Does the grounding prong on the British/Hong Kong plug for Mac mini M4 actually ground the computer?

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Level 1

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Does the grounding prong on the British/Hong Kong plug for Mac mini M4 actually ground the computer?

My M4 Mac mini was bought in Hong Kong, and as a result, it has a British plug with a large grounding prong as is standard on British plugs. I noticed that Chinese mainland Mac minis only have a two-prong plug, as do North American ones, like my 2014 Mac mini purchased in Canada. The AC socket on the computer only appears to have two prongs. Therefore, my question is, is the grounding prong on the British plug for the Mac mini M4 a placebo? Does it actually ground the computer? I went out of my way to buy a three-prong plug adapter to use it in the Chinese mainland, thinking it would preserve the grounding, but I suddenly realized it might be pointless. If it is not grounded, I feel I might sometimes hear a 50 Hz (60 Hz in Canada) hum when using headphones or doing things with audio (I found that touching my old 2014 Mac mini would ground it, and wrapping it in aluminum foil seemed to reduce the humming, or maybe that's just me.)

[Re-Titled by Moderator]

Mac mini, macOS 15.3

Posted on Mar 6, 2025 12:12 AM

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Answer 1

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MartinR

Level 7

23,535 points

Mar 6, 2025 06:13 AM in response to cutekids100

Technically speaking, the mini is not grounded; it is "double insulated." The 2-prong plug is an indication of that. A grounded electrical connection requires 3 prongs. But keep in mind that the Neutral line (one of the 2 prongs) is in fact connected to Ground because Neutral is always bonded to Ground in the electrical panel.

Because the mini has a non-conductive case ("double-insulated") there is no electrical requirement to have a separate (3rd) ground connection to the case.

You shouldn't hear any hum through headphones connected to the mini unless there is a source of EMI somewhere near the mini; it wouldn't come just from the line power. I have never experienced any hum with headphones or any amp or TV connected to my minis.

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Answer 2

Mar 6, 2025 07:46 AM in response to cutekids100

Well … the third prong DOES assist in plug orientation. 😉

And the fuse indeed IS a nice feature; making the orientation doubly-important to ensure that the fuse is actually connected on the “line.” (technically the “NON-grounded” conductor.)

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Answer 3

cutekids100 Author

Level 1

83 points

Mar 6, 2025 07:32 AM in response to MartinR

Thanks for the answer! I haven't experienced any hum with my M4 mini so far, but my old 2014 mini had this issue. The funny thing is, if you buy the mini from Hong Kong (and presumably the UK as well), it gives you a standard British plug with three prongs, and someone once told me the third prong is just for show. I just tested it with a multimeter, and apparently it really is just for show. However, it has a nice feature that the Chinese mainland and North American plugs don't have - apparently, it has a built-in fuse! So I'll just continue using my plug adapter and the British plug then. The fuse is a nice feature to have, especially since power bars in China don't have surge protectors.

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Does the grounding prong on the British/Hong Kong plug for Mac mini M4 actually ground the computer?

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