OK, I know this is an old thread but my S4 (purchased new less than a year ago) is having this problem. I can hear a distortion or crackling with some female vocals and other guitar tones and elements within the upper mids. This is even there using usb otg with FiiO E17 and have heard the problem at varying degrees with the stock earpads, Shure 940, NAD HP50, B&W P7, and Dt1350.
I'm using the rocket player pro and all my updates are current. Any suggestions to correct this would be very very very very very much appreciated!