I'm not sure exactly how you are connecting everything, but keep in mind that phono RCA's are different than line level RCA's. If you connect the phono out of your turn table to the CD/Tape RCA line in, it will sound like junk. Likewise, if you connect your line out RCA of your pre to the phono in RCA on your hi-fi, it will sound like junk.
If you care to detail your connections, I'm sure someone could point to the problem.
another way to make your audio sound like junk: connect the headphone out to a balanced line in with a TRS cable!
Are you DJing with 90Watt computer speakers? That could also make your audio sound like...