My Pocket Pod is almost  2 years, always been used but when I have my guitar fix for 2 weeks, I didn't use my pocket pod, but by the time I got my guitar back there is a noticeable humming noise comming from the unit, but I discovered that when I plugged it via usb through my Laptop that is not charging the humming noise will stop but if the laptop is currently charrging the humming won't stop. Please help I want to use my Pocket Pod everywhere without the need to plug it via usb..