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What is a Mini Plug?

M.J. Brower
M.J. Brower

A mini plug is a 3.5mm (1/8 inch) plug that connects an audio or video device to an external output, such as speakers or headphones. Mini plugs are also used for microphone input. Mini plugs are technically called TRS connectors because they use three parts—the tip, the ring, and the sleeve (TRS)—to conduct sound. They are also called audio jacks, stereo jacks, stereo jack plugs, headphone jacks, jack plugs, and mini-jacks. Any variation of "plug" is more accurate than "jack," because "jack" usually refers to the socket the plug goes into.

The mini plug is a smaller version of the 6.35mm (1/4 inch) audio plug invented for telephone switchboards. Originally, the tip and the ring parts of the plug served different functions in telephone calls: The tip carried the sound of the telephone's bell and the voice, while the ring carried the busy signal. Telephone switchboards are largely a thing of the past, but both the larger plug and the mini plug have become standard for video and audio equipment. An even smaller 2.5mm plug, sometimes called a sub-mini plug, is often used with headphones, ear buds, and hands-free headsets for cell phones.

Man playing a guitar
Man playing a guitar

Depending on the number of conductors it has, a mini plug may deliver mono or stereo sound, or even video. Mono means that there is only one audio channel; the sound is the same in both speakers or both headphone earpieces. Mini plugs with two conductors carry a mono signal. Stereo means that there are two channels, so the sound in each speaker is different, but they are mixed so that the user hears them together. A stereo signal is carried by a three-conductor mini plug. Mini plugs with four conductors deliver a stereo signal, plus video.

Mini plugs are used for output with most modern audio devices, from portable audio players and DVD players to cell phones, computers, and stereos. One particularly interesting use is with workout software, which uses audio tones to control electronic exercise equipment such as treadmills. Mini plugs are used for input, via a microphone, with camcorders, computers, and audio recorders. Professional audio recording equipment is more likely to use 1/4 inch plugs than mini plugs, and high-end consumer equipment often uses the larger plugs as well. Either size plug can be used with the other size socket with the use of an adapter; these adapters are easy to find in most stores that carry home electronics.

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Discussion Comments


Please give me an opinion. I want to use a PC audio jack (which I assume is a stereo jack) to connect to a single (one) old style "drive-in speaker". Should I use a special type of mini (1/8") plug for this. There's only one speaker involved here and I have read enough to be confused about balanced and unbalanced signals (mono and stereo) connections.

If the source is stereo, can I expect to here both channels in the one speaker? Is there a danger of harming the PC in this?


@Mammmood - The sound is actually quite decent. I don’t carry the cable along for more than 20 feet and it sounds fine.

Actually, there are some mini stereo microphones for my camcorder that will give me the audio I’m looking for. I’m not exactly sure how they work since it’s supposed to be a mono adapter. Maybe they switch the audio channels inside the microphone.

However, the reason I use the shotgun microphone and the boom microphone is that they have a focused range. I don’t want to be picking up ambient sounds; I just want the sounds right in front of the microphone. That’s why the pros use them for interviews and of course, in movies.


@David09 - What kind of audio quality do you get using only a mini plug adaptor for your audio – especially with the boom microphone?

My understanding is that if you’re using that kind of connector, you can’t string the cable along for too long without having some static and distortion of the sound. If you have an XLR plug that might be the best option; I don’t know firsthand, however, that’s just what I’ve heard.


I have a fairly sturdy, reliable digital camcorder that has a mono mini jack plug for microphone attachments. I’ve attached both baby shotgun microphones to it as well as “boom” microphones that have long cable wires.

The real professional boom microphones are supposed to attach to the XLR plugs on the camcorder (I have those as well) but I have a consumer grade boom microphone that works just fine using the mini plug.

As I said, the sound quality is mono, which is standard for shotgun microphones, so if you play the audio back through a stereo system you will only hear it in one speaker. What I do to work around that problem is that I edit the audio in post production. I can duplicate the sound channel so that it fills both left and right audio, and the resulting sound will come out in stereo.

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