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Thread: Noise from my audio only when engine is ON

  1. #1
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    Angry Noise from my audio only when engine is ON

    I know it has been discussed many times and I read a lot of threads but still cannot get rid of this noise. Here is my setup:
    An external sound card output is connected to PAC Turbo1. I need this amplifier because the volume is too low without it. From Turbo1 the output goes to my factory Bose system. When the engine is OFF everything is just fine, but when it is ON I can hear a noise in my speakers which changes as engine rev is goes high. When I disconnect the input from the Turbo1, so it is only connected to my factory stereo I can still hear the noise. In my opionion it means that the sound card and carPC have nothing to do with this noise. I power the Turbo1 from my car lighter socket. I also tried a ground loop isolator but it doesn't help at all. Any ideas ?

  2. #2
    FLAC greatwhite's Avatar
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    It's alternator whine.

    You still have a ground loop you must find.

    Where are you drawing power from for the PAC?

    Were/what is the ground for the PAC?

    You have to ensure a good solid ground for the PAC, draw power form a clean source (ie: not on a power line that also runs an electric motor) and install it away from fans, motors, electric pumps, etc. Otherwise, it will pick up interference.

    That's not the greatest line driver either.

    What did you pay for it? (guessing around 30 bucks) Remember the old saying:

    You get what you pay for..............
    For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return.
    Leonardo Da Vinci

  3. #3
    Maximum Bitrate bes51659's Avatar
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    No worries.

    Forget cig lighter power.
    Place the turbo thing (does it come with speed-stripes) right next the the bose amp! Place the soundcard there too.
    As short cables as possible, exept for the USB cable to the PC.

    You might have a ground loop via PC but it does not matter as long as ground cable between amp and turbo is really short.

    With your setup you've got every chans of getting rid of whining because of the simple fact that you do not have to wire analogue audio back and forth in the car.

  4. #4
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    Thanks guys. I change the power source for PAC Turbo1 from a ligther socket to 12V from my carPC and now even without a ground loop isolator everything is good. There is another problem, when I listen to a mp3 the sound quality is much worse than if I play a CD recorded with this mp3. I play this CD directly from the Bose system and the CarPC is connected to a DVD input of Bose. I use Creative X-MOD USB sound card. Do you have any ideas why the overall quality is so much different ?

  5. #5
    Maximum Bitrate bes51659's Avatar
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    Turbo? Try bypasing it just to see if quality improves.

    Edit:
    I just checked out your soundcard. http://se.europe.creative.com/produc...&product=15913

    Extreme hifi????!!! Veeery suspicious....

  6. #6
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    Hmm I'm not sure if I am able to check it without Turbo1 since the volume is very low and I can hardly hear something. Even with Turbo1 the volume is a little lower than the CD volume.
    Do you think that wires used in the installation can cause the quality issue ?
    I'm also wondering if you can recommend an amplifier which will give me good sound quality for a reasonable price ?

  7. #7
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    Hi FX35 -
    I have a '96 300zx that has a 'Premium' Bose system. I do not know if Bose changed the way they implement Car Audio, but the system I have is Balanced audio (+,-,ground) from the CD changer to the head and amplified speakers. The benefit of balanced audio is high noise rejection.
    Most Automotive audio systems and consumer electronics are unbalanced (+. ground). When connecting unbalanced and balanced components together balancing transformers are needed to make the system work correctly. The common symptom being loss of gain.

    Because of these issues and also Bose's history of using poor/cheap components, most Z owners replace the Bose system as quickly as possible. I'm sure this is much harder (if at all possible) on the new systems like yours with highly integrated systems and features. In your case you will likely need a balancing transformer. See if you can find the pin out for your Bose connector. On mine it listed the signals like this:
    Left front +
    Left front -
    Right front +
    Right front -
    ground
    etc.


    On some equipment you can strap the ground and the - together at the input and get some of your gain back, I would check with the equipment manufacturer if you can, but a transformer is always the better way.

    BTW - I am having the same issue. I am solving it through different means. My "EQ" is a pro audio DSP and is balanced, so it interfaces well with the Bose speakers. I have solved most of my ground issues, but still have a very faint alternator noise I am chasing down.

    You can read more about my system here:
    1996 300zx TT - Carputer w/ sound system upgrade

  8. #8
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    Quote Originally Posted by z_lust View Post
    Hi FX35 -
    I have a '96 300zx that has a 'Premium' Bose system. I do not know if Bose changed the way they implement Car Audio, but the system I have is Balanced audio (+,-,ground) from the CD changer to the head and amplified speakers. The benefit of balanced audio is high noise rejection.
    Most Automotive audio systems and consumer electronics are unbalanced (+. ground). When connecting unbalanced and balanced components together balancing transformers are needed to make the system work correctly. The common symptom being loss of gain.

    Because of these issues and also Bose's history of using poor/cheap components, most Z owners replace the Bose system as quickly as possible. I'm sure this is much harder (if at all possible) on the new systems like yours with highly integrated systems and features. In your case you will likely need a balancing transformer. See if you can find the pin out for your Bose connector. On mine it listed the signals like this:
    Left front +
    Left front -
    Right front +
    Right front -
    ground
    etc.


    On some equipment you can strap the ground and the - together at the input and get some of your gain back, I would check with the equipment manufacturer if you can, but a transformer is always the better way.

    BTW - I am having the same issue. I am solving it through different means. My "EQ" is a pro audio DSP and is balanced, so it interfaces well with the Bose speakers. I have solved most of my ground issues, but still have a very faint alternator noise I am chasing down.

    You can read more about my system here:
    1996 300zx TT - Carputer w/ sound system upgrade

    The DVD connector on the back of my head unit has the pinout you mentioned above.
    COuld you please have a look at this post where is a user guide I followed to connect my PC to my head unit: http://www.infinitifx.org/phpBB2/viewtopic.php?t=1457
    Do you have any suggestions ?

    I have no idea what this balancing transformer is. Could you please give me an advise ?

  9. #9
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    Lot of solutions out there. I was looking for an automotive solution I ran across, but now I can not find.

    You can look for Line Balancing transformers (Jensen is very good) or unbalanced to balanced line drivers. It is like the Turbo1 you have but with the addition of balanced outputs.

    Some Balancing transformers are passive and do not add gain and do not need power.
    You could use two of these:
    http://www.rdlnet.com/product.php?page=164

    I'll post here if I run across the automotive solution I was talking about. Look at all the usual car audio suppliers like Crutchfield etc.

  10. #10
    Maximum Bitrate bes51659's Avatar
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    Sorry, been away fro a while.

    Looked at your handy-man link and z_lust is absolutely correct. Your car has balanced audio. Theoretically you can connect - (or +) to ground and have a standard system (the other way cannot be done) but its possible that Bose has poor design and that this is not possible.

    I have a cheaper solution and that is to decouple the audio with capacitors. You might need a trafo later to get the quality you need, but it is a simple test to find out if this is the root of your gain problem. Just put a capacitor inbetween the (-) input and ground (common) output from your sound card. 10uF el.lyt. Oh, you need two caps. Do not connect the two (-) together.

    One more thing, you _can_ get amplification in passive trafos...

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