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Thread: Some help trouble shooting a ground loop!

  1. #1
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    Some help trouble shooting a ground loop!

    So i've been hunting down this GL for a few weeks now and am sick of taking out my setup and putting it back in. The usual alternator whine. So here is what i've tried so far.
    I'm storing my system in my glove box.
    I have 8 guage wire going from my batterby to m4atx, and then my atx back to my battery negative terminal.

    1. USB sound card, complete bust no help at all.
    2. Initially i had my motheboard mounted in a little minitix box, when so i took it off the m4atx and connected it back to a ac-dc psu, and no noise, so its a car issue not my pc.
    3. Went out, bought an aluminum sheet and went and waterjetted out a baseplate custom to my glove box and mounted EVERYTHING on that. I used same guage wire 8g, connected a small piece of it from my m4 atx to the aluminum sheet, and then grounded the whole sheet to my car chassis. This actually helped the most so far and now i can listen to music if i listen to it loud it drowns out the remaining whine. But its unbearable if i ever want to watch a movie, so i have to keep going.

    My only remaining theory:
    my sound setup....
    PC > clarion equalizer > Amp 1 > front component speakers
    > Amp 2 > subs

    Now my two amps are in my trunk grounded to some bolt. My pc setup being in the glove compartment is all grounded to some other bolt 6 ft away. My grounding points may be causing the difference in potential. I'm going to try and test a common ground see if that helps. But please feel free to analyze and spit ball ideas.

  2. #2
    FLAC PhilG's Avatar
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    Assuming all of the basic rules have been followed (power wires on one side of the vehicle, signal wires on the other, Wires on cross at 90 degrees, etc) then:

    I would remove the EQ from the setup and test. Then I would run RCA cables with the built in ground wires/terminals and ground at both ends. My next move would be to run all power wires relating to the system to a stand alone battery then one by one move them back onto vehicle charging circuit. Next step might involve dynamite......
    My 2007 Ford F350 Work Log located HERE

  3. #3
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    I have two audio sourced wired to the EQ, my PC's audio, and a aux line for phone plugins. When i switch to aux line it's crystal clear. So i don't think its an EQ issue. I've vaguely heard of grounding rca cables, how would you do that exactly? grounding the actual metal piece on the outside of the rca plug?

  4. #4
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    Well I took a guess at what i thought meant. So there is the inner positive portion and then the cylindar ring outer negative portion. So i wrapped some grounded wire around it and it helps out a lot. At this point if It never got any better i would eve be able to bear this i can now watch a movie. Really as long as its not silent you can't notice the whine. HOWEVER if there were a way to completely eliminate the rest I'd take it.

    I tried grounding just to a nearby bolt and also from my grounding bolt of my amps, and i noticed the amp bolt grounding produced cleaner results, makes sence.

    But I'm having a slight issue seeing as apart from twisting the grounding wires around the rca terminals, i can't figurea more mechanically stable method of connecting these ground leads to my rca lol, for those of you doing this how is this typically done?

  5. #5
    MySQL Error soundman98's Avatar
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    ^that's the way i typically do it.

    have you tried combining everything to a common ground point yet?

  6. #6
    FLAC PhilG's Avatar
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    Cables like these http://www.thesource.ca/estore/produ...roduct=4208026

    allow you to connect at both ends easily.
    My 2007 Ford F350 Work Log located HERE

  7. #7
    Newbie Gonkulor's Avatar
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    Quote Originally Posted by bossman137 View Post
    So i've been hunting down this GL for a few weeks now and am sick of taking out my setup and putting it back in. The usual alternator whine. So here is what i've tried so far.
    I'm storing my system in my glove box.
    I have 8 guage wire going from my batterby to m4atx, and then my atx back to my battery negative terminal.

    1. USB sound card, complete bust no help at all.
    2. Initially i had my motheboard mounted in a little minitix box, when so i took it off the m4atx and connected it back to a ac-dc psu, and no noise, so its a car issue not my pc.
    3. Went out, bought an aluminum sheet and went and waterjetted out a baseplate custom to my glove box and mounted EVERYTHING on that. I used same guage wire 8g, connected a small piece of it from my m4 atx to the aluminum sheet, and then grounded the whole sheet to my car chassis. This actually helped the most so far and now i can listen to music if i listen to it loud it drowns out the remaining whine. But its unbearable if i ever want to watch a movie, so i have to keep going.

    My only remaining theory:
    my sound setup....
    PC > clarion equalizer > Amp 1 > front component speakers
    > Amp 2 > subs

    Now my two amps are in my trunk grounded to some bolt. My pc setup being in the glove compartment is all grounded to some other bolt 6 ft away. My grounding points may be causing the difference in potential. I'm going to try and test a common ground see if that helps. But please feel free to analyze and spit ball ideas.
    Bossman137 it sounds, no pun intended, like you have tried the hard stuff. To bad everything gets so embedded inside the vehicle where-as troubleshooting does become difficult. Besides the EMF/RF bouncing to and through your boxes, which is the direction your going by grounding everything and shielding what you can, it's your power that is the problem. Since your clean when plugged into your aux, that aux drive has it's own power and battery. I would suggest you put filters in the power wires for your carputer and amps. You can also get your alternator checked to make sure it's not bleeding out unnoticeable electrons.

    Best regards
    Gonk

  8. #8
    Variable Bitrate djvillar's Avatar
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    1. Leave everything where it is.
    2. Disconnect the comp and EQ from the amp.
    3. Connect ipod or whatever mp3 player with a 3.5 to rca jack (a really short run).
    4. Turn the amp on. Is there noise, if not, play some music from the ipod, still no noise,.. move on to next test.

    5. Connect the rca's from that run from up front to the amp. Connect the ipod from up front. If there noise now, you know the rca's running the car length is the issue. If not, now connect the EQ have the ipod near the comp and connect to the eq. Test sound. If there's noise,.. then its the

    THE EASIEST SOLUTION:
    Move the computer to the trunk, run short rca runs to the computer. Done. If you want acces to turn the computer off, extend the power/reset/on off to the mtx buttons to the front.

    Trying to have emi under control around the dash is futile. Car manufacturers use the highest (thin) gauge wire they can get away with, copper is expensive. The thinner the wire the more power leaks you get. Moral of the story, if you don't want EMI, don't play around power lines. Stay far away from them.

  9. #9
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    I tried all that, i troubled shooted about every possible scenerio.
    grounding rca helped a bit as well as grounding motherboard to a big piece o aluminum and grounding that to car chassis. But it was so weird everything just came to be as it should be one day. I was disconnecting cables and plugging back in and it just worked... Its nothing big i did i tried all the big things.
    It was thanks to persistance i guess.

  10. #10
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    This post is way late for the dates of the topic but maybe in a future search the idea here will help someone.
    1.) Put a capicator on the alternator. (sold as a noise filter - or do you own calcs and select the best stuff)
    2.) When dc wires are twisted there is a canceling out of some magnetic field. This may help. Problem in a car is you need to undo whatever harness's there are twist the wires, which will make them shorter - possibly requiring you to add wire length. And totally mess up the nice wire package.
    3.) Take a close, thoughtful look at all the devices in the car that create sparks: the plugs, the fan motors, the alternator, windshield washer pump, windshield wiper motor, electric windows & mirrors, etc. A capacitor and diode working together, close to the offending device can greatly reduce electrical noise near the source.
    4.) Shielded wires (there is a great selection) will prevent some noise from either escaping a source wire or entering a device experiencing noise. Again, this may totally mess up the factory harness.

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