Moving up the Azur amplifier league, the 540A benefits from a custom designed oversized toroidal transformer and short path circuitry, while a completely new amplifier topology for low levels of distortion. Packing a mighty 50 watts at eight ohms, the 540A is a clear leader in budget amplifier circles offering a huge mumber of features and a build quality to embarrass more expensive rivals.

Electronics sit on a foundation plate to achieve maximum support and acoustic damping. Constant monitoring by the intelligent proprietary CAP5T protection circuit checks for overloads or faults, while clipping detection reduces volume levels if a problem is detected.

The 540A features full remote control and a second set of speaker outputs means the 540A can be enjoyed in more than one room. Six inputs with two tape loops are provided and two stand alone phono pre-amplifiers (the 540P and 640P) cater for vinyl lovers.

CAP5 (Cambridge Audio Protection 5) is an innovative and intelligent protection system. It constantly monitors your amplifier, without degrading signal purity, ensuring ultimate reliability. This incorporates a clipping sensor that reduces volume to keep levels in a safe range. There is also short-circuit detection and a solid-state temperature sensor with over-heat cut out. Combined these technologies ensure your Cambridge Audio Azur amplifier will deliver years of reliable high performance.

A proprietary non-invasive five-way protection circuit CAP5 was the subject of a separate research and development programme within Cambridge Audio. The aim was to develop a highly innovative protection system that would not affect the sound quality of their amplifiers.

Perhaps most innovatively the circuit measures the distortion of the output signal relative to that of the input. This means the CAP5 circuit is able to tell when the unit is being driven to hard and apply the protection. The mechanism triggers a two-stage response. For small excursions into clipping, CAP5 'nudges' down the volume control. For gross clipping the CAP5 protects the unit by going into Standby.

The circuit constantly measures the DC level at the output terminals. It immediately disconnects the speakers if any DC is detected. This protects the attached speaker in the event of an amplifier fault.

The circuit constantly monitors the current in the output stage and the voltage across it. It ensures levels remains within a safe operating area. The CAP5 immediately protects the amplifier should this be exceeded.

The circuit measures the temperature of the internal heatsink. If this exceeds a set temperature reading the unit is shut down.

Each time the amplifier is turned on, CAP5 measures the resistance across the speaker terminals. It checks for a short every time the unit is turned on before allowing use. The most likely time this occurs is when a customer changes his/her speakers.