Thank you maxamp for your prompt answer. I noticed that beats produces distortions, so I switched it off. The beats is worth nothing, anyway. I don't use is since the first day I have Poweramp. I noticed that tone is the reason of the distortions when listening very silent. When it is off I hear no distortions, but it makes no fun to listen to the film soundtracks without more bass (about 50%) and treble, and Poweramp has the best bass boost thanks to the tone on. With the equalizer I could not reach such a nice deep bass.