840A Class XD integrated amplifier

INTRODUCTION

Thank you for purchasing this Azur 840A Class XD Integrated Amplifier. This unit is part of our new '8' Series taking Cambridge Audio to new levels of audio excellence as part of our commitment to the on-going development of the Azur range. We hope that you will appreciate the results and enjoy many years of listening pleasure from it.

For the 840A we developed many new circuits and components, with many parts being designed specifically for this model. A unique proprietary to Cambridge Audio patent pending amplifier topology has even been developed called Class XD™ which can eliminate crossover distortion at low signal levels.

This technology creates a region of pure Class-A operation where the crossover zone would otherwise be. It should not be confused with Class AB, which gives a small area of Class A, at the cost of higher distortion as soon as signal levels moves outside it. Class XD circuitry not only removes crossover distortion from the zero-crossing point but also reduces distortion in the other parts of the amplifier's output range. A white paper on this technology is available on our website: www.cambridge-audio.com.

Please note that because of the Class XD technology the 840A runs slightly warmer than a conventional Class B/AB amplifier and the ventilation slots on the top of the unit must not be obscured.

Other features include the use of precision networks of resistors and relays for the volume and balance control rather than the more common solid-state or volume potentiometer schemes. Volume is controllable in 1 dB steps over most of the range, giving very fine control, an accurate logarithmic law and superbly accurate channel balance. Input switching is also by high quality relays.

The 840A features separate transformer secondaries for left and right channels, twin rectifiers and separate PSU's for dual mono operation of the left and right power amplifiers. A separate transformer supplies the preamp making the 840A effectively a Pre and Power amp combination in one box.

Input 1 features a balanced input using XLRs giving optimal performance with equipment such as the matching 840C Upsampling CD player which feature balanced outputs.

A completely new casework has been designed which combines massive structural rigidity with careful damping and control of acoustic resonance. An Azur Navigator remote control is also provided, giving full remote control of your amplifier in an attractive and easy to use handset.

We have also added many new features, including support for multi- room use. By plugging in one or two external Cambridge Audio Incognito keypads and a power supply unit your amplifier can become the hub of a simple multi-room system. In addition, Control Bus Input/Output, IR Emitter Input and RS232 control are provided to make it easy to integrate this unit into Custom Installation systems if desired.

Your amplifier can only be as good as the system it is connected to. Please do not compromise on your source equipment, speakers or cabling. Naturally we particularly recommend models from the Cambridge Audio Azur range. These have been designed to the same exacting standards as this amplifier. Your dealer can also supply excellent quality Cambridge Audio interconnects to ensure your system realises its full potential.

Thanks for taking the time to read this manual; we do recommend you keep it for future reference.

Matthew Bramble

Technical Director

Azur Class XD integrated amplifier 3