Need Help From All You Car Stereo Guys...

[codygjohnson]

So I've always been able to throw together a pretty good sound system even though I don't really keep up with car stereo technology...but this has thrown me for a loop:

In my boat, I've got a cheap, yet very adequate sound system. I'm running:

2 x 12" Sony Xplod subs on a 1200w Xplod amp
4 x 6" Sony Xplod full range on a 1200w Xplod amp
2 x 6' Sony Xplod full range on a 600w Xplod amp
2 x 4x8" Sony Xplod full range on a 600w Xplode amp
(I know its not the greatest...but I got a great deal on the Sony stuff.)

I also ended up having to add another battery and replacing the alternator to get some more juice out of it. It was running flawless for a couple seasons. Sounded absolutely fantastic and got lots of praise on the lake.

Flash forward to last season: I'm replacing the alternator (again) and if any of you have ever worked on an inboard, you know how tight it is... I've got a hot wire straight off the battery pushed to the side and I'm listening to the stereo as I work. All of the sudden I get this awful sound comming out of the speakers. I look over and the 12v alternator wire is sitting on one of my subwoofer leads. I yank it off and flip out, but everything seems to be fine, stereo is blasting and all is good. I get it all back together and start it up...AAAAAAAAAAAAAAAAAAAAAAARRRRRRRRRRRRRRGGGGGGGGGGGGG!!!!!!! There is TERRIBLE engine noise comming out of every speaker. Ignition, alternator, and blower fans all produce this electrical noise.

I've pretty much ruled out the alternator, I just had the shop replace the plastic internal fan with a metal one. I'm assuming I blew out the filters or ground loops on the amps. I've been planning to take everything out and reinstall one by one to see if it's all or just one amp that's doing it, but before I do, I thought I'd see if anyone had any ideas on what happened and if there is some kind of a fix for the problem, like noise filters or something that I could install cheap to keep from replacing the amps. It's really tough to get to all my amps to work on, so I'm trying to get as much advice as possible before I start working on it.

Any info you could give me would be much apreciated.

 

[dcfis]

How good is the alt to ground connection? Is the wire of adequate size for the uprated alt or did you just use the small factory one? In cars thats usually the biggest problem. Since you had a major surge I would check or replace all RCAs as those cant carry large voltage and are easy to damage the grounding legs creating huge ground issues with all that equipment. After that I would Run a large gague wire to the alt grounding point and use a brass grounding block to connect all your equipment to the same point (even the stereo)

 

[codygjohnson]

Great advice on the RCA cables, I never would've thought those might give me trouble. They'll be easy to replace as the amps are right under the stereo, <1' runs.

 

[codygjohnson]

I replaced the alternator wire with a battery cable when I upgraded so it should be good. Everything is grounded well to the grounding block on the boat except for the stereo. It's connected to the factory wiring harness, so no telling where it's going. I'm going to go ahead and connect it to the amp power cables as I know they're grounded well and it'll be an easy task.

I'm digging out an RCA to phono adapter too so I can plug my iPod straight to the amp inputs (they are easy to access) and see if I can isolate problems with the individual amps or stereo before I try to pull the whole thing out.

 

[MR Redneck]

You can get a noise suspressor from radio shack. Put it on the power wires to the radio. that will take all of the alternator noise out.
The noise you hear is always there. More power makes the noise more noticable. Try listening to the radio without the engine running and it wont make the noise.
Filter it out and you'll be fine.
BTW, Fosgate and Source already has those suspressors built into the components. Sony doesnt.

 

[Rum Runner]

I know enough to be dangerous, but by no means an expert. In my personal experience, it has always been a grounding problem. I have tried several filters and they never worked for me. Most recently, it was my antenna not grounding well and causing noise form everywhere including a POP when I hit the brakes and my taillights would go on. Another time, it was something faulty electrical item in my transmission/ignition that the dealer replaced and fixed the problem. My only advice is isolate components so you can trouble shoot a few pieces at a time and swap stuff and then start checking all your grounds.

 

[codygjohnson]

It ended up being the head unit ground. Must have flashed when the power surged. I tested each amp with my iPod and didn't get any noise. Hooked the head unit leads to the amp leads and it's crystal clear. Now to shove it all back in the compartment and zip tie all the damn wires back in place...

Thanks for all the replies guys!