A headphone jack is otherwise known as a phone connector, au.dio jack, phone jack, or jack plug. It is a member of a family of electric connector generally used for dealing with analog signals, including audio.

A headphone jack has a cylindrical shape, usually with two to five contacts. As with the history of a headphone jack, it was invented with the purpose of using telephone switchboards back in the 19th century. Down to this day, it is still used widely.

Headphone Size

When asked what size is a headphone jack, a lot of people and even manufacturers readily claim that the standard size is 3.5 mm. True, this is the most commonly used these days. However, if we go back to the original configuration, there were different configurations available. The original outside diameter size of the ‘sleeve’ conductor is 6.35 mm (1/4 inch). The ‘mini’ connector has a diameter size of 3.5 mm (0.14 inch), while the ‘sub-mini’ size comes with a diameter of 2.5 mm (0.098 inches).

Some models are termed with other names, including mini-jack, mini-stereo, stereo plug, microphone jack, headphone jack, or even referred to by size. For example, in the UK, the names jack socket and jack plug are more commonly used for the phone connectors. On the other hand, in the US, ‘jack’ is what is termed to a stationary electrical connector.

However, headphone jacks have a more specific use. They are plugs that are used to connect headphones to a device, such as mobile phones, computers, or tablets. Identifying the right headphone jack size is very important as it will determine whether or not a headphone or earbud model is compatible with a particular device or not.

Size vs. Use

Earphones or headphone jacks are seen as used on a wide variety of equipment. The 6.35 mm jacks are commonly used with residential, as well as professional components. 3.5 headphone jacks are the almost universal size for the use of portable audio equipment, while 2.5 mm headphone hacks are not as common. However, they are commonly used on communication devices such as mobile phones, cordless phones, as well as 2-way radios.

Electronic devices, including camcorders, digital cameras as well as portable DVD players, utilize 3.5 mm connectors for both composite audio and video output. Generally, headsets and handsfree sets use either 2.5 mm or 3.5 mm connectors. Phone connectors are typically used in mono audio out, together with an unbalanced microphone that comes with a shared ground.

It should be noted, however, that a 2.5 mm headphone jack is used with older phone models. This means that a 3.5 mm headphone jack is the size that is considered as commonly used with modern models. This applies to both handsfree headsets, as well as stereo headphones.

As such, there is no recognized standard size for connectors. This is because the connectors are assigned to various purposes, depending on the manufacturers. A 3.5 mm headset plug may be mechanically plugged to any socket, those some combinations are still incompatible electronically. The mono audio typically works, though microphone or stereo audio may encounter some issues. The compatibility on signaling also depends on the compatibility of both wiring and signals that are sent by the hand’s free controller, as interpreted correctly by the headphone.

Headphone Jacks on Smartphones

These days, most manufacturers felt comfortable with the use of 3.5 mm TTRS stereo plus mic models on smartphones. Two forms have been found, both of them placing the left audio towards the tip, while the right sound is located on the first ring. The difference, though, is the actual placement of the microphone, as well as the return contacts.

The first form installs the ground return at the second ring, while the microphone is on its sleeve. This design is shared among the iPhone line from Apple. However, it should be noted that with the new iPhone7, Apple chose to replace this standard size with its proprietary lightning connector. It is also common among the latest Samsung models, HTC devices, Sony, and Nokia phones, among other models.

The second form, on the other hand, reverses the contacts. It is the design that is common among older Nokia models as well as some Sony Ericsson models and older versions of Samsung smartphones. Some adapters switch the poles to allow a particular device to a standard that can be used together with a headset.

Bottom Line

Therefore, if you are looking for the right side of the headphone jack, it is highly recommended to check what your purpose for use is. If you are planning to use on a smartphone or other mobile devices, it is best to check the specs of your device so that you can determine the type of headphone plug used. This is to make sure that you do not end up getting the wrong size for a headphone jack.

However, most devices, especially smartphones, come with their headsets or earbuds. This is applicable, therefore, if you are planning to buy a different set of headphones or earbuds in addition to your current one. While 3.5 mm size of a headphone jack is usually the most commonly used, not just on smartphones, but also on desktop and laptop computers across different manufacturers, checking on the specs will help you make the best choice.