Same problem with my setup using a real amp and it happens with other gear sometimes as well....but for the $2000 price tag you’d think this was something they would have just built into the unit. I put an isolation transformer before the input of my amp which fixes it, but just more stuff I did not want and should not have had to do. To be clear the amps I use are all high end and it’s not a power issue, it’s a ground loop. Wish I had tried this before buying the Helix.