is not divulging all of them) is using a second generation circuit where the displacement current is modulated by the audio, but outside the feedback loop. This does not occur by DSP, but purely an analogue process.

Other tweaks include use of a silicon steel screen around the transformer to kill electromagnetic radiation and eddy currents. Four pairs of high current Sanken output transistors per channel can provide instantaneous currents of +/- 50 Amps. Another set of two output transistors provide the displacing current (to move the crossover point), and, as Matthew says, “…this is transparent to the loudspeaker system.” I certainly concur, as the 840W sounds more “see through” than the majority of solid-state amps I have heard.

As an indication of how glamorized affordable amps are becoming, observe the 840W’s solid copper gold plated bus bars. The gold allows routing of power to exactly the correct parts of the output stage without use of long PCB tracks. Matthew points out a more subtle tweak, “…the bars are stacked and arranged in such a way that the fields caused by the half cycles of current tend to cancel out.” I would keep the lid of the amps loose to lift off and show off the bus bars to audiophiles worthy of viewing them, but the powerful vibrations of the bass might make them rattle! Not really, but who can deny the allure of gold plated bus bars? With the price of gold soaring recently, one can rest assured that their amps are an investment. Try selling that line to the wife, “If we ever have hard times, I can pawn the bus bars…”.

Cambridge Azur 840W Top front

200 watts versus 1,000 watts

So, how would these Azur over-achiever amps fare against the big shot Jeff Rowland 501 class D amps? The Rowlands are a stiff 1,000 Watts mono, which means no pushover. I have had amps that are more tonally pleasing, more inviting sounding, but none which have matched the effortless force exuded by the 501’s. When they are placed into a rig their presence is felt in a tactile fashion due to their handling of transients with a vice-like grip on the drivers. How can any traditional amp hope to compete with such brute strength?

By now you are aware that the 840W is not just any class A/B amp. It’s a Cyborg class A/B! It’s got the brains of a traditional amp and the mechanics of a new machine. Of all the amps I have set up opposite the 501’s the 840W held its own, and did so without the whiteness or blandness for which class D amps are criticized.

The combination of the 840E Preamplifier and the 840W amp has been enthusiastically received in the press. Rightly so. What’s not been promoted is that two of the 840W’s in bridged mono is cause for far more enthusiasm! The freshly arrived Ayon Audio CD-2 player and Legacy Focus SE speakers I upgraded from the Focus HD version, proved providential for assessment of the Cambridge equipment. I still had the VAC Signature Preamplifier MkII and the Jeff Rowland MC-606 Multi-channel amp on hand which I had previously partnered with the CD-2 and Legacy SE’s. That combination coupled one of the most venerable tube component manufacturers with one of the most venerable designers of Class D amps. As to be expected, the results were marvelous. What was not to be expected was that the lowly-priced Azur 840E and 840Ws would keep pace. But that is precisely what happened. The Cambridge combo was not blown out of the water at all, but in fact presented every bit as compelling a presentation. There is one primary reason I see for that result – class XD is a far superior technology to Class D.

Allow me to announce it to the world: In my experience, Class XD is better than Class D – superior to any Class D amp. This is no condemnation of the quality of the MC-606. I have now experienced either at shows or in my room the major players in the Class D category. I have heard the economical and I have heard the astronomical. Rowland produces one of the best class D amps, bar none. Even though Cambridge’s funky moniker “XD” is their label, the technology hearkens back to amp manufacturers in the past who have built class A/B amps with high bias points. However, those amps have tended to run princely sums. The 840W is a welcome departure from that trend. The performance potential for a set of 840W’s is truly staggering.

Initially I thought that the Rowland Capri preamp was the ticket for the 840W amps. It was quite pleasurable, lending a sweet mellowness and a bit of roundness to the presentation. It sounded like I had put a tube preamp in the chain. The Capri is not harsh or biting as so many lesser solid-state preamps. However, its smoothness rounded the top-end a bit. I am not willing to admit warmth at the cost of sharpness of detail. I want it all!

Imagine my surprise (should I have been surprised?) when the 840E turned out to be the preamp achieving the Goldilocks Effect; just the right amount of detail and warmth. A pattern was beginning to emerge: the Azur pre was an all-round winner, as were the 840W amps. How good do the Azur amps sound? Allow me to discuss their performance in the following system.

Cambridge Azur 840W interior

10 Responses to Cambridge Audio Azur 840E Preamplifier & 840W Monoblock Amplifiers Review

  1. Rudy Velickovski says:

    Hello, and thank you for the wonderful review of the Cambridge Audio 840W Amplifier.

    I just went and bought one from a local dealer and I’ve fallen in love with it. Your review was bang on in all aspects of the units sound quality.

    I had a question in regards to the bridge mode of this unit. I would like to buy another one and use them in the mono mode to increase power output.

    Everything I’ve read when it comes to bridging stereo amps, is that is leads to reduced sound quality, primarily distortion, greater cross talk, etc.

    I do not want to impact the quality of the sound in any way, at any cost. Did you notice anything by putting this amp in bridge mode?

    Thank you kindly

  2. Rudy,
    God’s Joy to you,

    Perhaps the answer can be best answered in terms of measurements vs. the listening experience. The measurements may be less tidy with use of two amps in Bridged mode, however my experience has been that use of two amps is always superior to use of one in stereo mode.

    Now, if a person is suggesting that, say, a single 250wpc amp would be superior to two 125wpc amps run in a passive biamp mode, I will not argue that. Typically one would get better results from a more robust single stereo amp. But that does not preclude improvement by addition of a second stereo amp and running them both in Mono mode.

    I still use the two Pathos Classic One MkIII tube hybrid integrated amps in Mono mode because they are so blissfully rich and attractive sounding. So, in my experience the addition of a second amp always improves, perhaps not as much as a more expensive single stereo amp, but enough that it is well worth pursuing.

    The Azur was glorious when used with two units in Bridged mode; I preferred to run them that way in most installations, if that helps you to decide.

    Douglas Schroeder

  3. David says:

    Hi Douglas

    Thoroughly enjoyed your review of the 840E and 840W’s, so much so that off the back of it I went out, auditioned and eventually bought the combination. I have since sold the pre-amplifier but have kept faith in the 840W’s, so much so that I have managed to acquire another two, so now have four in total.

    My question or comment is in relation to their ability to drive speakers and impedance handling. Up till now I have been running all four in Bridged Mono mode running a pair of tri-wireable, three-way, 8 Ohm ATC scm35 apeakers (two per each speaker one for LF, and one bi-wired to M and HF terminals), and whilst the sound is superb, the treble isn’t as precise as I would like, thus I decide to add a supertweeter (8Ohm), and here is where my problems started.

    The supertweeter did exactly what I wanted it to do in terms of sound, however the amps started to run very hot, far hotter then they had in the past (you know how hot they can get), to the point that you could quiet easily burn yourself – something is not right? Do you think the supertweeter has altered the impedance figure and as such the amps (in Bridged Mode) are finding the load too difficult? and if so, should I switch them to Dual Mono mode to avoid problems?

    Also, the manual does not give the amps “wattage” into 2 Ohms, so does this mean that Cambridge don’t recommend the amps drive 2Ohm speakers, or that they simply can’t.

    Many thanks, I always enjoy your reviews.

  4. James Romeyn says:

    Mr. Schroeder,
    Hope you are well.

    I would most likely run one stereo 840W, not two. It would be nice to get a handle on the heat issue for one amp. Recently I employed one Atma-Sphere S30 OTL (current model). How might you compare the heat? Do you know how many watts the 840W dissipates while idling? For a thoroughly burned-in sample, what is estimated duration from “off” to close-to-maximum performance?

    The load is two separate full range speakers per channel (one is an “effects” system with late-arriving output). The impedance is ruler flat above the bass range, allowing the two speakers to wire either in series (ruler flat 20 Ohm above the bass range) or parallel (ruler flat 4.8 Ohm above the bass range).

    My lifetime experience with SS amps is the higher the impedance the less audible and less intrusive are noise and distortion spectra. I presume therefor the 20 Ohm load is preferred if 90W is enough power, which it might be (low 90 dB sensitivity). Your comments appreciated.


  5. Effi Ceon says:

    Thank you very much for this detailed review. It was a big help for my decisions. Running now 2x 840W biamped with Quadral Aurum Titan VII and it will be combined with 840E soon.
    Kind regards

  6. peter jasz says:

    The Cambridge Audio 840-E must be the most under-rated preamplifier in the history of Hi-Fi.

    It possesses the rare quality of excellent transparency/resolution with tonal realism; fleshed out instrument tone/hues from top-to-bottom. The entire frequency bandwidth is impressively revealed with particularly rare (but most welcome -and essential) low-frequency transparency and detail. The remainder of the music spectrum is equally finely resolved, nuanced and articulate, imbued with a graceful finesse – very rare, very desirable qualities.

    The interior layout precision is also impressive. As is the precision resistor/relay volume implementation.

    The 840-E also has ample inputs and control flexibility. The chassis styling, ergonomics and build quality is first rate.

    Highly recommended.

    peter jasz

  7. Marcin says:

    I’m reading about the Cambridge audio AZUR 840e & 840w set getting encourage to upgrade my current system which is Focal Chorus 836v with old NAD power amp C272 and Yamaha RX-A3040.
    1. I would appreciate your advice if, in your opinion, CA 840e+840w would be the good match with my Focals? Anybody tried that ?
    2. Would CA 840e+840w be an major step up in my stereo system ? as it cost a bit …

    Thank you for your advice

  8. peter jasz says:

    Reviews for the 840 E/W are collectively excellent -for good reason.

    Clearly, the reviewer heaps more praise upon the amplifier (W) than Pre (E).
    But, as a 840E owner (and long-standing experienced audiophile), rest
    assured that the 840E preamplifier is a superb line-stage. The resolution/clarity,
    layering, dimensionality, life-like musicality, low-noise and striking micro/
    macro dynamics are all very impressive. Interestingly, the Cambridge 840E
    wasn’t even on my radar as a possible/suitable contender. Thank goodness I
    stumbled upon it.
    ‘Pop’ the lid, and you’ll discover a beautifully laid-out interior; attention
    to detail that shames that of Constellation (garage-build) components
    (that are priced 10X that of the CA -lol)

    The down-side (and it’s something to seriously consider) is the problematic
    volume-control circuit/relay’s that fail early; resulting in nasty ‘run-away’
    ‘ volume’ levels, and or seriously loud “crackling” sounds that can easily take
    out tweeters. This appears to be due to under-spec’d relay’s, and very high
    internal heat levels; remarkably, there is no top plate ventilation on the 840E !
    (Removing the top-cover reveals ‘scorch’ marks on the underside – a sign of far too
    great heat build-up. How such an oversight escaped CA engineers is difficult to

    In any case, (superior quality) relay replacement is demanded, as would be addressing the
    ventilation concerns. So, if a used 840E becomes available, although a superb unit,
    be forewarned that a few-hundred dollars in repairs/upgrades WILL be required.
    The 851E is the 840’s “successor” -and possibly remains current. However, it’s NOT the same
    (not near as good) preamp.
    BUT, it does come with top-plate ventilation holes; the top-cover also ‘fits’ the 840E, albeit
    the color/finish does not match that of the 840E. Perhaps the 840W top plate for some much
    needed ventilation ?

    I have the amazing Classe CA-2100 as a main amplifier; the combination is amazing.


  9. Duane Gosa says:

    The 840E model is problematic.. due to the control knob for volume.. it went ballistic and blew up my 2000 dollars power amp. I turned it all on and the pre amp went to full volume before I could get the power shut down..I called Cambridge Audio and they knew about this issue, now I know mine is out of warranty which they were quick to point out. They said a few of these got out and is was not worth a recall.. so I bought the Vincent 232 power amp.. love it..but before I can turn anything on I have to make sure that the 840E is not going to do it again, once I get it stable then I turn on the rest of my amps. When I talked to them about this, they said I could ship it back for repair which they would charge me for. I live in the states they are in England and I would have to pay for the shipping and I should have the original box..or they told me that they would give me a half price on a newer model.. What a joke. Never again will BUY their product. They knew about it and still sent them out.. When I read the reviews on this pre amp oh it is so great, bullshit…no help, if they knew they had an issue like this these should’ve never been sold..some great reputation!!! Never again..this has been some time ago when I complained about this but it still pisses me off that they would not do the right thing.. who knows when I would’ve got it back and they were going to charge me for the repair also.. no good, never again.. such a great company, they do not stand by their product…yes again it was out of warranty but what pisses me off they knew about it..junk..I fight it everyday.

  10. duane gosa says:

    My 8403 preamp blew up m components. Do not recommended any Cambridge Audio stuff again, no support. Also I have a DAC from them, it quit in a month and I have called and left my number, no way will I buy this line of product..pisses me off. They do not stand behind their the product, it’s a shame that these bad ones got out but did not stop them for ending them out of protection.

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