The different jack connector formats

Jack connectors

Various possible applications

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The Jack connector format is one of the oldest and most widely used, particularly in the world of music. Introduced at the end of the 18th century for use in exchanges, it has since evolved into several different formats. Historically a 6.35mm jack, today we also find 2.5mm jacks, 3.5mm jacks, 4.4mm jacks and even 5.23mm jacks. But that's not all: a jack connector can be mono, stereo, balanced or unbalanced. So how do you choose the right jack connector?

History of the Jack connector

The invention of the Jack connector dates back to . This connector was invented as part of the installation of the first exchanges. The 6.35mm jack format, even though other formats such as the 4.4mm jack already existed, became the standard in terms of line connectivity. At the time, it was nicknamed the " plug" and was mainly used by switchboard operators, before its use gradually became more widespread. Indeed, thanks to its low manufacturing cost, it was used on amplifiers and electric guitars as early as the s. The miniature 3.5mm jack version was introduced in the s for the headphones of transistor radios, popularized by the famous SONY EFM-117J radio released in , then by the first Walkman, again from Japanese brand Sony, in . The 2.5mm jack was also used for small electronic devices. It can be used to transmit audio, but also a video signal in certain cases. Less conventional and less well-known formats such as the 5.23mm and 7.14mm jacks are generally used by the military for telecommunications, as well as by the aviation sector.

Different jack plug formats

Jack 6.35mm (1/4&#;)

The 6.35mm jack plug is still widely used, thanks to its robustness. In fact, it's the plug of choice for connecting electric guitars and basses, and therefore the socket of amplifiers, effects pedals and USB interfaces commonly known as "sound cards". On the Hi-Fi side, it's mainly used for connecting some headphones.

Jack 4.4mm

The 4.4mm jack, also known as Bantam, is mainly used for balanced headphone connections and professional audio connectors. This format is still widely used thanks to the Pentaconn standard, which makes it balanced with no less than five contact pins.

Jack 3.5mm (mini-jack)

A standard connector, the 3.5mm jack is still widely used for earphones, headphones and active desktop speakers for use with a , tablet or computer. In recent years, it has tended to fade slightly, as the standard for phones evolves towards a USB-C connection even for transferring audio signals.

Jack 2.5mm (subminiature)

Rarely used these days, because its small size makes it too fragile, the 2.5mm jack was once used for headphones or to power small devices. In Hi-Fi, however, it is found on the connectors of small devices such as portable DAC/headphone amplifiers, to save space and keep a small form factor.

Mono, stereo, unbalanced, balanced: TS/TRS/TRRS/TRRRS standards

Today, all formats are available in mono, stereo, balanced and unbalanced versions. However, due to specific standards, balanced jacks are often in 4.4mm jack or 2.5mm jack format, while 6.35mm jack and 3.5mm jack formats are used for mono or unbalanced stereo.

To distinguish the different types of connection possible, we use the TS/TRS/TRRS/TRRRS standards. "T" for "Tip", "R" for "Ring" and "S" for "Sleeve". This designation simply determines the number of contacts on a jack connector, whether in 6.35mm, 4.4mm, 3.5mm or 2.5mm format.

TS standard: 2 contact points

The 2-contact jack is generally used to transmit a monophonic signal. There is one contact for the signal (Tip) and one for ground (Sleeve - GND).

TRS standard: 3 contact points

Jack connectors with 3 contact points can be used for a variety of purposes:

• Transmit stereo sound.  "Tip" for the left channel, "Ring" for the right channel and "Sleeve" for ground.
• Transmitting a balanced mono signal, such as an XLR modulation cable. Tip" for the hot point, "Ring" for the cold point and "Sleeve" for ground.

TRS jack connectors are the most widely used on the market today. They are also widely used in professional applications, such as the insert function on mixing consoles.

TRRS standard: 4 contact points

TRRS jack connectors are generally used to transmit stereo sound and add a function such as a microphone or video signal. However, there is no standard pin placement for this type of connector. So always check compatibility with your device before using this type of connection.

For headphones and earphones with microphones, there are two main standards: CTIA (The Wireless Association) and OMTP (Open Mobile Terminal Platform). The difference between these two standards lies in the location of the microphone contact (AUX) and ground (GND), as shown in the diagram below. The CTIA standard is still the most commonly used today.

TRRRS standard: 5 contact points

TRRRS connectors are mainly used to transmit balanced stereo signals. This is the Pentaconn standard for the 4.4mm jack. TRRRS is also often used on 2.5mm jacks for balanced connections. The connection is shown below:

• Tip: left channel (+)
• Ring: left channel (-)
• Ring: right channel (+)
• Ring : right channel (-)
• Sleeve : ground

The replacement of the 3.5mm jack connector with USB-C on smartphones

Recently, many devices, such as the latest generation of smartphones, have tended to do away with their jack output in order to reduce their thickness. This has led to the emergence of earphones with USB-C connectors for transmitting audio signals.
The main question on most users' minds is: how am I going to listen to music and charge my at the same time? In the end, the answer is quite simple. All you need is a Y adapter and you're ready to go!
So what are the advantages of USB-C? There's the fact that DAC chips, DSPs and amplifiers will now be positioned on the side of headphone and earphone manufacturers. This means we'll have to worry more about buying headphones that we can make last over time, while still being able to change smartphones without affecting listening quality.
USB-C audio is promoted by Intel, which is nonetheless aware of the obstacles encountered in the 3.5mm jack/USB-C transition. That's why the company is even considering enabling analog transmission via USB-C for a smoother transition phase before going "all digital". However, as far as Hi-Fi equipment is concerned, this type of connection is still far from being replaced.

Thankfully, hooking up audio and AV systems is much more straightforward than it used to be. For most people, home entertainment systems no longer consist of large racks of individual components hiding a rat&#;s nest of wires and connectors, and we&#;re better off for it. But there are still times you need to connect audio hardware devices, and if you need to source cables (cords), connectors, or adapters, knowing the specific names of each type is necessary. Let&#;s go over the ones you&#;re most likely to encounter.

Editor&#;s note: This post was updated on July 7, , and again on December 5th, , to account for changes in our house style and formatting standards.

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How do I connect my headphones?

These are the two most common sizes of TRS jack connectors.

Wired headphones connect to a playback device&#;s analog headphone socket using a jack plug. Suppose they&#;re standard stereo headphones with no microphone. In that case, it&#;s a three-terminal tip-ring-sleeve (TRS) connector, easily identified by the two insulating bands (usually black) on the barrel of the jack. These are commonly found in two sizes. The smaller size found on portable devices is referred to as a minijack, or by its diameter, 3.5mm. It&#;s sometimes called a 1/8-inch jack in the US, though that&#;s an approximation. The larger size of headphone jack you&#;ll find is commonly known as a 1/4 inch (or 6.3mm) jack plug. Adapters are easy to find when changing one size jack plug to another.

This earphone&#;s cable terminates into a 90-degree TRRS jack.

Wired headphones with a built-in microphone use a modified version of the same-sized minijack plug but with an additional electrical terminal (to carry the mic signal) in the form of an extra ring. This makes it a tip-ring-ring-sleeve (TRRS) connector, which has three insulating bands visible on the barrel.

How do I connect my headphones when there&#;s no jack socket?

These end in a 3.5mm connector, so you&#;ll need to use a stupid dongle on new phones.

Since smartphones have abandoned the headphone jack, you have three options. If you already have wired headphones you want to use;, you&#;ll need a special adapter (a dongle) to connect to the &#;s system connector (a Lightning connector on iPhones or USB-C for basically everything else) and provide you with the analog 3.5mm headphone socket you need to plug in your headphones. These are also referred to as digital-to-analog converters (DACs).

If you want to stick with wired (for reasons) and don&#;t want to deal with dongles you can get a set of wired USB headphones to plug directly into your . If you prefer to avoid dealing with dongles or wires, you can also go down the wireless Bluetooth route.

What are the other types of headphone connectors called?

The Drop+Ether CX closed-back headphones come wired with a four-pin XLR for differential drive.

You may have run into premium headphones with other jack sizes, different pin configurations (4.4mm Pentaconn), or larger XLR-type connectors. These are required to run your headphones in a balanced or differential drive configuration.

What connectors are used at the headphone end of the cable?

The cable plugs into the bottom of each ear cup via 2.5mm jacks.

When the cable is removable, the plugs used at the headphone end vary quite a bit, and we won&#;t cover them all here. 3.5mm jacks with a twist-to-lock system are relatively common. You&#;ll also find 2.5mm TRS jack plugs on some headphones (Bose, for example), while others have 2.5mm TS jack inputs at the bottom of each ear cup for the wires to connect to (the Monoprice Monolith M, for example). Premium headphones can use mini XLR connectors; some use propriety connectors like Sennheiser&#;s two-pin push-fit connector.

The MMCX connectors are gold-plated and fit snugly into the SE215 female input.

Many in-ear monitor (IEM) headphones employ micro-miniature coaxial (MMCX) connectors. As the name implies, this connection standard is small enough to easily fit into a pair of in-ear monitors. These are used mainly for better-engineered in-ear monitors, where having a replaceable cable means the headset doesn&#;t become trash if the cable fails. Plus, the connection itself locks into place and allows for 360 degrees of rotation, so not only does it make the cable easier to replace, but it also makes it harder to break in the first place.

What else are jack plugs used for?

Jack plugs are also used to connect audio signals at &#;line level&#; in several contexts. 3.5mm TRS minijacks are found at the ends of the standard auxiliary (&#;aux&#;) cable to connect your directly to a portable speaker or car stereo system. The larger 1/4-inch plugs are used in semi-professional applications to connect signals using TS plugs (unbalanced applications) or TRS plugs (balanced applications).

What are XLR connectors?

XLR cables are used for microphones and other pro audio applications.

XLR connectors carry the tiny electrical signals produced by microphones and in other instances where signal integrity is essential &#; typically professional audio environments. Microphones have male outputs and mic preamps have female input connectors on the front; hence, the standard XLR cable has a female on one end and a male on the other. The locking connectors are relatively large and heavy, explicitly designed for carrying balanced signals and wired using a balanced (microphone) cable. This cable type is well suited to longer cable runs, as they have better shielding and noise rejection abilities.

What are RCA connectors?

RCA-type plugs are usually color-coded red (right) and white (left) for stereo interconnection.

RCA (or phono) connectors are smaller cinch-type connectors used in interconnects for connecting &#;line level&#; audio signals in consumer products. You&#;ll likely recognize the red and white color-coded stereo cables from their use in connecting older hi-fi system components or the yellow plugs that carry analog video signals to TVs from old DVD players, VCRs, or video game consoles. Since they can only carry unbalanced signals, they&#;re only suitable for relatively short-distance transmission of audio and video signals. They are still reasonably common, particularly for connecting record player turntables to phono input stages or connecting home theater subwoofers. They are also used for coaxial, digital audio connections (see the section later on).

Unlike a lot of connectors, the RCA name isn&#;t derived from a particular physical aspect of the connection. It&#;s named after the Radio Corporation of America, which developed and introduced the standard in the s.

What connectors are used for speaker cables?

Speaker wire comes in different gauges and can be terminated with bare connections or connectors like these gold-plated banana plugs.

Unless you&#;re hooking up a PA system, the primary connector you&#;ll likely need to connect your speakers is the banana plug, shown above on the right. Many speakers have binding posts or terminal clamps that will accept the bare ends of the speaker wire. If that&#;s the case, connecting the positive terminal at the source (amplifier) to the corresponding terminal on your speaker is essential to keep everything in phase. Most speaker wire has an identifying mark on one of the conductors to help you keep track of what&#;s what.  In some smaller powered speaker systems, the cable that connects the left and right speakers uses RCA (phono) connectors, as shown below.

Active loudspeakers have built-in amplifiers and require a power source.

How is speaker wire different from regular stereo wire?

Stereo interconnects, which usually have red and white (or red and black) labeled RCA connectors on the ends, are intended for low audio voltages (line level) with low current, and have a central insulated conductor surrounded by a shield (ground) for each channel (left and right).

Speaker cable, or speaker wire, consists of a pair of conductors surrounded by an insulating, flexible PVC or similar material that either has bare ends or banana plugs (see above) at the end. This cable should be specified to carry the power needed to drive loudspeakers to produce sound. Heavier gauge wire is required for higher power, and cables should always be kept as short as possible. As long as these basic requirements are met, there&#;s no point in spending a lot of money on cables, as this past experiment demonstrates.

How are digital connections different from analog ones?

Digital audio connections transfer signals between devices without converting them to analog and back again, which means the quality is preserved. Another bonus is that digital signals are less susceptible to sources of noise and interference, which makes cable quality even less of a concern than with analog.

What type of wire do I need for a digital audio connection?

HDMI cables carry up to 32 channels of digital audio.

Standard consumer-level wired stereo digital connections, often labeled &#;coax&#;(pronounced co-axe, not like the word coax), use the same RCA connectors we discussed previously, specifically with 75ohm coaxial cable. Home theater and AV systems are more likely to use high-definition multimedia interface (HDMI) cables, which also carry digital video signals. These allow eight or 32 audio channels (for HDMI version 2 and above) for surround systems, including Dolby ATMOS, and offer bidirectional capabilities in the form of HDMI ARC and eARC.

What are optical connections for?

An optical cable can transmit stereo digital audio signals.

Optical cables (also called TOSLINK) carry digital audio between devices in much the same way as a wired coax connection, using light to represent the binary data instead of electrical voltage levels. These are preferred in most applications for stereo as they provide electrical isolation between devices, and they can also carry up to eight audio channels in multichannel applications.

If you&#;re looking to transfer audio between devices, these are the most common ways, depending on the type and age of equipment you&#;re looking to connect. Hopefully, this has helped, and now, whether you&#;re looking to listen to music wirelessly or hook up a state-of-the-art soundbar, you&#;ll know what you need to do it.

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