plagued by engine noise

i have a 05 chevy avalanche w/ kenwood kvt512 and 2 mtx thunder amps. im getting alternator whine bad! so far ive tried grounding the rca's to the deck with no result. ive tried running a ground from the deck to the amp ground, ive tried new stinger twisted rcas, ran diffrent ways, ive tried grounding the amp directly to the battery, i grounded the deck and the housing under the dash. rca ground loop isolator helps but its still there. if i unplug the rcas the noise goes away. please help im ready to throw all this away and go back to my factory system!

You either have poor grounds creating a ground loop, grounded speaker wires, amp input gain way too high, a defect in your vehicle's ignition system or defective amps.  Read the grounding sticky in the Hot Topics section and verify your ground return resistance first.  Also make sure you have no line level or speaker wires laying across the vehicle's ECU computer.

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Try also taking a short ground wire length and grounding the shield of the rca cable where it attaches to the deck.

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Top Secret, I can tell you but then my wife will kill me.

The RCA shield connection is broken on the inside of the amp.  Remove the screw from the RCA input of the amp, now gently pussh the jack to the center of the amp, if it moves easily, the leg at the bottom, where it attaches to the circuit board, is broken.  Which amp do you have?  Does it have an input and an output jack?  If so try grounding the output jack.

Thanks for the suggestions! I took the amp apart and the RCA grounds are good , if I ground the rcas at the amp I get a loud hum . I moved the sub amp away from the other amp and this helped. I now can tolerate it I also turned down the eq and freq knobs on the amp. But once I plug the rcas back into the sub amp I get the engine noise again. The sub amp rcas are coming from the 4 ch amps output. I really think the problem is the amps are just cheap lol and maybe I should go back to Phoenix golds zx450 !

It is a very common problem for MTX amps to break the ground connection at the circuit board.  They usually pass a visual inspection.   With the screw out and the RCA cables unhooked from the amp, check the resistance between the shields of the input and output RCA jacks. 

Make sure to check your battery terminals are clean and tight too. You should also clean and secure the main battery ground. It is located just beside the driver's side tow hook. They are always bad on these trucks.

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sparky

Hello, I'd like to put my 2 cents in on this topic. I've owned GM trucks for a very long time, and I own an 08 HHR at the present. Before the HHR I had an 04 Avalanche. I've learned this about a GM vehicle: there is NO decent ground point except for the negitive post on the battery. Save yerself alot of agony and ground EVERYTHING back to the battery. I know it sounds extreeme, but it works great, and if you add up all of the frustration AND subtract the extra cost it IS worth it !! Just stop and think, if you are grounding to the body, you're putting faith in an awful lot of spot welds, body putty ect. And DEFINITLY ground your head unit this way. As far as sound systems go, GM is still stuck on AM radio for their factory methods of grounding,power supply ect. Thanks for letting an old feller rant !

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