So i'm trying to record bass.

I am using an Ashdown ABM evo iii head and I'm running the D.I out in to the zoom and it is making a horrible humming noise. It sound like an earthing issue.

This happened last time I tried to record bass at a band practice but it didn't do it when I ran a jack lead out of the headphones in put in to a PA mixing desk (was using that for play back)

Any advice on how I can stop this from happening. Some people have mentioned a plug not having a grounding wire or words to that effect.

Thanks again guys!