I just took home a used Fender Pro Jr. Tried it at the seller's place, very quiet. Took it home, and I swear it's much more noisy. I thought my old amp had noise problems and was going to have it serviced, but now I wonder if the real source of the problem is the wall outlet... The noise is a kind of static hiss, it's noticeable but moderate. Is there any noise filtering unit that I could put between the outlet and the amp?