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Unread 11-02-2010, 08:41 PM   #1
PeriwinkleZJ
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engine/eclectronics noise in subs

I installed my 2 12" kenwoods powered by a 1250W acoustix amp in my girlfriends car a while ago, and they've always had this hum to them which gets higher, and lower with the engine RPMs and with the use of power windows, etc. Which is what I assume is alternator noise?? I understand that this would normally mean that the power wire, and RCAs are crossed, but this is not the case. I wired them on the opposite sides of the car. I re-did the ground with seemed to help just a little. Is iut possible that I have a setting too high on the amp, or maybe there is some interferance that I'm looking past? Such as the RCAs crossing a wire that gives power the the power windows and such. Which doesn';t explain the hum caused by the engine. Also when the radio is turned on it gives a loud thump and then fades into the hum from the engine. When the car is not on there is no hum at all, unless a light is on. I'm not too electronic savy so this is tough to figure out. Everything I've searched says that the power and RCAs are crossed, but that simply isn' the case. Before they amp and subs were in her car they were in my jeep which I flipped, and could have possibly damaged the amp although it was secured to the seat, and did not move. Any help/tips are appreciated.

/rantoff

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Unread 11-02-2010, 09:05 PM   #2
97Formulaws-6
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Sounds like a bad pair of RCA wires. This based on you stating everything was checked and nothing is crossed. Does the car have the stock headunit and RCA adapters or an aftermarket headunit?

Also make sure the ground from the amp is going to bare metal, not painted metal.

How is the remote wire hooked up? (AKA what's supplying power to this?) This is typically the thumping you hear when things turn on.
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Unread 11-02-2010, 09:05 PM   #3
odinseye84
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I have installed countless systems, and if the system has a sub and amp only, no amp for the speakers, it doesnt matter if you run the power wire together with the RCA's since the crossover usually filters out the high pitched whine. Installed at least 50 systems like this with no problem.

Sounds like you have a ground loop issue. Is the ground securely attached to a sanded, bare metal part of the chassis? Are you using high quality shielded RCA's? Could also be a problem with the amp/head unit, but its usually ground.

If your gain is too high that can exacerbate noises like this... do you mean its a power acoustik stax 1250watt amp? If so, it does not put out 1250 watts... more like 500.

You can use "muting plugs" to find the source of the noise.
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Unread 11-02-2010, 11:11 PM   #4
PeriwinkleZJ
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When I redid the ground I scraped it clean, and made sure it was incredibly secure. The head unit is aftermarket, and worked absolutely fine when it was in my jeep. The RCAs are brand new. I know about the power acoustix, it sucks *** I regret wasting my money everytime she turns her radio on. I'll go back and check the ground tomorow. I'm not too handy with a multimeter so correct me if I'm wrong. To check the ground I need to check ohms from the power to the ground?
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BUILD THREAD:http://www.jeepforum.com/forum/f197/...-jeep-1133312/
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Unread 11-04-2010, 06:38 AM   #5
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Another thing you can check is to make sure the head unit is grounded also. Put the multi-meter away. That is not the correct way to test for ground. Ohms setting is for testing continuity and measuring resistance. It can be researched online. It is too much for me to explain here. I am not much on typing instruction. Google it and you will find better instruction. Here are a few I found:
Multimeter Tutorial
How to Use a Multimeter - wikiHow
How to Measure Resistance with a Multimeter :: Electronics and Radio Today

Good luck.

Re check all grounds and always have a spare set of RCA's for testing. There are great troubleshooting techniques available online.
Here are a few. I love using google for questions too.

Car Audio Noise Troubleshooting
Crutchfield Tech Support: Noise Problem Troubleshooting: Whining noise
How to Remove an Alternator Whine From a Car Stereo | eHow.com
Google
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Unread 11-04-2010, 09:45 PM   #6
PeriwinkleZJ
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Yeah I've never been much for electricity. I'm more of a it's broke now replace it, rather than trace wires for an hour and still have no clue what's wrong kind of guy. Thanks for the help, and the links. If I can't figure it out now then I need to get a someone else to look at it.
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BUILD THREAD:http://www.jeepforum.com/forum/f197/...-jeep-1133312/
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Unread 11-05-2010, 12:56 AM   #7
odinseye84
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Ah I forget the head unit ground as someone mentioned...

Grab another pair of RCA's and just plug them in and throw them back to the trunk area to see if RCAs are the problem.

Also, do a search on "muting plugs". This is a common way to track down noise.

NOISE ELIMINATION CHECKLIST
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Unread 11-05-2010, 10:35 AM   #8
gily25
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You can always pick up a ground loop isolator. It's not the way to fix this but it will reduce the noise while you work through the problem and should make the g/f happier about the install.
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Unread 11-05-2010, 10:42 AM   #9
Richd1963
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Quote:
Originally Posted by gily25 View Post
You can always pick up a ground loop isolator. It's not the way to fix this but it will reduce the noise while you work through the problem and should make the g/f happier about the install.
This is true.
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Unread 11-05-2010, 11:03 AM   #10
odinseye84
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FWIW, i have tried ground loop isos at least 10 different times in installs, and they never did squat... worth a shot though, i guess.
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Unread 11-05-2010, 01:22 PM   #11
Richd1963
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They can bring it down some, but if the noise is bad, it will take some other troubleshooting and fixes to totally eliminate it.
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