What Is An Audio Interface? A helpful introduction

apollo twin universal audio interface

If you have started to become more serious with music production you have probably stumbled upon the audio interface. When you first started building your studio, the audio interface was maybe not the first gear on your list. And now you may wonder if you really need it, what it does and if you even understand how it actually works.

An audio interface is a hardware device that you connect to your PC via USB, Thunderbolt, or FireWire. It is a professional sound card that gives you more input options and lets you plug in your guitar and microphone so you can record high-quality sound directly into your Digital Audio Workstation (DAW).

This post is for you who might be a little unsure of what the audio interface actually will accomplish for your music production. After reading this guide, your questions will hopefully have been answered.

Let’s have a look at how it works, what it does and if you really need it for your home studio.

How Does an Audio Interface Work?

First things first: the audio interface converts acoustic signals into digital signals so you can work on your computer. 

Its main usage is:

  • To help you achieve a high-quality result in your recordings
  • To tackle demanding audio processing and sampling latency
  • To offer a wide range of input and connectivity options for your instruments, microphones, and computer

To make this easy for you, these are the most common devices you can connect to an audio interface:

  • Guitar (both acoustic and electric)
  • Microphones
  • MIDI Controllers/Keyboards
  • Studio Monitors

If you want to record your acoustic guitar, voice, drums, etc, the audio interface gives you something that you won’t have if you don’t already own one:

The possibility to record acoustic instruments and voices directly into your computer with great quality. 

Notice that I wrote ‘great quality’. 

Because even though you can also record these things on your computer, which has a built-in sound card and microphone, using this will never be as good and accepted as a professional radio- or studio recording standard. 

The performance and sound quality that the built-in sound card is able to produce is simply too poor.

In addition, an audio interface lets you hook up your studio monitors. And even though I mean this is not always necessary, I will come back to why you might need this possibility later in this post.   

Most often, audio interfaces are connected to your computer via USB or Thunderbolt. Sometimes, you will also see older audio interfaces that connects via FireWire, but it is not the most common connector anymore.  

As you will see in the infographic I have put together above, you can hook up various devices and instruments to your audio interface. 

  • Typically, the microphone and guitar inputs are connected in the front (but I’ve also had audio interfaces that had microphone inputs on the backside).
  • Studio Monitors, MIDI Hardware, and other digital hardware are connected in the back.
  • Headphones might be connected both front and back, depending on the developer.

An audio interface almost seems like the heart of your studio when you look at the infographic. And there is some truth to that. It controls everything from volume, which signals to send, channels selected, and more.

Is an Audio Interface a Sound Card?

Maybe you have wondered if the audio interface is a type of sound card, like the one that is inside your computer?

Well, yes it is! It is actually a professional sound card.

But there are some differences between the one in your computer and the external audio interface:

Inside your computer, you have the sound card. The task of the sound card is basically to make your computer able to produce, process and record sound. 

If you have ever chosen the “Input: Built-In Microphone” option in GarageBand, you have been using the computer’s internal sound card.

The Audio interface is very similar to the internal sound card but it is, of course, external.

Not only that, the audio interface does perform better in most areas, including:

  • Low-Latency
  • Recording
  • Playback
  • Increased connector options


An important difference between the built-in sound card and the audio interface is that the Audio Interface is optimized to have less, to no latency.

This means, if your computer has a pretty weak sound card, it might be delays between the actual sound and the digital audio signal when you are working in your DAW.

Needless to say, that is not an ideal working situation.

Recording and playback

A standard built-in sound card is mainly intended for playback and casual use, which means it is pretty adept at playing sound from YouTube, Netflix, and Spotify. 

It is not, however, doing a pretty good job at recording.

The sound quality is often either ‘mushy’ or ‘boxy’ like you are talking into a tin can or something. 

And this is obviously no good for an audio professional.

The audio interface, on the other hand, does a great job with recording. As I mentioned earlier, the audio interface is converting acoustic signals into digital. 

This is what is called Analog to Digital. 

And this is where a built-in sound card is lacking a bit. The audio interface is much, much more skilled at turning the signal from your guitar into a rich, truthful, and beautifully sounding digital signal that just screams ‘quality’. 

Increased connector options

An audio interface expands your workstation’s input and output connector options. Now, you’ll suddenly have XLR for your microphone, dedicated guitar and microphone connectors and potentially lots more.

This audio interface has two connectors in the front – Guitar and headphones.

Common Audio Interface Features

We have briefly been touching this subject already, but here is a greater list with everything you get with an audio interface:

1. A high-quality AD/DA Converter

Converting the analog signal into a digital, and then converting back to analog so we can hear the sound, is one of the most important tasks featured in the job description of an audio interface. 

So, if you are going to be able to record professional-sounding acoustic music, you need a solid audio interface that converts the analog signal from your acoustic guitar into a digital signal and back again.

The performance of the sound card in your computer is not even comparable to how well the audio interface converts analog into digital and digital to analog.

So, when you combine this with a good microphone, you will get the results you want: excellent, professional sound quality.

2. An increased, improved set of connectors (inputs and outputs)

To work with professional music equipment, you need the right connectors. 

Your computer probably has the standard inputs – a couple of USBs, a jack-input, and… maybe not much more than that if you are working on a laptop. 

3. A control center

Thanks to having multiple connectors, the audio interface might end up being the control center in your studio setup.

Or as some people call it: the heart of your studio.

4. ASIO Protocol

This is short for Audio Stream Input/Output and. In short, this protocol provides low-latency and high fidelity (high fidelity means that the sound reproduced is of high quality).

What Does all the Technical Terms Mean?

If you have already been researching audio interfaces online, you have surely seen a lot of technical terms in their product description.

Here is a list over common audio interface technical terms, with explanations:

  • Line Out
    This is also referred to as sound out, or audio out and is a jack-input which you can connect headphones or speakers.
  • Monitor
    This is where you connect your studio monitors.
  • Latency
    As you now know, this is a description of the delay between the sound and the playback that might occur when sound cards are too weak to process the signals.

    Most commonly, a built-in sound card is not built for coping well with latency.

    So, look for audio interfaces that have near-zero latency.
  • Drivers
    This is a software that you download and install on your audio interface to make the audio interface communicate with the PC. This software will further help improve the latency issues. Software like this is also possible to install on many built-in sound cards. Drivers like Asio4all is free, and became the solution for me in the period I didn’t use an external audio interface.

  • Direct Monitoring
    If you click this button on your audio interface, you will hear the sound coming from the microphone connected directly into your headphones. Without any delay.
  • MIDI
    You might see this input on some audio interfaces. However, since most MIDI controllers operate via USB nowadays, a regular USB connector is sufficient.

  • 48V Phantom Power
    There are microphones out there (condensers mostly) that need power in order to work. If you own such a microphone, you need to look for an audio interface that has a switch for phantom power.
  • Sample Rate
    First, the human ear can generally hear frequencies in the range of 20 Hz – 20.000 Hz (20 kHz).

    To create a digital signal the initial sound has to be sampled. The sample rate is how many samples that are created per second. Sample rates are around twice the amount of the frequency rate: for example, the standard sample rate of 44.1 kHz makes it possible to record sounds up to a little over 20.000 kHz.
  • Preamps/Pre-Amps
    A microphone has generally a very low signal. To make it suitable to record something, the signal needs to be amplified. That is why good audio interfaces have good preamps.
  • MC/Line
    This is where you connect a microphone. Most often, this input is an XLR input. XLR is much more stable and balanced over long distances than a regular jack cable. In addition, since the signal level of a microphone is quite low, the XLR will make sure that the sound quality is not destroyed when amplified.

Do I Really Need it?

It depends, to be honest. If you mostly work with MIDI, and you are not planning to record an acoustic instrument or voices anytime soon, there are other components I would suggest you take a closer look at first.

(Check out my free infographic on how to build a music studio for more information on this.)

I have personally gone looong periods of time without using nothing more but the built-in sound card inside my computer. And that is without ever having any latency problems some people claim to happen if you don’t use an audio interface. 

(Note: not all internal sound cards support ASIO drivers, which is extremely important to install in order to optimize your built-in sound card for music production. If your built-in sound card doesn’t support ASIO drivers, which among other things deals with latency, you will need to get an audio interface.)

On the other side, if you are a singer-songwriter and you need to record your voice and instrument, you will definitely need an audio interface.

It is also important to remember what the audio interface actually aims to achieve: high-quality sound. 

So, if you are planning to record an album or just want your tracks to sound as professional as possible, you need an audio interface, which after all is a professional sound card.

I have owned a couple good ones over the years. For the longest time I used a big, chunky Line6 as my audio interface (the one in the back in the picture below). 

In fact, I still use it, when special circumstances call for it. It has a lot of microphone inputs, you see.

In my case, the special circumstance was the need for several mic inputs. Below, you will see other circumstances that will make you need an audio interface.

You will need an audio interface when:

  • You are planning to record guitars, drums, voices and other acoustic instruments
  • When you experience your built-in sound card is not coping with sample latency 
  • When you need a high-quality, professional sound quality in your recordings
  • When your computer’s built-in sound card doesn’t support ASIO drivers
  • Your computer produces an ongoing static buzzing sound when connecting your studio monitors. Yup, that could happen. My old iMac (late 2009 model) could not handle the direct input of studio monitors.

For greater control, you should always record everything on separate tracks. So, if you are in a band, the size of your audio interface needs to be larger with more microphone inputs. More people equals more instruments, especially if you are live-recording or recording a drum set.

I hope you feel a little wiser now that you have read the guide all the way down here.

If you are on the hunt for a quality audio interface and want to know what you should get, you must definitely check out this page, where I recommend my favorite audio interfaces. 

Thomas Leypoldt

Hey there! My name is Thomas and I have been a film composer for over 10 years, delivering music to feature films, documentaries, video games, and commercials. I share everything I have learned on this website, to hopefully be of help to your own development as a musician.

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