Cambridge Audio Azur 851W: High quality power amplifier

All products are developed by the best specialists using the most modern measuring equipment. The best components and high-tech production lines to date ensure the high quality and consumer value of each Cambridge Audio product. Before launching into production, all models are carefully listened to by groups of experts and are fine-tuned in terms of sound quality. Cambridge Audio Azur 851W is a power amplifier made using a number of proprietary circuit solutions, and its design has been significantly improved compared to the previous version of this model.

Compared to its already highly acclaimed predecessors, the Cambridge Audio Azur 851W is a multi-faceted improvement. At the heart of the amplifier is Cambridge Audio’s innovative Class XD system with 12 output transistors per channel. Combining the best of Class A and Class AB, and eliminating the shortcomings of both, Class XD amplification eliminates the crossover distortion inherent in Class A amplifiers and delivers the power efficiency of Class AB. Its exceptional performance has to be heard to be believed.

One of the distinguishing features of the Cambridge Audio Azur 851W is the use of a patented Class XD output stage circuit. It uses 12 powerful transistors in each channel, and in terms of its operating principle, it is a combination of the common Class A and Class AB circuits. From the former, Class XD has inherited the absence of transient distortion such as “steps”, which significantly degrade the sound quality, and from the latter – good efficiency and efficient use of power supply energy.

The Cambridge Audio Azur 851W amplifier uses a power supply with two toroidal transformers. One of them works on the output stages, and the other on the input circuits and all auxiliary circuits. This division, which is another find of the company's engineers, allowed to minimize crosstalk, expand the dynamic range and obtain a consistently high sound quality at any volume. Terrapin buffer input stages, also developed by Cambridge Audio, serve to accurately match the amplifier with any signal sources. And the CAP5 circuit protects the device from surges in constant voltage overheating, short circuits or signal limitation when it exceeds the permissible threshold level.

A useful function of the Cambridge Audio Azur 851W is automatic switching on when an audio signal appears at the input, and switching off the device when it disappears. The amplifier is equipped with balanced and unbalanced inputs (supplemented with corresponding transit outputs), and can operate in two-channel or bridged (mono) modes. Azur 851W can also be used for bi-amplifier connection of speakers, since the device is equipped with two pairs of output terminals in each channel. The device also has an input and output for an external control system (Control Bus and 12-volt trigger), as well as an input for an external IR sensor.

Cambridge Audio Azur 851W Specifications 

Output power 2 x 200 W (8 Ohm), 2 x 350 W (4 Ohm), 500 W (mono mode, 8 Ohm), 800 W (mono mode, 4 Ohm)
Frequency range 5 Hz – 80,000 Hz
Signal-to-noise ratio over 90 dB
Damping factor over 110
Harmonic distortion factor less than 0.001% (1 kHz)
Inputs XLR, RCA, trigger, IR sensor, Control Bus
Outputs XLR, RCA (transit), 2 pairs of screw terminals for speakers in each channel, trigger, Control Bus
Sensitivity 1.5 V (stereo), 0.775 V (mono)
Impedance 38 kOhm (balanced), 68 kOhm (unbalanced)
Power consumption 2400 W
Dimensions (WxHxD) 430 x 148 x 365 mm
Weight 19.1 kg