Issue with audio mac pro early 2009

My mac pro early 2009 is having audio difficulties. Every time I turn up the volume from the line out my speakers make a terrible sound. I went out and got new speakers and the same sound was emitting from the speakers. My suspicion is that the line out is malfunctioning or is damage in some way. Can anyone provide me information on how to prevent the static sound from occurring when I use the line out audio or some alternative. I am using a Samsung HDTV and the speakers I was using was Klipsch. This problem doesn't affect my monitor because it works fine when I watch tv.