Good Luck!
That does not look like a tube. Almost reminds me of a digital clock display. Let see some more pics.

Oh wow!  I read about the Nutube a few months back after seeing a reference to it her in the forums.

How did you get your hands on one 4K?  Super cool!

Jeff,  Yes, you can find the US dealer at eBay. Pmillet has opened a store in association with Korg.

 LR,  I have the same reservations as you about this. So far, I have not gotten past just getting it hooked up and am starting to experiment with the bias setting for the tube. When set at the recommended 2.5 volts, it is in clipping and of course, that just sounds bad. It clips hard at that bias setting, so I moved the voltage to 2.04 volts and so far, that seems decent. This is all using a 12 volt battery. I intend to try out an 18 volt battery, since the spec sheets show lower distortion characteristics.
I have to make an enclosure for it, and wire it up for use in my system upstairs. I want to use a pot on the input, as using a CD player seems to be a bit hot for the tube.

Got this mounted in a small enclosure. Using 2-9 volt batteries for power. Will be testing in the big system soon.

Last night, I used the Korg unit in my big system. In short, I am impressed by certain aspects of the sound. First off, it has about 14db of gain at 18 volts, so I am using a volume control for the input. The net effect is in the bass. Much fuller than without the unit in place. The midrange isn't as forward, but the price paid is, yes, in the presence of the performance. Treble comes out a bit soft, but not unusually so. In fact, I have to factor in my hearing and say that others may find it to be spot on.
I have ordered another kit, so that I may try it in other systems, without taking it in and out for all moves. i like using the two 9 volt batteries, but will try a wall wart affair later on.

Next step, getting the RCA jacks mounted.

A second shot is needed to show the RCA jacks, and the gain control. This allows the unit to be operated with sources that are a bit hotter than others.

.........Thanks! Let me tell you, these kits are about as easy as it gets. That is due to the silk screening on the high quality boards, a ready made BOM from designer P.Millet (although you may be better served choosing your own choice of capacitors and some other parts), and a parts list that makes populating the board simple. The power supply can either be battery or wall wart. I chose 18 volt battery because it lowers the distortion a bit.
...............Now, on to the sound. To make sure that the input isn't over driven, I have installed a 50k pot. I adjust it so that I don't see the tubes flicker even a tiny bit. Kind of like a VU meter just up to the edge of zero. When this is all done, the sound is pretty damned good. I am sure that it all matters about source, music selection and system synergy, but at this price, get ready to be surprised.
.................The headphone amp is another project that I have taken on, and it is spec'd to run at 24 VDC. For now, I am using the supplied switching power supply. Again same thing applies as far as kit simplicity. Pete Millet has made this easy for us. This kit even has a step by step process. Anyway, I didn't build it that way. I just did my thing. The amp has additional features appreciated by the fact that no one wants a popping sound when the amp is turned on, and so a muting circuit is put into practice here. The sound? Well, here we go again, I really love it. Here is the 'BUT' about it though. I don't care for it with the ORI headphones, or the Hi-Fi Man phones. It is absolutely perfect for the Grado phones though. I almost gave up on them until I heard them through this amp.

Next.

Actually, these are the most microphonic tubes that I have ever dealt with. Of course, in headphone use, that tends to be of little concern. This headphone amp has an output as a pre amp, so I tried it out. Let's just say that I am working with that issue, and trying to mechanically isolate the unit.