What an audio interface is, what it does, and why you need one

In short, an audio interface is a device that connects your microphones and instruments to your computer so you can record them in your DAW.

It takes the analog signal from your guitar, bass, or whatever audio source you have plugged in and converts it to a digital signal that the computer will understand. So, if you are setting up a home recording studio, an audio interface should be one of the first things on your list.

We will take a more in-depth look at what an audio interface does and why you need one, along with some of our top picks for beginners.

What is an audio interface?

Audio interfaces come in a range of shapes and sizes. Some are light and delicate, others are solid and built to last a lifetime.

The differences from one interface to the next can see you spend $100 or $1000, or more. But, the one thing that they all have in common is that they come with any number of inputs, outputs, gain control, and master volume.

At its core, the point is you can think of an interface as a middleman that receives signals and sends them out again, in different forms.

When we mentioned signals in different forms above, we are referring to an A/D converter. A/D converter is a common term that you might have heard but not known what it meant.

It means analog to digital converter, and the interface will convert digital to analog for playback, too. It converts the analog signal from your instruments, microphones, and other sources and converts them to digital so that your computer understands it.

In turn, the D/A converter then takes the digital signal from your computer and converts it to analog to send through your studio monitors or headphones.

It means what you put in is musical, what comes out is musical, and you don’t need to worry about the bit in between.

What does an audio interface do?

You might be thinking we just covered this question, but we only looked at the most basic function of an audio interface. Now, we can look at some other aspects and common features of a good audio interface.

Bit depth and sample rate

24-bit is the industry standard, although some audio interfaces still record at 16-bit. The higher the bit depth, the more accurate the digital recreation of the original analog source.

Similarly, the higher the sample rate, the more data captured in recording and playback, and ultimately, the better audio quality you get.

CD quality is 44.1 kHz, and some can argue that anything over that doesn’t make enough of a difference. But, it’s common to see audio interfaces offer sample rates of 96 kHz or 192 kHz as standard.

Gain control

Gain control is a pretty obvious function to point out, but we wanted to clarify the difference between gain control and volume for beginners’.

In a nutshell, gain is input, and volume is output. Newbies often don’t separate the two because increasing either one will result in a louder sound.

Gain controls the strength of the signal from your microphone to your interface, for example. Volume controls the output level that you hear through your monitors or headphones.

In many situations, if something is coming through too hot and seems like it’s about to blow the speakers, the natural instinct is to grab the master volume and drop it fast. Doing that works in terms of preventing any serious damage in the short term.

However, let’s say you are recording an electric guitar directly through an interface with the input channel gain maxed out. As soon as you dig into your playing even slightly, it’s going to start clipping badly.

If you lower the master volume, it might seem like it solves the problem, but you are still left with a track recorded at ridiculously high gain. So, at any point later on, when the volume is increased again, the clipping issue is still there.

Microphone preamp

Line level is the standard operating level of recording equipment. Microphone signals are much lower than line level, and they require a preamp to boost the low-level signal to line level.

Check out our previous articles to learn more about what are preamps and what they do, as well as what’s the difference between a preamp and a power amp.

Phantom power

Phantom power can be turned on/off and is a method of sending 48 V to a microphone via an XLR cable. The use of phantom power removes the need for any external DC power supply.

Headphone monitor

When you get more into recording, you will realize the importance of headphone monitoring. It allows you to record vocals or instruments with a click or track playing through headphones, but not through your monitors. That way, your click or backing track doesn’t get picked up by your microphone.

How do I connect an audio interface to my computer?

There are a few different ways that you can connect an audio interface to your computer. The standard connection types are USB, Thunderbolt, Firewire, and PCIe.

USB

USB audio interfaces are very popular with people who want to create a mobile recording setup with a laptop.

The upside is that the audio interface doesn’t require an external power source beyond USB; it’s plug and play. The downside is that some other options transfer data faster.

Keen in mind that there are different types of USB, some faster than others. Also keep in mind that some current USB-C interfaces are really just USB 2.0 but the cable has a USB-C connection at the device end. Just be fully aware of what you are buying.

Thunderbolt

Thunderbolt has become the standard that other connectivity types are judged against. It’s super fast with ultra-low latency.

The advantages are obvious; the downside is that Thunderbolt is an Apple/Intel creation that isn’t always found on cheaper laptops. The upside is that while Thunderbolt interfaces used to be reserved for the higher price range, there are now many entry-level options available.

Firewire

Firewire is somewhere between USB and Thunderbolt. While it does transfer data faster than USB, it’s far less widely available.

Many computers don’t have Firewire ports as standard, and that trend looks to continue. Over time, it’s likely Firewire will be even harder to come by.

PCIe

This kind of audio interface connection isn’t a likely option for a beginner; it’s often the choice for professional studios. Rather than an external device, a PCIe interface is an internal sound card that installs directly into your computer’s motherboard.

The advantage is that the transfer speed is as good as instantaneous, with little to no latency even when recording multiple tracks.

The drawbacks are that they tend to be expensive, can’t be used with a laptop, and are becoming increasingly rare. It’s more common that you’d have to build a custom PC to accommodate a PCI slot.

How many inputs/outputs do I need?

Well, there is no straight answer to that question. The answer depends entirely on what and how you plan to record. You could get a very basic interface with two inputs and left/right outputs for your studio monitors.

If you are a singer-songwriter, a beatmaker, or anyone who tends to work alone, that might be enough for you.

However, it’s not just about recording multiple musicians; it’s about the number of tracks at one time.

For example, if you are a YouTube content creator, you might want to make a live video where you move from vocals to electric guitar, to bass, to keys, and so on. If you had to stop to unplug one instrument and plug in the next, it would ruin the live, real-time flow of the video.

Another example could be that you want to mic up a live drum kit. There are too many scenarios to list that would require additional tracks, whether you work alone or not, so think hard about how you plan to work.

Obviously, if you want to collaborate with multiple musicians in a live setting, more inputs are vital.

When it comes to outputs, basic left/right outputs for your monitors might be enough, as we mentioned already. As a beginner, extra outputs might not interest you too much, but they soon might, so it’s good to try to plan ahead.

Some media composers use extra outputs to create a surround sound setup to match the format they are composing for. A more typical home recording use of extra line outputs would be to route your channels to outboard gear.

For example, you might have a drum machine on the input for channel one; you could then rout the output from channel one to an external compressor and the compressor’s output back into a new input on the interface.

If that sounds confusing at first, don’t worry, it’s very simple once you get used to it.

Basically, you’d end up with the uncompressed drum track on channel one and the compressed drum track on another channel, leaving you free to use either or a blend of both.

The more outputs you have, the more creative you can be with your recording chain/process.

Different types of inputs

Depending on what you are recording, you might want an XLR microphone input or an instrument input (1/4″ jack). Most audio interfaces, even the smallest, offer a mix of both.

Some small interfaces have a channel with both input types, then additional channels with only instrument inputs. It’s worth noting that instrument inputs are often labeled as Hi-Z inputs.

Electric guitars, for example, have a lower than line-level output, so when going directly into an interface, a Hi-Z (high impedance) input is best because it boosts the signal. For synths and other instruments with a line level output, line inputs are best.

Many audio interfaces these days use combo-inputs that offer both XLR and balanced line input connectivity.

Why do I need an audio interface?

Now that you know what an audio interface does, you probably realize that you need one if you want to set up a home studio. But, some of you might be wondering if you can do it without an audio interface.

If you exclusively use virtual instruments controlled by a USB MIDI keyboard, you might think an audio interface is a waste of money. There are also lots of USB microphones available that are plug and play. So you are ready to record straight into your computer, whether that’s vocals or acoustic guitar, etc.

Technically, that means you can record without an audio interface, but it’s not what we’d recommend.

For a start, USB microphones are awesome for podcasts and streaming but not as great for musical recording. If you want to record a synth or any instrument direct (without a mic), you’d need a jack to USB audio interface cable.

Furthermore, it’s unlikely that the A/D converter in your computer delivers the same high-performance bit depth and sample rate that you’d get from a dedicated audio interface.

Finally, you’d need to connect your studio monitors in a very convoluted way. You could take your monitor speaker cables into a 1/4″ to 3.5 mm Y-cable into your computer’s headphone output.

It works, but it’s far from ideal; alternatively, you could listen through your built-in speakers, which is further from ideal.

As you can see, there are workarounds for most things. But, realistically, if you are even halfway serious about home studio recording, you need an audio interface.

What audio interface should I buy?

There are so many choices to suit every budget and project size. So, here are a few suggestions that we love.

Let’s start with a couple for the songwriters and beatmakers:

If you want a few more inputs and outputs, we have a couple of suggestions:

Some notable manufacturers that we didn’t mention already include Audient, SSL, Universal Audio, and RME. Although, they can often be priced out of the average beginner’s budget.

---

Hopefully, you now have a better understanding of what an audio interface is, what it does, and why you need one. More importantly, you should have a good idea of what kind of audio interface suits your particular recording setup best.

The suggestions that we listed are a great place to begin, and they all offer great value for money. So, don’t wait; get your recording journey started now.