Rear amp whine

[treilley_at_BANKMARK@conseco.com (treilley)]

     I put in a rear amp and speakers to replace OEM last weekend.  The 
     problem is that I have an alternator whine present.  I have grounded 
     the amp more than sufficiently(12 guage to seat belt mount) but stil 
     have the whine.  I connected the amp ground to the receiver(Alpine) 
     ground and grounded that behind dash to 2 diff locations in addition 
     to the ground wire above.  This reduced the whine, but it is still 
     there.  Noise filters from Radio Shack do no good.  What is wrong?
     
     
     amp ground-----------rear seat belt mount under rear seat
                       |
                       |            
     receiver ground------OEM radio ground
                         |
                         |
                          ---bare metal under dash that ohmed out as ground
     
     TIA
     
     Tim 90CQ, 77Spitfire