I picked one of these up a few days ago for a good price at a local pawn shop. I didn't have a chance to play it at the store so when I got it home I hooked everything up an started fiddling. This is my first real head unit and I can only turn the gain up 1/4 turn before the hum comin through my cabinet is very prominent the knobs all turn smooth and don't crackle it's just noisy. I'm lost about how to make it go away and I feel like a dork bc I'm an electrician and I'm sure this will be a grounding problem I don't understand. I still have about ten day to take it back but thought I would use the collective TB knowledge first. Thanks if you read a really long post.