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Thread: perfect sound with an invertor

  1. #11
    Variable Bitrate
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    I'm using a Tripplite 140W inverter and have perfect sound. The audio output from the computer goes directly to an amplifier.

    I didn't do anything but ground all the devices well.
    Player: Celeron II 633MHz, 256MB RAM, 20GB IBM 9mm 2.5" Laptop HD (180G/2ms), onboard ethernet/sound/video/tvout, 10"11"x3" case, MPBS1 70W DC-DC PS w/auto-shutdown controller, in-dash lighted switches, 7" NTSC TFT widescreen in-dash LCD, touchscreen, rear-window brake light installed Garmin GPS35 GPS, credit card sized IR remote w/IRMan, mini-wireless keyboard/mouse (sits under seat), PowerMate black knob, MP3s and GPS Navigation (Winamp, CoPilot, SA8.0).
    Car: 1993 Nissan Maxima, Black Emerald

  2. #12
    Bj
    Bj is offline
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    another thing to note, if you use a high quality car amplifier, it will have isolated inputs already, meaning it has a line isolation unit built into it.(well it acts like one anyway) It does this with the type of "floating power supply" that these amps use to get high voltage and current. My Alpine amp runs @ 35V+/- at 3.5A per rail. But because of the switchmode design, the earth point floats.

    This basically means, if your amp is a goody, then you won't have any problems running the sound card directly into the amp. A quick test you can do to see if your amp is isolated, touch the rca input terminal (outside ring) with your finger, if it hums/buzzes, then you know that the RCA earth is floating.

    The rule of thumb is to keep one end of your rca cable earthed only. So if it is earthed at the computer, then you want the other end to be floating. A good amp does this for you, but you can do this by using a Line Isolation Unit, or disconnecting the sheild from the rca cable on the amp end.

    Just something to add....
    BjBlaster! Car MP3 & Carputer!
    bjblaster.com

    "The solution to one problem is only the beginning of another"

  3. #13
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    Oregon
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    Ok, this is very interesting, but I'm not sure I totally get it.

    I'll use my problem as an example. I have a pretty decent 4 channel Sony amp for my primary speakers (no sound problems there) and a cheap 2 channel amplifier for my subwoofer (because I'm broke right now). Obviously, I would expect _some_ problems with the cheap amplifier, but the engine buzz in the subwoofer is VERY LOUD. Oddly, if I connect a Ground Loop Isolator in line with the sub amp, it silences EVERYTHING. No sound at all.

    The audio signal comes out of the computer sound card, and into an EQ. The EQ splits it into front/rear and sub outputs. It's passive, so it's quite unlikely to be throwing any noise in itself.

    I haven't been able to find a good place to ground the sub amp that will make it quiet.

    How can I use this information about RCA grounding to see if it's the cause of my problem?

    -Matt

  4. #14
    Bj
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    try running your sub amp directly from the sound card to see if it has noise...if so, your passive crossover isn't balanced properly, thus causing noise from your amp. I suspect it's a bit strange, as you said your GLI cancels all audio when plugged in.

    Also try putting the GLI straight after the S/Card.
    BjBlaster! Car MP3 & Carputer!
    bjblaster.com

    "The solution to one problem is only the beginning of another"

  5. #15
    Low Bitrate
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    Oct 2001
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    Could anyone tell me why I would be getting very fuzzy output from a portable dvd player, when its powered by a DC adapter and sound is input to the stereo through a tape adapter? It sounds fine when the player is powered by its batteries, but fuzzy when hooked up to the DC adapter....

  6. #16
    Dustin Haug
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    Is the only thing you're changing the power supply? Or are you using something other than the tape adapter when you listen with the batteries?

    It could be the adapter, or if you're saying that all you're changing is the power and it gets noisy, then you power from your cigarette lighter could be noisy. Try running wires from another circuit or directly from the battery and see if it's better.

  7. #17
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    you dont have to earth anything, and dont use those lousey ground loop isulators !
    that just costs money and doesnt do the job well
    just remove the 2 condensators that are in your power supply connecting your power input to the computercase !
    these are the ones responsible for your engine/inverter noise
    ALL yes you read it right ALL your noise and whying wil be gone.


    [ 11-21-2001: Message edited by: gerard_NL ]
    time for the sig:

    '00 VW golf TDI upped to 130 HP - 18" RS 6 wheels - liliput 7" tft in indash housing - epia 10K - SB audigy - caliber 1 fahrad CAP - RF punch amp - hollywood 1.6K mono amp - boston acoustics pro - RF 10" DVD sub

  8. #18
    FLAC
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    Originally posted by gerard_NL:
    [QB]you dont have to earth anything, and dont use those lousey ground loop isulators !
    that just costs money and doesnt do the job well
    just remove the 2 condensators that are in your power supply connecting your power input to the computercase !
    these are the ones responsible for your engine/inverter noise
    ALL yes you read it right ALL your noise and whying wil be gone.QB]
    thats right...... check out this page at my website....


    http://members.optushome.com.au/magn...dware_psu.html

    also grounding the PSU metal casing is a good idea too... and using a central ground point for all equipment works well too...

    [ 11-21-2001: Message edited by: magnetik ]
    Project - GAME OVER :(

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