i'm guessing you're plugging the mic into a 1/4 input that is unbalanced. If you're using XLR it should be balanced. Maybe you're plugging the snake returns into something that is unbalanced? You will have to tell us your chain if you want us to help
Yea... if you are connecting the mic to the snake via XLR cable, and the other end of the snake to the preamp via XLR mic cable, there's likely something wrong with one of the cables. Try different mic cables and a different channel on the snake.