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It seems most audio sockets have the the ground pin connected the outside of the socket so that when it's fitted in a casing it will be contact with it. Why?

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  • \$\begingroup\$ How are you drawing this conclusion? Just because it's metal on the outside? Because most of the ones I see are not like that. The ones I see that are like that tend to have a nut that holds it to the face plate because metal makes better threads and nuts than plastic. I would not assume it is connected to a pin unless the datasheet says so. \$\endgroup\$
    – DKNguyen
    Nov 4, 2020 at 23:25
  • \$\begingroup\$ Hi tridash! Nice having you. May I counter this with a question: what problem do you see when doing this? What's the advantage you'd see? \$\endgroup\$ Nov 4, 2020 at 23:25
  • \$\begingroup\$ The metal thread has a metal nut. The nut will be in contact with the case. The end of the jack will be in contact with the end of the thread when inserted. This is the ground. \$\endgroup\$
    – user267895
    Nov 5, 2020 at 0:24
  • \$\begingroup\$ BTW at no point did I say all or every or any or ten or 10000000 have a ground connected such that it would become in contact with the case. I asked why would it be. I can google and been reviewing 10000s of these to find very specifics ones. \$\endgroup\$
    – user267895
    Nov 5, 2020 at 21:44

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On the contrary most of the 269 unique stereo 3.5mm jacks on Digikey's stock-on-hand are not what you assumed.

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But , let me re-phrase your question.

Why would you want chassis ground to be audio common?

Often the chassis serves to shield the electronics with a low impedance low RF current signal node that qualifies as a low EMI signal ground.

The speaker common ground ought to have a low-impedance for low mV drop with shared current ground return to eliminate common-mode impedance rise and stereo crosstalk.

Also the use of mobile devices with a noisy USB Charger that is floating but with high impedance common mode noise from leakage capacitance in the 5V SMPS magnetics can also interfere with high impedance microphone inputs.

Also the hand capacitively couple a large surface body dielectric serves to absorb stray e-fields radiated by poorly shielded SMPS magnetics and suppress analog signal noise shared by the mike and earbud COMMON ground.

The goal is to raise the impedance to RF and SMPS audio modulated noise and make the inputs linear to this common mode noise so it does not get rectified as mike audio noise or lower the ground impedance and raise coupling to bypass this E-field antenna or H-field loop area inductive noise ingress.

They still do have what you describe in both plastic and metal, thread-mounted panel jacks. which you failed to define in your question, but these are becoming less popular, yet give far better mechanical strain relief to the solder joints.

enter image description here Yet these cost over $3 vs the previous one much less $0.12 to $1.5.

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  • \$\begingroup\$ "which you failed to define in your question," Wow I never meet such a rude condescending bunch, ever. \$\endgroup\$
    – user267895
    Nov 5, 2020 at 22:09
  • \$\begingroup\$ @tridasha nothing in your question is true or at least supported or described accurately, are you just a hobbyist or a professional? You ought to reveal that in your Profile. You aren't alone, but why lower the bar for questions? This is an engineering site, not a backyard parking lot forum for simple questions. Curb your opinions and improve your questions in future if you want , otherwise dont \$\endgroup\$ Nov 5, 2020 at 23:23
  • \$\begingroup\$ not many unappreciative presumptive queries respond with trash talk. Rather immature. Don't take criticism easily? designs fail all the time and they don't take it personally ;) I'll put on my Kidd gloves next time \$\endgroup\$ Nov 5, 2020 at 23:28

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