Even without answers, we can already tell that the lack of remote
, display, power/source LEDs yet inclusion of phono spell retro in big bold letters. That and the low power rating don't suggest investment bankers. Instead they point at a more passion-driven endeavour which is happy to appeal to a far more select (translation: small) clientele. This is predetermined already by SET aficionados who only do costly direct-heated triodes. They heap scorn and refusal on faux triodes which here are really pentodes as used in guitar amplifiers. Clearly the folks behind G Lab can afford to be contrarious. They can support a labour of love which will never be a bookkeeper's triumph regardless of sonics. That is retro too. It harks back to High End's beginnings. Small audio companies did unreasonable things just because, not because there was as yet a market for it. In that sense, the Polish Block is retro squared (though having a big industrial company behind it for finance and engineering resources is rather more modern).

To de-square its retro and get down to present tech, I asked my designated contact Dionizy Konieczny what type of output and power transformers they used (toroidal, EI, C core, dual C core, other); how many gain stages followed the line-level inputs; how much additional gain the phono input provided; whether there was any local or global feedback and if so, how much; and basic specs like i/o impedance, input sensitivity, overall voltage gain and S/N ratio. For 300B SETs, it's not unheard of to encounter signal-to-noise figures of ~80dB. Contrast that with the 135dB of today's very best D/A converters. Likewise for output impedance. A class D champ might post 0.003Ω across the bandwidth, a SET might show 8Ω. Feedback can improve those figures but many valve designers prefer none or at best very modest amounts. In and of themselves, such numbers aren't terribly predictive of sonics. To most shoppers, they simply become part of the decision-making process. I also wanted to know what prior experience—if any—their engineering team had with valve electronics and the fine art of associated transformer design. With so much competitive choice available, that too is intel resourceful punters desire. It helps them draw up a more complete mental picture on any fine hifi product under final consideration. At €5'000, the Block is certainly a few blocks removed from the low-rent district of cheap Chinese tube imports. For G Lab's tariff, one wants not just the looks and fine fit and finish. One wants serious engineering that promises reliable operation. One wants the whole enchilada with extra sauce.

Dionizy Konieczny: "The output transformers are air-gapped C cores. The power transformer is a toroid with electrical screening between its primary and secondaries. Input impedance is 50KΩ line level, 47KΩ for phono. Optimum speaker impedance is 8Ω. 6-12Ω are acceptable. Line-level input sensitivity is 1Vpp. Circuit voltage gain is 24dB. MM adds 39dB/1kHz, sufficient for most moving coils. The line inputs are followed by three direct-coupled gain stages (6N6P, EL34). The S/N ratio for the line level inputs is 70dB." For a modern hifi appliance, the latter spec is shockingly poor. In this genre, it's simply not that uncommon. Now I wanted to know what was inside the fourth cube seeing that we've only identified the contents of three thus far; what the actual output impedance rather than recommended speaker impedance was; and how G Lab would address concerns that their corporate background didn't really seem to show any prior experience with hifi gear, tube gear in particular and the special demands of single-ended output transformers most especially.

Dionizy Konieczny: "G Lab Design Fidelity are a Polish brand new to the high-end audio market but we profit from the great experience of a team of specialists and engineers all of whom are passionate about high quality sound, design, audio products and business. The brand is owned by Comp Centrum Innowacji Sp. z o.o which employs specialized project managers responsible for successful progress and the delivery of the Block project. Mateusz Glowka's industrial design was the first spark of life. We needed suitable electronics for it so we wouldn’t end up with a jewel but no high-quality sound.

"For that we turned to Marian Kopecki, a well-known Polish electronics designer and founder of numerous products. Most of the final sound is due to his guidance. The idea of separating the audio board from the transformers resulted in a pure incredibly detailed sound that we never heard from the chosen EL34 tubes. Having the design and electronics ready and being more than satisfied with both, we still needed a company that could work wonders in metal.

"Since our team agreed that every part of the Block had to be made and/or developed in Poland, we turned to Elzab S.A. Yes they are known for cash registers and are actual giants in that field but also have great capabilities and resources in metal work. At that point, we had all our bases covered."

About the fourth cube, "it is empty". About the actual output impedance, Dionizy asked their lab to draw up complete tech specs. He also requested production photos to spare me disassembly and subsequent issues putting things back together properly.

Marian Kopecki: "I understand that you were interested in our damping factor. It was a great pleasure for me to turn on my old Bruel Kjaer 2409 tube voltmeter and the Elpo G502 tube AF oscillator, both instruments calibrated in 2015. I measured the Zs output impedance at the classic Philips audio frequencies of 100Hz, 440Hz and 4'400Hz, at output powers of 100mW, 1W and 3 watts and under the rated load impedance of 8Ω. The results are stable.

"Output impedance is 1.8Ω, hence damping factor is 3.7. The Block produces crystal-clear sound without any negative feedback, relying solely on the properly fixed working point of the tubes' most linear characteristics."