Don’t let confusing jargon and mismatched connections ruin your listening experience. Here’s a deep dive into headphone jacks and plugs.
Wired music listening should be straightforward: insert the headphone plug into the jack, and you’re good to go.
However, that’s not always the case. Without knowing how jacks and plugs work, you may experience a mismatch, introducing some sound quality issues. Unfortunately, this topic is full of unfamiliar terms, numbers, and complex diagrams that anyone can easily get lost in.
Overcoming this technical concept should be easy with a comprehensive cheat sheet. For this reason, we’ve created a guide to help you learn how jacks and plugs work and how they relate to your headphones’ performance. Read on!
Headphone Jack vs. Plug: What’s the Difference?
Simply put, the “headphone jack” is the port into which you plug your headphones. Sometimes, this is also called a phone jack, an audio jack, or AUX input.
The “plug,” on the other hand, is the part at the end of your headphones’ cable that you stick into the jack.
Jacks and plugs are assigned genders, as per the Association of Electrical & Mechanical Trades. The “jack” is the “female connector,” while the “plug” is the “male connector.”
In more technical terms, the headphone jack and plug are electrical connectors. Both transmit analog audio signals between your headphones and an audio source.
How Headphone Jacks and Plugs Work
The metal pin of the headphone plug has conductors that help transmit audio signals. These conductors come in a gold, nickel, or brass finish, offering varying durability levels.
In contrast, the jack is a hollow barrel lined with conductors.
The conductors in the plug and jack are assigned specific signals, so it’s paramount that they match.
The number of wires inside your headphones’ cable matches the number of conductors on their plug. So, two wires have two conductors, three wires have three conductors, and so on.
This, in turn, corresponds to the conductors in the jack. When you insert a plug into a compatible jack, all conductors should line up perfectly, allowing the audio signal to pass through.
What are headphone plug conductors and why do they matter?
Conductors are the contact points between the plug and the jack, which close the circuit. All headphone plugs, regardless of their size, have conductors. Some plugs have only two conductors, while others have as many as five.
As mentioned in the previous section, compatibility is a significant factor for conductors.
If a mismatch occurs between the conductors on the plug and jack, they won’t line up and make complete contact. This incompatibility can then cause some signals to override others, thus interfering with specific functions of your headphones. In other cases, mismatches can also trigger an electrical short.
How to Identify Headphone Plug Conductors
The different headphone plug conductors have specific names, which are:
- Tip (T)
- Ring (R)
- Sleeve (S)
All headphone plugs have a tip and sleeve. What differentiates each plug is the number of rings. For instance, plugs with one ring are 3-conductor plugs, while those with no rings are 2-conductor plugs.
The terminology for these different combinations is as follows:
- TS (Tip-Sleeve): 2 conductors or poles
- TRS (Tip-Ring-Sleeve): 3 conductors or poles
- TRRS (Tip-Ring-Ring-Sleeve): 4 conductors or poles
- TRRRS (Tip-Ring-Ring-Ring-Sleeve): 5 conductors or poles
Different Plug Conductor Configurations
As previously mentioned, the number of conductors indicates how many wires are inside the headphones’ cable. Each of those wires is connected to a specific conductor and carries a different signal.
So, which signals go to which conductor?
Generally speaking, the wiring schemes for conductors usually look something like this:
- Tip: Signal wire or left channel audio signal
- Ring: Right or left channel audio signal, common return and ground wire, mic audio
- Sleeve: Common return and ground wire, mic audio
However, manufacturers can choose to configure jacks and plugs in various ways.
But one thing remains constant regardless of the configuration: both must be complementary.
That said, it’s a good idea to familiarize yourself with plug conductor configurations to avoid functional errors in your audio devices. To help with this, we’ll break down each format and explain its uses:
- 2-conductor plug (TS)
- 3-conductor plug (TRS)
- 4-conductor plug (TRRS)
- 5-conductor plug (TRRRS)
- Lightning plugs
- USB plugs
2-conductor plug (TS)
Available Connectors: Tip, sleeve, and one insulating band
A TS configuration is relatively straightforward. The tip connector carries the audio signal, while the sleeve acts as a return path and ground.
However, since the ground is a reference point for the signal, it can pick up interference noises like an antenna. The longer the cable, the higher chance it’ll pick up more noise.
Common Usage: You can find TS connectors mainly with guitars, instruments, and applications that do not require a long cable connection.
3-conductor plug (TRS)
Available Connectors: Tip, sleeve, and one ring connector with two insulating bands
|Pin||Unbalanced Mono||Balanced Mono||Unbalanced Stereo|
|2||Optional (mic, etc.)||Signal - (Cold)||Right audio channel|
|3||Signal||Signal + (Hot)||Left audio channel|
Adding a ring conductor (R) opens up different possibilities, such as support for balanced mono signals and unbalanced stereo signals.
As the “Unbalanced Mono” column shows, the engineer can make the additional conductor carry a microphone signal instead. In cases like these, wherein the audio is unbalanced, we can refer to this as a single-ended plug.
Common Usage: These are the most common jack connectors; you’ll often see them on the end of most stock headphone cables.
4-conductor plug (TRRS)
Available Connectors: Tip, sleeve, and two ring connectors with three insulating bands.
|3||Right audio channel|
|4||Left audio channel|
Aside from transmitting stereo audio signals, the TRRS plug also has a dedicated conductor for a microphone. However, its position in the line-up varies depending on whether it follows the Cellular Telecommunications and Internet Association (CTIA) or Open Mobile Terminal Platform (OMTP) standards.
As such, this connection configuration is also called the CTIA or OMTP TRRS jack connector format.
For instance, the CTIA format transmits left and right audio channels through the tip and first ring. The second ring then acts as the ground, while the sleeve handles the mic signal. This format is common on newer smartphones, mobile devices, and gaming consoles.
Like CTIA, the OMTP format sends audio signals through the tip and first ring. However, the conductors for the ground and mic are flipped around. This format is more prevalent among older phone models from Nokia, Motorola, Sony Ericsson, and China-marketed products.
Common Usage: New and old smartphones, tablets, gaming consoles, and some laptops.
5-conductor plug (TRRRS)
Available Connectors: Tip, sleeve, and three-ring connectors with four insulating bands
|2||Right audio channel (-)|
|3||Right audio channel (+)|
|4||Left audio channel (-)|
|5||Left audio channel (+)|
TRRRS connectors have five conductors that support balanced stereo signals.
XLR connectors (3 pins, 4 pins, and 5 pins) are similar in that regard. However, they only have pins instead of tips, rings, and sleeves.
With this setup, each audio channel gets a dedicated conductor, allowing it to transmit clearer signals. So, it’s no surprise that when balanced headphone connections grew in popularity, the XLR became the go-to solution.
Today, 3-pin XLRs are the standard balanced connector in the professional audio market.
As for mobile devices, the additional ring on the TRRRS plug ensures compatibility with newer products that feature multiple microphones or other audio functions like active noise cancellation.
Common Usage: You’ll find TRRRS plugs often used in professional sound and music production settings.
Available Connectors: Eight pins
|2||Lane 0 positive|
|3||Lane 0 negative|
|6||Lane 1 negative|
|7||Lane 1 positive|
When it comes to audio, this is transmitted as digital signals, then converted into analog signals by the DAC (digital-to-analog converter) in your headphones.
Aside from music, Lightning also carries digital data (video, photos, etc.) and supplies power to charge other Apple devices.
Common Usage: You can find Lightning connectors on various Apple products, from Macbooks to EarPods.
Available Connectors: Twenty-four pins (USB-C) and four pins (USB-A)
|Pin (USB-C Plug)||Function|
|A1, B12B1, A12||Ground|
|A4, B9B4, A9||Power (VBUS)|
|B5||Power (VCONN), for powered cables|
|A6||Unshielded twisted pair, positive|
|A7||Unshielded twisted pair, negative|
|A8||Sideband use A|
|B8||Sideband use B|
|A2||Shielded differential pair #1, positive|
|A3||Shielded differential pair #1, negative|
|B11||Shielded differential pair #2, positive|
|B10||Shielded differential pair #2, negative|
|B2||Shielded differential pair #3, positive|
|B3||Shielded differential pair #3, negative|
|A11||Shielded differential pair #4, positive|
|A10||Shielded differential pair #4, negative|
|Pin (USB-A plug)||Function|
USB plugs (A and C) are standard digital connectors for headphones. Both, however, are vastly different in terms of size and configuration.
The larger USB-A plugs have four conductor pins, whereas the smaller Type-C plugs have twelve.
Like Lightning connectors, USB connectors transmit digital audio signals, transfer digital data, and supply power. But, the USB-C functions at a much higher and faster rate, thanks to a heftier power capacity of 100 watts.
Common Usage: Aside from headphones, you’ll also find USB A and C connectors on computer peripherals such as printers, smart TVs, scanners, keyboards, external hard drives, and more.
Different Sizes of Headphone Jacks and Plugs
Headphone jacks and plugs come in different sizes, and it’s essential to have a basic understanding of these differences to ensure compatibility between your audio devices.
Common size configurations for jacks and plugs are 3.5mm, 2.5mm, and 6.35mm. The 3.5mm jack, in particular, is practically universal for headphones and audio gear and thus is considered the standard headphone jack size.
That said, here’s a closer look at the different headphone jack sizes and their functions:
- 3.5mm (1/8″) headphone jack and plug
- 2.5mm (3/32″) headphone jack and plug
- 6.35mm (1/4″) headphone jack and plug
3.5mm (1/8″) headphone jack and plug
Otherwise known as a “miniature” or “mini” connector, the 3.5mm plug often comes in TS, TRS, or TRRS configurations. It readily outputs mono and stereo audio, plus video. You can find this type of connector on a wide range of headphones, mobile devices, portable media players, video recorders, etc.
If you need a 3.5mm cable, here are some good ones:
|AmazonBasics 3.5mm Male to Male Stereo Audio Aux Cable||3.5mm to 3.5mm||TRS|
|Zeskit Aux Audio Cable||3.5mm to 3.5mm||TRRS|
|Kingtop Combo Audio Adapter Cable||3.5mm male to 3.5mm female||TRRS|
2.5mm (3/32″) headphone jack and plug
Sometimes called a “sub-miniature” or “sub-mini,” the 2.5mm plug is a smaller version of the 3.5mm plug. Functionally, both are the same. The 2.5mm plug also comes in TRS and TRRS configurations and outputs mono and stereo audio.
If you’re looking for a 3.5mm to 2.5mm cable, here are a couple to consider:
|NewFantasia Replacement Cable with Remote and Mic||2.5mm to 3.5mm||TRS|
|NewFantasia HiFi Cable Balanced Male||2.5mm to 2.5mm||TRRS|
6.35mm (1/4″) headphone jack and plug
The 6.35mm plug, or ¼-inch connector, is this list’s largest and oldest connector. They were traditionally used as old-school telephone connectors and come in TS or TRS configurations.
Today, people use 6.35mm connectors mainly with professional audio equipment such as amplifiers, mixing consoles, audio interfaces, and musical instruments.
These are some examples of 6.35mm connectors:
|UGREEN Stereo Audio Adapter||6.35mm Male to 3.5mm Female||TRS|
|UGREEN Stereo Audio Cable||6.35mm to 3.5mm||TRS|
How the Headphone Jack and Plug Affect Sound Quality
Since headphone plugs and jacks are responsible for transmitting audio signals, they can:
- directly affect audio signals
- indirectly affect the overall quality of sound
- tell us what the cable is capable or incapable of doing (mic, stereo support, etc.).
Before we delve into how this happens, let’s first tackle two basic concepts regarding transmitted signals between headphones and audio sources.
Mono vs. stereo signal
There are two types of signals transmitted from an audio source to headphones: monaural (mono) and stereophonic (stereo.)
Stereo signals simulate “natural” hearing by creating the impression of sound coming from different directions. They do this by using two separate audio channels in each speaker, also called the “surround-sound” effect.
Mono signals, on the other hand, use only one audio channel and reproduce sounds only heard from one direction.
So, how do headphone jacks and plugs affect sound quality?
Again, it all goes back to compatibility. For instance, mismatched plugs and jacks will result in an incomplete circuit, leaving you with no sound. Similarly, if you hook up a stereo plug to a mono output jack, you will likely only hear sound from the left audio channel.
Balanced vs. unbalanced audio
Balanced audio is all about interconnecting audio equipment and transmitting signals in a “balanced” manner. To do that, you need an audio source (amplifier) that can produce balanced output and a cable capable of carrying that balanced output.
A balanced output has two signal phases (or a hot and cold signal) per channel. Each phase has an equal impedance relative to the ground, hence the name “balanced.”
A balanced mono cable typically has at least three conductors (TRS) – two to carry the left and right audio signals to the headphones and one for the ground. In contrast, a balanced stereo cable has at least five conductors (TRRRS) – four to carry both negative (cold) and positive (hot) audio channels and one for the ground.
Advantages of balanced audio
The advantage of balanced connections over unbalanced connections is the canceling of noise interference via Common Mode Rejection (CMR).
Any noise interference that hits the two balanced phases in the cable is imprinted equally on them. The receiving equipment (such as headphones) only cares about the difference between the phases.
So, interference that adds equally to both phases creates no difference between them and is canceled out when the amplifier recombines them. This process of canceling noise while preserving the original sound is known as CMR.
As such, balanced cables can run longer than unbalanced cables and operate in noisier environments because they can cancel out any noise interference.
So when is audio unbalanced?
When the requirements for balanced audio are not met, the audio is considered unbalanced.
- The audio source cannot produce a balanced output.
- The cable cannot carry a balanced signal (TS, single-ended TRS connectors).
The headphone plug is the key.
With the above two concepts, you should now know that you can send four signal types from the output (amplifier, for example) via a cable to a pair of headphones.
Here’s how audio signals flow with each type of output:
Whether a signal can be fully supported or not depends on the number of conductors on the plug.
That said, here’s a quick chart on what you need to get balanced audio:
|Output Signal||Jack Connector||Balanced Audio Connection|
Is it confusing?
You’re not alone! The technicalities can be hard to digest when reading all this for the first time. The part about stereo audio using two channels and balanced audio needing two copies of the same signal with reverse polarity tripped me up, too.
An easy way to understand is by first acknowledging the bottom line – that you need conductors to send and carry signals.
The more signals you send, the more conductors you need.
For example, if you want to send a balanced stereo signal, you’ll need:
- one right channel (R+),
- one flipped right channel (R-),
- one left channel audio (L+),
- one flipped left channel audio (L-).
In total, you’ll need four signal wires and one ground wire which only a TRRRS connector can provide.
Thus, if a jack with an inadequate connector is used (like a TRS connector), the headphones won’t receive the complete set of signals to perform CMR. Hence, the entire audio connection becomes unbalanced.
Other Headphone Jacks and Plugs Factors That Affect Sound Quality
As you saw in the previous section, audio issues can occur due to incorrect or incompatible plug configurations. Moreover, these issues can also arise from external causes like dirt or damage.
Here’s a closer look at the other headphone jack and plug factors that affect sound quality:
The headphone jack clamping mechanism
The internal mechanism of the headphone jack includes two clamps designed to push down on either side of the headphone plug.
When inserted, these clamps are firm enough to keep the plug steady and centered. This ensures the conductors of the jack and plug are in constant contact. However, they also have a decent amount of springiness that lets you easily insert and pull out the plug.
The simplicity of this design means that these clamps can become loose over time, especially if you’re constantly yanking and reinserting your audio cable. As such, you end up with a loose headphone jack that causes static interference in your audio.
Dirt in the headphone jack and plug
Headphone jacks accumulate dirt over time simply because it’s too easy for dust and lint to enter and get stuck inside the jack. Too much dirt can eventually obstruct the conductors, leading to static noise, muffled sound quality, and other audio issues while using your headphones.
Although made of metal, headphone plugs can still easily bend or break if you accidentally rip them out hard enough. Doing so can result in irreparable damage that will cause audio issues in your headphones.
Essentially, a bent headphone plug means its conductors are out of alignment. As such, you won’t achieve proper contact with the headphone jack conductors. And because the audio signal can’t be transmitted fully, you may only hear sound from one speaker, hear static, or have a low volume.
Let’s Practice Our New Skill
Let’s see if you can put our newfound skills to good use.
Remember the “3 pole plug” term mentioned earlier in the article? What does it mean?
3 Pole Mini
Answer: 3.5mm TRS jack
Answer: 3.5mm TRS jack (Bonus Qns: why do we think it is TRS and not TS?)
3.5mm single-ended cable
Answer: 3.5mm TRS jack (Bonus Qns: Is this a balanced cable?)
2.5mm balanced cable
Answer: 2.5mm TRS jack that can carry balanced signals
Can you see the two outputs on the FiiO Q5? One with a headphone logo and another with a “BAL” sign. What does that mean?
Lastly, another practice question:
See if you can read the “Headphone Output” specifications of the Sony TA-ZH1ES and understand their meaning.
If you do, congratulations! You just leveled up your audiophile knowledge.
Did you like this article? Did we miss anything? Let us know in the comment section below.