Leben cs300xs electrical noise in tweeters?

Try a variac, lower power=lower hum. Its very efficient with the leben CS 300 and the right chanel noise. 

Try a "cheater" plug to temporarily lift the ground. If that clears it, you have a ground loop issue. If it doesn't clear it, remove all input cables. Is the noise still there? If so, you have an amplifier issue.

Hi, yes, I talk with the dealer and says that is a normal little noise of the tube amps. Is not a problem of tubes, the noise is also with another tubes, and the noise is the same in the two speakers. When the music play I do not hear the noise, but it bothers me to know that the noise is there! 

Maybe tubes? Have you tried replacing? Is it both sides or just one? If one side swap tubes from side to side and see if noise follows. 

Have you talked to your local dealer?

Hi!, in all inputs, the noise is like a " RRRRRRR" "fast vibration electrical", is posible that are the 50 hz noise?... Is posible to eliminate this noise, or are a typical of tube amps?.... The another noise, the hiss, is very little and up and down if I move the volume, I think that is a normal thing.... 

Buzz, hum or hiss?
Any specific input?