I don't have one of these, so I can only guess at a few possibilities:
You may be getting some hard drive noise (magnet hum, or other noise just from the drive moving around close to your soundcard) or some weird grounding issue. If you have a laptop this is a pretty high possibility, as it's happened to me before with audio gear. I ended up using an external audio card, which solved the problem.
You may want to see about plugging in via the audio outs of the TT if you can instead of via USB and see if that solves it.
I don't know about the bass issue though. Are you able to monitor the audio going into your computer as it plays through and see how it sounds live? Just to be sure that it's not the program you're using to rip the audio that's causing issues.