Hissing sound at low volume

I have only just brought this Panasonic SC-VK660 yesterday, and am annoyed with it aleady. At low volume all I hear is a hissing coming through the speakers from 1 to 15. I can still hear it with the volume cranked up but the other notes make it less noticable. It occurs on all the functions, tuner, cd, aux. I have adjusted the EQ in different settings and also adjusted the trebble so it is -3 but still it hisses. I have also made sure the speaker wires are not near the power cords.
What's next? Is a hissing sound normal for these kinds of units or do you think I should take it back? Any ideas would be great. Thanks