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Computer front panel headphone wiring....should it be grounded?

Discussion in 'Digital Sources' started by 78_towncar_4, Jun 4, 2018.

  1. 78_towncar_4

    78_towncar_4 Member

    Messages:
    99
    I have a computer case that I occasionally use the front panel headphone jack (3.5mm or 1/8" TRS style). This is an older computer case and has two USB 2.0 inputs, a firewire input, and then a microphone and headphone jack. I was prepared to replace the old USB module with an updated USB3.1 module from the manufacturer, but decided not to....however, upon disassembly of the case, I noticed that there was a ground wire coming off of the front panel module which was screwed to the metal case.

    Now, the USB connections have their own ground to the motherboard as does the firewire port. Is it normal for a headphone or microphone jack to have a separate chassis ground? I am wondering because this is a fairly noisy headphone jack (electrical noise). When the ground wire is removed, there is no noise through the headphones. The power switch, reset, and LED hard drive activity light have their own separate wiring. As far as I know, a standard TRS jack has ground at the base of the jack and that wire runs as one of three wires inside the insulation of the headphones.

    What would this separate case chassis ground be for? I imagine it has to be for the audio jacks. I was told by the manufacturer to remove it, but it has to be there for a purpose.....the only thing I can think of is that since there is only one ground inside the front panel audio connector to the motherboard, it is just a second ground. Is it safe to remove?
     

     

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  2. sKiZo

    sKiZo Hates received: 8642 Subscriber

    Normal headphone jack is insulated from the chassis to keep stray noise out, and you've got your three standard connections for left, right, and common audio ground?
     
  3. 78_towncar_4

    78_towncar_4 Member

    Messages:
    99
    I cannot see the actual headphone jack wiring. It simply comes off the front panel along with the microphone wiring and falls into the typical motherboard HD audio header. 9-pin with one blank. Pin 2 is a "ground" and must be for both the headphones AND the microphone. That is why I am sort of leaning towards this separate exposed chassis ground being some sort of common ground between the two.

    1 PORT 1L Analog Port 1 - Left channel (Microphone)
    2 GND Ground
    3 PORT 1R Analog Port 1 - Right channel (Microphone)
    4 PRESENCE# Active low signal that signals BIOS that an Intel® HD Audio dongle is connected to the analog header. PRESENCE# = 0 when an Intel® HD Audio dongle is connected.
    5 PORT 2R Analog Port 2 - Right channel (Headphone)
    6 SENSE1_RETURN Jack detection return for front panel (JACK1)
    7 SENSE_SEND Jack detection sense line from the Intel® HD Audio CODEC jack detection resistor network
    8 KEY No pin
    9 PORT 2L Analog Port 2 - Left channel (Headphone)
    10 SENSE2_RETURN Jack detection return for front panel (JACK2)
     

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