I have done this before and never had any problem. Today, I am trying to plug a cable to output the audio of the laptop into the sound system. So, the only place I could see that it would fit would be to use the headphone output connection. But, when I do that, I keep hearing a background noise which is kind of irritating. The only other place on the laptop where this cable would fit would be to use the microphone jack but this is not the right one. What am I missing?