The first step is to determine what type of buzz you are hearing: Is it ground, DC, or just the Mac itself. If the buzz is in the speakers or subwoofers, it is usually some type of ground issue. You should check the outlet with a polarity tester to make the sure there is a proper ground: Next disconnect the modem/router if hard wired. If the buzz is still there, the you can disconnect the mac and see if it goes away: If it is ground issue, a ground loop isolator will usually work, most conditioners do nothing for ground or DC issues from my experience. Also, from my experience in install and sales, most issues are the equipment picking up something either electrical or in the ISP and then passing it through the speakers. So if you send the unit in for service, there is high probability of a no problem found diagnosis.