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Here is a technical drawing for a 3.5mm stereo audio plug, taken from a product datasheet (http://www.tensility.com/pdffiles/50-00396.pdf):

enter image description here

The right-hand end is a standard 3.5mm audio plug. The left-hand end also seems to be some sort of male plug. Into what is it designed to be plugged?

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    \$\begingroup\$ The "left" part will be molded into the plastic plug. \$\endgroup\$ – Turbo J Feb 15 '17 at 12:21
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The ends of wires in a cable get soldered to the left end of that assembly. Then the assembly is placed into a mold and hot plastic is injected around the wire to form a handle for the end of the cable. The plastic molding often includes a flexible strain relief for the cable.

Typical result:

enter image description here

Often times the best way to understand something is to take it apart. Here I show the wire attachment to a miniature jack by having cut the cable molding away. You can see that the wires are simply solder tacked onto their appropriate pads. Note that the back ends of these things will vary from manufacturer to manufacturer.

enter image description here

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  • \$\begingroup\$ Actually, I'm kind of curious, what is the mechanical attachment to the jack? Do they just coil the wire around the post and solder? \$\endgroup\$ – pgvoorhees Feb 15 '17 at 12:56
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    \$\begingroup\$ Typically no wrapping. See picture I added to the answer. \$\endgroup\$ – Michael Karas Feb 15 '17 at 13:11
  • \$\begingroup\$ Thanks a lot. Is it possible for a hobbyist to make a custom audio cable like this? Presumably the sealing requires special equipment. \$\endgroup\$ – Jamie Vicary Feb 15 '17 at 14:18
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    \$\begingroup\$ A hobbyist would probably use a housing like this or more likely just tape it up or heatshrink or something. \$\endgroup\$ – Batman Feb 15 '17 at 15:15
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    \$\begingroup\$ Hot glue is very handy for rebuilding molded plugs after repairing them. \$\endgroup\$ – Ecnerwal Feb 15 '17 at 15:36
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That part is a plug (male part) not a jack (female part). It gets plugged into a jack. Eg. (From Digikey):

enter image description here

This kind of plug part is not designed for small quantity use- the wires will be welded (not soldered) to the plug. It is a much faster process and the joint strength is greater without taking so much space up.

Following that, the plug body and strain relief is insert-molded onto the cable/plug combo using a low-pressure PVC vertical injection molding process.

See this video for the process.

Screen capture: enter image description here

Above you can see the girl loading the cable assemblies into a mold while another mold is filling and cooling. When the cycle finishes the second mold rotates into place and the operator goes to work filling the first mold.

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  • \$\begingroup\$ Thanks a lot for your answer, and also for clarifying "plug" versus "jack" for me. \$\endgroup\$ – Jamie Vicary Feb 15 '17 at 19:29
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    \$\begingroup\$ That's American usage, Jamie. In British English it's OK to say "jack plug" and "jack socket". \$\endgroup\$ – Mike Spivey Feb 15 '17 at 21:04
  • \$\begingroup\$ Probably in certain parts of North America too \$\endgroup\$ – Reversed Engineer Feb 16 '17 at 16:53

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