Overview:
The best sounding amplifier Cambridge Audio has ever made
The CAMBRIDGE AUDIO 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 system, with 12 output transistors per channel. 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 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 world.
- 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 aluminium to create massive structural rigidity, careful damping and control of acoustic resonance.
Features:
- 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
1. Standby/On - Switches the unit between Standby mode (indicated by dim power LED) and On (indicated by bright power LED). Standby mode is a low power mode where the power consumption is less than 0.5 Watts. The unit should be left in Standby mode when not in use. When the 851W is switched out of Standby mode it will automatically check for faults and allow the power amplifier stages to stabilise before un-muting the speaker outputs
2. Output - Indicates that the Left or Right output is active. The LED (light-emitting diode) is on for an active output, off for inactive (i.e. muted).
3. Protection - If this LED is constantly on the 851W has detected a fault on either the Left or Right channel and is protecting itself.
4. Clipping - This LED indicates that the 851W has detected that either the Left or Right channel is being overdriven or clipped
5. Bridged - This LED indicates that the 851W is being used in Bridged mode. (The Mono LED will also be illuminated.)
6. Mono - This LED indicates that the 851W is being used in a Mono mode.
Rear Panel Features:
1. Loudspeaker terminals - For normal wiring, connect the wires from your left channel loudspeaker to the LEFT + & - terminals, and the wires from the right channel loudspeaker to the RIGHT + & - terminals. In each case, the red terminal is the positive output and the black terminal is the negative output
2. Balanced Audio - For connection to the balanced XLR outputs of suitable pre-amplifiers that have this kind of output (such as our own 851E model)
3. Unbalanced Audio - For connection to the normal (single ended) RCA/Phono outputs of a suitable pre-amplifier (such as our own 851E model). The pre-amplifier used should be capable of providing at least 1V rms of output (more is fine). Nearly all modern pre-amplifiers fulfil this requirement.
4. Input Type switch - Use to select a balanced or unbalanced connection type for the input.
5. Stereo/Mono mode switch - Switches the 851W between ‘normal’ Stereo operation (where one 851W is used for a pair of speakers) and Mono operation (where two 851W’s are used one for each speaker).
6. Mono Mode Switch – When mono mode has been selected, switches the 851W between Bi-amped mono and bridged mono.
7. Control Bus
- In - Allows un-modulated commands from multi-room systems or other components to be received by the unit.
- Out - Loop out for Control Bus commands to another unit.
8. Trigger In, Out/Thru - For Custom Install use or with preamps and with trigger outputs, the 851W can be turned on and off (i.e. brought in and out of Standby mode) by the presence of 5-12V DC at the Trigger input.
9. IR (Infra-Red) Emitter In - Allows modulated IR commands from multi-room systems or IR repeater systems to be received by the unit. Commands received here are not looped out of the Control Bus
10. AC power socket - Once you have completed all connections to the unit, plug the AC power cable into an appropriate mains socket then switch on. Your unit is now ready for use.
11. Power On/Off - Switches the unit on and off. If the 851W is not going to be used for long periods of time it should be turned off using this switch.
12. Mains Voltage Selector Switch (CU version only) -Switches the 851W mains voltage between 100V and 115V. Note: For use by Cambridge Audio service personnel only!
Unbalanced Stereo Connections:
The diagram below shows the 851W connected to an 851E using the Unbalanced Audio inputs via phono/RCA connectors, single wired to a pair of loudspeakers.When using unbalanced (phono/RCA) connections, the Left and Right Input Type switches on the 851W must be in the ‘Unbalanced’ position. Note: In this configuration the 851W must be set to Stereo mode.
Note: AZUR 851E sold separately
Balanced stereo connections
The diagram below shows the 851W connected to an 851E using the Balanced Audio inputs via three-pin XLR connectors, single wired to a pair of loudspeakers.
When using unbalanced (phono/RCA) connections, the Left and Right Input Type switches on the 851W must be in the ‘Unbalanced’ position.
Note: In this configuration the 851W must be set to Stereo mode. When using balanced (XLR) connections, the Left and Right Input Type switches on the 851W must be in the ‘Balanced’ position. Note: In this configuration the 851W must be set to Stereo mode.
Note: AZUR 851E sold separately
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
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
- Frequency response............5Hz – 80kHz
- S/N ratio (ref 1W / 8 Ohn)............>90dB (unweighted)
- 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 (42.2lbs)