KR Audio “Kronzilla SD” power amp:

Riccardo Kron was a tube maker. He worked with Alesa Vaic before to found the KR Audio. He have made improved versions of famous tubes, like the 300B or the 845, but then he went further and realized also some “new” tubes, which should have been even better than the old project. Among these, the T-1610 DHT is the most expensive, powerful and... big! Its small brother is called T-100. To show the world how good these triodes were, Riccardo has to build also some amplifiers and the KR Kronzilla SD is one of these.

Unfortunately, Riccardo is not anymore with us, but the KR Audio is still working near Prague (Cech Republic) and is now leaded by his wife, Eunice Kron, while the new projects are signed by Marek Gencev. When Eunice asked me for a review of the Kronzilla I was very scared to have something so expensive in my flat and also was tinking that it was at a level much higher than the rest of my system, so that I could only write that it was a very good amplifier, which is not so interesting for you to read. But at the end I accepted and... here we are!

The KR Audio Electronics “Kronzilla SD” front...

... and its back.

On the back there is the main power switch, while on the front there is the stand-by button. You can also select 115 or 230 V~ input main voltage.

The output impedance is selected among 4 or 8 Ohm moving two screws.

Nel Audio (slovenian importer of KR Audio) was so kind to let me have his Kronzilla SD demo sample for two weeks. The SD is a single ended using one T-1610 triode working in class A per channel, for a total output power of 22+22W (when powered with 230 V~). The Kronzilla SX is very similar, but has 50+50W of output power, so I think that the tube is in a different working point. Interestingly enough, the input stage uses J-FET while the driver stage is made with power MOSFET, so there are no tubes there. That was an explicit choice of Riccardo Kron, who thought that small signal tubes has too many problems (e.g. microphonicity) when compared with FET devices.

The first thing that you note when you see a Kronzilla is how much BIG it is. Its weight is 50 kg and I can assure you that it is very hard to move if you are alone! But immediately after that you will be stunned by the T-1610 tube itself. That is really a huge tube! And nice too!!!

Bottles for each age.

Other different bottles...

When you consider a single end A class power amplifier you needs basically three main parts: the main power supply (which should be very well done), the very good output tube and finally the high quality output transformer. About the main power supply I can't say much, but just note that the main power transformer was “buzzing” a little too much for my small living room. Nel Audio told me that the new models have replaced this transformer with a toroidal one, which does not buzz anymore. About the output transformer I can say that it is a KR design and that it is really huge. I believe that the 50W version uses the same OT, so you are really sure that it is surdimensioned for 22W. On the output tube I can tell you that it has a maximum power dissipation of 150W and an internal resistance of about 370 Ohm, which I believe is half of that of a 300B and a quarter of that of an 845, not so bad, eh?. I can also show you some close pictures, just to understand how well it is done. Each one costs about 1000 E!

The two output transformers and triodes.

The KR T-1610 DHT.

Two things popped up in my mind the very first moment that I have connected the Kronzilla SD in my system. The first thing was how much different was its sound from its visual aspect. If you look this amp (and in particular if you move it for about 100km up to your living room, where your wife will start to cry when the huge 60kg wooden box will invade her home) then you will have the feeling of a Dark German Tank. If you listen it, the first image associated by your mind is that of an orchid. A gentle, fragile and graceful orchid! The second thing that hit my mind was how much deep was the soundstage. In comparison, my CJ MV60SE power amp produces a “flat” scene. The sound produced by the Kronzilla was coming from far-far behind. In my living room, I think that only the Air Tight ATM-1 has produced a comparable deep soundstage. Interestingly enough, I have found that also the apparently unique defect which I was able to find in this amp, was a sort of lack in the bass response, as I have found also in the Air Tight.

After a few days that the amp was in my system I had also the feeling that it started to sound even better and that is strange if you consider that this unit has been already break-in. In particular the high frequencies was even more pristine and I had the feeling of a more complete bass. The second day that I had this amp I called my uncle for an audition. He is not an audiophile but he is a bassist and used to be a trumpeter. As usual, I played for him “High Life” (Jazz at the Pawnshop) from a FIM SACD sample. He said that it was the most realistic he has ever listened in my system (but this time I have also the Faber reference speaker cable), but that the bass was “soft”. Exactly one week after I called him back to listen the same track and he also had the feeling that the bass was improved, even if it was still too damped.

Since in the Nel Audio system I had not this feeling, I tried to figure out where the problem was. I contacted Marek Gencev and he told me two things. First, the damping factor of this amp is quite low (as usual with SE), having about 1 Ohm of output impedance when the 4 Ohm tap is selected (my Acoustic Zen Adagio has about a flat 5 Ohm impedance curve). The second thing was that the amp should be powered with 230+-5% V~, while during the last week of test I have measured in my flat 215+-5V~. Only once I reached 220V, but once I had only 210V! That is really too low for the Kronzilla: the maximum output power will be lowered and the damping factor will deteriorate even more. Of course, that is a problem with my flat power, not with the Kronzilla amp!

A part from the soft bass, the Kronzilla SD was able to produce the best sound I ever experienced in my system. Do you know that very “tight”, very “lucid”, very “exploding” sound that many Hi-Fi amplifiers can generate? Then, forget it! I would define the Kronzilla sound as the “less Hi-Fi” sound that I have listened and yet the most realistic one. The Kronzilla SD played disarming natural. No extra shining highs, no special effects, no dramatically slamm bass (OK, there it could have been more tight). When my 13 months daughter was listening her CDs, she continuously turned her head to look for the invisible child speaking in centre of our living room. But the most unexpected award came from my wife. At the beginning she was crying for the Kronzilla invasion, while at the end she said that it was able to produce the most truthful human voice that we have ever heard in our living room. Also my friend Znort gave to this amp the “Best Spanish Harlem (Pidgeon, Chesky) Ever Heard” prize. In conclusion, is this amp the “perfect” amp? No, at least not with my AZ Adagio speakers and with my too low main power supply. But if your speakers have a quite constant -and possibly high- impedance and maybe have more than 88 dB, then you can seriously consider this amp as a definitive choice. If you can afford it and your wife will stand its 50 black kilograms in your living room (please, no babies or pets around) the Kronzilla will not disappoint you. Honestly, I have really enjoyed the two weeks spent with him and would like to repeat the experience with some “smaller” KR amps, like the VA350 based on the T-100.

Nel Audio sells a new Kronzilla SD for about 8.5 kE. This demo sample is on sell for just 3.5 kE, which is a bargain if you consider that only the two T-1610 will cost 2 kE. That is just because of the buzzing main transformer... If you are interested, please don't write to me but directly to Nel Audio at

A comparison in Nel Audio system:

Since I had the feeling that in the Nel Audio system the amp had more bass than in my system, we planned another listening session for the day that I brought back in Ljubljana the Kronzilla SD. I said “we”, because there were 5 of us, including Faber, the cable maker. At the beginning we listened the Nel Audio system with the Ear 509 monoblocks (100W each). The second stage was to Faberize all the Nel Audio system. Faber put his Reference cables everywhere, replacing AZ and Dueland cables. This brought more resolution and larger soundstage. Finally, we replaced the Ear monoblocks with the Kronzilla SD.

A match made in haven.

Someone told that I was prostrating in front of an idol, but I was only taking a picture!

With the 22W Kronzilla the bass control improved a lot with respect to the EAR 509. Also the general feeling was of a more realistic music reproduction than with the De Paravicini EARs. Only one of the us said that the EAR had a more shining treble, but also for him the Kronzilla was better as a whole. The match between the Kronzilla and the Reference 3a Suprema Corian was magic. In particular, the subwoofer was more generous in the bass region than my Adagio speakers. Sometimes I had the feeling of a little harsh high frequencies, but I think that it was due to the Reference3a tweeter, which is not so sweet as the one produced by Robert Lee for the AZ Adagio. Ah, Nel Audio has also 230V~ perfectly constant!

Tino © September 2008