"Competes with the Very Best in Class"
The Cambridge Audio Azur 851A Class XD integrated amplifier combines a gu "Refined and Tonally Rich"
The Cambridge Audio Azur 851A Class XD integrated amplifier combines a gutsy and powerful performance with unprecedented detail and staggeringly low distortion. The 851A also takes Cambridge Audio's original Class XD design to another level with even lower high frequency distortion without affecting the amplifier's efficiency. And thanks to such huge power reserves, allowing the 851A to deliver 120 watts-per-channel at 8 ohms, it's genuinely capable of comfortably driving premium speakers of all types.
"It is distinctly more refined and tonally rich that its predecessor the 840A," Jason Kennedy, Hi-fi Choice magazine for June 2012. "What did surprise me is the increase in musicality; the melody is far more obvious and you are drawn into the music to a far greater degree."
In his joint review of the 851A integrated amplifier and 851C CD player, Kennedy concludes, "They now compete with the very best in class when it comes to sound and are pretty much in a league of their own when it comes to features."
When asked about the sound qualities of the 851A that his team developed, Cambridge Audio's Electronic Design Manager Chris Woolrych described it as "big and punchy... Unlike many high end amplifiers which tend to be smooth but lacking in ultimate power, Class XD gives the 851A much more potency and it's got the ability to drive any speaker we've paired it to with ease."
"Deserving of Garish 'Buy Me' Stickers"
"No matter how challenging the music, the system kept a tight grip on proceedings while appearing calm and unflustered," notes John Bamford in his August 2012 joint review of the Cambridge Audio Azur 851C CD player and Azur 851A amplifier for England's Hi-Fi News magazine. "If ever there was a combo deserving of garish 'Buy Me' stickers on the fascias, it's these latest Azur components."
Class XD Technology
Cambridge Audio first launched its game-changing Class XD methodology in the 840A amplifier. It quickly found favor for its ability to offer levels of refinement more commonly associated with Class A amplifiers combined with the gutsy performance from the best Class AB designs. During the 851A development process, Cambridge Audio further refined this system and has now upgraded and retuned Class XD to offer even lower distortion at the highest of frequencies without introducing any heat gain.
The unique design of Class XD 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, actively displacing the crossover point 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 gain transition of a Class AB amplifier.
Seriously High-End Design Techniques
Such attention to detail extends even further and the 851A features some seriously high-end design techniques, including two pairs of very high current output transistors per channel which offer excellent integration with the Class XD circuitry. Twin rectifiers and separate transformer taps enable the power amplifiers to operate in dual mono mode for the very best channel balance.
Part of the 851A's ability to perform so proficiently comes courtesy of not one but two custom-designed toroidal transformers. The larger is charged with providing the 851A's huge 120-watt power reserves, incredible bass response, and its ability to operate at extremely low noise. Meanwhile, a completely isolated smaller toroidal transformer takes care of the delicate pre-amplifier processes.
Power is nothing without control and the 851A offers perfect channel balance and stunning accuracy. This comes courtesy of an all new volume control design using parts from critically acclaimed Finnish manufacturer MAS. This one example is typical of the way Cambridge Audio selects premium components from around the world to best match its products' needs.
A Host of Inputs
The 851A features a host of inputs for connection of all the latest entertainment sources. The amp has sources labeled 1 through 7, plus record-in and record-out (labeled 'In8/Tape' on the remote); two of those source inputs can be either balanced or RCA, the other six are RCA.
The fully balanced XLR inputs offer the highest quality connection and are perfect for the matching 851C (DAC, preamplifier and CD player), Stream Magic 6 (network music player) or DacMagic Plus (DAC). The RCA inputs are ideal for connecting other devices like tuners, phono stages, or recording devices.
CAP5 Protection System
To protect the 851A from the rigors of real world use, Cambridge Audio has developed an even more advanced version of its proprietary CAP5 protection system. CAP5 prevents potential disasters from causing damage to the amplifier and connected components by performing diagnostics during power-up and usage.
Over current/over voltage protection protects speakers from being driven too hard. Temperature protection is provided in case of inadequate ventilation or air circulation in humid environments. DC Detect protects against the most common user errors in set-up. Short circuits runs a check on power-up to detect incorrectly connected speakers. Clipping gently nudges the volume down if the 851A is driven too hard and distortion is detected.
tsy and powerful performance with unprecedented detail and staggeringly low distortion. The 851A also takes Cambridge Audio's original Class XD design to another level with even lower high frequency distortion without affecting the amplifier's efficiency. And thanks to such huge power reserves, allowing the 851A to deliver 120 watts-per-channel at 8 ohms, it's genuinely capable of comfortably driving premium speakers of all types.
"It is distinctly more refined and tonally rich that its predecessor the 840A," Jason Kennedy, Hi-fi Choice magazine for June 2012. "What did surprise me is the increase in musicality; the melody is far more obvious and you are drawn into the music to a far greater degree."
When asked about the sound qualities of the 851A that his team developed, Cambridge Audio's Electronic Design Manager Chris Woolrych described it as "big and punchy... Unlike many high end amplifiers which tend to be smooth but lacking in ultimate power, Class XD gives the 851A much more potency and it's got the ability to drive any speaker we've paired it to with ease."
"Deserving of Garish 'Buy Me' Stickers"
"No matter how challenging the music, the system kept a tight grip on proceedings while appearing calm and unflustered," notes John Bamford in his August 2012 joint review of the Cambridge Audio Azur 851C CD player and Azur 851A amplifier for England's Hi-Fi News magazine. "If ever there was a combo deserving of garish 'Buy Me' stickers on the fascias, it's these latest Azur components."
Class XD Technology
Cambridge Audio first launched its game-changing Class XD methodology in the 840A amplifier. It quickly found favor for its ability to offer levels of refinement more commonly associated with Class A amplifiers combined with the gutsy performance from the best Class AB designs. During the 851A development process, Cambridge Audio further refined this system and has now upgraded and retuned Class XD to offer even lower distortion at the highest of frequencies without introducing any heat gain.
The unique design of Class XD 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, actively displacing the crossover point 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 gain transition of a Class AB amplifier.
Seriously High-End Design Techniques
Such attention to detail extends even further and the 851A features some seriously high-end design techniques, including two pairs of very high current output transistors per channel which offer excellent integration with the Class XD circuitry. Twin rectifiers and separate transformer taps enable the power amplifiers to operate in dual mono mode for the very best channel balance.
Part of the 851A's ability to perform so proficiently comes courtesy of not one but two custom-designed toroidal transformers. The larger is charged with providing the 851A's huge 120-watt power reserves, incredible bass response, and its ability to operate at extremely low noise. Meanwhile, a completely isolated smaller toroidal transformer takes care of the delicate pre-amplifier processes.
Power is nothing without control and the 851A offers perfect channel balance and stunning accuracy. This comes courtesy of an all new volume control design using parts from critically acclaimed Finnish manufacturer MAS. This one example is typical of the way Cambridge Audio selects premium components from around the world to best match its products' needs.
A Host of Inputs
The 851A features a host of inputs for connection of all the latest entertainment sources. The amp has sources labeled 1 through 7, plus record-in and record-out (labeled 'In8/Tape' on the remote); two of those source inputs can be either balanced or RCA, the other six are RCA.
The fully balanced XLR inputs offer the highest quality connection and are perfect for the matching 851C (DAC, preamplifier and CD player), Stream Magic 6 (network music player) or DacMagic Plus (DAC). The RCA inputs are ideal for connecting other devices like tuners, phono stages, or recording devices.
CAP5 Protection System
To protect the 851A from the rigors of real world use, Cambridge Audio has developed an even more advanced version of its proprietary CAP5 protection system. CAP5 prevents potential disasters from causing damage to the amplifier and connected components by performing diagnostics during power-up and usage.
Over current/over voltage protection protects speakers from being driven too hard. Temperature protection is provided in case of inadequate ventilation or air circulation in humid environments. DC Detect protects against the most common user errors in set-up. Short circuits runs a check on power-up to detect incorrectly connected speakers. Clipping gently nudges the volume down if the 851A is driven too hard and distortion is detected. | 
