Hissing noise through my earphones

I have a 3rd generation iPod nano. Recently I have noticed the before even pressing play there is a hissing crackling noise that comes through my earphones. This noise doesn't go away even when I do press play. sometimes the noise is so bad it interferes with what I am listening too.
The problem is not with my earphones as I have use the same pair in other devices and have never had this issue before. Have also tried different earphone with the same iPod and have the same issues.

iPod plays perfectly when plugged onto a docking station.