I just ordered a Workingman's 10 from Musician's Friend. It's the perfect size ans volume practicing. I love everything about it. The thing is, it's my first bass amp, so I don't know what it's supposed to sound like. There is some mild hissing at low volumes and some major hissing at high volumes. Is this normal? If so, is there a way to get rid of it? If not, should I return it?