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Thread: DAB DAB+ FM Digital Radio Development Board

  1. #271
    Maximum Bitrate Mickz's Avatar
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    Quote Originally Posted by mos33y View Post
    Re noise issue: I still have issue. JB from Dabmonkey recommends Mickz's solution of earthing the board's earth onto pc chassis - have not yet tried this. If all else fails, I have been recommended a groundloop isolator connected inline with dab board and linein of pc. You will lose some midrange sound with this solution.
    Mos
    The correct earth point is critical. It "must" be soldered to the Tin Shield covering the Audio In/Out sockets on the PC MB and it should be at least 8G. The other end should be soldered to aerial socket if possible.
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  2. #272
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    Quote Originally Posted by Mickz View Post
    The correct earth point is critical. It "must" be soldered to the Tin Shield covering the Audio In/Out sockets on the PC MB and it should be at least 8G. The other end should be soldered to aerial socket if possible.

    what would you recommend for those who have their dabboard under the dash and pc is in the boot?

  3. #273
    Maximum Bitrate Mickz's Avatar
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    You could still try it with a nice multi strand soft cable. I'd try it just running over the seats to make sure it works, you may even get away with a thinner cable.

    The second option, especially if you don't want to loose quality, is to use a small $40 USB to RCA sound card input module. JB used a more expensive unit to fix his problem but the low cost units are really good and simple as straight 2 channel input device.
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  4. #274
    ibf
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    Quote Originally Posted by mos33y View Post
    Hi IF,

    Re ebay link: I did try that but it says the item has been removed from ebay - all good thanks anyway

    Re noise issue: I still have issue. JB from Dabmonkey recommends Mickz's solution of earthing the board's earth onto pc chassis - have not yet tried this. If all else fails, I have been recommended a groundloop isolator connected inline with dab board and linein of pc. You will lose some midrange sound with this solution.

    Also, are you using amped aerial or supplied aerial?

    Ill be playning with the carPC abit shortly to solve these issues once and for all. Will report any fixes

    Mos
    Relisted again

    http://www.ebay.co.uk/itm/Car-DAB-DA...item51a92aca25

    A bit expensive I thought, might be better getting a proper antenna. Just incase you missed it, monkeyboard use SMA this adaptor use SMB connector.

    I dont have it installed in the car, the supplied antenna works as well as the wire antenna.

  5. #275
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    Quote Originally Posted by Mickz View Post
    You could still try it with a nice multi strand soft cable. I'd try it just running over the seats to make sure it works, you may even get away with a thinner cable.

    The second option, especially if you don't want to loose quality, is to use a small $40 USB to RCA sound card input module. JB used a more expensive unit to fix his problem but the low cost units are really good and simple as straight 2 channel input device.
    Sorry Mick not following. How would the 2channel usb sound card fix my dabboard's earth/noise issue?

    Ibf: I agree, a propert dab antenna would prob work best compared to something like this

  6. #276
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    I believe he is suggesting a USB sound card for input because it will help isolate the PC from the radio. You could actually mount the USB unit right by your radio and run a long USB cable to your PC without issue. The USB card will convert the sound from the sound board to digital information and then transmit that to your PC where it can be turned back into sound on your computer and outputted without having issues with ground potentials being different or the wires picking up noise along the way.

  7. #277
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    Thanks redheaderod for explaining. Makes sense but just thinking out loud here, but if iam going to feed a analog signal from my dabboard, this signal will have the noise in it and send this noise (along with wanted radio noise) to this device which in turn convert to a digi signal. My thinking at the moment is that the groundloop noise will also be still heard, right?
    I guess not if jb has tested this,

    Just trying to understand how this works

  8. #278
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    A ground loop as I understand it is where you have different ground potentials. Which can easily happen in a car when you are using the body as a wire when you don't have solid connections between the body and the frame. Normally you don't notice a small difference but when you involve audio you can hear the difference. Basically what happens is if there are different ground potentials the voltage seen against this ground is different.

    To visualize this imagine you have a long positive wire directly from your battery. You use a meter and you connect one lead to the positive of the battery and the other to the body of your car in two different locations. It is quite possible you will see two different voltages because of the differing of ground potentials. If you hook up a radio using the ground at one location and you hook up an amplifier at the other ground and wire the audio between the two you will get noise induced into the signal because of the difference in grounds. The difference could be in as little as .01 volt and you can still hear this as noise with some systems. Generally you will see a difference of .1 or .2 volts or more between two grounding locations.

    Apparently this board doesn't have a good ground between the board and the computer so running a wire between the board and computer allows this ground potential to be greatly reduced thus reducing the noise.

    My guess is that with a USB sound card you are somehow breaking this ground loop. Either because the power from the computer is filtered when using the USB port so you don't have a direct ground connection to the computer or the audio inputs are isolated from the actual electronics that digitize it.

    I am making guesses here based on my past experience but I am sure if I am wrong someone else will correct the information. But does it make better sense?
    Generally this is why if you run a ground wire between two components in car audio that have noise you can tell if it is due to a difference in ground potentials because the noise will either go away all together or greatly reduce.

  9. #279
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    Yes sure. I guess our 1st stop is to equilise the grounds 1st and see if I can get joy. If not, well have to take try some of these gizmos

  10. #280
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    Ok guys, jb from dabmonkey provided a good explanation on why the usb sound card will work:
    Hi Mos,

    The main issue causing the ground noise is the PC's internal sound card.* If you are using an earphone, you won't hear any noise.

    The USB sound card separates the ground of the DAB board and the PC's ground.

    Cheers
    JB

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