Azur 851W

Power Amplifier


Delivering immense power and incredibly low distortion, the 851W power amplifier is perfectly matched to partner our 851E pre-amplifier and 851N network player; taking their pure signal and amplifying it with huge presence and authority.

"One of the most transparent, thrilling and richly rewarding amplifier combinations I have encountered."

- Andrew Everard, May 2014


    Rather than use a Class A design, which is sonically brilliant but generates vast amounts of heat, or a Class AB design, which is efficient but sonically limited, we developed our own Class XD amplifier design which the 851W takes advantage of. This has the sonic purity of Class A and the efficiency of Class AB for the best of both worlds. For more information on our unique patented Class XD technology watch the video at the bottom of the page or click here for a full description.


    When designing a stereo system, listeners are often encouraged to think about system matching, where components are handpicked to provide the best overall sound quality. People often assume this is due to the different audio characteristics, but frequently it is due to impedance (the relationship between voltage and current input/output) matching components. Products perform at their optimum when their input and output impedances match. This isn’t always possible though so we decided to develop our unique Terrapin impedance buffering module. This enables the 851W to be paired with a huge variety of audio sources and pre-amplifiers of varying impedance without risking any sacrifice in musicality or overall audio performance.


    To build the 851W to be the best toroidal transformers were essential. But rather than use one for everything we designated one for the sound amplification itself, and another for the input circuitry. This means the signal is unaffected by audio output volume, so always sounds fantastic. The primary toroidal transformer provides unrestricted power to the dual mono amplification blocks. It’s a true audiophile transformer that will operate without distortion and with no buzz, interference or hum. The second smaller toroidal transformer takes care of pre-amplification processes. View the videos below for an insight on why we use toroidal transformers.


    The 851W can be used in stereo, bi-amped or bridged mono configurations. In bridged mono mode into 8 Ohms the 851W is a 500W monoblock amplifier. Into 4 Ohms, this figure increases to an incredible 800W. It can be paired with our 851E pre-amp, any of our digital pre-amps such as the 851N or CXN, or any other analogue pre-amps, and thanks to our Terrapin buffering module it will always sound perfectly matched. 


    Our proprietary CAP 5 protection system protects the 851W, plus any connected equipment and speakers, ensuring ultimate reliability and peace of mind. For more information on this unique development have a watch of the video below. 

  • Press reviews

    • Australian Hi-Fi

      Australia, July 2015

      "With its 851E preamplifier and 851W, Cambridge Audio has built a pre/power combination that offers not only 'holy grail' audio performance, but also an almost complete suite of features and facilities.  If you're in the market for separates (and you should be if you want seriously good audio!), this 851 duo should be high on your short list... if not at the very top of it.  Highly recommended."
    • Knoxville News Sentinal

      United States, December 2014

      "If you are looking for a high-end amplifier that provides the performance of the $25,000 exotics but without the crazy price, the new Cambridge Audio Azur 851W is impressing many reviewers in the audio world."
    • The Idaho Statesman

      United States, December 2014

      "The new Cambridge Audio Azur 851W is impressive. I recently tried the 851W in my system and was really wowed by it."
    • Andrew Everard

      United Kingdom, May 2014

      "Simply, this is one of the most transparent, thrilling and richly rewarding amplifier combinations I have encountered, with fine grip on the speakers with which it’s used, vast amounts of information delivered and never even the slightest sense of the music being held back or sold short."
    • Hi-Fi News

      United Kingdom, April 2014

      "These amps represent a genuine introduction to true high-end amplification at the same time offering real value for money. Features-wise they’re fully loaded."
    • Audio Appraisal

      United Kingdom, March 2014

      "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."

      Customer Reviews

    • The details

      Power output – stereo/mono 200W per channel into 8 Ohms 350W per channel into 4 Ohms
      Power output – bridged mono 500W 8 Ohms 800W 4 Ohms
      THD (unweighted) < 0.001% 1 kHz < 0.005% 20 Hz - 20 kHz
      Frequency response 5Hz – 80kHz
      S/N ratio (ref 1W / 8 Ohn) >90dB (unweighted)
      Sensitivity – stereo or mono 1.5V rms unbalanced 1.5 + 1.5V rms balanced
      Sensitivity – bridged mono 0.775V rms unbalanced 0.775V + 0.775V rms balanced
      Input impedances Balanced input 38 kOhm Unbalanced input 68 kOhm
      Power amp damping factor > 110 at 1 kHz
      Max. power consumption 2400W
      Standby power consumption Standby <0.5W
      Colour Black or silver
      Dimensions (HxWxD) 148 x 430 x 365mm (5.8 x 16.9 x 14.4”)
      Weight 19.1kg (42.2lbs)
      In the box Azur 851W Power Amplifier, Power Cable, Control Bus Cable