That sound is right for me.

@clearthinker ​​​​​​ He is not doing business, and  does not sell me anything.

He said he made the preamplifier and amplifier by himself and I believe. That's it.

Flat clear, ok.

Was not meant to be insulting you. You may just have a more advanced knowledge of the english language  than I do. I stand corrected.

@baylinor  it's meaningless to say my English good or bad here. If you are not clear for whatever reason, you can just ask me.

Does that work for you? Let's go into the topic.

You may be able to contact the author of the video and ask questions. They may be able to give you clues of how to find what you’re looking for. 
 

Best wishes-

@uncledemp  you are definitely go into the core. He replaced the original crossover of the speakers and redesign a new tube crossover for the speakers and he said his crossover is much better. So now I have some clue, it is not just preamplifier and amplifier.