Cambridge Audio Azur 840A V2 Class XD Integrated Amplifier

When the Azur 840A was introduced it broke the mould by introducing an entirely new class of amplifier design in the shape of Class XD™ and marked the zenith of Cambridge Audio’s critically acclaimed Azur line-up. The 840A V2 now embraces the second generation of Cambridge Audio’s patent pending proprietary technology and has employed some subtle but significant updates to improve upon this already outstanding design. The second generation Class XD is now complemented by a new output stage carefully adjusted to integrate with this novel technology, revised balanced inputs for lower distortion and noise and a new more accurate volume control with even lower crosstalk for greater stereo imaging.

At the core of the 840A’s strength is a patent pending, Class XD (crossover displacement) technology which has been subtly revised following continuing post-launch development and critical evaluation. This unique design gives pure Class A operation at low levels, moving smoothly into an enhanced version of Class B at higher levels. This system should not be confused with Class AB, which inherently generates greater distortion at high levels than a pure Class B design. XD technology feeds a controlled current into the output stage actively displacing the crossover point in a new way so that the usual Class B crossover point no longer occurs at zero volume - the worst possible position in terms of distortion – but at a significant output level. The result is a smooth and linear transition between the two modes of operation, which differs significantly from the abrupt, gain transition of a Class AB amplifier.

The Azur 840A amplifier includes a massive, oversized low flux toroidal transformer, incorporating a silicone-steel screen. To separate the delicate signals needed by the pre-amp from those needed by the power-amp, the 840A features a completely separate pre-amp toroidal transformer, mounted to the rear casework.

In addition to this innovative technology, the 840A also uses an extremely sophisticated resistor ladder / relay attenuator with gold-plated contacts for volume and balance control. This gives extremely low distortion with superb channel balance and incredibly accurate control in 1dB steps over the whole range.

Relays are also used for all input switching, more normally associated with designs costing many times that of the 840A, these components deliver extremely high isolation between inputs, whilst remaining completely free from the distortion associated with conventional semiconductor switching.

In our ongoing development of Class XD we have conducted exhaustive research into further improvements of our amplifier designs to squeeze everything out of this innovative technique. This in turn led to a new output stage topology being developed which has been incorporated into the version 2 of the 840A. Two pairs of very high current output transistors are used per channel (for the amplifier output) plus an extra high current transistor per channel for the XD circuit. Also included is the latest development of Cambridge Audio’s proprietary CAP5 protection system.

The Azur 840A makes room for eight inputs, one of which has both fully balanced and unbalanced (XLR) connections, ideal for use with the matching Azur 840C upsampling CD player. These inputs can be named as desired by the user on the custom-designed display to show CD, iPod™, Phono etc. This means it’s much easier to identify and select your source equipment. This is particularly useful for other members of the family who may be less familiar with your hi-fi set-up.

The 840A also features bypassable tone controls, tape record out, a preamp output, and two sets of speaker outputs, all of which are gold-plated for low contact resistance and freedom from oxidisation. Any input can be set to fixed gain (allowing the 840A to be used for the front channels of a surround-sound system for instance) and all inputs have individual trimmable gain.

Completing the rear panel is an RS232 control port, and multi-room outputs to connect the 840A to Cambridge Audio’s Incognito system. This plethora of connections enables complete integration with multi-room entertainment systems including two way interface with touchscreen control panels.

Alternatively, the 840A is Incognito Ready. This means that two additional rooms can access the source components connected to the 840A via the Incognito system’s amplified keypads and passive speakers or active in-ceiling speakers. An independent Incognito power supply links to the 840A, enabling audio and low voltage power to be transmitted to each Incognito keypad using only one run of CAT5 cable.

As with all Azur products, the foundation of its excellence is a bespoke chassis. This comprises an incredibly thick 7mm front panel and extruded side panels, both fashioned from aluminium, which combine with a 2mm formed steel base plate and specially designed vibration absorbing feet. The result is an ultra rigid, low resonance, acoustically dampened platform for the electronics to sit in.

The 840A is available in either silver or black and comes complete with the latest elegant, slim-line navigator style Azur remote handset offering full control. This remote also controls iPod track skip and volume functions when used with a universal dock, Cambridge Audio Azur CD players and Incognito keypads and discrete commands for custom install use.

Click here to see why Hi-Fi Choice gave the 840A V2 92%!
Azur 840A (Version 2) Class XD amplifier Features

Second generation proprietary Class XD technology
120W per channel into 8 Ohms or 200W per channel into 4 Ohms
Oversized low flux toroidal transformers
Completely separate pre-amp and power amp toroidal transformers and circuits make the 840A effectively a pre and power amplifier combination in one chassis
Sophisticated resistor ladder and relay based attenuator for extremely accurate volume/balance control
Two pairs of very high current output transistors per channel in revised configuration for improved integration with Class XD
Twin rectifiers and separate transformer taps for dual mono operation of the left and right power amplifiers
RS232 port, IR emitter In and Control Bus In/Out for seamless integration with custom install systems
A-BUS™ / Incognito™ Ready connections compatible with Cambridge Audio’s new Incognito multi-room keypads or other A-BUS compatible keypads allow the 840A to form the hub of a simple but highly effective 3 zone multi-room system
Fixed level inputs allow the 840A to provide the front channel amplification when integrated with home cinema systems that use an AV processor
Cambridge Audio proprietary CAP5™ protection system
8 inputs including 1 balanced XLR connection in addition to single ended RCA inputs
Nameable inputs
Backlit LCD screen
Extruded aluminium side panels and solid aluminium front panel plus an ultra rigid, acoustically dampened chassis
Navigator style Azur remote which also controls
o iPod™ track skip and volume functions
o Azur CD players
o Cambridge Audio’s Incognito keypads
o Discrete commands for custom install use