Leben cs300xs electrical noise in tweeters?


Hi!, I have a Leben cs300xs amp and I like the sound, but I discovered that the amplifier produces a little "electrical" noise in the tweeters of the speakers ( philips miniwatt with 91dB) if my ears are in tweeter... This is normal?.... Another owners of the Leben with the same experience?.... Thank you! 
thebalance
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.... 
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, 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!