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Amplifiers - Class XD explained

Relevant Products: Azur 851A, Azur 851W

 

What is Class XD?

Class XD is Cambridge Audio’s proprietary amplification system which combines the best of Class A and Class AB amplification, delivering the sound quality of a Class A amp while retaining the efficiency of a Class AB amp.

Above all it is the attention to details that brought about this state-of-the-art technology – it is for this reason that you will find it in only our best amplifiers.

You’ve mentioned that regular amplifiers operate in Class A or Class AB – what does that mean?

The two most common forms of amplification in hi-fi stereo amplifiers are ‘Class A’ and ‘Class AB’.

Class A

Class A is typically used in extremely expensive amplifiers because it produces phenomenal sound quality.  However, it’s also very inefficient, generating substantial heat which needs to be managed – normally with many expensive heat sinks.

Class A amplification delivers the purest possible sound, which is why it is typically used in extremely expensive amplifiers. This produces phenomenal sound quality.

Using only one transistor to conduct comes at a cost, however, because it is energy inefficient with many expensive heat sinks.

Class AB

Class AB is more commonly used because it is far more efficient. However, this doesn’t deliver quite the same sound quality as Class A because it generates distortion at the crossover point in high-level frequencies, which is audible.

Class AB involves both transistors conducting simultaneously and is more commonly used because it is far more efficient.

However, this doesn’t deliver quite the same sound quality as Class A because it generates distortion at the crossover point in high-level frequencies, which is audible.

What are the benefits of using Class XD, and how does it work?

Not satisfied with either of the above options, our engineers developed our patented Class XD amplification which adds voltage to a traditional Class AB design to shift the crossover point to a position where the audio distortion is not audible to the human ear.

Class XD, therefore, combines the sound quality of a Class A amp with the efficiency of a Class AB amp and also means that customers’ money is spent on further premium hi-fi components and technologies for great sound, rather than on dealing with heat.

Which products use Class XD?

Given the technical requirements of Class XD, we knew that any product that included it had to be a true audiophile product, where the sound quality was paramount.

The Azur 840A was the first ever Class XD product and the result of over two years’ worth of development.

Just like the 851A, the 851W also runs our proprietary Class XD amplification.

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