Twelve-inch tonearms have traditionally been a part of hi-fi's far left field. Perhaps that's why there's no way you can refer to them as '30cm arms', as metric never reached the UK vinyl fraternity.

In the past, you would have had to scour the furthest reaches of the audio galaxy to find a turntable designed to accept one, but not any more. SME has been making twelve-inch arms for some time, because they have a cult following in the Far East, and now it has developed a puprose-built deck to go with these longer arm designs.

The long arms have a theoretical advantage over their nine-inch (22.5cm) counterparts, because tracking error is reduced. This is because of the shallower arc that the cartridge follows as it crosses the vinyl. The reason why you don't see many twelve-inchers is that there is a trade-off: the longer an arm is the more likely it is to resonate at a frequency that will affect the stylus.

And the fact you need a turntable plinth the size of Hampshire to house the thing. With its massive, die-cast magnesium beam, the SME Series 300 Model 312S is designed to give you the benefits of the breed without its shortcomings. Except for size.

Which is where the deck comes into play. The name of the turntable launched to partner this arm, the SME Model 20/12, suggests accurately that it is a version of the SME Model 20 that's been extended to cater for a twelve-inch arm. However, the extra wide newcomer bears very little resemblance to its namesake.

Almost any other company in hi-fi and beyond would have given this turntable another name for clarity's sake as much as that of marketing, but SME does things differently. It builds its components to a standard that Rolls Royce should emulate and it pays more attention to detail than the finest watch makers. Then it arrives at a retail price that takes not the slightest notice of marketing norms. It's enough to make you proud to be British.

Weighty proposition

If anything, it actually looks more like a widened SME Model 30. With a 6.5kg platter sitting on a 19mm spindle and an all-up weight of 33.5kg, it comes pretty close to SME's range topper in many respects. In truth, it is a completely new turntable that shares very few parts with either range-mate. The two slabs of machined aluminium that make up its chassis are considerably thicker than the Model 20 (but not as thick as the Model 30) and the suspension towers in each corner fall somewhere between the two designs, too.

Those suspension towers support the top plate on 40 rubber 'O' rings, with high-frequency movement resisted by fluid damping in a central reservoir around the bearing housing (you can see it if you look between the top and bottom plates). The large platter is, at 324mm in diameter, wider than a vinyl LP and has greater inertia as a result. It also makes it a little more difficult to remove a record and discourages non-clamped record changes without stopping the platter.

But the sonic benefits of using the clamp make it worth using for all but casual listening - that and the fact that you get to handle a lovely piece of metalwork with a fast acting coarse thread that's a joy to use.

Ritualists will want this turntable purely for the set-up procedure. Many turntables are fiddly things to put together and to set-up properly, but the 20/12A (the 'A' signifies the inclusion of a Model 312S tonearm) is a pleasure to get going thanks to a comprehensive set of instructions and carefully thought-out procedures for every stage, including the potentially messy business of injecting the bearing oil. A machined and chrome-plated component is especially supplied for this activity, even though most are only likely to use it once.

The Model 312S arm looks similar to the standard 312 but is made of magnesium like the Series V. It also sports the arm damping system found on that model, plus silver internal and silver-plated copper external wiring from Van den Hul. It can only be purchased with this turntable.

The external power supply is a three-phase device that uses a microprocessor to control speed, the software for which is apparently related to that used in the management of fuel cell engines currently in development. Speed can be adjusted via the buttons for 33, 45 and 78rpm and SME supplies a twelve-inch strobe disc so that this can be done accurately.

Having used a Model 20A (Mk1) for many years it was quite surprising how much more revealing and refined the 20/12A proved to be. It would seem that when you execute a twelve-inch arm this well, its advantages easily outweigh its limitations. This is apparent in the total ease with which it reproduces all manner of music and digs out the smallest nuances, while swinging major league dynamics.

In the past, SME's turntables have been criticised for being dull, but in our book this equates to having the minimum of personality, which is a good thing as we want to hear all the character of the recording and none from the transcription device. The 20/12A does this with astonishing success and makes it very hard to take listening notes that do more than refer to the style and techniques used in the studio and mastering suite where the original sound was created.

We ended up with pages of notes on discoveries about the sonic differences between various albums - the way that compression had been used, for example, or the significant differences in absolute clarity that exist between one recording and another.

After a while, we managed to get down to what the 20/12A was doing to achieve these ends. Essentially, it is both cleaner and faster than the competition, while also pushing the noise floor down and taking distortion with it. It might seem as though it lacks the excitement of a regular nine-inch arm turntable, but what you are getting is less distortion; the turntable is remaining 'quieter' and allowing more of the signal to be picked up by the cartridge.

When that cartridge is sensitive enough, which is definitely the case with a Van den Hul Condor, the results can be staggering in their range and depth.

We wondered whether the guys in the studio could hear the extent of the bass on Stevie Wonder's Superstition through the relatively limited bandwidth of their monitors back in the day. Burnt Friedman's rather more recent Secret Rhythms did even more to reveal the low frequency prowess of the 20/12A, the bass rippling out into the room in a steady, fluid pulse that vibrates everything in its path.

The way it opens up 'difficult' records is also rewarding, revealing considerable quantities of timbral and spatial information in electronica recordings. It was, however, the genuinely acoustic recordings, the live ones in particular, which delivered the greatest realism - Hot Tuna's debut played on the SME recreates a musical event from nearly 40 years ago as if it had happened yesterday.

The 20/12A is both a superb piece of engineering and an extraordinary transcription device for all vinyl recordings. It delivers both precision and flow whilst delving into the deepest details with ease. If you want to get the best from your record collection and have a wide enough support (and a deep enough bank balance), book a demonstration now!