One measure of truly excellent hi-fi components is that they will sound exciting and stimulating regardless of the sort of music you play through them. They won't restrict you to listening to those vacant, over-polished demo 'favourites' we've come to loathe over the years.

Naim's new entry-level pre/power combination - the NAC 122x preamplifier and the NAP 150x power amplifier - falls squarely into this 'exciting and stimulating' camp. In fact, when first listening to the duo, it's hard to believe that they are entry-level offerings: they seem far more composed and effortlessly informative than any 'starter' combination has any right to do.

The £750 NAC 122x replaces the NAC 112x in Naim Audio's preamp hierarchy, and draws on the heritage of the more upmarket and expensive NAC 202. In terms of improvements over the model it replaces, the new design uses a hard-wired, motorised, Alps volume control for better performance, lower noise in use and an improved feel over the resistor ladder control of the NAC 112x.

Its six inputs are relay-switched rather than being multiplexed, as were those of its predecessor, which, again, is said to enhance its performance.

Furthermore, great care has been taken to make the casework and PCB as low resonance as possible and to isolate the PCB from the environment and any deleterious vibrations present therein. This means that you'll encounter a little play when plugging in connections but this is intended to be there and is nothing to be concerned about.

The £825 NAP 150x represents Naim's first step on the power amp ladder and its design also owes much to more upmarket Naim models; in this case, the flagship NAP 500. It features many improvements over the original NAP 150, including a hefty toroidal transformer for improved regulation, with discrete windings for each audio channel. There's also an enhanced power supply for the preamplifier.

As is common with most Naim preamps, the NAC 122x can be upgraded - or, perhaps more accurately, users can explore the full potential of what it has to offer - by using an external power supply unit. This is an approach to design that seems outwardly unusual, but one that makes perfect sense when you hear the improvements that it can bring.

Power supplies

Past reviewers have preferred the sound of the superior power supply coupled to a lesser CD player over that of a notionally better CD player with a lesser power supply.

As a Naim user for many years, and having experienced the efficacy of numerous power supply improvements in my own system, I have no problems accepting Naim's standpoint on the crucial effects that power supplies have upon musical performance.

For the purposes of this review, Naim also supplied a £550 Flat-Cap 2x discrete power supply, which sits in the signal path between the preamp and the power amplifier. The Flat-Cap 2x, or similar, would be obligatory were you planning on using the preamplifier with another manufacturer's power amplifier, as the NAC 122x has no integral power supply.

We listened to the NAC 122x and NAP 150x, along with the Flat-Cap 2x, giving a system with a total price of £2,125. Given the substantial performance increase when using the Flat-Cap 2x, which no one would describe as subtle, not using it seemed churlish.

It's worth noting that the external power supply will also power the analogue stage of Naim's CD5x CD player, which is handy given that this is the level of player we'd most expect to see used in this system.

Sound quality

From the outset, the NAC 122x, Flat-Cap 2x and NAP 150x combination is surprising. The ease with which it copes with an array of demanding discs is beguiling. It reveals the beauty within discs - which we've heard other systems disguise or even completely eradicate - while simultaneously exposing their occasionally less than smooth edges.

On tracks from one such disc, Terence Trent D'Arby's Vibrator, the combination excelled with its portrayal of timing. It picked out each instrument distinctly, then knitted its contribution together with others superbly to provide a cohesive, well-judged sense of drive and impetus.

Dynamically, it proves equally faithful, no matter whether it is dealing with overt contrasts or the subtle variations of elements buried further back within a mix.

It doesn't show undue favour to any part of the musical spectrum, lucidly portraying high frequencies without any emphasis or aggression while displaying a notable control over the bass. This is both sonorous and precise, with full-bodied notes starting and stopping with outstanding acuity.

Tonal portrayal

The system handles tonal texture with equal aplomb, which in the past wasn't a quality people would always associate with Naim amplifiers. On suitable recordings, it delivers a portrayal of tonality that could be mistaken for that of a fine valve amplifier, while still being able to temper that with appropriate jagged edges where necessary.

On tracks from the Nirvana CD Unplugged, Krist Novoselic's acoustic bass sounded fittingly warm, rounded and almost plummy while Kurt Cobain's vocals simultaneously displayed a raucous, strained quality when he pushed his voice near to the edge of his range.

Again, though, what really shines though is the amplifier's insistent rhythmic confidence. Even on notoriously difficult music, such as Edgar Varèse's Ameriques or Henry Kaiser's collection of guitar improvisations, Lemon Fish Tweezer, the Naim combination would unearth any semblance of a rhythm, no matter how obscure, perverse or deeply buried, and lay it out for you to appreciate and enjoy.

As Henry Kaiser observes in that album's sleeve notes, "Music isn't about notes - it's about feeling". If you find yourself nodding in agreement with that sentiment you'd be well advised to take a listen to this system. That it also sorts out each of those notes in all its unadulterated, perfectly formed glory is more than just a bonus.

The NAC 122x and NAP 150x are delightfully communicative and musically sympathetic devices. They revel in delving into the most complex of music and laying out its various strands such that they instantly come together and make sense. Give them an easier task, such as a simple guitar and voice playing 4/4, and they simply sail through, dishing out resolution and insight by the shovel-full.

Wholly satisfying

And make no mistake, they love such music and deliver superb renditions of it: Nic Jones' Canadee-I-O, for example, came across with a hard-to-describe sense of correctness that we found truly and wholly satisfying.

Sure, all the hi-fi artefacts were there - the gentle creak of his guitar body as he bent notes by pulling back on the neck - but that wasn't what brought a smile to our faces. That was down to a sense of his near-tangible presence in the room and the feeling it conveyed that he was thoroughly enjoying what he was playing.

Indeed, the NAC 122x might be the baby of Naim's preamp family but it betrays very few signs of its junior status. In fact, it probably warrants being called the NAC 122xp, with the 'p' standing for precocious. The NAP 150x exhibits equal confidence and assurance and makes the ideal partner for it.

And, if your budget can be stretched to accommodate the Flat-Cap 2x power supply, you definitely won't regret the extra expenditure. And that also aids the CD5x, the logical CD partner here.

With or without that power supply, whether using a Naim CD player or not, this is a very accomplished pre/power combination and part of a range in which spending more genuinely buys you significantly greater performance and satisfaction.