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Thread: Power noise - the horror!!!

  1. #1
    Variable Bitrate
    Join Date
    May 2001
    Location
    Toronto, Canada
    Posts
    355

    Red face Power noise - the horror!!!

    I just did the first test of my carputer and (drum roll) - REALLY bad power noise! Here is my setup:
    - Compaq Presario 5250 (K6-2 400)
    - 110W proprietary power supply
    - 140W Whistler inverter
    - FM Modulator
    Now, I know what you're all thinking - this is a recipe for disaster! An inverter AND an FM modualtor, this guy deserves whatever happens to him!
    When I hooked everything up, there was an awfull amount of noise comming through the stereo, and I could hardly hear the music from the computer. I added a ground loop isolator, but this did not help. I tried hooking up a portable CD player to the modulator to see if the computer was the problem, and as soon as I turned off the inverter the noise went away and it sounded great, so I know that the inverter is what is causing the noise comming through the modulator. How can I get rid of this? I am thinking of something like this:

    It's a power noise filter from radio shack (part #270-051) and it's rated for 10A. Would this help if I installed it between the FM modulator and the 12V from the car?
    Sorry for the really long post, but please help! I'm so close to having my install completed, plus I'm going on a long roadtrip this weekend and desperately want a few thousand songs at my disposal!!

    Thanks!
    Mike.

  2. #2
    Dustin Haug
    Guest

    Post

    Check all of your system grounds, make sure they're all solid. A ground loop isolator is a band-aid fix. You really shouldn't need it. Also run your power wires away from your audio wires and if you need to cross them do it at ~90 degrees to minimize interference. If after all this you still have noise. Try running an extension cord from your garage to your computer in the car and completely disconnect the inverter. If you have no noise then the inverter is your problem, if the noise is still there, then it's likely wiring. Good luck.

  3. #3
    Variable Bitrate
    Join Date
    May 2001
    Location
    Toronto, Canada
    Posts
    355

    Post

    Thanks for the advice Dstin. The noise is only present when the inverter is powered, so I'm guessing that the inverter is causing some noise in my car's 12V. I tried running a portable CD player into the modulator and it sounded great, as soon as I turn on the inverter (even though the computer is not providing the audio) the noise is there. I just picked up a power noise filter, and I'm going to try putting this betwwen the modulator and the 12V, so hopefully this will help.

    Mike.

  4. #4
    Variable Bitrate
    Join Date
    May 2001
    Location
    Toronto, Canada
    Posts
    355

    Post

    Well, I went out and purchased a 20A noise suppressor (Pyramid Phase III Tenna) and the noise problem has been solved. In fact, I've removed the ground loop isolator as it was not making a difference. I just spent the night in the car playing with the carputer, and the sound still is not great. However, if I use the portable CD player through the modulator the sound is excellent even when the inverter is running, so I'm guessing it's the cheap onboard ESS sound that's the culprit. I'm going to try borrowing the SoundBlaster 512 PCI from my home PC to see if this helps. Thanks for all the help, my installation is almost done thanks to you guys! If anyone out there is wondering, it IS possible to get decent sound using a modulator and an inverter, but the sound quality is on par with an FM radio station so it's far from excellent. If only I didn't have a leased GM car with that stupid 1.5 DIN faceplate then I'd put in a new deck that could take an input. I think the carputer is going to play a huge factor in vehicle selection when this lease is over.

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