Just bought a brand new Stomp and am having the exact problem. There is a high end buzzy noise. Tried noise gate (works a bit but not great), different guitars, leads, distance from computer, headphones and monitors. Same problem. Have put in a ticket to Line 6 three days ago (weekend), no response yet. May have to go back. I have a Line 6 Firehawk and have no noise except with big dirty amp sims which is expected. This noise is on any amp sim, any cab, effects or no effects. Sad as I love the product and the sounds it creates.