Following is the press release from Cambridge Audio about their new amplifier…
"Cambridge Audio launches the 840A Class XD integrated amplifier, which marks the zenith of Cambridge Audio’s critically acclaimed Azur line-up. Embracing Cambridge Audio’s patent pending proprietary Class XD™ technology, the 840A brings together the quality of Class A amplification, the power economy of Class B designs, and most amazingly of all, avoids many of the distortion pitfalls inherent in Class AB designs. So innovative is this technology that it is the subject of a patent pending and planned Audio Engineering Society white paper.
Key features:
* Proprietary Class XD technology
* 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
* 120W per channel into 8 Ohms or 200W per channel into 4 Ohms
* Sophisticated resistor ladder and relay based attenuator for volume/balance control
* Two pairs of very high current output transistors per channel
* 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 one with balanced XLR connections in addition to single ended phono/RCA
* 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 control which also controls Azur CD players
* Available in silver or black
At the core of the 840A’s strength is a patent pending, Class XD (crossover displacement) technology. 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 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, distorted 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 preamp from those needed by the power-amp, the 840A features a completely separate preamp toroidal transformer, mounted to the rear casework.
In addition to this innovative technology, the 840A also uses an extremely sophisticated resistor ladder and relay attenuator for volume control and the same high quality relay switches for input selection. More normally associated with designs costing many times that of the 840A, these components deliver extremely high isolation between inputs, very accurate channel balance and leave the amplifier completely free from the distortion
associated with conventional semiconductor switching and volume control.
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, low noise transistors and many proprietary circuits. 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 balanced (XLR) and unbalanced connections. These inputs can be named as desired on the custom-designed display.
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. Any input can be set to fixed gain (allowing the 840A to be used for the front channels of a surround-sound system) and all inputs have individual trimmable gain. Completing the back panel is a RS232 control port,
and multi-room outputs to connect the 840A to the new Cambridge Audio 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™ Type II. This means that two additional rooms can access the source components plugged into the 840A via the Incognito system’s amplified keypads and passive speakers or active in-ceiling speakers.
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.
For more information click here."
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