Front speakers HISSING, WHY!!!

[seankeane1337]

I know there are many threads on engine noise and what not, but I don't believe my problem is that simple.. So here's the problem: When my system powers up, theres a low volume buzz/hissing noise that is constant through the front speakers only, and gets louder with louder volume. When the unit is off, or at 0 volume, there is no noise. The head unit is well ground, as is the ground in the trunk. There are three sets of RCA's, but only the RCA's for the front speakers buzz/hiss. The cables are run opposite the side of the power line, and I'm not sure what to do! .. Is it a HU problem? all cables are fine/no hissing until I plug the front speaker RCA to the HU. Help Alpine HU