Mini Stereo Jack Wiring

by J.T. Barett

    A mini stereo jack is an electrical connector found on many kinds of audio equipment, including personal computers, MP3 players, smartphones and related accessories. The jack is the female counterpart of the mini plug; the jack accepts the plug and the two form a solid electrical connection. Its small size makes it ideal for portable and desktop audio devices, many of which have limited space.

    History and Description

    The mini stereo jack is a smaller version of the larger 1/4-inch jack design invented in the late 1800s for telephone switchboards. The mini jack made early appearances on pocket transistor radios and tape recorders in the 1950s and 1960s, where it served as a cable connector for microphones and earphones. Engineers refer to the design as a "tip-ring-sleeve" connector, and it incorporates three separate conductors: the tip of the male plug, an intermediate shaft ring and a sleeve, all of which mate with corresponding parts in the female jack. Plastic insulators between each conductor prevent any two from shorting out. The stereo version of the connector has three conductors: the tip and sleeve carry the left and right channel "hot" signals, and the sleeve serves as the ground. The mini connector is 1/8 inch or 3.5 mm -- half the size of the 1/4-inch plug.

    Mini Jacks vs. Other Connector Types

    Stereo equipment and professional audio gear uses RCA, XLR and full-size phone plugs in addition to the mini jack. RCA connectors have a cylindrical shape in which a central pin fits into a circular connector, a metal shroud on the male fits snugly onto the outside of the female jack. These come only as two-conductor connectors; stereo cables have two separate connectors, one of which is red, indicating the right channel. You find XLR connectors on professional audio equipment, such as microphones and mixing consoles. The XLR male has a spring-loaded latch which snaps securely into the female, preventing cables from being pulled out by accident. Unlike a TRS plug, which can produce a loud transient hum or buzz when making a connection, the XLR makes all connections simultaneously, eliminating connection noises. Full-size 1/4-inch jacks are larger and can handle more abuse than mini jacks, although they cost more and take up more room on equipment. Their larger size also means they can carry more current, making them suitable for loudspeakers and other power-hungry equipment.

    Adapter Cables

    Although mini jacks are common among audio equipment, some devices have RCA and 1/4-inch jacks, making adapters frequently necessary. An adapter has two different connectors, letting you use RCA plugs with mini jacks, minis with 1/4-inch plugs and any other conceivable combination. A gender changer adapter has two of the same type of connector; for example, if you have a cable that ends in a female mini jack, you can connect it to another device also having a female jack. In this case, an adapter with two male plugs, one for each female, completes the connection. Adapter cables have a different type of connector at each end, making a convenient accessory for busy audio-visual technicians and recording engineers.

    DIY Mini-Jack Cable

    To make your own mini-jack cable, first determine whether you need male or female connectors. A typical cable has a male at each end, but your own requirements dictate what components you need. Obtain good-quality audio cable which has two inner conductors and an outer shield. Slide the connector's plastic or metal outer cover onto the cable and strip about an inch of the outer plastic jacket, taking care to not cut the braided shield underneath. Pull the shield back, revealing the two inner wires, and strip 1/4 inch of insulation from the ends of each. If the wire is color-coded red and black, solder the black wire to the tip connector lug and the red wire to the ring lug. Twist the braid in your fingers so it forms a tight bundle and solder it to the connector's sleeve lug. Trim any excess with wire cutters. Slide the outer cover back onto the connector and screw it in on. Repeat the process with the other connector at the opposite end.

    About the Author

    Chicago native J.T. Barett has a Bachelor of Science in physics from Northeastern Illinois University and has been writing since 1991. He has contributed to "Foresight Update," a nanotechnology newsletter from the Foresight Institute. He also contributed to the book, "Nanotechnology: Molecular Speculations on Global Abundance."

    Photo Credits

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