Ground Loop Help

Head unit: Pioneer DEH-X6700BS

4x Door Speakers: Kicker 41DSC6934

4 Channel Amp: Rockford Fosgate Prime R400-4D

Sub Amp: Sound Ordnance M-1500

Sub: Alpine Type-S D4

I've tried re grounding the headunit and the 4 Channel amp, with no success.

Forgot wiring too. Power is simple. I have a 0 gauge from the front to back on drivers side, to a distro-block into 8 gauge for sub amp and 4 gauge for 4 channel. Passenger side has 4 plug RCA, sub amp control, and remote turn on wire. RCA goes back to 4 channel, plugs into there, and then I have a 2 RCA cable that plugs into the 4 channels pass through, to the inputs of the sub amp. 4 Channel simple has one speaker wire down each side (for the left and right front door speakers) and 2 speaker wires up the carpeting of the trunk to the 2 rear deck speakers.

By ground loop do you mean alternator whine? And does it go away when you unplug the RCAs from the HU?

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Yes. When I rev the engine the pitch of the whine increases. I don't know of alternator whine is specifically called a ground loop but that's what I meant. Sorry about that! And I'll check unplugging the RCA's to see if it's coming from that (I'm fairly sure it is)

For starters, do not run power or ground for your H/U from the stock wiring harness. Run a dedicated power wire from the fuse panel to the H/U. Ground the H/U to an appropriate chassis ground. This will eliminate the most common ground loop issues. If this does not correct the problem, start focusing on the ground wiring of your amps. Ground them together (via a distro block is best). Make sure the ground is cleaned of paint/debris, sealed, and in an appropriate location to allow current flow back to the battery via the chassis. If all else fails, use trial and error on ground locations.

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My only problem with that is when I take out the Headunit, there is no metal insight that I could ground to, mainly plastic. Would it be okay to use a longer ground to reach a piece of metal? I know a lot of people say to use short grounds but that's a little hard. As for the power, would I just look in the cars manual an find a fuse that turns on with the car and just put a wire into the fuse hole?

audioholic definitely makes some good points, especially using a distribution block to ground the amplifiers. that will rule out differences in resistance between grounding points as the issue. i'd also make sure i was running 4ga power and ground to both amplifiers instead of the way you have it now. finally, the headunit you have has 3 sets of preouts, i'd personally run a dedicated set to to the sub amp rather than jump from the 4 channels outputs. not a huge risk for noise doing it the way you are now but, since noise is there you might as well tidy up the install from top to bottom. doing that will also give you subwoofer control from the headunit.

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My sub amp can only accept 8 gauge (pretty **** amp ahaha) I plan on upgrading to a 1500w soon so that should be fixed when I get that.

Yes, run a wire as long as necessary (but as short as possible) to reach an adequate chassis ground for the H/U.
And yes, just find a circuit/fuse that is ignition switched. I recommend using a multimeter (or similar device) because you will also want to determine which side of the fuse to mount your wire to (with fuse removed and ignition on, one side of fuse connection will be hot, the other isn't. The non-hot side id the protected side.

8ga wire inputs are fine for most sized amps.

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does the fuse need to be reading a certain amount of volts or are they all the same?

Okay, I made an interesting discovery while working on my system just a few minutes ago. The alternator whine and white noise is only coming from my front 2 speakers. This tells me there is a problem elsewhere if my rear two speakers are completely silent. Any advice?

Dont give up on grounding adding the pwr wire for your h/u.
As for the noise only coming from the front speakers, try isolating the problem. For example, reverse the RCA cables going into the amp (switch front for rear and vice versa). If the problem switches from the front speakers to the rear, you know its either the RCA cable, their connection, or a piece of equipment upstream (the h/u). The when you switch the RCA's, the problem stays with the front speakers, this tells you the problem is downstream (amp or its connections, speaker wire or their connections, etc).

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Okay I did a quick check, and switching the RCA's did not resolve the problem. What should I do to further isolate what is wrong?