IPad 2 sounds distorted over headphones?

I got my iPad and it was working fine. I'm a guitarist, so I also got the iRig, which lets me connect my guitar to the iPad via the headphone jack. Using GarageBand, when I'm recording something everything sounds great. But if I try to play music or videos or anything else, the sound is distorted, as if someone was playing with the EQ an completely messed it up. Does anyone have any idea as to what can be done?