I was getting 60 cycle hum from the Helix LT 1/4 " outputs using a blank patch . I tried all sorts of ground lifting options (including the switch ) but had no success . I was able to solve the problem using a passive transformer isolator . I used an ART DTI . This is not an uncommon problem when connecting gear but a bit of a shame to have to deal with . If you plan to never use the unbalanced outs then there is no issue . Ive had no hum issues using the balanced outs .