Think iv got ground loop problems

Discussion in 'The Projects Forum' started by jmh474, Jul 9, 2019.

  1. jmh474

    Thread Starter Member

    Jun 26, 2014
    27
    0
    So I'm retro fitting a xbox 360 with a raspberry pi 3b+, I'm planning on running multiple os with the pie.

    Iv connected my pie to a amplifier in the 360 housing and its picking up all sorts of noise. The amplifier is picking up every little bit of noise from everything and it's horrible.

    Iv got a single 12v power supply power running everything 12v to the sata to usb to run the hdd and the 5v from the pie, 12v to the twin fan the original xbox fan, 12v feeding the amplifier, 12v to 5v feeding the pie and 12v feeding a few leds.

    If I was to isolate the amplifier on its own power supply and have a ground loop isolate from the pie to the amplifier would this rid me of the noise.

    The noise only appears when the pie is plugged into the amplifier via 3.5mm jack.

    Or dose anyone have any other ideas as not really got the room for an additional power supply.

    Thanks for any help
     
  2. KeithWalker

    Member

    Jul 10, 2017
    266
    83
    Can you supply a simple diagram showing how you connect the power and wiring between the different devices? It would make it much easier to understand your problem and to help you.
     
  3. jmh474

    Thread Starter Member

    Jun 26, 2014
    27
    0
    Sorry its not the best of drawing
     
  4. KeithWalker

    Member

    Jul 10, 2017
    266
    83
    Do you have an operating system loaded on the Pie or is it just idling?
     
  5. jmh474

    Thread Starter Member

    Jun 26, 2014
    27
    0
    Just powering up no os loaded
     
  6. Sensacell

    Moderator

    Jun 19, 2012
    2,344
    752
    Tricky problem, digital systems (like the Raspberry Pi) draw large supply currents, rich with nasty noise frequencies.

    1) Improve the ground configuration - super short and robust - a 'star' ground with short and heavy wires.
    2) use a 1:1 audio isolation transformer between Pi and amp.
     
  7. KeithWalker

    Member

    Jul 10, 2017
    266
    83
    With nothing running on the Pie, the output pins are floating. You have a high gain amp connected with no volume control so you are hearing the static charge on the output. Try loading a simple audio program (music or something like that) and see how it sounds then.
     
  8. jmh474

    Thread Starter Member

    Jun 26, 2014
    27
    0
    It's not really the pi I'm getting feed back from its the hdd and twin fans that's making the noise
     
  9. KeithWalker

    Member

    Jul 10, 2017
    266
    83
    The amplifier input is connected to the audio output of the Pie I presume - not to the HDD or fans. As I mentioned above, with no program running on the Pie, it's output is floating and it will pick up every bit of electrical noise generated anywhere in your system which will be amplified by your amplifier. You can either load an audio program on the Pie and see how it works or you can chase phantom noise until you damage something.
     
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