I might be missing something here, but when I get to around -5 on my 3803, small blood vessels in my eyes begin to explode. I'm not even sure what the thing goes to in the upper range (+10 or so?)
Every receiver has a top stop. That point where you just can't turn it up any higher. If that is the issue, then there really isn't much than can be done.
If the issue is that you can get to +10 and the unit is only mildly loud, then I agree with JohnK, there is a setting issue you might want to look at. I'd suggest you get into the manual in some detail and see what it might tell you.
