This is a stab in the dark, but along the lines of what elklandercc said, have you tried a different cable? How close are you to the amp? How about trying plugging in straight into your amp with no pedals? There's been times I've been plugged in with my pedals on, then go turn my amp on with guitar in hand and practically blow my eardrums, depending on which guitar I'm using. Oh, I just notice you said, "amp loud using distortion"- have you tried turning the gain and or level down? I know on my distortion box, depending on the guitar, if I have the gain up too much, I get a deafening screech.

How about plugging straight in clean, and see what happens? Maybe a gear guru like Lordathestrings can add some insight if he sees your post. Good luck.