Discovery of this discussion saved me a lot of time in resolving the same issue with noise in my computer speakers due to a powerline device. I have a Windows 7 machine and the same Cambridge speakers as Disco. I installed a Netgear Powerline 500 WiFi Access Point, model XWNB5201 and got sporadic soft crackling sounds coming from the computer speakers. When I unplugged the powerline device at the computer (VS what I'll call the remote powerline device) the sound stopped. When I shut the computer down the sound stopped. The computer is in my home office and the remote powerline device is in a family room in the opposite side of the house. In the office I have a DSL connection to the internet. The crackling sounds became more constant and frequent as my internet browsing activity increased. When streaming a Netflix movie the soft crackling was constant. It was irritating enough to make me search for a solution and I found this discussion. I moved the powerline device at the computer to every outlet in the office, the sound persisted. All outlets in the office are on the same circuit breaker. Finally I moved the powerline device to an outlet on another circuit and the sound was gone. I was lucky to have an outlet on a different circuit close to my office. Wanted to add my experience in hopes it may help others the way this discussion helped me.