Sergei71,
I am still not sure how to answer your original question.
My own opinion, based on having owned both the OTO SE Phono and having built a couple of Audio Note Kits, is that the build and parts quality of the factory product is probably higher than the kit. But it's apples and oranges - they are are designed for different markets. Both are very good and represent good value IMHO.
Having said that, it's difficult if not impossible to compare the 300B Kit 1 to the EL84-based OTO SE. The tubes just sound very different, period. Have you heard either one of these units? Have you heard 300B amps and EL-84 amps? If not, I don't know how to describe the differences to you. How would you describe the difference between yellow and purple?
I am still not sure how to answer your original question.
My own opinion, based on having owned both the OTO SE Phono and having built a couple of Audio Note Kits, is that the build and parts quality of the factory product is probably higher than the kit. But it's apples and oranges - they are are designed for different markets. Both are very good and represent good value IMHO.
Having said that, it's difficult if not impossible to compare the 300B Kit 1 to the EL84-based OTO SE. The tubes just sound very different, period. Have you heard either one of these units? Have you heard 300B amps and EL-84 amps? If not, I don't know how to describe the differences to you. How would you describe the difference between yellow and purple?