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My acoustic guitar's "piezo pick-up" contains a really big audio jack with about 7mm borehole. It is basically a hollow screw, fixed on the guitar surface with a nut and washer. This is much different from a computer's tip-ring-sleeve jack and RCA jack.

the guitar

Fig. 1 : From outside.

enter image description here

Breakout of an old connector.

Internet shows very little information about this jack and generally terms as "jack" or or "guitar jack" although there are other types of guitar pickup jacks.

Now my questions are:

  1. Does this type of audio jack have any specific name or term?

  2. What kind of plug/ "male" jack do I need to connect this guitar to a speaker or sound system or computer?

  3. Is there a specific circuit symbol for this type of jack and plug?

  4. What would be the pin-out and circuit diagram for using this connector (both "female" and "male" type?)

  5. Is there a specific name for the hollow 'screw'-like fastener?

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    \$\begingroup\$ Looks like a regular 1/4 inch jack, aka phone jack (though the GPO/BBC ones were slightly different) I think you meant about 0.7cm or 7 mm - really, 6.35mm. About twice the size in all dimensions compared with the 3.5mm computer ones. \$\endgroup\$ – user_1818839 Sep 24 '20 at 17:19
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    \$\begingroup\$ "Really big" and 0.7mm do not seem the same here. Perhaps you mean 7mm, which is pretty close to 0.25 inch, and that's exactly the size a 1/4 inch guitar TR plug uses. \$\endgroup\$ – JYelton Sep 24 '20 at 17:20
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    \$\begingroup\$ StackExchange keeps making me feel old... It doesn't seem that long ago that this was also the standard connector for plugging headphones into HiFi equipment. (Back in the days when "Fi" actually stood for something!) \$\endgroup\$ – TripeHound Sep 25 '20 at 5:42
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    \$\begingroup\$ @TripeHound Ah yes, the good ol' HiFi device stack of the 80s/90s ... with the turntable on top :) \$\endgroup\$ – orithena Sep 25 '20 at 11:21
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    \$\begingroup\$ It is pretty much a tip-ring-sleeve type. \$\endgroup\$ – fraxinus Sep 25 '20 at 13:50
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  1. That is a 1/4" Mono Jack sometimes also called a 1/4" Phone Jack.
  2. It takes a 1/4" Mono Plug. (These are very common)
  3. The circuit symbol looks like this:

quarter inch mono jack

  1. See above. The upper terminal is the signal, and the lower is 'common'
  2. That is just the 1/4" female mono (or phone) jack

Look HERE for an example. These are extremely common and should be easy to find.

These are the same as the old-fashioned headphone jacks/plugs from many decades ago.

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Search for 6.35 mm mono jack socket.

enter image description here

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  • \$\begingroup\$ Yep, this was the design about 20 years ago. The plastic bodied design has apparently taken over of late. This style was virtually indestructible, while the plastic bodied style obviously was not. \$\endgroup\$ – Hot Licks Sep 25 '20 at 17:14
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Looks very much like a standard 1/4" Mono jack. These are standard for guitars and much other musical equipment.

You can safely replace it with a Stereo 1/4" jack by connecting the Ring and Sleeve pins together.

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Other answers have identified the connector as a 1/4" jack. However, note that if you think you might want to use this guitar with a guitar strap in the future, this might be a good time to replace the jack with an "acoustic endpin jack". This functions electrically the same as a 1/4" jack, but it adds a machined flange around the opening onto which you can attach a standard guitar strap. The other end of the guitar would get a strap button, and you're done.

Acoustic endpin jacks are widely available from music stores and online musical supply houses.

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  • \$\begingroup\$ Why not use some high quality industrial connector like M8, M12,... at best with revolved pins and sockets. I cant understand why people pay multiples for less quality. \$\endgroup\$ – schnedan Sep 25 '20 at 19:10
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    \$\begingroup\$ @schnedan I guess it's a combination of tradition, inertia and interoperability concerns. If I'm the first one in my neighborhood to use pin and socket connectors on my guitar instead of a 1/4" phone jack, I'm going to be the only one who can't plug into any random guitar amp and use any random guitar cable. Since 1/4" phone jacks and plugs work well enough, there is little motivation to try to change an entire industry and become incompatible with around 70 years worth of installed base. \$\endgroup\$ – MTA Sep 25 '20 at 22:37
  • \$\begingroup\$ Jeah, that of course is true,... 70 years ago it was state of the Art I guess. I googled the jacks... some parts on amazon have prices way of any reason. To end it, just an Idea: you can use a better connector and have cables / adapters which are compatible with the rest of the world. One person must start the new trend, right :-) ? \$\endgroup\$ – schnedan Sep 26 '20 at 6:42

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