My initial though was what currawong suggested. I blew it out with compressed air and used a LED light to look inside the jack but there was no obstruction blocking the way. The plug was all the way in because you could feel it "click" in.   I talked to an Apple representative over the phone...

I have restored the iPod but I still have the same problem.

I have tried that with no success. It`s hard to describe the sound. It`s not as if some parts just sound off, its more like certain parts are completely missing. 

BUMP

Hello I'm new to the site and I'm hoping I can find some help here. I have a 4G iPod touch and when I plug in either my Sennheiser HD555's or Shure SE115's, music sounds extremely off. On some songs, vocals and beats are missing, or some sounds are extremely quite. These headphones work...