DH77EB sound problem

Hi
Have just acquired a Hackintosh with the above Motherboard. When I put my headphones in the headphone out (Green socket) on front I get a constant hissing sound through the headphones and only occasionally hear the actions of my computer interacting. Can anybody give me any idea as to what might be wrong?
Thank yo

Update;
just installed my audio interface and sound is working fine from there. Might help pinpoint the issue with the on board sound. Person I acquired it from said to go to the voodooHDA settings in the preference panel, which I have but the options seem limited and nothing fixed the hiss.