Alternator whine threw Sub Amplifier RCA

[HoneyBadgerRy]

I have 3 pair of RCA's ran out of my head unit. Two pairs are ran to my Alpine PDX-F4, one Pair is ran to my Poseidon P1000.1 . When the SUV is off no noise is present. With the SUV on a whine is present that gets higher pitch as you rev the motor (I'm assuming either coil or alternator whine).

I have DB link double shielded RCA's.

When I only plug in the RCA's for the Alpine I get no whine. When I plug in all the RCA's I get whine from my 4 speakers. I also put a jumped from the grounding point shared by both amps (distroblock ran to battery terminal) to the sub amp rca ground to see if that would help and it made it much worse.

What should I do? I think a pair of rca isolators for the sub amp would likely do the trick.

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[HoneyBadgerRy]

It doesn't make a difference if the head unit is on off plugged in etc.

Chassis grounding the amp ground or the RCA's make no difference.

I have no idea.

 

[HI-C 10+ year member]

what's your grounds like?