The KR Audio VA350i amp is hand-built, as are its enormous tubes, in Prague and it costs £11 500 in the UK and €12 900 in Europe. Stuart Smith takes a listen. 

KR Audio is based in Prague in the Czech Republic and hand makes all their own valves as well as their amplifiers. On test here, we have the VA 350i Integrated amplifier which uses two KR Audio T100 output tubes to give a power output of around 30 Watts per channel in pure Class A.

The company began the research to make improved triodes in 1992 and started its life as a tube manufacturer, first of all with reproduction of Marconi valves and then audio valves intended as up-grade options for amplifiers in 1994.

The company design and build 15 different tube amplifier models and two completely solid state amps. The tube division currently makes 12 models of valves

At this point, it should be noted that initially the amplifier was sent to our reviewer Dan Worth who felt that it did not match at all well with his Ayon Seagull C loudspeakers and it was thought the amp would be better matched to our Avantgarde Duo XD horns and hORN Mummy loudspeakers.


Bombproof is a term often bandied around when describing audio products and the term certainly applies with the VA 350i with the unit weighing in at 37kg and having me put my back out when I tried to lift it out of the wooden packing crate. I’d have liked to have seen a box used that allowed either two people to get at the amp or that had fold down sides – dead-lifting 37kg is not to be advised. Visually the unit is certainly imposing and the T100 output tubes are massive and dominate the front of the amp in their protective cages. It’s an all-black affair save for the silver volume knob, four silver selector buttons with red LEDs above to show which input is being used, a power button and LED and a KR Audio nameplate.

Around the back we have four RCA inputs a single pair of RCA outputs, some pretty standard but perfectly adequate binding posts that accept bare wire, spades or banana plugs, an IEC inlet and a master on/off switch. There is also a little screw switch to change output impedance. 

The whole is well finished and all in all it’s quite a handsome beast with a decidedly industrial and purposeful feel to it with metal fins around the side for heat dissipation and two heptagon casings each side the valves and their “cases” and a further case for transformers.

A basic but adequate remote is included in the package.

KR Audio amps are a little different to the vast majority of valve amplifiers and whereas you would normally see more tubes than simply the output valves adorning the top of the amp (drivers and rectifier) these amps use solid state JFETs and MOSFETs. This is an unusual topology and not one I have come across previously.

The T100 tubes are as mentioned massive, though not as big as the T1610 output valves used on the company’s Kronzilla amps, and they do get massively hot which may be a consideration if you have inquisitive kids, though I’ve always been of the mind that you would naturally put valve amps out of reach until they are old enough to understand hot things burn.


From the off, it is clear that this unit was a good performer with initial reactions being that it had good power and poise and with an engaging feel to its presentation. The first thing we played (on the Avantgarde Duos) after leaving the amp to warm up a bit was The Jam’s This Is The Modern World and the opening blasts of the title tune had us look up and the amp had our full attention from there on in. The amp was reasonably fast and lithe, though not as fast as our Class D amp, but not as tonally uncoloured in the mid-band as our reference amps and I’d definitely suggest it has a character to its sound – slightly rolled off at the very top end, though clearly a musical and engaging listen. It’s a funny thing, we listen to our Class D amps a lot as they are our reference tool and we believe them to be very transparent indeed, but every once in a while we like to plumb in our 2A3 amp as we just love the more musical character that brings to the table and I’d suggest that many will enjoy the presentation of the KA 350 from purely a listening pleasure perspective, though I preferred our Trafomatic 2A3 amp’s presentation overall on the Duos, finding it more open in the mid-band and with less background noise – others will, of course, prefer the KR Audio amp and why home demonstration is absolutely imperative.

On the hORNS Mummy speakers, with passive bass (the Duos have active bass), I found that the grip and control the KR Audio amp had on the bass of Hardfloor’s Once Again Back was not as tight as our Class D amps, though perhaps somewhat better than with the 2A3 amp. I’m sure many may scoff at using this kind of music to evaluate a piece of Hifi, but well-produced techno can be a very useful tool in uncovering failings.  Hi-hats at the start of this tune fly about the soundstage when done properly and I had no complaints with this amp in this regard, though I’d suggest that the soundstage thrown is not so wide or deep as either our two aforementioned amps. Hats were crisp but failed to have that last degree of sparkle the Class D brings to the table and I’d perhaps suggest that the KR Audio amp was less analytical in its presentation –  again some may say more musical and would no doubt prefer it.

Back to the Duos and a bit of Miles Davis’ Sketches Of Spain and it is apparent that when compared to the Class D amps, which are silent on these 107db sensitive loudspeakers, the VA 350 is not absolutely quiet, but this was not so evident when using the less sensitive hORNS loudspeakers. I enjoyed this album greatly with this amp in place, with the music again having character to it, even if the not absolutely silent background did detract from my enjoyment a tad on the Duos. Here’s the thing, most things in the Hifi world come down to trade-offs and often the need to carefully match components to get the best from them – it’s interesting to note that G-Point Audio, the UK distributor of KR Audio products, also sells hORNS’ loudspeakers and there may well be a good reason for this. On the hORNS Mummys the same record came from an almost silent background and it may be that the Duos are just too sensitive for the VA 350, but it would be remiss of me not to mention this point. Musical is a term I keep wanting to use for this amp and speaker combo, which is to say it is an engaging and enjoyable listen. The full tonal range of Sketches is there in all its glory and the presentation is believable with the amp reacting quickly to dynamic changes. The amp felt speedy and agile and there was good and convincing space around the music with natural reverbs being (again) believable – that is to say not over exaggerated. Detail in the tone of flugelhorn and trumpet were excellent and the slightly “stepped back” playing style was represented well, bringing a real feeling of connection to, particularly, Concierto de Aranjuez.

If I’m sounding slightly critical of the amplifier here, specifically using the amp on the Duos and with electronic music, then I don’t think I would be doing my job properly if I didn’t highlight what I heard, but I did actually enjoy its presentation in many ways and with other music. Those opening lines of The Jam’s album really did make me sit up and take notice and throughout my time with the amp, I felt that it had a certain and uncanny rightness to the sound with the Mummys. It is mellifluous in its presentation on the right speakers and not at all fatiguing to listen to for hours on end and in that way it is very much like the 2A3 reference I’ve mentioned. I don’t believe the amp is one that is necessarily right for those whose main choice of music is techno etc based as I don’t think it quite has the required grip in the bass end, but with vocal, jazz and “lighter” program it is very enjoyable indeed – perhaps it could be said that this amp is made for audiophiles that enjoy “audiophile music”? Again, this is a balancing act when buying Hifi as some products do lend themselves to certain styles of music and listening tastes and why we for reviewing purposes came to the choices we came to.

Playing another of our reference records on the Mummys, Gil Scott-Heron and Brian Jackson’s Winter in America showed that the partnership allowed a good insight into the recording of the tunes and the space they were recorded in (there is a good reason we use this record as it is recorded in a particular style). Vocals were presented very nicely indeed with Gil-Scott’s somewhat fragile (read emotional) at times voice bringing a real connection to the music. Flute on A Very Precious Time was also nicely presented sounding honey-rich with nice fluidity to the sound. I found the same connection when listening to John Martyn’s Solid Air.


It is clear that this amplifier is very good when it is partnered with the right speakers, but get this partnering wrong and the amp does have limitations, and this is why I strongly advise that before you spend your hard earned, a not insubstantial amount in this case, I would insist on a home demonstration using your own speakers, that way you will know if you have an amplifier/speaker partnership that will last you a lifetime.

I don’t believe this amp is tonally neutral (like most SET amps) and I do think it brings a character of its own to the show, BUT I do think it will find favour with audiophiles who enjoy a softer style of musical program – think light jazz and female vocals. I say this because I do feel there is a somewhat softening to the bass registers which is particularly evident on synthesised bass. There is also a slight roll-off at the very top-end which makes for an easy and non-fatiguing listen, but purists looking for absolute out and out fidelity and faithfulness to the recording may wish to look elsewhere – again a balancing act.

The price of this amplifier put it in the serious money category and whilst more expensive amps are certainly out there, and KR Audio do more expensive amplifiers, £11 500 is still a big number and our much less expensive Class D amplifiers are more transparent and have better bass response than this amp in the final analysis, but then they are not as easy to listen to in a musical sense in that they lay a recording bare at the top end. What you do get for your money is a well-built statement piece that will please many with its presentation.

With the right speakers, I heartily recommend an audition if you are able to afford and justify the ticket price.


Build Quality: Tank like in its construction and very nicely put together. Remote is adequate

Sound Quality: With the right speakers and program this is a nicely musical amplifier that could tame harsh sounding electronics before it in the supply chain. It is a very easy to amp to listen to and become engaged with.

Value for Money: This is a matter of taste really. You are getting a big chunk of amp here with a unique set of features but sonically, depending on your taste, more accurate amps can be had for less.

Pros: Mellifluous and easy and engaging to listen to for long periods of time. Very well built.

Cons: Slightly rolled off at the very top end and not the best control in the bass. Slightly noisy with VERY sensitive speakers. Inability to tube roll – you have to use the T100s and only KR Audio make them.

Price: 12,900€ or in the UK : £ 11,500

Stuart Smith

Technical Specifications

Output Tubes 2 x T100
Output Power 2 x 30 Watts RMS (THD=3%)
Bandwidth 20 Hz-20 kHz (-3dB)
Output Impedance 4 / 8 Ohm
Input 4 x 0.75V RMS / 47 kOhms at 30 W
Dimensions – w x h x d 53.5 x 30.5 x 41.5 cm
Weight Approx. 37 kg

Review Equipment: Melco Library, Lampizator BIG 6 DAC, Origin Live Resolution Turntable, Origin Live Zephyr Arm, Gold Note Tuscany Red cartridge, Music first SUT and phonostage, Tellurium Q interconnects and speaker cables, Atlas Cables mains distribution and cables, Balanced mains unit.

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