After about 3 months of very light usage (home use, ~20 hours), my Code 50 developed a harsh noise problem: https://youtu.be/S2cTK8fsfTE. It's on every preset and can be heard via the speaker and when using headphones. I tried using different guitars/cables/power cords/rooms/outlets, reloading firmware, and resetting the presets to factory default; but the noise continues.  Anything else I can try before I return it for replacement/warranty work?