I want to thank Wiesław Kurnicki from Eufonika and @Claus-DK from hoved-fi.dk giving me a change to test this amplifier as a part of hoved-fi.dk's review tour. After my test period amplifier was sent to a next reviewer and I received no compensation for my review.
Prologue
I have to admit I'm no expert when it comes to headphone amplifiers. Especially tube amplifiers. I've been using SPL Phonitor for about five years now without feeling a need to upgrade or try anything else. First desktop amp I had was xiangsheng dac-01a (aka Grant Fidelity DAC-09
/Maveric Audio Tube Magic DAC), then I moved on to Lehmann Rhinelander and Schiit Vali. Every amp better than the last until I got phonitor and was finally happy. As a portable amp I've been using Chord Mojo for a while now.
So, what is Eufonika Model H7?
Long story short: Its a OTL tube headpone amplifier build and designed in Poland. H7 uses 6N1P & 6N13S tubes and retails for £299 which translates to 332,65€ and $383,43. If you read this, you propably know more about OTL design and the tubes than I do so I won't get into details. Specs are as follows:
Input impedance: 10 kohm
Sensitivity: 700 mV
Frequency range: 15 Hz - 300 kHz
Output power: 300 mW
Optimal headphone impedance: 50 - 600 ohm
Built-in headphone socket: 6.3mm + 3.5mm adapter
Power supply: 220V - 230V AC
Power consumption: 50 VA
Dimensions: 350x200x125 [mm]
Build quality:
It is pretty much what you get from the picture. A beatiful thing in a wooden casing with a metal top plate. Design is simple and tastefull in my opinion. It has some diy vibe to it but looks very professional. It does make the Lehmann Rhinelander I mentioned earlier look like a tincan with rca sockets. And yes, Rhinelander is the more expensive one.

So lets dig a little deeper on the build of Model H7. It is quite large, only a tad smaller than SPL phonitor.
Air vents are cleverly placed underneath the amplifier. Great design because you don't want dust to get inside the amplifier. As you can see Phonitor is nothing but perforated metal on the sides and top. Every six months I take the amplifier apart and try to get rid of the dust that got inside.

Not much to say really, its simple but classy without going overboard. It looks like a object with a purpose not some design ornament to decorate your house.

It looks even better whan the lights go out and tubes start shining.
Volume adjuster has nice hefty feel to it. It is not as nice as one on SPL phonitor but it feels solid and does what is supposed to do. Very easy to adjust the volume even by small amounts. I wish it had some numbers for positions but can't complaing considering the price. I'm glad money that went into designing and building this amplifier was not spent on something as irrelevant as volume knob.
Quite standard 6,35mm socket. Nothing extraordinary about it. However this is the only gripe I have regarding the build quality. I wish the red release switch was on front of the plug. When it is behind a hefty plug like Sennheiser hd800 on the picture it is bit tricky to reach. It is quite difficult position and I have to use quite a bit of force to make the connector release the headphone plug. I don't know if it is because of faulty part or heavy use of the review unit but I noticed that rubber feet on the right front corner is lower than others. Amplifier does stand even even without that rubber foot but the amp does tilt towards right front corner when pressed. Either case, constantly appying pressing force to the right corner could have caused this anomaly. If that is the case I wish Eufonika will find better rubber feets for their future models.
Sound quality:
This is what matters. How it sounds. And boy was I in for a surprise. First of all I was expecting somewhat less power. Simply put I was expecting I would have to push Model H7 louder with Sennheiser HD800 to reach same volume levels as I do with SPL Phonitor. Phonitor afterall is a $1500 amplifier designed for running high impedance headphones. If going just by sheer numbers it has crazy 1.6W at @600ohm's. With that and SPL's 120v rail system it is quite a piece of kit. Ok, its just numbers, I know. But those are numbers hardly any amp can match regardless of price. Yet, here we are. Model H7 does have more room to spare than Phonitors. Without measuring I'd estimate that with hd800 Model H7 reaches good listening volume 10-15% earlier than phonitor. Same also happened with my lower impedance headphones.
Actually there is not so much to say about the sound quality. It does what it is supposed to do, amplify a signal. Of course it has it's tube traits. I tested Model H7 with Beyerdynamic DT770 pro 80ohm, a headphone I think greatly suffers from tizzy highs and occasional sibilance. Model H7 actually made Beyers quite compelling sounding headphones.

SPL phonitor is considered a neutral but easy to listen amplifier. Very much like Model H7. I don't think Eufonikas spread butter on sound where it does not belong. Something I did kind of expect it to do, especially with lower impedance headphones. Model H7 performed really well with iBasso SR1 that has only 22ohm impedance. It was great with JVC HA-DX1000 with 64ohm impedance and only failed with Audioquest Nighthawk Carbons which have 25ohm impedance. That in my opinion is only because Nighthawks have a "creamy" tonality by their own and just a hint of extra warmth pushes them over the edge from creamy to...well, slimy.
So sound quality considered Model H7 goes toe toe with a lot more expensive SPL Phonitor. Compared to Chord Mojo Eufonikas have better authority to the sound. Regardless of headphones Model H7 sounds more robust, lifelike and bigger than Mojo. Sure, Mojo is just a portable amplifier(and dac) but it does cost quite a bit more than H7 so some sort of comparison is called for. When compared to Phonitor I have difficulties figuring out what it does better to justify the price difference. Besides SPL's exemplary build quality and extra knobs( crossfeed, mono switch etc) I could not really come up with anything. I think, MAYBE Phonitors do a slightly better job at spreading the stage and imaging but the difference is so small that it might aswell be in my head.
I wish I had some other harder to drive headphones at hand. Only headphone that proved to be difficult for phonitor has so far been akg k340 which is notoriously one of the most difficult headphones to drive well. And Phonitor did do a pretty decent job with it too. Would have been fun to see if H7 could have lured more bass out of AKG's than SPL could. Again regarding how H7 does with Sennheiser HD800 I can't compliment it high enough. Phonitors are considered one of the best solid state amps for HD800 and Model H7 easily performs at the same level. Bright and somewhat thin tonality remains but I can't really say bass is lacking like it occasionally feels with Chord Mojo. Just going by my memory I'd say both Phonitor and Model H7 are better match for HD800 than Sennheiser's own HDVD800.
Conclusion
Model H7 is a well built, easy to listen and very powerfull amplifier that does not just excell with high impedance headphones but works well with many lower impedance headphones too. I'f I was to build an audiophile headphone rig for "cheap" I would propably get a decent affordable dac, used hd800 and model h7 and be done with it.
Will I be buying a unit for myself? Well..Even how much I like H7 it is not THE amp for me. I enjoy crossfeed on Phonitor too much and tube amp with too small kids is just too risky. Either it would be burned hands, shattered glass or electric shock. I wish that in the future Eufonika will offer a metal cage for their amplifiers as an accessory available to be bought for extra cost.

my higher impedance headphones (Sennheiser HD600, HD6XX, AKG K240 Sextett).