Group test: Stereo amplifiers £500-£750

Overview Price: £750 More info: Cambridge Audio Size: 115x430x385mm Weight: 15kg Power output: 120W Line level inputs: 8 Key features: Balanced input, tape & preamp output, twin speaker outputs, variable input levels

Cambridge Audio Azur 840A

This is a very unusual beast. It has the sort of features that one usually only finds on kit costing several times this price such as the ability to adjust input gain and to type in your own input names. There is a balanced input, presumably for the matching 840C disc player when it arrives, and it has separate mains transformers for pre and power amp sections. Initially it seemed a bit expensive for a Cambridge, but the reason soon became clear. It also includes the brand's class XD (crossover displacement) technology which claims to operate purely in class A for the first few watts, which are the important ones, and then “move smoothly” into class B at higher levels. Cambridge rates output at 120 watts and claims that its XD system offers lower distortion than regular class AB designs.

With all these features one is naturally a little sceptical as to whether the 840A can actually deliver the important bit, the music. We're happy to say that it can, and with an impressive degree of transparency at that - there might be something in this XD technology. It delivered the greatest resolution and finesse in the group with a grasp of subtleties such as micro-dynamics that belies its price tag. It's not quite as tight in timing terms as the Naim but is more even-handed and revealing in its presentation. There is a vitality to dynamics and a nimbleness across the band that makes for gripping listening. It's expensive for a Cambridge but it's a bargain nonetheless.

Verdict Plus points Unheard-of features at the price combined with remarkable transparency and evenness Minus points Timing not as tight as some

Overview Price: £725 More info: Naim Size: 432x70x301mm Power output: 50W Line level inputs: 4 (phono and DIN) Key features: Tape output

Naim Nait 5i

The long-running Nait is the only integrated amp in this established brand's comprehensive range of components. The 5i is described as “the most powerful and best-sounding Nait ever”, but in the scheme of things its 50 watt rating doesn't seem a big dea. However, the specs suggest that it can deliver a peak 500 watts into a one-ohm load, so there's clearly a stiff power supply inside. The casework is made from a mix of aluminium and zinc which is designed to keep out vibration and the socketry includes two of Naim's favourite DIN connectors. These are said to offer a sonic improvement over phonos but are of limited use if you don't have a Naim CD player or tuner.

Fortunately both DIN and phono inputs are available as well as the ability to set one input to unity gain for use in a surround system. The remote, it has to be said, is the least inspiring in this group and its effect on the volume level does little to improve ones perceptions, if small volume differences are required you need to visit the volume control proper.

Naim amps of yore have made their name on skill in the timing department, a quality that is intrinsic to the reproduction of music. The Nait 5i follows that credo with a taut and precise rendition of events that feels right on the money. One side effect of its approach is that notes in the upper midrange are slightly hardened. It's a subtle effect though and not one that undermines the music but it is a coloration of sorts. That said the vivacity and freshness that it brings to the sound cannot be argued with and it's not hard to hear why this amp has been converting music lovers to the Naim sound for so long.

Verdict Plus points Taut, precise timing, plenty of energy and tremendous coherence Minus points Slight forwardness to the upper midrange, crude remote

Overview Price: £750 More info: Primare Size: 430x100x385mm Weight: 13.5kg Power output: 75W Line level inputs: 4 Key features: Two preamp outputs, tape output

Primare I21

Although this is the base model in the Swedish company's range of electronics its build and styling are on a par with its best kit, its stainless front panel means it certainly looks like the most expensive amp in this bunch. A 75-watts-per-channel design, the I21 uses extensive output stage protection to stop you damaging either it or the speakers attached to it. Its power is derived from an 800VA toroidal mains transformer with separate windings for each channel and seven steps of regulation for both preamp and power amp stages. The circuit board uses surface-mount devices (SMDs) to minimise signal path lengths while the volume control is a digital device that's said to ensure good channel balance and a flat response at any level.

The I21 delivered the most expansive and relaxed sound of the group which meant that it could be listened to for longer and louder than the others. On the other hand, some will find it a little on the diffuse side, it lacks precision in both imaging and timing terms and those after a tight sound should look elsewhere. We enjoyed the fact that it could spread the sound wider than the speakers and do so in an effusive yet engaging fashion. There is a touch of exaggerated openness but this space allows notes to form a fuller image. The least hi-fi sounding but easiest amp to listen to in the bunch, this attractive Swede deserves your attention.

Verdict Plus points Open, relaxed and expansive sound, superb build Minus points Not as precise as some

Overview Price: £598 More info: Rega Size: 432x70x301mm Power output: 60W Line level inputs: 6 Key features: Two tape and preamp outputs, power amp input

Rega Mira 3

Mira is the top integrated in Rega's small but neatly formed arsenal of amplifiers, it is rated at 60 watts-a-side and is confusingly equipped with only one control knob that covers both input selection and volume adjusting duties. Press it in to change inputs or use the attractive Solar remote for instant access to this and other Rega components. Unusual features include microprocessor controlled volume via switched resistors with level steps indicated by an LED display around the knob. No balance control is available but Rega claims a channel match within 0.2dB at all gain settings. It has the option of being used solely as a preamp or power amp and is claimed to be able to “drive the most of awkward of speaker systems”.

The Mira 3 turns out to be sonically closer to the Nait than the other two amps in this group but is not the same, it comes close to providing the same quality of timing for instance which is not bad considering the price difference, and it has a similarly focused presentation. It doesn't however have quite the same resolution of depth information, but that said, there is a degree of calm to its delivery which makes for relaxing listening. The bass, while well articulated and precise, could extend further and the treble likewise is a hint curtailed compared to the best in test. What it wins on is its coherency which makes sense of the music's rhythmic intricacies whatever the style.

Verdict Plus points Good coherency and a nicely articulated sound Minus points A bit flat in stereo terms

Final verdict This is an impressive collection of amplifiers, the standard across the range is particularly high and in the case of the best is good enough to worry designs costing almost twice as much. Even in a group this good, of course, not everyone is a winner, however, at its price the Rega put up a good fight and delivered an engaging and clean sound. The Primare offers a more expansive and convivial version of events that will suit many tastes while the latest in a long line of Naits can hold its head up high with a sound that sounds so right that one is easily converted to its style of presentation. But top honours have to go to the Cambridge which combines features galore with a degree of transparency that's not been available for less than a grand for a long time.

AVR Glossary