Help w/ star grounding (50Hz hum problem)!

Discussion in 'Pro Audio' started by Brian Huether, Oct 30, 2003.

  1. First a recap of my previous post: I have a mackie 1402, and a delta1010.
    When the computer is turned on, and a channel insert from the mackie goes to
    a delta input, there is a 50Hz hum at the delta input (which is preventing
    me from recording!). If I remove the cable from the channel insert (happens
    regardless of cables - balanced, unbalanced and happens regardless of
    whether or not there is an input connected to the mackie). Sometimes after
    an hour or so, this 50Hz hum will go away at the delta input. For more info
    as well as pictures showing the delta signal levels and spectral peaks see
    this link

    www.guitar-dreams.com/misc/deltaproblem.html

    Basically there seems to be 2 problems. For a year, I have been plugging my
    US delta power adapter into a step down xformer (I am living in Germany).
    Now upon powering up the computer, the delta has full scale signal levels
    across all channels regrdless if anything is plugged into it (and regardless
    of motherboard, etc,etc). I think this 50Hz has caused too much heat to
    dissipate in the adapter and things have gone awry. So the ground hum that
    occurs when something from the mixer is plugged in to the delta is either a
    separate problem or is related to the first problem (again see the above
    link for more info).

    I have read the FAQ. It wasn't very helpful. I am not a technician and the
    stuff in that FAQ seems geared in that way. I am pretty visual, so when the
    FAQ starts talking about star grounding I can't see how to physically do it.
    I just know what in principle needs to be done. So if somenoe can give a
    clearer description or point me to another resource that would be great! I
    am a guitarist first and a sound engineer second (i.e. I am my own sound
    guy). Give me a guitar and I can work my magic with it, but give me a bunch
    of cables and tell me to implement a star ground, well, I am lost...

    regards,

    brian

    www.guitar-dreams.com
     
    Brian Huether, Oct 30, 2003
    #1
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  2. Brian Huether

    Dale Farmer Guest

    All star grounding means is that all the ground wires in the system go to
    the same common grounding point, and there is only one electrical path to
    the common ground point for each piece of gear or cable. This is easier
    said than done.

    I'd first go and spring for a new local power supply for your computer,
    a power supply that will operate on your local 50 hz power. These are
    available in computer supply stores, and take only a few minutes with a
    screwdriver to replace. Try things again.

    --Dale
     
    Dale Farmer, Oct 30, 2003
    #2
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  3. My computer power supply does plug into the local power outlet. It is
    switchable from 115V to 220V and I am sure internally it is fine with 50 or
    60Hz. But do you really think that could be an issue?

    -brian
     
    Brian Huether, Oct 30, 2003
    #3
  4. Brian Huether

    Dale Farmer Guest

    Perhaps I misinterpreted. What do you have plugged into " Delta Power
    Adapter." ? Get the euro power supply for those devices.

    --Dale
     
    Dale Farmer, Oct 30, 2003
    #4
  5. For the delta I do not have the euro adapter but I am ordering it today...

    -brian
     
    Brian Huether, Oct 30, 2003
    #5
  6. Based on this new description of your problem, I think that your
    Delta1010 is broken and needs to be repaired or replaced. If I
    understand what you're saying, it's not an interface problem or a
    ground problem. It's just broken.

    ulysses
     
    Justin Ulysses Morse, Oct 31, 2003
    #6
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