My code 100 started making a noise recently. It is a high frequency hum. It is particularly loud with spicific presents, but it there with everything. I updated the firmware and that didn't fix it. When I factory reset it, it goes away until I turn it off and on again. Also, if I turn on the amp while holding down the "amp" button, and don't conferm the reset it also goes away (until I restart it.) Thoughts?