I had a new amp installed yesterday (JL 450/4) - my 2nd amp, and since
the 1st amp (JL 500/1) was running off 8 gauge wire, they wanted to
run 4 gauge. So now I have 2 runs of 4 gauge, 1 to each amp; but he
also ran 2 runs of ground back to the battery. I have read numerous
times that ground should be short and to the chassis. And it's a long
run since this is a Suburban. He said JL recommends grounding these
amps directly back to the battery and so that is what he did. Well
now I have alternator whine that fluctuates with the speed of the
engine; worse the higher the gains are set. The RCA's & speaker wire
don't run along with the power wires, so I'm hopeing I can rule that
out (they do cross where they all meet up at the amps, but that
shouldn't be a problem?)
I don't want to go back and leave the car there again, it's a pain - I
am skilfull enough to run a ground - there is a seat bolt right there.
So I have 2 questions; Is the ground probably the problem? And if
so, should I disconnect the long ground and replace it with the short,
or just add the short and leave the long ones too?

Thanks,
Mike