Cambridge Audio Azur 851W Power Amplifier

Model: C10539 UPC: 5055300406781 Item: 2477

Cambridge Audio Azur 851W Overview

Fully embracing Cambridge Audio’s “Sound First” philosophy, the Azur 851W Power Amplifier is in a class of its own, designed to deliver serious power with total audio finesse. It all begins with the 851W’s robust metal chassis and thick brushed front panel, an acoustically damped exterior that shields the amp’s dual monoblock design comprised of separate transformer secondaries, dual rectifiers, and separate PSUs. And it ends with three output modes that allow the amp to push 200 watts across two-channels or up to 500 watts (8 ohms) when bridged. Add to that Cambridge’s unique XD amp design for minimized distortion and heat, and you have an amp that’s capable of driving a true high-end audio show.

Product Information

Product highlights

  • Power output: 200 watts stereo (8 ohms), 500 watts bridged mono (8 ohms)
  • Power output: 350 watts stereo (4 ohms), 800 watts bridged mono (4 ohms)
  • Max power consumption: 2400 watts
  • Frequency response: 5Hz – 80kHz +/-1dB
  • Analog inputs: 2xBalanced XLR, 2xRCA
  • Analog outputs: 2xBalanced XLR, 2xRCA
  • 8 speaker posts for 3 operation modes: stereo, mono, bridged mono
  • Cambridge Audio’s unique XD amplification design for low crossover distortion and efficiency
  • Dual mono amp design for excellent stereo separation
  • Separate toroidal transformers: 1 for amplification, 1 for preamp circuitry
  • CAP5 protection technology
  • Dimensions (H x W x D): 5.8” x 16.9” x 14.4”
  • Weight: 42.2 lbs
  • Warranty:  2 years – World Wide Stereo is an authorized dealer for every brand we sell
  • Included: World Wide Stereo 60-day guarantee and expert product support

Low distortion, efficient amplifier circuitry

Cambridge Audio’s engineers struck pure gold when they created their unique Class XD amplifier circuit.  XD is the perfect balance of Class A’s coveted low distortion properties and Class AB’s cooler running efficiency, shedding Class A’s inefficiency and heat along with Class AB’s higher level of crossover distortion.  Its design allowed Cambridge to budget more R&D into amplification and power supplies, and less into large heat sinks, giving the 851W the ability to push an astounding 200 watts per channel with utter refinement.

Boosting the 851W’s performance are multiple playback configurations, including stereo, bi-amped, and bridged mono modes, all selected via simple switches on the rear of the unit.  When used in bridged mode, the 851W taps both monoblock amps for output between 500 watts (8 ohms) and 800 watts (4 ohms). And with Cambridge’s CAP5 protection circuitry, you can be assured your gear will remain safe and protected in the event the amp clips or is driven too hard.

Dual toroidal transformers

Why have one power supply, when you can push cleaner output with two? The 851W houses two distinct toroidal transformers: one oversized transformer with robust extruded heatsinks for power to the 851W’s dual mono amplification blocks, and the other for sensitive preamp input circuitry.  This separation of power keeps signals free of cross contamination, allowing the 851W to perform optimally even when handling demanding musical dynamics and high levels of volume.

Pair with a wide range of sources

High-end componentry often requires system matching (aligning amp and source impedances) for good performance.  The 851W frees you from that burden by offering Cambridge Audio’s unique Terrapin impedance buffering module, which allows for peak performance even if impedances don’t align.  That gives you greater freedom in selecting components of your choice, without worrying about sacrificing what counts the most: clean and fluid sound.

Convenient connectivity

Aside from four sets of speaker binding posts for both single and bi-wired connections, the 851W also provides both balanced XLR and unbalanced RCA inputs and loop outputs to accommodate multiple amp configurations.  And to boost convenience, you’ll find IR and Control Bus inputs for integration with multi-function systems, in addition to a 12V trigger for instant power ups.

Build the ultimate Azur system

There’s nothing quite like a system of matching separates, especially considering Cambridge Audio’s drive to design gear that works perfectly together.  While the 851W Power Amplifier can anchor your system with serious sonic muscle, it pairs perfectly with the versatile Azur 851N Flagship Digital Preamplifier and Network Player for networked music access, and the Azur 851C Upsampling DAC, CD Player, and Preamplifier for the best from your compact disc collection.  Both are excellent digital sources that house preamp and volume control functionalities, allowing them to work in concert with the 851W.



  • 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% 1kHz <0.005% 20Hz - 20kHz
  • Frequency response: 5Hz - 80kHz
  • S/N ratio: >90dB (unweighted)
  • Sensitivity - stereo/mono: 1.5Vrms unbalanced 1.5 + 1.5Vrms balanced
  • Sensitivity - bridged mono: 0.775Vrms unbalanced 0.775V + 0.775Vrms unbalanced
  • Input impedances: Balanced input 38k-ohms, unbalanced input 68k-ohms
  • Power amp damping factor: >110 at 1kHz
  • Maximum power consumption: 2400W
  • Standby power consumption: Standby <0.5W
  • Dimensions (H x W x D): 5.8" x 16.9" x 14.4"
  • Weight: 42.2 lbs.

What's in the Box

What's in the Box:

  • Azur 851W Power Amplifier
  • Power supply
  • Manual



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Does this amp get very hot?
A shopper on Mar 10, 2020
  Thanks for your question. Note that because of the Class XD technology the 851W runs
slightly warmer than a conventional Class B/AB amplifier and the
ventilation slots on the top of the unit must not be obstructed. IMPORTANT The unit will become hot when in use. Do not stack
multiple units on top of each other. Do not place in an enclosed area
such as a bookcase or in a cabinet without sufficient ventilation.
Do not remove the feet from this product they are required to ensure
enough air flow.