Cambridge Audio Azur 851W Class XD Power Amplifier

Cambridge Audio

Out of stock

The Azur 851W improves over its already highly respected predecessors in just about every way. At its heart is Cambridge Audio’s innovative and proprietary Class XD the system, with 12 output transistors per channel.
  • Remote Compatible entire 851 range
  • Cambridge Audio’s Class XD amplification
  • 200W into 8 Ohms stereo mode
  • 500W RMS per amp mono


Out of stock

The best sounding amplifier Cambridge Audio has ever made

Combining the best of Class A and Class AB and removing the downsides of both, Class XD amplification eliminates crossover distortion like a Class A amp while offering the power efficiency of Class AB. Its performance has to be heard to be believed.

Class XD amplification ? Cambridge Audio’s proprietary amplification system switches dynamically between Class A and AB systems. Class A amplification delivers the purest possible sound, using only one transistor to conduct, but can be energy inefficient. Class AB involves both transistors conducting simultaneously but makes it impossible to maintain a balance of low crossover distortion and power efficiency. Our Class XD the system operates in both Class A and Class AB mode, dynamically moving the crossover point depending on the audio output volume. This combines the near-zero crossover distortion of pure Class A with improved efficiency of Class AB at higher volumes, without any compromises in performance for the best of both worlds.

Serious power ??200W into 8 Ohms stereo mode is serious power. But for those with bigger plans, the 851W is usable in a mono bridged configuration with each amplifier delivering 500W RMS.

Two toroidal transformers ??Separate, high-end transformers for the power amplifier and input and other circuitry ensure audio performance is unaffected by the dramatic current output swings required to drive demanding speakers, by keeping power supplies entirely separate.

Terrapin impedance buffering modules ? Cambridge Audio’s proprietary modules replace the op-amps commonly found in similar amplifiers. At the critical low-level gain stages, these offer far improved stereo separation and imaging ? unheard of at this price point.

CAP5 proprietary protection ??Protects the integrity of your system by avoiding DC spikes, overheating, short circuits, or clipping.

Integration ??Smart auto-standby mode detects incoming audio signals to simplify integration with Cambridge Audio preamplifiers.

All-metal chassis ??Including extensive use of aluminum to create massive structural rigidity, careful damping, and control of acoustic resonance.


  • Cambridge Audio’s Class XD amplification with 12 output transistors per channel combines the best of Class A and AB amplification
  • Separate toroidal transformers for power amp and input/other circuitry
  • Cambridge Audio’s Terrapin impedance buffering modules ? separating amplifier and signal impedance
  • 200W into 8 Ohms stereo mode or 500W RMS per amp mono bridged mode
  • Cambridge Audio’s CAP5 protection from DC spikes, overheating, clipping, etc.
  • <0.5W smart auto-standby mode for integration with preamplifiers
  • All-metal chassis with premium components, creating massive structural rigidity, careful damping, and control of acoustic resonance.
  • Remote Control ? Compatible with the entire 851 range
SKU: 851W Category:
Weight 19100 g
Dimensions 365 × 430 × 148 mm

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
Dimensions (H x W x D) 148 x 430 x 365mm (5.8 x 16.9 x 14.4”)
Weight 19.1kg