Pioneer hiss noice

I have a pioneer A-10-AE and let's just say I have a VERY noticeable hissing sound, I tried tricks like having everything on one outlet and proper grounding (which you have to do yourself with this amp and then I picked up some other static noise) But nothing helped, even if I change chanels to some where I don't have anything connected, it's still hissing. It only goes away when I turn wolume down, but it's still there. Any ideas?