Having been well and truly educated by manufacturers such as Croft and AudioValve, I am loath to enter the 'premium valve' fray. Both have shown that intelligent design can more than compensate for tube variation and quality; AudioValve's circuitry is so clever that you can even mix tube in certain of their amps. What they're both saying is the valve codicil to 'Frankly, life is too short to piss around with cables and accessories': Get your components right in the first place.

Conversely, I can't rule out the fetish for upscale replacement tubes, having long ago learned about and experienced matched pairs, brand-vs-brand quality (e.g. Mullard vs Telefunken, M-O vs the rest, etc), military spec over civilian grades and other pursuits. And I hate to admit, to the marrow, that you can hear differences, and they are NOT subtle. The problem is that neither are they consistent, and simply replacing stock tubes with something of the hot-rodded variety won't necessarily yield an improvement. For instance, I can almost guarantee you that valve substitution in a Croft pre-amp will ruin the sound.

So now, in the 21st Century, along comes a Czech operation with the utterly ludicrous name of EAT. [EAT is an acronym for European Audio Team, further proof that you shouldn't come up with international names if English is not your first language.] And while they exhibit Swiss rather than Eastern European standards of production and presentation - their tubes could have been made by a watch manufacturer - they also exhibit Swiss pricing and that loathesome 'former Commie-now-neo-Capitalist' greed. To me, £140 for a KT-88, £288 for a matched pair and £599 for a matched quartet is somehow lunatic when eBay shows unused, boxed GEC KT-88s for £56 each.

So here we have, yet again, KK holding back his bile in an attempt to be fair to a brand for which he has mild contempt based solely on prejudice. Oh, if only the EATs were crap! Such I could enjoy! But they're not. In fact, they're sensational.

EAT says that their KT-88 Diamond (they also manufacture 300Bs, 6550s and other popular tubes) were conceived to operate securely as replacements in situations as demanding as 100W from a pair of valves in Class AB1 operation. Considering that most 100W/ch, KT-88-equipped amps in my experience use four per channel, then EAT is being very conservative; most users are unlikely to hammer these into 100W per pair operation. More likely, you'll be demanding a mere 50W from two EATs. And in the case of the review set-up, I only asked them to yield ca. 40W per pair/channel.

Regarding the valve matching, the price increases reflect the extra labour and the higher rejection rate, as opposed to measuring and selling a single valve. Absolute Sounds confirmed that their chief technician retested some sets, and was staggered by the precision of the matching. If running utterly identical pairs or quads is one of your fixations, the EATs will vindicate you.

Because I have been using the PrimaLuna Prologue Two as my budget reference amp, and as PrimaLuna shares distribution with EAT in the UK, I asked the importer to set up a Prologue Two with a matched quartet of EAT KT-88s. This would enable me to warm-up both amps at the same time, instead of doing tube swaps which would add a half-hour between listening tests. It was as close to A/B testing as possible, requiring only the swapping of speaker and source leads. Speakers, by the way, consisted of PMC DB1+, Rogers LS3a, Rogers LS3/5a and - ulp! - Sonus Faber Guarneri.

It took, oh, all of two seconds to justify their existence, even in an amp costing a mere £999 - or only £400 more than the set of valves on its own. I know, I know, I know: there's nothing rational about stuffing £600's worth of glass into an amp £1 shy of a grand...or is there?

Think about it. Even though the measurements indicate no gain in power, the sound is somehow more robust, certainly giving a subjective impression of increased wattage. The bottom end was transformed from already-credible performance to something I'd associate with, say, £2500's worth of Audio Research: convincing weight, palpable mass. The treble was cleaner, faster and still without the sort of edge that causes fatigue. But the real gains - however improved the frequency extremes - were in the midband.

Indisputably amazing though the PrimaLuna is (and we needn't go into its price advantage due to Chinese origins), the EATs cranked it up another notch. A notch. The first and most blatant gain came in transparency. Although the stock tubes are good by any standards, the EATs peeled away a layer of texturing, akin to removing an extra speaker grille. The net effect, especially on vocals such as Joss Stone's or Aimee Mann's, was to increase intimacy by strengthening the sensation of the singer being in the room. Spatially, it was as if they moved forward a few feet.