I had a similar-but-different issue with my Rogue. Went to a band rehearsal, there was a Quilter combo there so I plugged in and played a few tunes on it. Band members complained that there was a high frequency noise (that I couldn't hear). Brought in my trusty GK Backline 112, problem solved. Some digital gear (and this includes phones, routers, computers etc.) will induce various weird noises, and just to make it more fun, not the same noises in different instruments.