Audio is not hard to understand, and we have plenty of pieces going explaining everything from how active noise cancelling works to what a Bluetooth codec is. So why the hell are audio connections so damn complicated? If you’ve ever spent time flipping through inputs on your TV or receiver trying to figure out why there was no audio to go along with the picture, this is for you. We’re breaking it down once and for all and explaining every audio connection as well as what they’re used for. Just as a heads up so you don’t waste your time reading about things you don’t care about, we’re going to be over the headphone jack, USB-C, MMCX, Bluetooth, XLR, banana clips, speaker cables, RCA, optical cables, and HDMI ARC in that order.

Let’s start with the good ‘ol headphone jack

Beyerdynamic Aventho Wireless headphones Bluetooth aptX HD portable On-Ear

Wired listening is available as long as the source device has a headphone jack.

The one audio connection that most people are probably familiar with is the headphone connector. This comes in a few different varieties depending on the use case. There’s the ¼” connector, which is the largest and one that you might recognize if you’ve spent any time around audio equipment, high-end headphones, or switchboards from the late 1800s. Then there’s the 3.5mm connector, which is most common and what you probably think of when you hear the phrase “headphone jack”. It’s widely used on portable devices because of its size. Lastly, there is the 2.5mm connector which is the smallest and least common, but still used at times when space is at a premium. For example, the Monoprice Monolith M1060 headphones have 2.5mm inputs at the bottom of each earcup for the wire to connect to.

RHA MA390 review: The MA390 headphone jack on the left (all black) next to the MA750i headphone jack, which is stainless steel with a spring stress-reliever.

The 3.5mm headphone jack is gold-plated but could use a beefier stress-reliever like the MA750i is equipped with.

But that’s not all you need to know, because these connectors aren’t just used for transferring music. Sometimes, as in the case with most headphones, they also have to be used for transferring your voice while you’re on the phone. In some cases, they also need to be used to split the audio to either one or two channels (mono or stereo). This is where the terms TS, TRS, and TRRS come into play. It might seem complicated, but just like everything else in audio, it really isn’t. Just a bunch of smart people trying to seem smarter.

The letter “T” stands for tip, “R” stands for ring, and “S” stands for sleeve. When you see a TS plug, that means that it’s mono, or it doesn’t split the audio into left and right signals. The tip acts as to send or receive signals, while the sleeve is the ground. In a TRS connector, the tip acts to split the signal to the left, while the ring is for the right. Here too, the sleeve acts as the ground. So what happens in a TRRS connector? You guessed it, it just has a second ring in the middle. That second “R”, or ring, acts to transport signals to the microphone so it’s what you’ll most commonly find in headphones meant to be used with phones. Fun fact, but Apple uses a slightly different TRRS connector where the ground and microphone sections are switched, which is why the “MAde for iPhone” headsets is a thing.

What is USB-C?

USB-C, headphone jack: Google Pixel 3 with USB-C headphones connected and Nintendo Switch controller in top left corner of image.

You may also have heard of a brand new kind of plug called USB-C, and it’s supposed to be the latest and greatest plug that will solve all our problems. Engineers from some of the top companies all came together to create this new standard plug which is supposed to do everything from transfer huge amounts of digital data to charging your devices. Included in this plethora of use cases is the transfer of audio data. We highly recommend reading the full explanation on how USB-C works and why it is different than the analog 3.5mm jack, but in short, what you need to know is that the goal of USB-C audio transfer is to keep the data in its digital for as long as possible so that by the time it gets converted into analog sound waves that you can hear there isn’t much degradation in quality.

The Libratone Q-Adapt in-ears work perfectly with the Pixel 2XL

It sounds great in theory, but the problem is that even though the standard is supposed to be universal, there have been more than a few hiccups when it comes to compatibility between devices. Some USB-C headphones work on certain devices, while others do not. Not to mention that if you have a device with only a single USB-C port (like a smartphone), then you’ll need another dongle in order to charge your device and listen to music simultaneously which simply is not convenient. Hopefully, the USB-C market will grow into something worthy of the headphone jack, but currently, it isn’t a suitable replacement just because it can technically transfer audio.

What’s an MMCX connector?

When you leave the realm of cheap earbuds and start looking for something that’s going to put a bigger on sound quality, you might come across a few pairs rocking MMCX connectors. But what does that mean? MMCX stands for micro-miniature coaxial and as the name implies, they’re miniature. Small enough to easily fit into a pair of in-ear monitors. This attachment is used mainly in in-ear monitors because usually, those kinds of earbuds aren’t cheap. They’re feats of engineering that are difficult to make, and it doesn’t make sense to need to throw them away every time the audio cable gets damaged or becomes frayed over time.

Shure BT2: Overhead image of the RMCE connectors at the end of the cables with the detached SE215 earbuds shown, too.

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

Using an MMCX connector allows the user to just swap out the cable in those instances when it becomes damaged versus needing to buy a whole new pair of in-ears. Plus, the connection itself locks into place and allows for 360 degrees of rotation, so not only does it make the wire easier to replace but it also makes it harder to break in the first place. Then there’s the added benefit of versatility. If you buy a pair of quality in-ear monitors for your phone, you might only require a standard 1.2m cable. But if you and the band make it big and are performing at Good Morning America next week, you can get a longer cable fit for performing on stage without needing to buy a brand new pair of headphones. Though at that point you can probably afford to buy whatever you want, but I digress.

Obviously, then there’s Bluetooth

Jabra Elite 85h: Straight-on image of the headphones and the USB-C and 3.5mm inputs on the ear cup.

You can connect via Bluetooth or use the included 3.5mm cable for wired listening and optimal audio quality.

If you don’t want any wires on your headphones, then you basically have to go with Bluetooth. Bluetooth audio has become wildly popular and the fact that the Bluetooth speakers and headphones market have been increasing is the reason we all have jobs here at SoundGuys. But that doesn’t stop us from saying that Bluetooth is pretty terrible, at least when it comes to sound quality. While it’s definitely improved since its inception and most people won’t hear a difference, our testing shows that wired is still king when it comes to quality.

Graph of Average Bluetooth Codec Latency

Bluetooth is going to be useful when you want to ditch the wires and is popular in consumer headphones and portable speakers. You’ll rarely find Bluetooth in any professional equipment because of the sound quality, but as it improves I wouldn’t be surprised to see it pop up here and there. The biggest problem with Bluetooth is that if you want to use it to hook up a pair of headphones or speakers for watching movies, it requires a low latency codec to help keep the audio and the visuals in sync. Otherwise, if you’re using the standard SBC codec, the lips of the actor on the screen are going to move before you hear what they’re saying which, needless to say, can be really annoying. So if you’re going to be using Bluetooth headphones or speakers, make sure it features a low latency codec.

Why should you use an XLR cable?

This seems like a good time to bring up another important type of audio connection: XLR. Most people will probably never need to know anything about XLR cables, but if you plan to spend any time around professional audio equipment then you should get familiar as XLR is pretty much the standard for professional microphones. XLR cables have a female and male end to them, and usually, have a number of pins inside that match up when connecting to equipment.

Close-up shot of the pins in an XLR cable and on a microphone and audio interface

The most common XLR cable for microphones feature 3 pins

The most common that you’ll likely come across has three pins and is called XLR3, but there are others that can have more. Again, the most common use case for XLR cables are professional microphones but if you’re just starting out in audio and still don’t want to deal with all of the equipment involved in XLR microphones, don’t worry. You can still pick up a pretty decent microphone that goes directly through USB so you can plug it directly into your computer.

What’s a banana clip?

When you start looking into setting up home audio speakers, banana clips are another kind of connection you should probably be familiar with. Why it’s called a banana clip is beyond me, but I guess to some people it must look like a banana? The unique shape is due to a tiny spring inside that pushes outwards, ensuring good contact of the metal when you plug it in. These are typically used in speakers and loudspeakers when you need to connect wires to power them or join to other kinds of equipment. Putting these at the end of your speaker cable allows for a more stable and more efficient connection. Plus, this means that you can cut the speaker wires to exactly the length you need avoiding an unnecessary mess of speaker cables behind your receiver.

Let’s talk speaker wires

A photo of two speaker wire terminations, and two TS plug terminations.

Who will win, the coathanger, or the well-engineered consumer cables?

The most direct method of hooking up a pair of speakers or amplifier is to simply connect everything yourself with some speaker cables. This is fairly simple and is going to use the same binding posts as the banana clip we mentioned earlier. The only difference is that instead of plugging in a piece of metal like you would with banana clips, you’re going to unscrew the binding posts. Not all the way, but just enough so that you can see the holes that you need to stick the speaker cables into. Now you’re going to want to expose some of the wire and twist it so that it’s easier to stick through the hole. Once you do, you can screw the binding post back down The red post is going to be the positive terminal, while the black one is negative.

What exactly is an RCA connector?

Fluance Ai40 review: The remote, adapter wire, and RCA cable all shown on top of the speaker units.

Aside from the Ai40, the package includes a remote control, an 18-guage speaker wire, and a three-foot RCA cable.

If you were alive before the age of 4K Ultra-high def curved TVs, then you probably found yourself holding a trio of colorful cables at one point in your life. Those cables are RCA plug, which stands for the original manufacturer of the cables, the Radio Corporation of America. An RCA cable splits into three plugs at the end. Typically one is red, one white, and one yellow. In modern times, these are used when audio and video need to be transferred simultaneously between devices. The red cable is the right audio channel, the white is for the left audio channel, and the yellow is responsible for transferring composite video. My first memories of this connection were in the early 90s when connecting VCRs and gaming systems like the Nintendo 64 to a TV was a thing. Thankfully, the corresponding plugs on the back of the TV were also color coded which made setting everything up fairly straight forward.

What is an optical cable?

An optical cable is another way of transferring both audio and visual data simultaneously. They are used for similar reasons that an RCA connector is used, which is to connect any device that has a visual component, like DVD players or even gaming systems. The biggest difference is that where RCA cables use copper wires to transmit signals, an optical cable uses super thin plastic that is able to transmit light.

Pictured is both ends of an optical cable.

An optical cable can transmit signals with less degradation because it uses light instead of electricity.

This drastically improved the quality of the signal over long distances when compared to RCA cables, because RCA cables transmit electricity which can degrade with distance. That isn’t a problem with light, so the end signal of an optical cable ends up being much much closer to the initial information. This is why the optical cable has largely replaced RCA in newer devices. As we mentioned, you’ll most likely find an optical port on anything that needs video and audio to co-exist, like a gaming console, DVD player, or soundbar.

Another great option is HDMI ARC

While we’re on the topic of connections that transfer both audio and visuals, there’s one last one that we should cover and that’s HDMI ARC. You’re probably already familiar with HDMI as the main form of connection between screens, but what does the ARC mean? HDMI ARC stands for “High Definition Multimedia Interface Audio Return Channel”. It sounds like a lot, but when you think about it’s aptly named. All that HDMI ARC really does is allow audio to pass through the same HDMI cable that’s used to transfer video.

Along the back are all of the inputs and outputs.

You’ll get inputs for a 3.5mm audio cable, HDMI ARC, and USB-Type C along the back. Along with a 3.5mm output for daisy chaining.

Rather than needing to plug an HDMI cable along with whatever audio cables you need to get sound, you can do it all with just one. The biggest problem with this is that not all devices are compatible, and even a TV that has HDMI ARC might only have a single compatible port. So you just need to be on the lookout for which one that is so you can take advantage. Just like the optical cable, you’ll most likely come across HDMI ARC in situations where you want the video to match up with the audio. So again, be on the lookout when you’re shopping for your next gaming console or soundbar.

If you’re looking to transfer audio between devices, these are the main ways that you’re going to achieve it. The biggest differences come down to the kind of equipment you’re looking to connect and what the purpose is. 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 to do.

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