KR Audio Electronics Kronzilla SX-Eco Hybrid SET Power Amplifier (Hi-Fi+ 85)

In the world of high-fidelity, big generally equates with good and bigger with even better. These days, being asked to part with nigh on £30,000 for a 50 Watt per channel power amp isn’t going to provoke headlines, even if that amp is a single-ended design, deriving that output from a single device a side. The 50kg dead weight, whilst it’s physically impressive, doesn’t break new ground either. But what on earth are we to make of output tubes that are each the size of a serious anti-tank round? The weight alone tells you that there’s plenty of metal in the power and output transformers and they are pretty imposing – but they are de-warfed by the associated glasswear.

Okay, so how big is big? Try on 300mm tall and 85mm in diameter – or about the size of my (fairly meaty) forearms. These are big, big tubes. So big in fact, that combined with the severe black and deeply finned chassis and transformer housings, that the Kronzilla would look perfectly at home on the set of a particularly dark and brooding Batman movie – except that the props department would probably reject it as over the top! They are actually T1610 output tubes, designed and manufactured by KR in their own Czech factory, high-powered, all-new direct heated triode designs that bring the origins of valve technology slap, bang up to date. And if appearances are anything to go by then this amp clearly means business, an impression that’s reinforced by the gentle quiver, the quickly dissipated huummmm as you power it up. So if big is good and bigger is even better, what does that make the Kronzilla? Well worth a look and listen, that’s what.

Not that this amp is all about mass and muscle. Indeed, one of the serious associated problems with all that hot glass is the effect this amp has on the ambient temperature of your listening room. No doubt welcome on a dull autumn day in Dunstable, high-summer in the UK, let alone the tropics, makes this thermal dissipation an uncomfortable addition to your listening experience. Enter then, KR’s solution – which, with stunning originality, they’ve dubbed Green Power.

The various Kronzilla amps (there are five models in the range, including an integrated and mono-blocs) are all hybrid designs, using solid-state circuitry to drive the output tubes: So why not just add a second, basic, solid-state output stage that can be selected for less critical listening? It’s one of those lateral suggestions that comes winging in from way out in left-field – and normally gets dispatched straight back out there. Except that in this case, KR were open-minded (or just plain mad enough – they did design those tubes!) to take it seriously, making the Kronzilla SX-Eco a hybrid in more ways than one. Is it a problem worth dealing with? Let’s just say that the vast majority of the listening for this review occurred during a distinctly average British August, but the effect of the KR amp on the listening room’s temperature was all too apparent: and this is a big room with a lot of height. In this case, the thermal impact was considerably greater than that of the 16 KT88s in a pair of VTL 450 mono-blocs; thankfully I didn’t need to fire them all up together. Of course, the Kronzilla’s heat signature is aggravated by its class A nature; any power that’s not used to produce music can only be dissipated as heat – which goes some way to explaining the amp’s appearance. All those black fins are for more than just show and in use the entire chassis is more than just warm to the touch. Depending on your point of view I guess you’ll either conclude that this is a seriously serious amp – or a seriously inefficient space heater. Actually, it’s both, but more on that later…

Operationally, there’s not too much to say about the KR amp – but what little there is, is quite important, mainly because it’s not covered in the instruction manual. Installing the tubes is easy enough; align the four, jumbo-sized pins and slide them home. But in doing so you’ll notice that the valve sockets are numbered. Logic suggests that somewhere on the valve (normally written directly on the base or on a small sticker) you’ll find a corresponding number, ensuring that the correct valve goes in the correct place. Well, on the Kronzilla you could spend a long time looking, ‘cos the relevant number is stamped on a small plate, actually inside the valve and perched right on top of the internals. That’s a first for me! Secondly, the small switch that selects the Green Power setting is on the rear panel, and although it’s labeled, there’s no indication as to which setting is which – unless you start peering at the inside of the tubes to see if they’ve lit up. Come on KR, if you are taking the eco-argument seriously then that switch needs to be on the front-panel and you need an LED or some other clear indicator as to the output mode selected.