Integrated Amplifiers

Still in this mode but with sensitivity set to Low, there was a good deal less gain, and although I did detect a slight improvement in bass grip, this varied between loudspeakers. For example, it was more obvious when the amplifier was driving my classic Yamaha NS-1000M monitors [HFN Oct '18] than when hooked-up to a pair of modern, easier-to-drive Cambridge Audio AeroMax 60 floorstanders. In the High sensitivity setting, things seemed more balanced and natural sounding, and there was less of a need to wind the volume towards its maximum position.

In its optimal configuration for my system – Triode mode and High sensitivity – the Stereo 40 MkIV's bass proved tuneful and supple while the general exuberance of its music-making pulled my attention away from any small failings. For example, there's a slight amber glow to its smooth, sweet midband so even a dry-sounding '70s rock production such as 'Aja' comes over ever so slightly softer and fluffier-sounding than perhaps it should.

In this respect, this amplifier gives you the famed 'magic of valves', sacrificing transparency at the altar of euphony. The sound of hi-hat cymbals, for example, was particularly silky although it lacked real bite, so while some will love this amp's romantic nature, others will perhaps be less enamoured of its slightly opaque and coloured character.

Heavy Lifting
George Benson's funky 'Give Me The Night' [Give Me The Night; Warner Bros 32XD-348] sounds tangibly brighter and tighter than does 'Aja', and the Stereo 40 MkIV caught this difference in production well, giving an especially beguiling feel to the up-tempo rhythm guitar work. It's still not the 'quickest' amplifier on the block, but it knits the beats together very deftly, allowing your mind's eye to enjoy the spectacle of the performers in full flight.

Although this tube integrated puts out a healthy amount of power it's still no bottomless pit of watts. For example, the latter part of Supertramp's 'School' [Crime Of The Century; A&M Records CD-3647] becomes really loud, calling for some heavy lifting on the amplifier's part. The Ultralinear mode is the best option here, ensuring the Stereo 40 MkIV runs out of puff only when the volume knob is abused. And here the output stage 'clipping' is not abrupt, as it might be with a similarly-powered solid-state amp, but realised as a progressive compression of the sound as dynamics are increasingly 'sat on'.

Teeming With Detail
At more moderate levels, or with more sensitive loudspeakers, the Stereo 40 MkIV proved a great all-rounder. It also sounded impressively detailed, despite the inherent levels of harmonic distortion, excavating lots of low-level information from almost any recording. Even the relatively lo-fi sound of The La's 'Timeless Melody' [The La's; Go! Discs 828 202-2] came over in a most satisfying way.

True, you don't get the same sort of forensic retrieval here that you might from the best solid-state rivals at this price, yet still the sound was vibrant and teeming with detail. Lee Mavers' fingerwork on the frets of his electric guitar was very well carried; I loved the scratchy, rich, raw Rickenbacker sound, and the sheer energy that his hands were channelling into the instrument. His voice was also beautifully handled – it's hardly one of rock's finest but has an earthiness that really matches the music. Although it quite rightly sounded hard and acerbic, it never grated or made listening a chore. This song was mixed in a forward and compressed way, yet the amplifier certainly didn't dwell on this.

Many tube amps excel at recreating a believably spacious soundstage, and the Stereo 40 MkIV was no exception. Here the difference between Ultralinear and Triode modes was obvious, the former sounding wider and more expansive. As well as the extra air and space, additional bass and treble energy further augmented the big, out-of-the-box sound.

Yet, overall, I still preferred its Triode mode, which was capacious but also tidier and better ordered with superior image location between the loudspeakers. Some classic techno in the shape of Goldie's 'Inner City Life' [Timeless; FFRR – 828 646-2] had elements of the mix more tightly located while depth perspective was better too. The result was a joyously wide and enveloping electronic soundscape.

Hi-Fi News Verdict
Now in MkIV guise and better value than ever, Icon Audio's latest Stereo 40 can take on both tube and solid-state amps at this price. It offers more power and control that you might expect from the former, plus a natural charm that one doesn't always associate with the latter. A real improvement on its predecessor, the Stereo 40 MkIV combines great sound with the bonus of Triode and Ultralinear modes.