CAP5 - FIVE WAY PROTECTION SYSTEM

Cambridge Audio has developed a proprietry protection system to ensure reliability and a long life to its amplifiers. This protection system comprises of five main protection methods:

Intelligent clipping detection

CAP5 has the ability to detect when the amplifier starts to clip or overdrive its output, which can damage Loudspeakers, the amplifier power supply and most importantly degrade the sound. When CAP5 detects clipping the volume will be automatically nudged down until CAP5 detects an undistorted* output (*the volume is nudged down until the distortion is less than 2% which listening tests have shown is difficult to hear).

It is possible to disable only this feature by holding down the Standby button during power up (whilst plugging the unit into the mains power). The unit will indicate this by flashing the protection LED for several seconds. Disabling the clipping detection is not advised as this feature has been added to protect the amplifier.

Over temperature detection

CAP5 includes temperature detection which constantly monitors the heat generated by the output transistors. When the monitored temperature reaches a high level (suitably within the limits of the output devices) the amplifier will automatically switch into a fault mode (indicated by double flashing of the protection LED). The unit should ideally be left for 15 minutes in this state to cool down adequately. If the unit has not fully cooled down then the temperature may reach the limit soon after the amplifier is powered up.

If the Loudspeaker impedance is low the temperature of the amplifier may rise faster as the amplifier is working harder. If the amplifier is mounted in a cabinet or the ventilation slots are obstructed the over temperature detection may activate/reactivate after a short listening time.

Short circuit detection

During power up from standby or during input channel selection CAP5 performs a check on the Loudspeaker terminals to see if a short across the terminals has been accidentally introduced. If the resistance measured across the Loudspeaker terminals is too low the unit will stay in Standby mode until the fault has been removed and Power up is re- attempted.

DC detection

CAP5 offers Loudspeaker protection if the output of the amplifier goes to DC because of some internal fault. This is a rare fault although it could just save those expensive Loudspeakers.

If the amplifier is switched out of standby when the input signal to the amplifier is too high (with the current volume setting) the CAP5 system will detect this and reduce the volume to a suitable level.

Overvoltage/overcurrent detection

CAP5 offers V/I protection by constantly monitoring the output transistors to keep them working inside their Safe Operating Area (SOA). The SOA is a set of limits given by the output transistor manufacturer to ensure reliability. Many amplifier designers include V/I limiting in the

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Cambridge Audio 540A user manual CAP5 Five WAY Protection System
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540A specifications

Cambridge Audio has established itself as a formidable force in the realm of high-fidelity audio equipment, and the 540A and 640A amplifiers exemplify the company's commitment to delivering exceptional sound quality at a competitive price point. These integrated amplifiers, known for their detailed sound reproduction and robust performance, cater to audiophiles who appreciate both quality and value.

The Cambridge Audio 540A is part of the company's entry-level range, designed for music enthusiasts seeking an affordable yet high-performance amplifier. The 540A boasts a powerful 50 watts per channel output, allowing it to drive a variety of speaker types with ease. The design emphasizes simplicity and user-friendliness, featuring straightforward controls and a sleek finish that fits well in any audio setup.

One of the standout features of the 540A is its dual-mono circuit design. This architecture minimizes crosstalk and signal interference, allowing for a cleaner, more precise sound. It also incorporates high-quality components, including a toroidal transformer, which contributes to improved efficiency and reduced distortion. Additionally, the amplifier features a range of inputs, including multiple line-level options, making it versatile enough to accommodate various audio sources such as CD players, turntables, and streaming devices.

On the other hand, the 640A is an upgrade that builds upon the strengths of the 540A. With a more powerful output of 75 watts per channel, the 640A is designed for users who demand more from their audio systems. This amplifier incorporates an improved power supply and enhanced components, further refining the sound quality. The 640A also introduces features such as a high-quality phono stage, enabling direct connection to turntables without the need for separate equipment.

Both amplifiers incorporate Cambridge Audio's dedication to quality with a focus on analog circuitry. This is particularly evident in the warm, rich sound signature that these amplifiers provide, making them ideal for a range of music genres. The build quality is robust, with a solid chassis designed to reduce vibration and resonance, ensuring a stable platform for audio performance.

In summary, the Cambridge Audio 540A and 640A amplifiers offer a compelling combination of sound quality, versatile connectivity options, and robust design. Whether you are an entry-level audiophile or a seasoned listener looking for an upgrade, these amplifiers provide an engaging listening experience that highlights the nuances and details of your favorite music. With Cambridge Audio's unwavering focus on high-fidelity sound, both models are captivating choices that continue to impress users worldwide.
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