Headphone jacks and plugs have made using our beloved audio gadgets easy for decades. Who would have thought a plug from 1877 could endure until now? While the first plug/jack was 6.35mm, new standards emerged over time. Currently, headphones support up to 5 different connectors. Let’s take a closer look at each of them, learn their pros and cons, and when you can use them. CONTENTS (show more) The Difference Between Headphone Jack and Headphone Plug “Plug” is a type of connector that gets inserted into a “jack”. For example, the plug is at the end of the headphone’s cable, whereas your smartphone or laptop has a jack. To avoid confusion (especially since plugs are sometimes called jacks), the cable industry uses male/female wording to describe jacks and plugs. Female connectors have one or more sockets (holes), and male connectors have one or more pins that sit in those holes. These connectors exist so that people can easily plug and unplug cables from one device to another. A female “jack” is on the left, and the male “plug” is on the right. How Headphone Jacks and Plugs Work Male headphone plugs are usually a pin with 2 or more conductors (or poles). In contrast, female audio jacks are a socket with conductors that make contact with male conductors. Headphone jacks and plugs work by exchanging the signal from one to the other. Both female and male sides can act as input or output. What are headphone plug conductors? Headphone plug conductors are different poles you see on a plug itself, separated by a black (or another color) band. Looking at a typical headphone plug, 3.5mm connectors with a TRS cable, those conductors are called: T-tip, R-ring, and S-sleeve. Each of those poles connects to a different wire in the cable. How to Analyze Headphone Plug Conductors Most headphone plugs use TRS cables, which stands for: T – tip R – ring S – sleeve We also know different versions of the TRS cables: TS cables only have 2 conductors (or poles) as they only have a tip and a sleeve. TRS cables have 3 conductors. TRRS cables have 4 conductors. TRRRS cables have 5 conductors. Between poles, there are black bands made of nonconductive material that separate the poles from touching each other. Looking at the number of poles, you can immediately tell what you can expect from the connection. More on that later. Let’s go a bit deeper into how are different TRS configurations wired. TS This plug has a tip and a sleeve. The tip carries a signal, whereas the sleeve acts as ground (and a shield). TRS This plug has a tip, ring, and sleeve. Depending on how you use the connector, the pole can take a different role (except the sleeve, which is always ground). Unbalanced mono: the tip is for signal, and the ring is for the microphone or other things like remote control. Balanced mono: the tip is for the positive signal, and the ring is for the negative signal. Unbalanced stereo: the tip is for the left channel signal, and the ring is for the right channel signal. TRRS This plug has a tip, 2 rings, and a sleeve. Typically, this kind of plug is used for headsets since it uses the extra ring for the microphone signal. However, you can get a balanced signal with 2.5mm connectors. Unbalanced stereo (with a mic): the tip is for the left channel, ring 1 for the right, ring 2 for the microphone, and the sleeve is ground. Balanced stereo: the tip is left channel (+), ring 1 is right (+), ring 2 is left (-), and the sleeve is the right channel (-). It’s worth mentioning that there are 3 different 3.5mm TRRS connector standards: OMTP, CTIA, and Apple’s version of CTIA. OMTP is an older standard used in older phones from Nokia, Sony Ericsson, and Motorola. It is still currently used in China. CTIA is an international standard used everywhere except China. The only difference between CTIA and OMTP is that they use different conductors for the ground wire and a mic signal. Apple’s CTIA is a proprietary solution to prevent users to use Apple Earpods with devices other than Apple’s. Just like between OMTP and CTIA, you need an adaptor to use Apple’s CTIA with other audio jacks. TRRRS This plug has a tip, 3 rings, and a sleeve. It’s pretty rare and primarily used in audiophile cables for balanced connection. Balanced stereo: the tip is the left channel (+), ring 1 is the right (+), ring 2 is the left channel (-), ring 3 is for the right (-), and the sleeve is for the ground. Here’s a comparison of TS, TRS, TRRS, and TRRRS: Different Types of Headphone Jacks TRS cables described above typically terminate in 2.5mm, 3.5mm, 4.4mm, or 6.35mm plugs or jacks. We also know XLR headphone plugs, but those aren’t common. While 3.5mm and 6.35mm are the most common types of headphone connectors, 2.5mm and 4.4mm are mainly used among audiophiles due to their balanced connection capabilities. More on that later. Explanation of the 3.5mm plug and its different types The 3.5mm plug is the most used type of headphone connector for consumer headphones. Designed in the 1950s, it’s also known as a phone connector, audio plug, headphone plug, AUX plug, etc. Since you can find 3.5mm jacks in most consumer gadgets, from PCs, tablets, and smartphones, the connector evolved into 3 different types. TS version supports an unbalanced mono signal, mostly from an external microphone. TRS version supports an unbalanced stereo signal thanks to extra wire in the cable, and it’s the most widely spread version of the 3.5mm connection. It can also support a balanced mono signal, but that’s rare. TRRS version has a total of 3 signal wires, so it can also receive a microphone signal and commands from inline controls, on top of supporting an unbalanced stereo signal. Don’t confuse this configuration with the 2.5mm TRRS version used for a balanced connection. Explanation of the 6.35mm plug and its different types A ¼ inch plug is another widely used connector for headphones, often found in studio headphones or pricier models. Power-wise, 6.35mm and 3.5mm offer the same capabilities, so even if you use adaptors to convert from one to the other, you don’t experience any power loss. That said, a 6.35mm headphone connector is more suitable for professional use since it is more robust (apart from XLR one). ¼ inch connections normally come in 2 different types: TS cables support unbalanced mono connection, typically used for instruments like guitars or synthesizers. TRS cables support unbalanced stereo connection and are a common type for a 6.35mm plug for headphones. Explanation of the 2.5mm plug and its different types The 2.5mm plug is a relatively new format from the 2000s, which isn’t as widespread. Mostly because it’s the most fragile, and the 3.5mm offered everything users needed. While you can see it in some headphones with a detachable audio cable (like Bose headphones), a 2.5mm plug is mostly known for providing a balanced connection. There are 3 different types of 2.5mm plugs: TS version is used primarily in detachable cables in headphones where each driver is powered separately. TRS version is used primarily in detachable cables you get with your Bluetooth headphones. For example, Bose headphones have this type of jack under the earcup. TRRS version supports balanced headphone connections, but that isn’t a true balanced connection. More on that later. Explanation of the 4.4mm plug and its different types The 4.4mm Pentacon is by far the rarest plug, mainly used by audiophiles using special headphone cables. It was developed in 2015, and it only comes in TRRRS cable configuration. It can send a balanced stereo signal to headphones, although not in its proper balanced connection form. Explanation of the USB (USB-C and other types) USB cables for headphones fall into 2 sections. One covers headphones that use USB-A or C plugs, and the other covers USB audio dongles. Let’s start with the latter. USB audio dongle/adaptors After the fast removal of the headphone jack from almost all mobile phones, USB audio dongles became an alternative for listening to a wired headset on the go. Nowadays, you can get digital USB-C audio dongles with built-in DAC that terminate to a 3.5mm jack. The latter supports TS, TRS, and TRRS plugs. Micro-USB vs. USB-C plug. Headphones with a USB plug As for the headphone cables with a USB plug, they are mainly used for headsets as an alternative to double 3.5mm TRS plugs for audio and mic or a single TRRS plug. For a short time after the headphone jack removal from smartphones, some headphones and earbuds started using USB-C plugs, but the trend didn’t catch on. Nowadays, gaming headsets primarily use USB plugs to power RGB effects, possibly using separate 3.5mm plugs for audio only. Explanation of the Lightning The lightning connector introduced by Apple in 2012 is still used in iPhones, cheaper iPads, and AirPods for charging and data transfer. Since it can also transfer audio, just like USB, it came in handy after removing the headphone jack. It became the only plug for some headphones and earbuds, but it didn’t catch on. Nowadays, you can only get Lightning audio dongles that terminate to a 3.5mm jack. Apple AirPods Max use a proprietary cable with a Lightning plug on one end and a 3.5mm TRS on the other. Lightning audio dongle connected to the RAPTGO x HBB in-ear monitors. Explanation of the XLR plug and its different types XLR connector, or “External Line Return”, was invented in 1950s, and it has since become the most trustworthy connector in the professional audio industry. Primarily used for connecting audio equipment like instruments, microphones, and mixing tables, it’s the most optimal choice for professionals due to its durability and true balanced connection properties. When it comes to headphones, there are two versions of XLR plugs. 2x 3-pin XLR connectors. 4-pin XLR connector. Both versions offer a balanced headphone connection. The two 3.5mm plugs terminate into a 4-pin XLR plug. Different Types of Headphone Y Splitters Headphone Y splitters fall into two groups; they either split a single signal into 2 or more, or they have a dedicated jack for a microphone. It depends on why you want to use a splitter. If you want to share music with others or divide a signal so you can send it to different amplifiers (for audio mixing), you need a regular stereo Y splitter (with a TRS connector). If you plan to use your headphones and an external mic with a 3.5mm connector, you need a stereo Y splitter with a designated microphone jack (the splitter should have a TRRS plug). Antlion’s splitter for laptops offers 3.5mm TRRS headphone jacks. Ensure you buy a good quality Y splitter, preferably with a short cable. Even with cheaper ones, the design ensures less stress on the splitter and a better chance of getting a good connection. From our experience, Y splitters with a plastic shell that immediately separates into multiple ports suffer from poor connection and terrible buzzing. Note that nowadays, due to the absence of the headphone jack from most smartphones, Y splitters also arrive with USB-C or Lightning plugs. How Headphone Jacks and Plugs Impact Sound Quality How headphone jacks and plugs impact sound quality depends on the quality of their construction and whether you mismatched a plug and a jack. When it comes to quality, worse plugs can be out of tolerance. They might not sit correctly in the jack, or have an improper connection with the ground, making a buzzing noise. Mono signal vs. stereo signal The difference between mono and stereo signal is that in mono, you only have a signal for one channel, whereas stereo has two channels with different signals. However, mono uses a TS connection and stereo TRS or TRRS. If you mismatch the cables, you might connect the stereo plug to a mono jack. As a result, you will only hear a signal coming from the left channel (the tip of the plug always carries the left channel audio signal). A little bit about mono vs. stereo Stereo audio exists because humans have two ears, and we hear the world in stereo. By using psychoacoustic tricks, people can experience full-blown surround sound just by using left/right channels. However, sounds like voices and instruments are very directional, so it’s enough to record them in mono. That’s why microphones use the mono connection. Of course, that doesn’t mean a speaker system with one driver only outputs a left audio channel signal. In that case, both audio channels are combined. Outdoor Bluetooth speakers with one driver (JBL) work like that. JBL Flip 6 uses a woofer and a tweeter, both having a mono audio output. That said, if you insert a mono plug into a stereo jack, the signal won’t combine. You will only hear a left channel. Balanced audio vs. unbalanced audio Balanced audio is better than unbalanced audio since it can cancel out unwanted noise picked up by the wires. However, this only works when connecting balanced cables from a device to a device. There’s some confusion regarding this term, as its use in headphones is misleading. Balanced headphone cables don’t cancel noise like audio devices can. Instead, they offer “differential signaling.” Let’s explain. With unbalanced headphone cables, the negative signal wire from both drivers is tied together, so you end up with 3 wires in total (TRS). In contrast, balanced headphone cables have an additional 4th wire so that each driver can run separately. That ensures up to double the voltage. With differential signaling, headphones run more efficiently, have (supposedly) better crosstalk, and can get louder or quieter. Balanced is recommended for high-impedance headphones. Premium headphone amps offer a balanced headphone connection with differential signaling. The nasty thing is that not all headphone amplifiers with balanced output support differential signaling, which defeats the purpose of such a connection. When buying an amp, ensure that the balanced output power is twice as higher as the unbalanced one. Otherwise, they’re selling you snake oil. Problems with Headphone Jacks and Plugs Jacks and plugs exist to make our lives easier. However, all the pulling in and out can take a toll on the connectors. Here are the most common issues you might encounter with headphone jacks and plugs. Loose headphone jack Inside a headphone jack, there are golden pins, each designed to touch either a tip, ring, or sleeve. They’re slightly bent and springy to better grab the plug. When using the jack for the first time, it grabs firmly with a reassuring click. However, after years of use, the plug might come out of the jack with just a little push. The reason is that those pins inside the jack lost their springiness, and they no longer securely grab the plug. In the case of the loose headphone jack, you can’t do much except be careful not to pull on the cable. The best you can do is to limit the number of plug/unplug cycles. According to Mouser Electronics, their audio jacks have a lifespan of 5000 plug/unplug cycles. Dirt Smartphones were usually in your trousers’ pocket or inside a purse. In both cases, various debris, like pieces of fabric and gunk, slowly accumulate inside the headphone jack. You would be surprised how much gunk gets stuck in your smartphone’s ports. At some point, there’s so much debris that the pins can’t make proper contact, even if the plug seems sited in. If your headphone jack suddenly stops working, inspect the socket with a flashlight. If you see debris inside of it, use a small, elongated tool like a paperclip to scrape the dirt out. Be gentle when scraping out, and don’t use tools that could latch on the pins and rip them out. If that happens, you will need to replace the jack entirely. Learn more about how to clean a headphone jack. Damage If you accidentally step on the cable and hear a loud crack, you probably broke the plug. Due to the headphone plug design, they are susceptible to bending and breaking. Thankfully, they’re also pretty robust, so they keep on working, even if slightly bent. Furthermore, to fully break them, you have to pull hard and at an angle to snap them in half. We split our 3.5 mm plug on the image by hitting it multiple times with a rock. A broken tip of the 3.5mm plug. Wear & tear Apart from breaking the plug, which is unlikely, pins inside the jack might scratch the conductors to the point where they no longer receive signal. Pins are thin wires that scratch the plug while it is rotating. Eventually, they form grooves that become deeper and deeper. At some point, pins no longer create secure contact with conductors. And you start experiencing problems like the right channel stopping producing sound or inline controls and the mic not working anymore. Similar wear and tear situation can happen with USB plugs. Thankfully, USB-C is much more robust in practice than Micro-USB, even though they’re both rated for 10000 plug/unplug cycles. Uses and Devices As the headphone industry leans towards wireless solutions, wired headphones are slowly becoming a niche product for a selected group of users. That means that the number of everyday gadgets that support a headphone audio jack is getting thinner every day. Fortunately, you still find headphone ports in devices like: Laptops PCs Headphone amplifiers Home theater AV receivers Mixing tables Budget smartphones & tablets 6.35mm port in the front panel of the speaker amplifier. Professionals, audiophiles, and casual users still use wired headphones. Professionals use them due to their reliability and simple plug & play operation. Studio headphones are often robust and have zero latency by design, which is vital for monitoring audio. Audiophiles use wired headphones for multiple reasons. Most important is that no wireless headphones have yet reached the performance of premium audiophile headphones. Secondly, wired headphones can have a more scalable performance, meaning that changing cables, DAC, or amp can influence the audio quality. Casual users use wired headphones mostly because they like the convenience of simply plugging the cable and not constantly charging the headphones. Or they were once disappointed by Bluetooth performance, so they returned to wires. Frequently Asked Questions (FAQ) Are all 3.5mm headphone jacks the same? Not all 3.5mm headphone jacks are the same. Some only output stereo headphone signal, some can input microphone signal as well, and some only act as mic input. For example, your laptop supports audio and mic from one port, but your amp can only do audio. What does 3.5mm headphone jack mean? A 3.5mm headphone jack means it supports 3.5mm headphone plugs and primarily transfers analog audio signals. What is the difference between AUX and 3.5mm? AUX ports are meant for receiving audio, whereas a 3.5mm port is meant for broader use for headphones. You find AUX ports in your car, Bluetooth speakers, or home amplifiers. How do you tell if a jack is 2.5mm or 3.5mm? You can tell them apart visually since the 2.5mm jack is about 50% smaller than the 3.5mm. If you often use 3.5mm plugs and jacks, the difference should be noticeable immediately. What is the difference between a 3.5mm mono jack and a stereo jack? A 3.5mm mono jack only receives the audio signal from one channel, whereas you get both the left and right channels from a stereo jack. 3.5mm mono jacks are usually microphone inputs, so there should be a mic icon near the jack to avoid confusion. Conclusion These are the most essential facts about headphone jacks and plugs. Hopefully, you better understand how headphone connectors work and can make an educated decision before buying a new headphone cable or amplifier. If you want to learn more about analog and digital audio signals or understand a more comprehensive range of audio connectors, feel free to read our separate in-depth articles LINKZ. Peter SusicPeter’s childhood interest in audio has grown into a full-blown quest to find the best headphones. He’s got many years of editor experience trying out numerous audiophile and consumer headphones. His words: “After many years, I can confidently say which ones are good and which ones are terrible.” Find his honest opinion in his reviews and guides.