If you have a noisy 12V supply try a capacitor. Get a large computer grade capacitor from a local electronics wholesaler. 22,000 uF should do the trick. Voltage rating is unimportant. Connect the + of the capacitor to the + of the stereo and the - of the cap to the ground wire. Put it as close to the stereo as possible. Also you can try (along with the capacitor) a large 1 H choke. Put it inline with the 12 volt wire. If you have a noisy 12 V these two things will solve that problem. They'll be expensive, though.

I think your issue is simpler than that. Improperly shielded RCA cables (a classic problem), or one of your speaker wires touching ground, perhaps or an internal ground loop in one of the components.

A surprisingly good quality (and inexpensive) long shielded RCA cable can be found at Radio Shack in lengths up to 20 feet.

Try this first (after you verified the speaker wires and the RCA cables). Take one of the RCA plugs apart and de-solder the ground shield from the plug at the amplifier side, but not at the head unit side. The shield will be connected to ground at the source but not at the destination. This will eliminate any ground loops for sure including internal ground loops within the equipment. If this solves the problem then the equipment you bought is either defective or of low enough quality that you should consider something else. However if the un-grounding trick works, you may want to stick with it anyway. The system will work fine.

 

I was just wondering if you were going to add any subs along with the rest of the great gear you have added. I, too, have begun that great journey towards reaching audiophile Nirvana in my Magnum. Started out with some MB Quart DTE169s in the rear, DKE116s in the front door, an 8" powered Bazooka sub (temporary until my boxes get completed). The sub boxes will fit in the storage space on each side of the storage area and will hold 1- 10" isobaric sub in each. The whole thing is going to be powered by one amp, the Infinity Reference 5760a which delivers 56W x 4 + 107W x 2. You can check all the amp specs at
http://www.crutchfield.com/S-lsiNS2e...fo&i=108R5760A

I'll post pics of the install when it gets completed.

 

I know for sure it's not a grounded speaker wire, or ground loop. Radio and amp are grounded at the battery. I had all the speakers laying out in the open with about 3 feet of wire connecting them to the amp. I used muting plugs (basically the same as the rca trick you describe below) and the noise is still there.

Tried several different pairs of RCA's as well. Rockford Fosgate, Scotsch, and Monster Cable.

Both the head unit and the amp have been tried in a different vehicle with no problems.

Here's a kicker
with the 6.5" components not plugged in to anything, just a loose wire laying in the front passenger floor, I can hear the noise coming out of the speaker...

If I skip using the amplifier and power the speakers directly from the head unit, there is no noise. But I also tried 3 different amplifiers, they ALL had the problem.

I was also going to hook up my Concept 800 amp powering a 15" treo sub, but it too gets the noise. So I've narrowed it down to a really noisy car. I don't know if this is common with all magnums or just mine. Is anyone else running an amplified aftermarket system???

Talking to local installers, they recommended some other things to try that I did, and it didn't help.
1) feed the amp via the high-level input connector instead of RCA's. Hi-level speaker wires are less likely to pick up noise than rca's. Didn't help, noise still there.
2) connect the hi-level of the head unit to LOC's and then feed the amp that way. Also the same thinking, plus LOC's can act as ground loop isolators. Didn't help, noise still there.

I can take the RCA's from the amp, power it up, WITHOUT the head unit, and just touch the center pin of the rca cable with my finger and the noise is there. If I touch the center pin to a ground on the car, the noise is even louder.

I have a video with the noise, will put a link up for it later.

 

Divx Video with noise

 

Have you tried grounding the amp by itself on a bare piece of metal on the car right by it, as short of a wire run as you can. How close is the amp to the radio? And why didn't you use the factory speaker wires? In all your wire runs have you crossed any wires?

 

I know this sounds stupid, but did you mistakenly take the 12V supply from the CAN-Bus wire? Or did you run dedicated fused lines directly from the battery?

Henry

 

Yes, the amp was originally grounded directly to the body with a 1' length of 8 gauge wire.
Didn't use stock wires, as I needed the wires in the back of the car where the amp is.
I have had the radio in the dash and amp in back, as well as the radio next to the amp about 2' away from it...

No crossed wires. Have tried stock speakers, and 2 sets of aftermarket speakers. All same results.

Amp and radio were both powered via direct connections to the battery.

Keep in mind I get the noise with the radio sitting inside my house, no where near the car. It's not a radio issue... It does it with 4 different amps that all work in other cars.... Illiminates amps. Have tried numerous sets of speaker wires, rca wires, etc...

 

Since you get the noise with the radio in the house and car. It would seem to me it is the radio. But you said it's not? Have you tried a different radio? if you did everything Henery said, then I Would be looking at some piece of the puzzle is faulty. I would start by tiring a different head unit. Or you have come across a Magnum problem. What Radio are you tiring out?

 

You didn't understand what I said..

I can take the radio, box it up, return it to the store, come back home, turn on the amp, and the noise is still there. So it's not the head unit.

I can even take everything out of the system, put in ONE speaker (front right 6.5" component) not connected to ANYTHING, and I can hear the noise in the speaker.

 

Poltergeist.

Or something inside the door is causing the speaker cone to vibrate.
It isn't possible the the speaker can buzz with the same loudness whether its connected or not unless there is something vibrating inside the door causing the speaker cone to resonate in turn.

Have you tried to short out the input RCA jacks on the amplifier to see if your amp is generating oscillations due to a noisy environment or bad power (or a crappy amp - unlikely if it's an Autotek).