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Speaker Hum and buzzing

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  • Speaker Hum and buzzing

    Hey I am pretty new at this stuff but I have always been interested. I got the idea to make a carputer out of my mom's old HP laptop to try and be as cheap as possible. I got a 400 watt power inverter and tested it out for the first time in my car (95 toyota corolla). whenever the audio jack is plugged into the laptop and the car is on there is a very annoying hiss/hum/buzz coming from the speakers. Even when everything is off. For instance when i plug the power inverter with it switched off to the car, either cig lighter or straight to battery, it starts making the sound when the key is turned. when i turn the inverter on it gets louder. And when i boot the computer it gets louder still. its very irritating and i can easily say it is intolerable when listening to music. I have a feeling something needs to be shielded and/or grounded but i don't know what. Any ideas?

    ps. none of these sounds were made when plugged into the house at all.

  • #2
    This is called a ground loop. Search on terms "ground loop" and check the faqs for advice on how to remove a ground loop.

    My advice would be to not to use an inverter but instead try a car adaptor for the laptop that is DC powered and plugs into the cigarette lighter. Inverters - especially inexpensive ones, are known for introducing noise into the system.

    The way to test if your inverter is the culprit is to run the laptop off of battery and remove the inverter from the system. If the sound improves, the inverter is certainly part of the problem.
    Originally posted by ghettocruzer
    I was gung ho on building a PC [until] just recently. However, between my new phone having internet and GPS and all...and this kit...Im starting to have trouble justfiying it haha.
    Want to:
    -Find out about the new iBug iPad install?
    -Find out about carPC's in just 5 minutes? View the Car PC 101 video


    • #3
      Inverter- CarPC

      Inverters are really the best way to go.

      You will get ground loop feedback from any Power supply due to the name (GROUND LOOPBACK) Means it goes in a circle. You ground the stereo and the pc and the buzz and noise will be there no matter what source you use "Unless it has a ground loop filter built in".

      There are tutorials out there if you know anything about soldering. You can pick up two old modems at the thrift stores for a couple dollars and make a ground loop feed back filter. This will be the same as any you buy. You can also buy one. some places sell them really cheap.

      Do a search there is tons of information out there on this.