Cambridge Audio Azur 851A
Cambridge Audio Azur 851A
Cambridge Audio Azur 851A

Cambridge Audio Azur 851A: Class XD signature integrated amplifier

The Cambridge Audio Azur 851A is a Class XD integrated amplifier.” Class XD is Cambridge’s signature amplifier circuit design that they say delivers incredible sound quality compared to existing amplifier configurations. In other words, Class XD is a dynamic shifting of the switching zone that provides Class A operation at low levels and eliminates the distortion associated with conventional Class B operation, where a weak audio signal passes through the neutral point from transistor to transistor. The result is smooth and linear signal transmission between two operating modes, classes A and B.

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The Cambridge Audio Azur 851A develops 120 watts of output power, and its power supply contains two toroidal mains transformers. On one of them a source for signal pre-amplification circuits is built, and the other provides energy to the output stages. Separate transformer windings are used to power the stereo channels, and thus the “dual mono” concept was implemented in the device’s circuitry. To adjust the volume in this model, a custom balanced potentiometer is used, which ensures high accuracy and smooth changes in the sound level in 1 dB steps, with a minimum of noise and distortion.

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The most eye-catching feature of the Azur 851A’s front panel is its attractive blue display with adjustable brightness. In addition to the tone control, which can be disabled, the front panel contains a headphone jack, 7 buttons corresponding to various sources, and the user can rename them at will, smooth volume control and a “Mode” button that allows you to switch between Volume modes, Balance and Program. In Program mode, the gain level can be limited for selected signal sources, allowing the user to use the maximum signal level for each source.

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On the rear panel there is a power switch, two sets of connectors for connecting speakers (A and B, switching is done on the front panel), an IR port, RS232C for external control, a line output and an input/output for recording. For two inputs, you can select the operating mode: RCA or XLR.

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The device has a rather impressive sound, while trying to be as neutral and attentive to nuances as possible. The high energy and excellent dynamic qualities immediately captivate you, allowing you to adequately reproduce any musical genre. We also note the strict control of acoustics in the low frequency region, where the tenacity of the amplifier results in deep, fast and neatly designed bass. In the upper range, sound accuracy does not decrease at all. The device demonstrates a solid and pleasant-to-hear midrange and a high-quality sparkling top. Meanwhile, in some cases in the midrange there may be a feeling of excessive sterility and intimate presentation, and treble notes may seem a bit dry. There were basically no questions about the sound stage. The space captivates with its correct scale and precise placement of imaginary sources – everything is like the highest class technology.

Characteristics Cambridge Audio Azur 851A

Output power 2 x 120 W (8 Ohm)
Inputs 7 line (2 x XLR/RCA), Rec, remote control, Control Bus, RS232
Recording outputs, headphone outputs, Control Bus
Signal-to-noise ratio more than 93 dB
Total harmonic distortion less than 0.001%
Dimensions 430 x 115 x 385 mm
Weight 15 kg