I have a pair of KrK Rokit 5 speakers hooked up to the audio out on my mac book pro. I know the speakers are fine because when hooked up to my ipod everything is fine, but when hooked up to my MBP, the speakers work, but i am constantly getting a hiss/static sound. It is not imparing, but does get very annoying. It seems like something inside the MBP is not properly grounded, but it has had a new MLB. What SHould I do?