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Thread: got sound?

  1. #1
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    got sound?

    Hola people.. Been a while since I was last here.

    I just got my epia 800 mobo back after 6 months. I sent it for repairs when I found out that no sound was coming out, I think I must've fried the built in sound card.

    I setup my carPC thru an inverter and a small 140W psu. I tested everything on my table desktop and it was all working fine. Then I put the setup into my car, and it boots fine. Just when I connect a stereo cable from the built-in sound card of the EPIA to the aux-in of the car radio, I hear the epia shut off.

    To my dismay, I realized that the sound card was burnt again.

    I put a lower fuse in the inverter and bought a cheap sound card to plug it into the PCI slot. However this pci sound cards have a higher tolerance than the built-in sound card on the epia. When I connect again the stereo cable from the audio-out of my sound card to the radio, it shuts off.. but this time only the fuse gets burnt.

    I went to get a ground loop isolator.. it looks like a closed cylinder but I think it has transformers inside. I made a couple of stereo-to-RCA male and female connectors because the input/output of the isolator are RCA type connectors. So when I connect the setup to the radio using the ground loop isolator, the fuse no longer blows and I can listen to the sound fine. I think this works because no longer is the current flowing from the battery->inverter->PSU->epia->sound card->radio->battery because the transformers have no DC connection, I mean electrically the transformers dont touch each other. The stereo cable must've completed a loop back to the battery that is of the lowest resistance, hence burning the fuses due to the high current.

    So you n00bies out there.. watch out before you plug in your sound card directly to the radio if you're using EPIA! I learned the hard way and I think I may have to go repair the mobo again.

    Now I have a different problem..

    1/ I can hear some static noise coming out of the radio and the radio screen is picking up some sound that I can see due to the animations.. it seems like some high frequency noises. I dont know how to fix this. I already have a ground loop isolator. Could it be because I made the stereo-RCA cable myself and I did a poor job at it? If I were to buy a ready-made stereo-RCA connector, should I replace the one connecting the sound card to the ground loop isolator or the one connecting the ground loop isolator to the radio?

    2/ To hear songs on the speakers, I cant plug in the stereo plug perfectly inside, because then I'd hear sound coming from only 1 speaker where as the other is distorted. To hear the sound perfectly, I have to slightly pull the stereo connector out so that it doesnt completely go in but still connects into the aux-in of the radio. This sucks because when I hit a bump in the road, the connector comes lose and I lose audio and I have to carefully place the connector back in slightly again.

    The stereo connector looks somewhat like this:
    (incoming cable)===|==|=- (stereo tip)

    I have the two grounds from the RCA (outer ring) connecting to the stereo tip and the one from the white RCA core to the middle and the one from the red RCA core to the other end of the stereo plug. I say white and red RCA core to mean the connector is white and the other is red.. there are two incomings to the RCA connector.. one to the outer ring which I assume is ground and in the middle there is a male center that looks like a shaft which I assume to be the core..

    I have no idea what to call these components so I hope you guys understand what I mean. I'm new at these sound things so I hope you can shine some light on what I'm doing. I just connected stuff which I thought to make sense.

    Thanks in advance.

  2. #2
    FLAC DodgeCummins's Avatar
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    This is by far the weirdest thing I have heard of.

    I am curious...

    What brand/model of receiver do you have?

    Does it have AUX in rca plugs, or does it have some kind of connector that you connect to?

    What size fuse did you have in the first time (when it burnt up) and what was the smaller sized fuse you put in?

    Without looking at it, I can almost guarantee that you have some stuff mis-wired...but you probably already realize that by now.

    For the mini headphone jack on the computer, the tip is one channel, the middle is the other channel, and the base part is the ground.

    If the only way you can keep you system from blowing up is to run it through an isolator, I have to believe that something is horribly wrong in your wiring to the stereo...not just slightly wrong, but horribly wrong.

    I have connected all sorts of audio things, to all sorts of other audio things, and never has it caused a short (that is what happened to your mobo).

    Why? because there is no power going through the line level circuits...a couple of volts max, barely enough to measure.

    HOWEVER, if you have a positive ground vehicle/stereo equipment (like some european things) then you could have hooked 12v positive to 12v negative...that WOULD be bad for your computer.

    If you have no idea what I am talking about, then you had better back away from the computer and stereo, and go get some help quick.


    My guess is you have a HU like the pioneers with the multipin plug to add cd changers, and audio input...and instead of connecting the GND from the audio plug of your computer to the -R/L in on your stereo you connected it to something else.

  3. #3
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    Thanks for your reply. Hrmm what do you mean by the line level circuit? To be honest I dont really know what you mean by having some stuff miswired.

    The receiver is non-branded, to that I mean its not one of the popular brands. It has the mini headphone jack as the aux input. I didnt install the receiver myself, it came with the car.

    How do I check if the receiver is wired correctly?

    And where do you think is the problem? The wiring for the receiver or the wiring for the PC/inverter setup?

    If I have to pull the plug slightly out to get sound on both speakers, does that mean the receiver is mono and not stereo? If that's so then which of the three sections on the stereo plug are really being used? Only the base and the tip?

  4. #4
    FLAC DodgeCummins's Avatar
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    By line-level, I mean the power output is low...not designed to power a speaker,(but will power a set of headphones) like the rca plugs on the back of stereo equipment...there is not enough voltage available to hurt anything, let alone burn out equipment and blow fuses.

    Have you tried plugging a portable cdplayer, or tape player into that AUX-IN jack on your stereo?

    Like I said, something is very wrong to cause the blown circuit.

    Now for the second issue...
    If you have to pull the miniplug out a bit, then your mini plug is mis-wired.

    The standard for a stereo plug is...tip-one channel+, middle-other channel+,the base is the ground, or return line, or - depending on how it is labeled.

    If your receiver input was mono, then you would either hear sound out of both speakers, or out of none.

  5. #5
    Raw Wave Rob Withey's Avatar
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    Quote Originally Posted by masch
    I have the two grounds from the RCA (outer ring) connecting to the stereo tip and the one from the white RCA core to the middle and the one from the red RCA core to the other end of the stereo plug.

    This is not the normal arrangement. The usual arrangement is: tip is left, ring is right and sleeve is common (ground).


    Rob
    Old Systems retired due to new car
    New system at design/prototype stage on BeagleBoard.

  6. #6
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    I have tried wiring it that way (base = ground) before, but the sound volume was really low. WHen I rewired the way I described, I could get good volume but then I have to pull it slightly out. Hrmm maybe I should try again.

    So is it right to
    1/ connect the two outer rings of the RCA connector to the base of the stereo plug
    2/ connect the base of the black RCA connector to the tip of the stereo plug
    3/ connect the base of the red RCA connector to the middle of the stereo plug? ( I mentioned color so not to confuse )

    I havent tried plugging in a CD player or anything into the aux-in of the receiver. I have tried plugging a headset into my carPC setup and that works fine. I think if I put a CD player into the aux-in then there'd be no problems if it were running on portable batteries, unless the CD player was also plugged in to charge with the car battery - then I dont know what might happen. Is there an easy way to check?

  7. #7
    FLAC DodgeCummins's Avatar
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    I am assuming you are using standard wiring.


    The tip of the rca plug or jack...the inner part...the center...is the +

    The outer part, the ring, the shell of an rca plug or jack is the -

    The tip and first ring of the stereo plug are the L+ and R+ respectively.

    The base, longest part, nearest the wires, of the stereo plug is the -



    I still want to know what size fuse you had in that blew, and what size you had in when you smoked the equipment.

  8. #8
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    The one that didnt blow was 20A.. that's the one that blew the sound card/chip/connector. I dont know which blew, because I can still see that the mobo detects the sound card and can play songs.. but only no sound is coming out.

    Once I replaced the soundcard, I've been changing the fuse with 5A, 10A and 15A. I havent tried 20A. But even then, I think the standalone sound card has higher tolerance.. it could stand 15A!

  9. #9
    FLAC DodgeCummins's Avatar
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    A 140W power supply will only draw about 12 amps at full pull...normally less (plus inefficiency)

    It is no wonder you blew something up.

    I would run it with no more than a 10A fuse. (maybe 15A if you have a bunch of hard drives, a gaming card, and cdroms.

    The fact you were blowing fuses should be a warning flag that something is wrong somewhere...fuses are there to protect equipment and wiring...putting a bigger fuse is looking for trouble.

    20A at 12V = 240Watts of power...double of your rated output.

    10A at 12V = 120Watts of power...more like it.

  10. #10
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    Hrmm let me get this clear..

    Under normal circumstances.. if I plug in a CD player that is hooked up to the car battery via the cigarette lighter.. and plug the CD player's Line-Out to the receiver's Audio-In, should I expect the CD player to burn or no?

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