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Thread: Noise, Noise, and no Noise

  1. #1
    Variable Bitrate Splash-X's Avatar
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    Noise, Noise, and no Noise

    Ok, so after migrating from a on-board sound card that simply did not work to a Turtle Audio USB sound card I've run into a problem.

    On my bench in the house it sounded perfect. The audio was supurb.

    I have a Mazda 3 with a factory aux jack. I took the acc line directly from the radio harness and I also grounded the carPC to the ground in the radio harness.

    I took it out to the car, hooked it up and gave it a shot. With the engine on acc so the radio would come on I turned the carPC on and it booted. Radio sounds fine. I switch over to the "Media" (aux jack) and I hear fuzz. The engine is NOT on at this point.

    Crank the car over to turn it on and when the car runs you get the alternator noise.

    So, maybe a bad audio cable. Swapped it out, nope, not the cable. Plug in head phones and no noise what so ever (other than the audio of source).

    I hooked up my house dvd player using a power inverter and a RCA to 3.5 standard audio jack (monster cable) and the audio is just fine, even with the inverter

    So, I'm left with noise when using the Aux Jack with the carPC only. Plug anything else in to the aux jac and it works. Plug headphones into the carPC and the audio is great.

    What gives? Yeah, I'm sure you're going to tell me its the ground wire or maybe even the acc wire. What give, shouldn't the radio do the same thing when I switch back to it while the carPC is on?


    I did run across this site:

    http://www.crutchfieldadvisor.com/IS...de.html?page=2

    I'm not sure where I should supress the noise though. Any thoughts?

  2. #2
    Variable Bitrate
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    Don't tap into existing power wires when connecting your car pc. Run a new wire direct to the battery.

  3. #3
    Variable Bitrate Splash-X's Avatar
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    I ran the powe from the battery to the carPC directly. I ran the ground from the radio to the carPC and from the Remote/Acc to the carPC.

    I understand what you're saying by running the ground to the carPC but I'm not looking to run more wires until I can isolate what the problem really is.

    The only time I get noise from the alternator/power is when the audio cable is hooked up to the carPC and the radio is set to Media (aux).

    1.) The car can be on radio and the carPC on and plugged into the aux jack but no noise
    2.) The car can be on Aux with the carPC on and the aux jack disconnected but no noise
    3.) The car can be on Aux with the carPC on and any other audio source hooked up to the Aux but no noise (including a mp3 player, laptop, dvd player, tested them all).

    ONLY when the carPC is on, hooked up to the aux, and radio on Media do I get the noise.

    From my understanding, if it were a grounding issue the noise would be present ANY time the carPC were on, not just when it was hooked up to the aux.


    I'm mainly looking for some sort of resource (person or web page) that can outline causes for noise and how to correct them. Car Audio is not really my thing so I don't know alot. I will run a ground wire today to the battery and hook up the aux to the battery line to see what I get but I have a feeling its going to be the same, but you never know.



    thanks for your input, it was much appretiated (even if it doesnt sound like it from my above post)

  4. #4
    Fusion Brain Creator 2k1Toaster's Avatar
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    It sounds exactly like a ground loop with the PC. Obviously your HU isnt going to sound weird because it is not in a ground loop. Your PC is because you even said you grounded it to the factory harness, which is rediculous.

    Ground it properly.
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  5. #5
    Variable Bitrate
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    What Toaster said.

    I ran the ground from the radio to the carPC and from the Remote/Acc to the carPC.
    The electrical power needs to travel down the ground as well as the +power. Hence sharing of either +power or -ground with factory equipment on factory wires is a big no no.

    If you don't want to run a long ground wire, go direct to the chassis. Remember to sand back any paint and bolt it down solidly.

  6. #6
    Variable Bitrate Splash-X's Avatar
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    2k1Toaster,

    Why so negative, I am trying to troubleshoot the problem. If you don't approve of what I have done, or what anyone else on the forum has done for that matter, simply post constructive criticism for ways for them to improve their knowledge and their setup. Being flat our rude helps no one at all.

    As i said, car audio is not a strong area for me so I knew OF a ground loop but not WHAT it was.


    pokki,

    the Pc is under the passenger seat and provides very little access to mount to the chassis. It would be just as easy to run the ground wire to the battery, that way I can be sure to have a proper ground.


    Can I still use the radio Acc line for PSU? for the ignition sensing of the PSU.

  7. #7
    Fusion Brain Creator 2k1Toaster's Avatar
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    Quote Originally Posted by Splash-X View Post
    2k1Toaster,

    Why so negative, I am trying to troubleshoot the problem. If you don't approve of what I have done, or what anyone else on the forum has done for that matter, simply post constructive criticism for ways for them to improve their knowledge and their setup. Being flat our rude helps no one at all.

    As i said, car audio is not a strong area for me so I knew OF a ground loop but not WHAT it was.


    pokki,

    the Pc is under the passenger seat and provides very little access to mount to the chassis. It would be just as easy to run the ground wire to the battery, that way I can be sure to have a proper ground.


    Can I still use the radio Acc line for PSU? for the ignition sensing of the PSU.
    Ground Loops are covered multiple times in the FAQ, and also return a bagillion results when you search all with what it is, hence the bluntness.

    Also if you are under the seat, then does the seat have a seatbelt? I bet you that is bolted to the chassis. Ground it there.

    And running to the battery is a good way, but you have to be even more careful. If the wire passes by audio cables, video cables, or whatever, it is just as bad if the +!2v power cable passes by. So you are making your chances of having a ground loop even higher if not done properly.
    Fusion Brain Version 6 Released!
    1.9in x 2.9in -- 47mm x 73mm
    30 Digital Outputs -- Directly drive a relay
    15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
    Buy now in the MP3Car.com Store

  8. #8
    Variable Bitrate
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    Can I still use the radio Acc line for PSU? for the ignition sensing of the PSU.
    Yes, using the headunit/radio acc for ignition sensing/remote turn on is perfectly acceptable.

  9. #9
    Variable Bitrate Splash-X's Avatar
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    2k1Toaster,

    It isn't a problem of not having searched the forum. Let me put it this way, what good is searching for "grounding loop" to get results that say "hey, don't do it" if you don't understand what it is, what causes it, and the symptoms.


    I'm having trouble understanding what +!2v is. I think you may mean +12V (the power line from the battery to the carPC) and if so, that is where I had intended to run the wire but from your advise I see that doing so may also cause another ground loop.




    As for the actual grounding to the seat belt, I'll look in to it to see if I can trace where the actual bolt for it is and if it is easily accessiable.

    Thanks for your help

  10. #10
    Fusion Brain Creator 2k1Toaster's Avatar
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    yes +!2v = +12v.

    Basically run all the power lines, positive and negative on 1 side of the car, and data signals like video and audio and data (usb), on the other side. If you can run down the centre, then seperate the video from the rest. But usually you only have 2 channels on the far left and far right.

    And all seats are bolted to the chassis in at least 4 places. Usually covered by little bits of plastic that just snap off. Your seat probably goes back and forth right? Look at the very end (towards the back of the car) of the track, and there should be a little cover there over a bolt. That is a good bolt. Just sand away the paint and greasy grimy stuff.
    Fusion Brain Version 6 Released!
    1.9in x 2.9in -- 47mm x 73mm
    30 Digital Outputs -- Directly drive a relay
    15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
    Buy now in the MP3Car.com Store

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