Issue 8 - November 2000
© Images and text copyright Absolute Multimedia UK Ltd 2000

The Iso was the first generally available, stand alone, moving-coil to line level phono amplifier. It marked both a point of no return, and the dawning of a bright new era. On the one hand, from this point on we all accepted that vinyl was marginalised as a mainstream source. From this point on you were going to have to pay extra if you wanted it. On the other, the elevation of phono stages to the "specialist" realm removed them from the status of electronic after thought and brought a welcome leap in performance. Like I said, the Iso didn't cause any of this, nor was it an overnight occurrence, but this unassuming little plastic box certainly gave the whole sequence of events a very healthy shove simply by recognising this situation and establishing a new status quo.

The reasons for the Iso's staggering success were two-fold; it was the right product at the right time, and it offered sensational performance for the money. It may not have looked like much (in an industry which is notoriously guilty of equating quality with physical mass), but for £400 it granted access to the hallowed halls of serious phono performance, previously the exclusive reserve of high-end heavy hitters like Audio Research, Vendetta Research and Spectral. Indeed, in terms of phase coherence and transparency; it set new standards.

The Iso was Tom Evans' first product as an independent designer, and both it and he have travelled a convoluted path in the intervening years. Yet fittingly, just as the original Iso bows out, Tom has launched his crowning glory, `The Groove', a no holds barred phono stage which sells for £1500. And just as the original Iso upset the high-end apple cart, `The Groove' has ruffled more than a few feathers, as well as fixing its fair share of inane grins on previously morose mugs. The problem of course is, not everyone can afford £1500 for a phono stage, so with that in mind, let me introduce its little brother, the `Micro-Groove'.

At this point, Iso owners could be forgiven for doing a double take. Yes, it does look similar to say the least, but closer inspection will reveal a number of important developments. The familiar perspex case work is larger than before, by ten percent or so, but more importantly, so's the socketry. Gone are the nasty PCB mounted phono sockets, the push in three pin from the power supply, and thankfully, the fiddly little earth post on the underside. Instead you get solidly mounted and well spaced phonos, a screw home power plug and a nice big earth post, all arranged on the back panel, along with a power LED to tell you that it's on. The plug top power supply has been improved and very slightly enlarged too (I was never a fan of the massive Hera transformer when used with the Iso, feeling that it lost more on the swings than you gained on the roundabouts). Decoration is limited to the same sticky labelling that graces (or should that be defaces) original models of `The Groove', although the big version now comes with the option of an engraved front plate. Inside, the circuit has more than a little in common with its illustrious forebear, although higher performance silicon is used throughout. Otherwise, consider this as an evolution rather than a revolution. Gain and cartridge loading are still individually matched to the purchaser's cartridge, a system which seems limiting at first but which actually maximises performance whilst dispensing with a set and forget adjustment that most owners will rarely if ever use. The phono stage comes in three basic versions to suit cartridges with outputs between 0.1mV and 0.6mV, greater than 0.6mV and moving magnets. The manufacturer simply selects the appropriate model for your cartridge and then trims the gain and impedance accordingly.

But the best news I've kept `til last. The Micro-Groove costs £400, which is the same price that the Iso started at! What's more, it's upgradeable, another £300 buying you Lithos regulation of the type used in `The Groove' proper, effectively turning the starter unit into half of its dual-mono big brother. Scary. (There's also a switchable equalisation version available to special order and called the `Shellac' .... Okay, I'm only joking!)

The `Micro-Groove' is simplicity itself to set-up. The nicely spaced sockets provide solid connections, and the only real concern is positioning, which wants to be relatively distant from large transformers and other hi-fi equipment. It likes alight-weight support, and wood is better than glass or metal (especially steel). Otherwise it's just a case of plug and play. Burn-intakes about a week, and the unit should be left powered at all times. Unfortunately, simply leaving it cooking isn't enough, and the `Micro-groove' needs to pass a good few hours of signal before its tonality settles down. From the off it sounds pinched and bright, but the more you use it the more its harmonics will round out and fill the sound with some much needed substance and body.

The obvious place to start is with a comparison to the original Iso. The one I had to hand was a late production model, but running from a better power supply than the plugtop normally supplied. A smaller transformer than the Hera, it seems to carry all the tatter's benefits, without its muscle bound downside. Inserting it into the system produced that same warm sense of comfortable familiarity that you get arriving home from a long holiday. The winning combination of transparency, organisation and musical coherence was instantly recognisable, and just as musically valid as when I first heard it ten years ago. With the normal attention paid to siting, and amplifying the healthy output of my CIearAudio Accurate, noise levels were low and performance completely trouble free.

With both units connected and warmed through for several days, I played half a dozen tracks on the Iso, just to re-familiarise myself before switching to the `Micro-Groove', and very nice they were too. But swapping to the newer incarnation revealed a far more resolute performance. Greater top to bottom transparency and extension at the frequency extremes left the Iso sounding rather "comfortable" and rounded off, lacking its offspring's clarity and bite. In fact, the `MicroGroove' sounds exactly like what it is: a cleaned up and altogether more solid evolution of the Iso, retaining the older unit's musical integrity, but offering greater insight and overall clarity. Which begs the question, should owners of the Iso chop it in for the new model?

Well, that depends. If you are running the Iso as a way of enjoying an existing record collection while your main musical focus has switched to CD then the answer is probably no. Assuming you'd get around £200 for your old unit, the £200 cost of replacement could be better spent elsewhere. However, if you've recently rediscovered vinyl and see yourself as a candidate for future upgrades then a change is well worth considering, for one reason and one alone; Lithos. There is of course, nothing stopping you having the Lithos regulator fitted to your Iso, but to really get the full benefits of the improved noise performance the increased transparency of the `Micro-Groove' is essential.

Comparisons between the standard 'Micro-Groove' and the 'Plus' version are little short of astonishing, considering that the signal circuitry is identical. The Iso established itself as the benchmark for acceptable phono performance, a position that was never seriously challenged. The `MicroGroove' comfortably inherits that mantle, but the `Plus' is something else entirely. Compare the two and you'll I see what I mean; get used to the `Plus' and you'll wonder how you ever found the cheaper models acceptable. So what does the Lithos regulator bring to the party, apart from a blue LED rather than the standard green one? In a word, clarity, but clarity in every sense. There's an obvious gain in transparency and solidity of the images, and the whole sound stage becomes far more defined and stable. But these are merely the most obvious symptoms. That improved definition applies to the leading edge of notes, their harmonic envelope and decay. In other words, the `Plus' has far greater low-level accuracy, and here's the interesting bit; unlike most "accurate" hi-fi which generally sounds as dull as dish-water, the Lithos-ed `MicroGroove' sound altogether more musical and involving. The dramatic increase in low-level resolution produces music that is full of immediacy, presence and sophistication.

Now the immediacy and presence are easy enough to understand, given the increased transparency and harmonic definition, but what's this sophistication? The increased definition of individual notes has clear temporal as well as spatial implications. Because we can now tell so much more clearly where individual notes start and how long they are sustained, the relationship between notes, and precisely where and how the musicians place them becomes much more apparent. This provides a direct insight into the chemistry of the performance, the interplay of the musicians, bringing the whole thing to life. Forget rhythmic integrity as an issue, here's the entire musical skeleton, clear to see. (For more on-this see the reviews of the Final Music amplifiers in Issue 2, and `The Groove' in Issue 4.) The `MicroGroove Plus' might not match the astonishing, almost master-tape solidity, presence and authority of its more expensive brother, but it gets you a fair way along the same road. In order to understand why that should be, it's necessary to appreciate exactly what the Lithos regulation achieves.

Built from fifty discrete components onto a small pcb, the Lithos circuit is around a thousand times quieter and fifty times faster than the high quality Linear Technology 317AT/337AT ICs used in the standard `Micro-Groove', and those are amongst the best conventional regulators available. The result of this is that not only does the circuit running from the Lithos regulator get power devoid of the overlaid ripples and distortion that the vast majority of signal circuits have to tolerate, but the circuit can react faster and to smaller signals, retaining their contribution and correct position in the overall picture. Its this that makes the `Micro-Groove Plus' sound so stable and immediate, and makes it communicate the musical message so directly. It's this which moves you so much closer to the original performance.