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Power is something in which Krell always believed. Although one of its greatest achievements was a 50-watt stereo amp, Krell's street cred is based on unbridled power. If it wasn't simply a case of sheer wattage - the company still offers an integrated with "only" 200 watts per channel - then it was a notion that Krells could drive any load without complaint. With the Evolution series, and the latest incarnation of CAST technology, the bar has been raised substantially, but then, so has the price.

At a time when the green movement wants everyone to feel guilty about everything, it's hard to talk about hi-fi equipment that utilizes so much of the Earth's resources in manufacture and then sucks up a lot of juice when in use. But this is not New Scientist and I'm not Jonathon Porritt, so let's just accept that such stuff exists and that it's far less contributory to the world's ills than, say, the filth spewing out of factories in China.

Utterly inexcusable, though, is manufacturing a power amp weighing a ludicrous 61.1kg in materials, with high shipping costs and user-unfriendliness. Whatever sonic excuses Krell may choose to come up with, I'm not about to be convinced when I also have before me a genuine 600-watt monoblock, weighing 10kg, from a rival. The Krell's 5000 VA power supply, massive construction, whatever: the words "balls" and "swinging" spring to mind. What morons judge hi-fi on size and weight? End of rant.

But once you've manhandled the Krell Evolution 600 into place (would it have killed them to fit handles?), a magical journey commences. Even ice-cold, the Krells were doing something so right and so impressive that I was almost able to overlook the fact that a pair costs the same as a BMW 320i M Sport.

In order to experience the full-on Evolution event, I also used the Evolution 202 preamplifier, connected in balanced mode with CAST II in play. I also used other preamps, but the serious listening involved the 202 and CAST II because, in my experience, it's the best way to extract all that this amp can deliver.

Krell employs what they call Active Cascode Topology to eliminate global negative feedback, using only nested local feedback around individual gain blocks. This is said to produce "an extraordinarily open, liquid, effortless sound." No arguments here: for an overkill solid-state amp, the sound is deliriously lush.

Equally, Krell opts for - as it always has - arch detail, control and precision, much of which can be credited to Krell Current Mode and CAST II circuitry in the signal path. Briefly, in Krell's words, CAST uses "proprietary multiple-output current mirrors in a complementary and balanced arrangement for extraordinary open loop linearity." I don't know what that means either, but I can tell you this: having tried the '600 with and without, the effect of employing CAST is like tightening up the screws in a head-shell, or ensuring that a wrecking ball couldn't dislodge your speakers. It improves control and focus, and the effect is not subtle.

Sheer complexity contributes, no doubt, to the aforementioned weight. The massive power supply section features "extensive electrical and magnetic shielding to keep radiated interference out of critical amplifier circuits." The Krell proved relatively indifferent to the four types of AC rings in my room, thanks to its internal line-conditioning circuitry, which filters RF noise from the mains. Krell also points out that this compensates for asymmetric power waveforms and DC on the mains, so there are probably few gains to be made by adding an outboard line purifier. Or even a regenerator. Moreover, the rails powering the amplifiers' low level and gain stages are regulated twice, as Krell puts it, "for total immunity from fluctuations in the AC mains and virtually noise-free output."

Everything is monitored with the thoroughness of the latest Lexus, with microprocessor control to continuously monitor all critical operational parameters. These include bias, load impedance, regulator output voltages and operating temperature. The amps didn't misbehave once. The only disarming thing about the Evolution 600 was that the lights dimmed momentarily when I switched on the primary mains toggle at the back.

For primary listening, I fed the 202 with the Musical Fidelity kW two-box CD player and SME 30/SME Series V/Blue Angel front-end via the Audio Research PH5 phono stage. Speakers were Sonus faber Guarneri and Apogee Scintilla, wired with Yter cables. It was like a throwback to one of hi-fi's golden ages, 1983-90.

In that unashamedly non-green era, the wattage race was like the arms race of the 1950s. Every month, a humongous new amplifier would emerge. (At least, from the USA. Prior to the arrivals of Musical Fidelity, Chord, et al, the British were content to putt-putt along with wimp amps.) I distinctly remember being wowed by the sheer presence that music had back then, rather than the politically correct, washed-out, downsized nonsense that passes for it today.

Put it down to the iPod, fear of upsetting neighbors or whatever. The only sound systems with guts today are, unfortunately, the in-car systems owned by morons with backward baseball caps, listening to that most hateful of music, hip-hop. Amps like the 600 allow you to reclaim the high ground. Amps like this bring back (deep breath) the reality of music.

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