(Last Updated On: May 6, 2019)

You will never look at the headphone jack and plug the same way again.

Headphone jack is dead!

Apple has killed the headphone jack.

Sounds familiar? Ever since Apple removed the headphone jack from the iPhone 7 in favor of a lightning port, other smartphone companies have quickly followed suit with the removal of the once omnipresent port.

“I am Jack’s complete lack of surprise.”

-Fight Club

There are still a few major companies like LG and Samsung who choose to release their flagships with the headphone jack, but I suspect that could change with the upcoming trend of true wireless headphones.

The truth is that most mainstream consumers don’t care for the headphones jack. Good riddance, they say.

So, why should you care then?

Who Is This Guide For?

  • Do you want to enjoy audiophile headphones that only have a wired connection?
  • Are you looking to buy an amplifier for your headphones?
  • Are you looking to buy and upgrade your audio cable?
  • Do you want to try balanced audio?

If you answered yes to any of the above questions, this guide is for you.

By the end of the guide, you will be comfortable with terms like:

  • 3-pole mini
  • Stereo mini
  • 3.5mm single-ended (or unbalanced) cable
  • 2.5mm balanced cable
 

Difference between a Headphone Jack and Headphone Plug

The Sony TA-ZH1ES with many strange looking holes at the front.

Do you see these sockets that the above Sony TA-ZH1ES have? Those are headphones jacks. It is where you insert the headphone plugs to receive audio signals.

A variety of headphone plugs

The headphone jack is a family of electrical connectors that are typically used for analog audio signals. It is also known by other names like phone jack, audio jack, aux input, etc.

There are cases where headphone jack are used for digital audio signals. For example, the Google Chromecast can output either analog or digital signals off its single 3.5mm output jack

Female and male connectors

From Amazon. Male Connector (L) Female Connector (R)

In electrical and mechanical trades and manufacturing, each half of a pair of mating connectors or fasteners is conventionally assigned the designation male or female. – Wikipedia

Unfortunately, the audio industry has not unified in the way the electrical and mechanical trades have to describe the different gender of connectors. You will often find the word “plug” used to describe the male connectors while “jack” used to describe the female connectors.

Evolution of the Headphone Jack

Who is jack?

The origin of the term “jack” can be traced back to 1874 when C.E. Scribner patented, what he calls, a “jack-knife” connector.

Patent of C.E. Scribner

The earliest known jack was a ¼ inch (6.35mm) version and still has mainstream usages which we describe below.

Rounded to pointed tip profile

In the early development days, there were many different jack designs. The rounded tip design was particularly popular because it was compatible with different manufacturers. The rounded tip quickly gained traction as the de-facto tip profile for audio equipment.

But with the rise of stereo audio, a different tip profile was needed to prevent the old rounded tip from frying the circuit when inserted into incompatible equipment. A pointed tip jack will prevent a rounded tip plug from being inserted fully, hence solving the problem.

Anatomy of a Headphone Plug

Conductors

Regardless of the plug size, all headphone plugs have conductors. Conductors are the contact points of the plugs that close the circuit.

A headphone plug has a minimum of 2 conductors and commonly up to 5.

If it has 3 conductors, it may be called a 3 conductor plug. Some manufacturer uses pole to replace conductor. Hence, it can also be called a 3 pole plug.

Identifying conductors.

Each conductor has a specific name:

  • Tip (T)
  • Ring (R)
  • Sleeve (S)

All plugs have at least a Tip and Sleeve. It is the number of Rings that differentiate them. If the plug only has one ring, it is a 3 conductor plug or a TRS connector. If it has two rings, it is a 4 conductor plug or a TRRS connector.

Don’t mistake the black band as a ring. It is an insulating band. The band separates the parts of the plug from being shorted together.

Nomenclature of the Headphone Plug:

  • 2 conductor, 2 pole, TS
  • 3 conductor, 3 pole, TRS
  • 4 conductor, 4 pole, TRRS
  • 5 conductor, 5 pole, TRRRS

Different Plug Connectors configuration

Depending on available conductors, manufacturers can choose to configure jack and plug in various ways. Both must be complementary to each other.

2 conductor plug (TS)

Available Connectors: Only the tip and sleeve connectors are available.

Connectors Connection:

PinFunction
1Ground
2Signal
The connection is fairly straightforward here. One connector is used to carry the audio signal while the other acts as a return path and ground.

The ground acts as a reference point for the signal but it also picks up interference noises like an antenna. The longer the cable, the higher chance the more noise will be picked up.

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: Aside from the tip and sleeve, there is an additional ring connector with two insulating bands around it.

Connectors Connection:

PinUnbalanced MonoBalanced MonoUnbalanced Stereo
1GroundGroundGround
2Optional (Mic etc)Signal - (Cold)Right Audio Channel
3SignalSignal + (Hot)Left Audio Channel
With the addition of another conductor “R”, we open up different possibilities such as supporting balanced mono signals and unbalanced stereo signals.

As seen in the “Unbalanced Mono” column above, the engineer can choose to make use of the additional conductor to carry a microphone signal instead. In this case, where the audio is unbalanced, we may also sometimes refer to this as a single-ended plug.

TRS still cannot carry a balanced stereo signal. For that, see TRRRS connector below.

Common Usage: Most common form of jack connectors. You see these on the end of most stock headphone cables.

4 conductor plug (TRRS)

Available Connectors: With a 4 conductor plug, we have two additional rings with three insulating bands.

Connectors Connection:

PinFunction
1Microphone
2Ground
3Right Audio Channel
4Left Audio Channel
The above connection configuration follows the Cellular Telecommunications and Internet Association (CTIA) standards. Such a connection format is also called the CTIA TRRS jack connector format.

Common Usage: It is the most commonly adopted standard for modern smartphones and gaming consoles where the cable supports a microphone and stereo audio connection at the same time.

5 conductor plug (TRRRS)

Available Connectors: For a 5 conductor headphone plug, we have 3 ring connectors.

TRRRS connectors are used to support balanced stereo signal. You will find that XLR connectors (3 pin pairs, 4 pin, and 5 pin) are also a common choice for stereo balanced headphones. XLR connectors have been the standard balanced connector in the professional audio market for decades.

It is no surprise that when balanced headphone connections grew in popularity, the standard XLR became a go-to solution.

XLR5 Female (L) XLR5 Male (R)
Unlike TRS connectors, XLR connectors have pins instead of tips, rings, and sleeve. However, they work the same way. The XLR5 connector has 5 conductors just like a TRRRS connector.

Sony did make a TRRRS headphone jack – 4.4mm Pentaconn connector.

Penta means “5” and conn is short for connector.

Please be aware that the Pentaconn connectors are new and not adopted widely by the industry. You either have to get an adaptor to accommodate the 5 pole connector or purchase a compatible Sony amplifier.

If you are looking to make your own DIY cable with the 4.4mm Pentaconn connector, check out moon audio store.

Schematic of a headphone jack and plug

From https://www.cui.com/blog/understanding-audio-jack-switches-and-schematics

If you are interested in the schematic of a headphones jack, you can hop on over here for a more detailed article.

Different sizes of headphone jacks/plugs

When we describe the size of the headphone jack or plugs, we are referring to the diameter of the connector.

  • 6.35mm Connector

This is the largest connector among the jacks. It is otherwise known as the ¼ inch connector.

NameSizeConductors
UGREEN Stereo Audio Adapter6.35mm Male to 3.5mm FemaleTRS
UGREEN Stereo Audio Cable6.35mm to 3.5mmTRS
  • 4.4mm Connector
NameSizeConductors
Yinyoo Upgrated 6 Cores Copper Stereo Earphone Cable4.4mm to MMCXTRRRS
FiiO 8-Stranded High-Purity Monocrystalline Silver-Plated Copper Cable4.4mm to MMCXTRRRS
Geekria Apollo Balanced Gold-Plated Adapter4.4mm male to 3.5mm femaleTRRRS
  • 3.5mm Connector

Known as the miniature size or mini for short. You can call it a ⅛ inch too.

NameSizeConductors
AmazonBasics 3.5mm Male to Male Stereo Audio Aux Cable3.5mm to 3.5mmTRS
Zeskit Aux Audio Cable3.5mm to 3.5mmTRRS
Nacodex Audio Cable3.5mm to 2.5mmTRS
Kingtop Combo Audio Adapter Cable3.5mm male to 3.5mm femaleTRRS
  • 2.5mm Connector

Known as the sub-miniature or sub-mini for short.

NameSizeConductors
NewFantasia Replacement Cable with Remote and Mic2.5mm to 3.5mmTRS
NewFantasia HiFi Cable Balanced Male2.5mm to 2.5mmTRRS

Why does a headphone plug matter?

A headphone plug:

  • directly affects the audio signal it transmits.
  • indirectly affects the overall quality of sound.
  • tells us what the cable is capable or not capable of doing (mic, stereo support, etc).

Let us first understand two basic concepts with regards to the transmitted signal from the audio source to our headphones.

Mono VS Stereo Signal

Two types of signal can be transmitted from the audio source to the headphones

  • Monaural (Mono)
  • Stereophonic (Stereo)

A mono signal uses only 1 audio channel while a stereo signal uses two audio channels (left and right).

Stereo signal simulates “natural” hearing by creating the impression of sound coming from different directions. This is accomplished by the separate audio channels producing sound in two different speakers (or stereo headphones). You can call this the “surround-sound” effect.

As for mono signal, the sound reproduced is intended to be heard from one position.

Balanced VS Unbalanced Audio

For a more in-depth discussion on balanced and unbalanced audio, you can read “Balanced vs Unbalanced Audio Connections

Balanced audio is all about interconnecting audio equipment and transmitting signals in a “balanced” manner.

To do that, we need a combination of an audio source (amplifier) that can produce balanced output and a cable that is capable of carrying that balanced output.

From boxcast

A balanced output has two signal phases (or a hot and cold signal) per channel. Each phase has an equal impedance relative to ground, hence the name balanced.

A balanced mono cable typically has at least three conductors (TRS) to carry the signal to the headphones. A balanced stereo cable has at least five conductors (TRRRS).

Advantage of Balanced Audio

The advantage of balanced connections over unbalanced connections is the canceling of noise interference via a technique named Common Mode Rejection (CMR).

Any noise interference that hits the two balanced phases in the cable is imprinted equally on them. The receiving equipment (headphones in our case) 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 they are recombined by the amplifier. This canceling process of noise while preserving the original sound is known as CMR.

This means that balanced cable can run longer than unbalanced cable and operate in noisier environments because it cancels any noise interference.

So when is audio unbalanced?

When the requirements to meet balanced audio are not met, the audio is considered unbalanced.

For example:

  • The audio source is unable to produce a balanced output.
  • The cable is not capable of carrying a balanced signal (TS, single-ended TRS connectors).

Plug is the key

With the above two concepts, you should know that you can send 4 types of signal from the output (amplifier for example) via a cable to a pair of headphones.

  • Unbalanced mono
  • Balanced mono
  • Unbalanced stereo
  • Balanced stereo

Whether a signal can be fully supported or even supported at all depends on the number of conductors found on the plug.

Output SignalJack ConnectorBalanced Audio Connection
Balanced MonoTSN
Balanced MonoTRSY
Unbalanced StereoTRSY
Balanced StereoTRSN
Balanced StereoTRRRSY

Is it confusing?

It can be hard to digest if you are reading all this for the first time. The part where stereo uses two channels and balanced audio needing two copies of the same signal with reverse polarity tripped me up pretty good, too.

An easy way to understand is to first acknowledge that we need conductors to send and carry signals.

The more signals we need to send, the more conductors we need.

For example, if we want to send a balanced stereo signal, it needs to send

  • one right channel (R+),
  • one flipped right channel (R-),
  • one left channel audio (L+),
  • one flipped left channel audio (L-).

In total, it needs 4 signal wire 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 headphone doesn’t receive the complete set of signals to do the CMR. Hence, the whole audio connection becomes unbalanced.

Let’s Practice Our New Skill

Let’s see if we can put our new-found skill to good use.

Remember the “3 pole mini” term we mentioned right at the start of the article? What do you think it means?

3 Pole Mini

Ans: 3.5mm TRS jack

Stereo Mini

Ans: 3.5mm TRS jack (Bonus Qns: why do we think is TRS and not TS?)

3.5mm single-ended cable

Ans: 3.5mm TRS jack (Bonus Qns: Is this a balanced cable?)

2.5mm balanced cable

Ans: 2.5mm TRS jack that can carry balanced signals

From https://www.fiio.com/q5

Do you see that the FiiO Q5 had two outputs? One with a headphone logo, another with “BAL” sign. Do you understand what that means?

Lastly, another practice question.

See if you can read the “Headphone Output” specifications of the Sony TA-ZH1ES and understand what they mean.

If you do, congratulations! You just leveled up your audiophile knowledge.

Do you like this article? Did we miss anything? Let us know in the comment section below.