What Does An Audio Interface Do?

When it comes to setting up a home studio, the backbone of it will be your computer and the audio interface.

As an audio interface is such a key component, understanding exactly what an audio interface does is crucial. But the waters are muddied slightly because the myriad of these boxes available can serve slightly different purposes.

Starting with the most basic description in order to answer the question "What does an audio interface do?" An audio interface is what you need to better process sound going into, or out of your computer. In a way, it's like an external soundcard that you can control directly through interacting with it, or through the computer.

Although with any modern computer, or even a tablet, you can make recordings to get a proper sound, something approaching professional recording quality, you will need a good quality soundcard, and also maybe a good quality audio interface.

So let's take a detailed look at what an audio interface does, and why you might need to look at adding one to your recording setup. In most circumstances, the audio interface sits at the heart of every good home studio.

The 3 Essentials A Good Audio Interface Should Have

There are a wide range of audio interfaces out there, from the very basic to the incredibly advanced which can also partly fill in as a mixing desk and effects processor. But at the heart of any decent audio interface, there should be three things:

  • 1. A/D converters. These take the analogue input signal and then convert it into a digital format that your computer can work with.
  • 2. Microphone preamps. These are special inputs that take the weaker signal from a microphone, and digitally boost it.
  • 3. Phantom Power. This will provide the condenser microphone with enough power to function. You should look for an audio interface that has the full 48V of phantom power.

So Is An Audio Interface The Same As A Soundcard?

The answer to this question is a confusing yes and no.

A computer's internal soundcard does basically do the same job as an audio interface. To put sound into your laptop or computer, or to get it out, for playback and processing, you have to have something in the middle that converts sound to a digital signal, and back again.

So in the simplest sense, an audio interface works as an external soundcard. This means that if you are working with a laptop or tablet, which has very limited internal sound capabilities, that you can increase the quality and professionalism by running everything through an audio interface.

The bottom line is that with a modern computer, laptop, Mac or tablet you will be able to record music, often very well. But an audio interface will take you to the next step into being able to construct a more professional level of sound.

Even if you think you have got a good quality soundcard, it's also about ease-of-use and avoiding latency issues.

An audio interface has the size and range of inputs for maximum flexibility that a soundcard can't. If you have several people recording at once, then plugging in and out of the audio interface is going to be far simpler than trying to fudge getting everyone connected directly to the computer.

This means you can quickly record all types of input, from guitars, microphones, through to MIDI keyboards. When you add this flexibility to the generally higher audio quality you will get, in most cases, spending a bit of money on an audio interface makes sense even though you can manage with just a soundcard.

Connecting An Audio Interface To Your Computer

Depending on your choice, most audio interfaces are, at their heart, a USB soundcard. As long as there is a USB port available, or an adapter for one if you have a tablet, then you can simply connect your audio interface through it.

This is not always the case however, you can still buy FireWire audio interfaces, although these are becoming less common now that the new Thunderbolt audio interfaces are becoming available.

FireWire and Thunderbolt are both faster than USB audio interfaces, but they also tend to be more expensive. And of course you will need to have the input or adapter to connect one of these types of interface to your computer.

Although latency can be an issue, which we will discuss later, it's not such a problem with the most modern audio interfaces, and the faster USB2.0 standard.

One last point on connecting via USB, you may be surprised that there are virtually no USB3 interfaces out there. This is because although USB3 is faster, the information processed doesn't actually reach its destination much quicker, the latency, so not many manufacturers have adopted this.

That's why you will see a lot of the most current audio interfaces adopting Thunderbolt instead. And that's great because Thunderbolt is superior, especially as it can support 10W of on-board power to deal with mic preamps, but you have to make sure you can connect it to your PC.

Do I Need A Good Computer And A Good Interface?

The limit on the quality of the recordings you can make will depend on the quality of your computer equipment.

There is absolutely no point in buying a top-end audio interface if you are pushing sound through to a computer that simply isn't powerful enough to cope.

At the end of the day, you need to make sure that the computer equipment you have is going to be powerful enough to deal with the amount of signals you want to push in or out of it. If the computer isn't powerful enough, then it doesn't matter how good the audio interface is, you will end up fighting against sound quality issues and latency all the time.

So What About Latency?

Latency occurs when the signals being pushed to the computer for recording can't be processed at the same speed.

What happens is that a noticeable delay occurs between the actual sound and its playback in headphones or speakers. This can be incredibly distracting for musicians, because you are hearing an echo which can throw off your timing.

A good quality modern audio interface will help to improve latency so that it's not such an issue. The best modern audio interfaces can deal with latency so well that the few milliseconds of delay has become almost inconsequential.

So if you have been making music, perhaps singing through a microphone straight into your computer, and noticed a bad delay with headphones on that has distracted you, or you've used a MIDI keyboard and felt the same issue happening, then investing in an audio interface will help to deal with this problem.

Having said that, if your computer equipment is badly outdated or underpowered, then no amount of money spent on the audio interface will stop latency from happening. It really is about making sure your computer equipment is adequate, and then using an audio interface to put the icing on the cake.

One feature to look out for is something called zero latency monitoring, sometimes known as direct monitoring. This is where an audio interface has a switch that enables you to listen to the source of the sound directly, rather than after it is processed on the computer. This can be really helpful for monitor headphones and speakers, and is definitely something you should look out for.

The Input Types On An Audio Interface

A better question than “What does and audio interface do?” is to ask “What can an audio interface do for me?”

To answer that question you need to know what sort of things you want to record. When shopping around to buy an audio interface, the amount and type of inputs and outputs (I/O) you need is going to be one of the most important factors.

At one end of the scale, you can get a very cheap desktop audio interface that will allow you to record two mono signals, or one stereo signal at once. At the other end of the spectrum, you can buy a large interface that can handle dozens of channels and lots of different inputs simultaneously.

With so much scope and choice, understanding what each type of audio interface can do, and which one is right for you and what you want record, is vital.

If you are a singer songwriter, and all you need to do is capture voice and an acoustic guitar, just using microphones, then all you need is a pair of balanced mic inputs. If the mics are condenser types then you will need to be looking for phantom power on the audio interface to boost them.

If your setup will involve connecting external gear like samplers, drum machines and external processors such as multi-effects units, then you are going to need line level inputs and outputs. Many monitors and headphones amps that allow a separate headphones mix will also need line level I/O as well.

On top of that, some external devices may need digital connections, such as S/PDIF and ADAT these will allow for multi-channel microphone preamps to be connected, which will allow you to increase the amount of simultaneously available preamps, which will allow you to record from more input sources at the same time.

One important point to make about inputs and outputs is that cheaper models of audio interface tend to use unbalanced inputs and outputs. This can lead to interference, which is known as "ground loop". If you go for an audio interface with balanced inputs and outputs, then ground loop problems will virtually disappear.

It's probably a great idea to make a list of all the gear you plan to connect to your audio interface. If you are unsure about the number of connections you will need, or the type, then it's worth investing a bit of time researching.

On top of that, you are going to need to think about scaling things up in the future. So for example, if you record as a duo, but you're thinking about adding extra musicians to make a full band in the future, then it would make sense to buy an audio interface that is ready for that scaling up of your musical ambitions.

What Does An Audio Interface Do – Summing Up

Through this discussion you now understand that an audio interface works between the input sources and the recording equipment, basically voice and instruments and your computer.

It acts as an external soundcard, allowing you to process sound better for recording and playback. The better quality the audio interface, the better quality recording and playback sound will be, the better the sample rate, and the lower the latency.

Some of the better models allow for you to monitor your recordings through the audio interface, rather than after processing, removing latency and allowing for a much more real time sound, which is important if you use headphones for singing vocals, or playing a MIDI keyboard. But it can also be a problem if you play guitar.

And if you use effects, some of the better audio interfaces have built in effects processors, allowing you to hear effects such as reverb in real time, again cutting out the loop which can create latency.

The bottom line is to understand exactly why you need an audio interface, and understand your exact requirements before buying one.

You can get a really good quality audio interface for under $300, which will come equipped with everything you need if you pick the right model. But make sure that whichever one you buy, it has A/D converters, mic preamps, balanced I/O, and phantom power.

And my final word here is that in order to understand what you can do with an audio interface, you have to understand how it will be limited by the quality of your computer technology.

There is absolutely no point in spending $500 on a fantastic audio interface, if you are pushing sound in an out of a 10 year old single core Pentium processor machine, with outdated equipment, running Windows XP. The driver conflicts, latency issues and connectivity problems will give you a world of pain that a high quality audio interface will never solve.