ground loop issue?

hey guys I just finished up the system in my f350. 2 amps 1 for my speakers and 1 for my subs. a ran 2 separate power wired for them and grounded them both individually to the body of the truck. I have a cheap pioneer deck in it that I had laying around from my last truck (,also had a sound system in that with no issues with same amps).

Im having what I would think is a ground loop issue. I hear noise through the speakers and subs mostly through the subs its a pretty loud humm. The hum doesn't occur unless the truck is running and it follows the engine rpm. The only time it will go away is the the head unit is turned off but when its on it sounds the same no matter if the volume is on 0 or 50 it sounds the same. I was thinking it could be the rca cables but when I unplug the rca's the noise is still apparent. also the gain is up high and the subs are not loud at all which makes me think it could be the rca's still? idk im lost any help would be appreciated!

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Im at a little bit of a loss at this point I've tried the pico fuse fix by grounding my rcas jack to the head unit chasis. I've also grounded the head unit and no changes at all. No noise when head unit is off but when its on it makes noise even when all rcas are unplugged from the amp and head unit. Any suggestions at all at this point would be great

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Have you tried grounding your amps to the same spot? You mentioned they're individually grounded and that could be causing your issues. If it still happens with rca's unplugged the noise isn't coming from your signal. Of course the noise will go away with headunit off because the remote wire should be turning the amps off.

I would unplug the RCA's at the amp to see if it goes away. If the noise goes away, then it's definitely something in the signal chain.

when the rca's are unplugged it changes nothing it still makes the engine noise. it only goes away if I cut power to the amp

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I have not tried grounding both amps in the same spot im thinking that might be next thing I try. I did however ground my sub amp in 3 different locations with no change at all. If grounding them to the same spot doesn't work im thinking maybe the old school rockford has an issue? I literally just pulled it out of my old truck a few weeks ago though and had no issues with it before

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Also make sure the paint is scraped away good and sanded clean at the grounding point and make sure it's in a location near the frame. My gut feeling thinks you just have a classic ground loop from different impedance between the two grounding spots. If it's isolated to just the sub amp do you know someone you can borrow an amp from to troubleshoot with?

yes I have a buddy with another old school rockford I can throw in. also have a system in my mustang done the same way and it all worked out just dont feel like ripping the amp out of it to possibly have the same outcome. I will ground them in the same location and give it a shot. Just strange I've wired the system in my previous truck and mustang and also grounded them in 2 different spots and it worked out. Guess every vehicle is different. Should I put both just under the same bolt? And of course I made sure there was clean metal i was grounding to

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hey everyone reporting back... so at this point I have narrowed it down to i think I need a new amp. I put the ground to both amps under the same through bolt I drilled a hole through the floor sanded the paint off both sides and through bolted them both down and no change. I bought a new Sony head unit bc my pioneer was a cheap junk one and that did nothing I ran new rcas for the amp and that did nothing. The only thing that changed it was swapping my buddies old school rockford amp in then it made the noise very quiet unless you have your head up to the subs you can't really hear it. I think a new amp may solve my issue

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