Dedicated line 20A.

 Second question. There are 4 more sockets on the dedicated line at different angles, but they are not under load, they are antennas for additional noise, and how to remove this?

Dedicated means direct. If the line goes directly to the system with no outlets along the way then it is dedicated. In that case the four at the end are okay, and probably useful. But if the outlets are along the way then it is not a dedicated line, you are correct they are a source of noise, and it will sound a lot better to bypass them.

@OP,
PM Jea48. He knows his stuff.
B

What country are you in?

’’PM Jea48. He knows his stuff.’’
  Yes

I live in Ukraine.

@OP, 
Ukraine?
Now, if you could do us a favor....
Just kidding...
B