Kronzilla Sxi (£16,190)

If you don't mind the cost of running a Class A SET amplifier, then you're bound to be enthralled by the Kronzilla SXI's fabulous high-end music-making ability
Yes, those valves  – made in-house – really are a foot tall! And they radiate substantial heat once the SXI has been powered up for a few minutes, but KR Audio’s amplifiers are beautifully engineered.

The company is based in Prague, founded by electronics engineer the late Dr Ricardo Kron in 1992. It’s a boutique firm of only a dozen or so people – skilled artisans who blow the glass and hand-craft the tubes.

Such is the transparency of KR Audio’s Kronzilla amplifiers that at least of couple of German recording studios use them in mastering suites. The SXI integrated model here is a single-ended pure Class A design, with four line inputs; one of these is balanced (XLR). It’s a hybrid amplifier, with a solid-state front end employing FETs to drive the ’1610 valves, the latter offering a low input impedance due the cumulative effects of their parallel triode elements.

Aside from the chromed volume rotary placed centre front of the Kronzilla’s chassis, with a small red LED built into it so you can see the approximate volume position from a distance – a nice touch since it helps avoid giving your loudspeakers any unwelcome surprises – a row of buttons switch the inputs via relays. The volume control is a motorised potentiometer, the amp being supplied with a nicely formed aluminium handset featuring volume up/down, input up/down and power on/off keys.

Forensic precision

Fire the Kronzilla up and a front panel LED glows red for approximately five seconds before changing to green, signalling the amp is ready to go. It may look old-fashioned, but there’s nothing antiquated about the amp’s capabilities. It sounds vivid and dynamically light-footed, with a powerful and tightly-controlled bass that allows you to analyse low-end detail with forensic precision, together with an open midband and sparkling highs which emanate from a black background.

The renowned recording of the Oscar Peterson Trio’s We Get Requests [JVC/FIM] sounded tremendous. The snare shuffles and hi-hat were described exquisitely by the Kronzilla while the bass was woody and satisfyingly full-bodied, the amp painting a wonderful sonic picture of the musicians’ performance and the acoustic space they occupied.

In a different vein, the title track from Steely Dan’s Royal Scam album sounded similarly fresh and ‘open’ – we were playing a rip of a 2008 Japanese SHM-CD [Universal]. The track’s elements – the piano and percussion patterns, the charmingly cheesy electric organ motifs, parping muted brass embellishments and the song’s female backing singers – were all pulled out from the recording’s rather murky production. The electric guitar positioned stage right, the sublime key to the piece, occupied its own space behind the plane of the speakers in what was a spacious sound image.

Playing ‘Revised Music For Low Budget Orchestra’ by the Omnibus Wind Ensemble, from the Danish ensemble’s Music By Frank Zappa album [Opus 3], revealed the Kronzilla’s ability to recreate the sounds of instruments devoid of colourful adornment. We were simply entranced.

The only listeners we can imagine not liking its precision and lucidity are lovers of ‘softer’ SET valve amplifiers enchanted by the romance of a euphonic, rose-tinted rendition of musical events. Hearing this Kronzilla playing BB King’s ‘Keep It Coming’ from Deuces Wild [MCA] showcased its impressive low-end ‘grip’ and vivid HF, the pumping bass and snappy percussion delivered with great exactitude. One should never judge a book by its cover!


If you don’t mind the cost of running a Class A SET amplifier and the heat it generates, you’re bound to be enthralled by the Kronzilla SXI’s fabulous high-end music-making ability.

Originally published in the 2013 Yearbook