I have a similar, but high pitched buzz occasionally when I use a certain cord, too. I'm live in Korea, so 220v, euro-style plugs. I replaced the part of the cord from the wall to the converter with a local cord so I don't need a wall adapter. The one I use at home is fine, no noise. The cord I use at the office has a high-pitched buzz. So I'm pretty sure it's just the cord in my case. Try a different cord and make sure it's jammed tightly into the converter. A new cord will be a whole lot less than sending your edge back for repair for what sounds like not a problem.