Ipad headphone jack problem

Hi there, my ipad retina has recently started to crackle when playing music through headphones, I've tried multiple headphones that work with other devices but have same problem. When playing audio through headphones a loud crackle can be heard, so loud in fact, can be heard across a room when volume set on minimum, the crackle seems to be in time with the bass on a song, and music is still audible through headphones. The ipad speakers themselves work fine also.

Any help would be appreciated.

many thanks

Sam