I had really bad alternator noise on my Z1, previous owner of my vehicle/z1 had shorted something on install and had put in the hack of grounding the rca wires, but I was still getting some static. I sent in my unit to Pioneer, they said there is a standard $200 repair fee for this model. I got the unit back pretty quick, i believe it was just under two weeks including shipping time. The problem was totally fixed and i undid the rca ground hack. The paperwork from Pioneer said the fix was just a fuse! (part number CEK1260). I looked up the part number on Pioneer's website and they list it for $8.50.
I don't know how hard this fuse is to replace, or even what it looks like. I can't see any fuses on the external case, so I am sure this replacement requires opening the case. If you have the ground loop problem and are mechanically and/or electrically inclined, I would think its worth it to order this part and try to replace it yourself. Even though the part was listed at $8.50, I didn't get any of my $200 back. 