The Sugden A21a is something of a living legend, a Class A integrated amplifier that has been in production for over 20 years, but whose earlier incarnations date back as far as the sixties.

It has maintained its appeal thanks to a sound that can charm the pants off the most hardbitten of reviewers and inspires genuine affection among its many users. However, time would seem to have caught up with it in many respects, and Sugden Audio felt the moment had come to bring it up to date, albeit while attempting to retain the characteristics which have won it so much admiration.

The brand new A21a is not particularly well differentiated on paper; the name has been extended by the letter L in upper (line level) or lower (phono) case and the words Series 2. Marketing was clearly not at the forefront when this revision was conceived - in fact, judging from the stealthy approach that Sugden takes to all forms of promotion, we suspect it's a dirty word in that part of Yorkshire.

However, there have been significant changes both internally and externally to this solid integrated amplifier. As you can see, the front panel is no longer made of bent steel but 10mm-thick aluminium with chunky machined control knobs to match.

It's a faceplate style that'll be very familiar to anyone who has seen the A21SE or any of Sugden's Masterclass series, and one that's a dramatic improvement on its predecessor. It's not just a facelift, though - the chassis is 50 per cent thicker and made out of a single piece for increased rigidity.

Possibly this was a necessity brought about by the introduction of a beefier power supply, one that means the A21a's output is no longer compromised by speakers with a four-ohm load.

The preamplifier section has also been completely reconfigured and sited behind the fascia in order to reduce the length of the signal path.

The overall circuit has been straightened by removing the tape-monitor and mono-switching options of the previous model, facilities which some people will no doubt miss, especially given the scarcity of mono switches on contemporary amplifiers.

But if the result is worth the candle, so to speak, then it'll have been a worthwhile sacrifice. Another victim of the straight lining process is balance control, again something that has become a bit of a minority interest these days, and something we only ever use to check for a fault.

Sugden describes these various changes as evolutionary, but the removal of three functions strikes us as being closer to radical, more so even than the cosmetic revamp. However, the model still retains the horizontal cooling fins along its flanks, and there's the option of adding an MM/MC phono stage for a very reasonable £100, though this does take up one of the five line inputs.

Another radical change is the introduction of remote volume control, something, which in our view, more than makes up for the features lost. Remote input selection would also have been nice, but this is still a proper 'hair shirt' product.

So much so, in fact, that there are no input markings on the front panel - you have to find your source blind, though the radial nature of the inputs means that you soon learn where they are.

As previously mentioned, although the power output remains at 21 watts per channel, the increase in power-supply stiffness means higher current is available, which makes for greater control over the loudspeaker load.

It's still hardly a bone-cruncher in power terms, but its Class A operation means that when it runs out of steam it does so in a far smoother style than Class AB amps, which is why low-powered valve amps get away with so much. Nonetheless, speakers that have higher sensitivity are always a good idea with most Class A designs.

One practical advantage of Class A is that the amp warms up very quickly, and within half an hour is too hot to leave your hand on. This isn't exactly economical, but Sugden does suggest you turn it off when not in use, which means it probably has a similar carbon footprint to an AB design that's permanently left on.

Having said that, an easy load would be best for the A21a. Given a spin with the mighty B&W 802Ds in our listening room, it doesn't seem phased by the task, so long as the volume is kept to a sensible level. The pairing enables the amplifier to show off its delicate touch through the midband, one which brings forward subtleties of the music that aren't usually apparent with more powerful amps.