I would imagine with everything wiping past each other during insertion, that the following can happen briefly:

    <== plug
  T   R   S
 / \ / \ /
T   R   S
jack

Is this just something that systems that allow hot-plugging have to accommodate? Is there something in a spec to prevent this? If this scenario isn't possible, but something slightly less bad can happen, please explain?

(That is, I'd accept "Yes." as an answer, but "No." would require justification.)

Can internal switches in jacks help mitigate this? I assume most are normally-closed and break as soon as insertion starts, so that's not very helpful. Are there jacks with internal switches that only change state at full-insertion?

  • 1
    In audio applications, you will usually have an output resistor that will prevent a short from causing damage. That is not necessarily specific to this problem/issue, but a general protection against inevitable shorts (ie touching tip of the far end of the cable to a metal chassis). Note: this is standard for line-level outputs, but not necessarily power outputs! – Daniel Oct 21 '16 at 20:50
  • 1
    If the information contained in Wikipedia was sufficient to answer your question (which is basically all that is contained in the answer you accepted), why did you not just google the words in your question's title and read the #1 result? The Wikipedia article on Phone connector (audio) is the #1 result for many/most combinations of the words in the title. – Makyen Oct 21 '16 at 22:35
  • I actually get this question as the #1 result for that now, but it's a fair question. I thought I had read that page before asking, but apparently I'd failed to read the "Balanced Audio" and "Mono and stereo compatibility" sections -- I would not have expected to find the answer in either. I'm fine with voting to remove this question, but I do think it offers a clear question and a clear answer that is a bit difficult to sift out of that Wikipedia article. Maybe I should edit the article. – Rob Starling Oct 21 '16 at 23:48
  • @Makyen - if a topic is on-topic here, there's nothing wrong with asking a question that's easy to answer on Google. This site aims to be a library of detailed answers to every question about electronics design... not a library of answers that aren't easily found on Google. The top hit on Google might be the right answer today, but might be the wrong answer tomorrow... or ideally will be this stack exchange answer. – Johnny Oct 22 '16 at 5:01
up vote 9 down vote accepted

Quoting Wikipedia:

Heavy-duty  1⁄4 in loudspeaker jacks are rated at 15 A maximum which limits them to applications involving less than 1,800 watts.  1⁄4 in loudspeaker jacks commonly are not rigged to lock the plug in place and will short out the amplifier's output circuitry if connected or disconnected when the amplifier is live.

And:

A disadvantage of using phone connectors for balanced audio connections is that the ground mates last and the socket grounds the plug tip and ring when inserting or disconnecting the plug. This causes bursts of hum, cracks and pops and may stress some outputs as they will be short circuited briefly, or longer if the plug is left half in.

So, yes.

Also, about standards:

Due to a lack of standardization in the past regarding the dimensions (length) given to the ring conductor and the insulating portions on either side of it in 6.35 mm ( 1⁄4 in) phone connectors and the width of the conductors in different brands and generations of sockets there are occasional issues with compatibility between differing brands of plug and socket. This can result in a contact in the socket bridging (shorting) the ring and sleeve contacts on a phone connector, or where a phone plug is inserted into a two-conductor TS socket in some cases the intended 'sleeve' contact in the socket making contact with only the 'ring' portion of the plug.

So, unless you can control what kind of plugs are going to be used, I wouldn't be too optimistic about standards as well.

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