It's hard to tell if this is really a ground loop or a preamp noise problem.
Try, temporarily only, using a cheater plug on the preamp. See if this resolves your problem.
If it does, that pretty much guarantees it's a ground loop issue. If NOT however.... it's a preamp noise issue.
E
Try, temporarily only, using a cheater plug on the preamp. See if this resolves your problem.
If it does, that pretty much guarantees it's a ground loop issue. If NOT however.... it's a preamp noise issue.
E