Akai s3000 (not XL) - weird static on inputs

Hi guys. Well, I have a weird problem on my s3000.
When using the inputs, there is A LOT of static. But, when playing imported sounds, no static at all.
So I know the problem is on the inputs. The problem is there either I use the 1/4 or the XLR.
Has any of you ever experienced this before?
How can I fix this?
Do I have to use the "ground" on the rear pannel?
Thank you

I haven't had that issue myself on an S3000 but yes the ground screw is well worth trying, that's what it's for, to solve ground issues. What source are you sampling from?