Audio Interface

Choosing An Audio Interface

With such a massive choice out there both in types and brands, choosing the right audio interface for your recording needs can be a little overwhelming.

There are so many different kinds of input and output configurations, formats and connection types, that's when you start adding in other options as well such as the number of audio channels, the sample rate and on-board effects, it's no wonder that the choice becomes agonizing.

So what we going to do in this guide to choosing an audio interface is to demystify the choice a bit so that you can make a clear decision on the audio interface that best meets your recording needs.

What Is An Audio Interface?

Let's cover the basics here just to make sure we are on the same page. An audio interface is hardware that connects microphones and other audio equipment to the computer where it will be recorded and processed.

It does this through several types of connection, depending on the audio interface you buy, either Thunderbolt, USB, FireWire or an internal PCI/PCIe card. We will cover the details of these types of audio interface connection in a moment.

The audio interface also works the other way, taking information from your computer and converting it into an analog signal, which can then be played normally on monitors or headphones.

A decent audio interface will include line level analog inputs and outputs, pre-amplifiers for microphones (essential as this brings their signal up to the right level before it's converted into digital format) and in some cases additional types of digital input and output (for example AES).

Do I Definitely Need To Invest In An Audio Interface?

One of the key reasons you would need a dedicated audio interface, rather than relying on a standard sound card within your computer or laptop, is that for anything approaching the power you will require if you need to record professionally, record as a band, or have a flexible home studio, is that the quality will be too limited, as will the low I/O.

The other problem with anything other than a good quality audio interface is that with anything other than a couple of track inputs, interference and latency can make it impossible to work as a serious option.

Just in terms of recording a band to give you an example of why you need an audio interface, just a drum kit would require four microphones - kick, snare and two overhead mics.

So the bottom line is that unless you are recording something as simple as a single singer and synthesizer then the only logical option is to invest in a dedicated audio interface.

What Is It You Want To Record?

This is a vital question, because it will help to determine the type of audio interface you should be looking at buying. What you are creating will determine the number of simultaneous inputs, and what types of input, you're going to need. The simplest form of input is a "line level" one, which is suitable for connecting other physical equipment such as CD players and synthesizers.

If you are going to use a lot of microphones, and as we have already briefly mentioned these output a much lower level of signal, they require an internal preamp to bring their signal up to the normal line level. If you are going to be recording with multiple microphones, possibly the best option for you will be to choose an interface that has preamps built in. This shouldn't be difficult as most new models of audio interface include these, but it's always worth checking.

Some audio interfaces don't have preamps built in, and you can buy them separately, but I would suggest you don't really want to mess around doing that when you can have everything in a single box.

So in terms of the inputs you will need, it will depend on what you want to record. If you are mostly working with pre-recorded stuff, samples and loops, or software synthesizers, then simple stereo line level inputs are more than enough. But if you are recording instruments and voice then you're better to look for what are known as versatile inputs that can accept line signals, instrument signals and microphone signals.

How Many Input Channels Will I Need?

Again, this question will be answered by being clear on the type of things you want to record. If you are recording musicians and instruments then you will probably want an eight input interface. This is because from experience it's the minimum number of inputs you could probably get away with recording a standard four piece live band. If you go down this path, you can put four microphones on a drum kit, plus a guitar, bass, keyboard and single vocal, all without having to mix down.

Audio interfaces featuring four track input are getting rarer, but they will be fine if you are only recording a couple of inputs, four example acoustic guitar and vocals. But considering the price differential, you might as well go for an eight channel audio interface.

At the high end, if you need more of everything so that you can handle any type of recording, then you should probably be looking at an audio interface that has more flexibility, for example the MOTU Ultralite which has two mic/line inputs, an additional six line level inputs, and 10 analog outputs.

You could go a step further than that, by creating a super interface. This is where you combine two identical eight channel audio interfaces. If you want to mix onto a PC, then the audio interface must offer multi device drivers. On top of that you will have to make sure that there is a way to lock the digital clocks of every device together in order to maintain perfect sync.

Choosing Computer Connectivity For Your Audio Interface

A key consideration when choosing an audio interface is how it will connect to your computer, where you will do your digital recording, mixing and playback.

The good news is that things are a lot more flexible than they were even a few years ago, but there are still a few options for you to consider, especially in the fast moving world of technology. You're looking for something which is well supported and is not going to die a death in the next few years.

Your options really are:

1. Thunderbolt

This has low latency and high speed. It is the new standard for connecting audio interfaces. On the latest Mac computers Thunderbolt 3 is twice as fast as version 2, and eight times as fast as USB 3. This means it can easily support transfer rates of up to 40 GB per second across up to 100 meters of optical cable, making it perfect for any type of recording in any type of studio venue.

2. FireWire

Although not as good as Thunderbolt, its advantage over USB is that it can transfer data at a more consistent rate. This makes it more reliable, especially when you are having to record a lot of channels in one go. On the downside, FireWire is not supported in as many audio interfaces, so you will have less choice of what to buy. On top of that, not as many computers and laptops have FireWire ports, although you can buy a card to install.

3. USB

The big advantage of USB over the other formats is that it's incredibly well supported. There are also many options of interfaces that can run on USB bus power, therefore not even needing an external power supply. This makes them perfect if you are aiming to record on the move using a laptop.

4. PCI Express (PCIe)

This is an internal card interface. You install it directly into the motherboard of your computer. The downside is you cannot really use this with laptops. So you would require a permanent desktop station to use as your audio interface. The advantage of this format is that because the audio interface sits within the computer you avoid some of the issues around latency and data transfer rates. This makes them ideal for high numbers of tracks and ideal for professional production. But they are quite costly, although some entry-level PCIe cards are affordable.

How Many Outputs Do You Need On An Audio Interface?

Everyone talks about how many inputs and the format of those inputs because the primary focus is on recording from the source.

Especially when it comes to musicians, that focus is on getting everything recorded in the best quality possible so that it can be mixed well. Usually it's then played back using two channel audio on monitors.

The good news here is that you don't have to think about it too much, because there is usually an equal number of outputs as there are inputs. So an eight channel audio interface will have the same eight outputs as it has inputs.

If you are mystified as to why you might need all these outputs, the answer is mainly about surround sound.

So for example if you work producing a soundtrack for an advert that was going to be shown in your local cinema, where they would have at least 5.1 surround sound, then having the ability to playback in that format to fine tune your mixes is an obvious advantage.

On top of that, there are other uses for additional outputs. A very common use for spare inputs and outputs is patching and analogue mixer in, so you can mix computer compositions externally. Basically you allocate each audio track to a separate hardware output, and then route the resulting mix back in.

Do You Need An Audio Interface With Onboard Effects?

The line between an audio interface and other gear in the studio is getting more blurred everyday. For example, some audio interfaces combine the standard interface with effects, or a MIDI keyboard modeling software built in.

The main reason you might want effects built in is around recording and latency (delay). For example, vocalists monitor their performance is what recording usually through wearing headphones rather than through monitors. Even with the most modern high-speed equipment and interfaces, if they are needing effects for the vocals, then just a few milliseconds of latency can cause significant issues, which would be the case with external effects.

So if your vocals need reverb, then by using built in reverb running from the audio interface, you can bypass annoying delays. And if you were a guitarist, you can plug your instrument directly in, but hear it if it had already passed through the guitar amp/speaker combo.

On top of that, you can bypass latency using what's known as zero latency monitoring features within some audio interfaces. These send the output of the A-D converters direct to the D-A converters. This means you can monitor the recording without the latency you will get if you listen from the computer.

At the high end of this, some of the top quality audio interfaces now have a range of physical modeling features included. For example, Edirol interfaces such as the UA4FX offer composite objects sound modeling. This has 14 built in effects allowing you to take hearing a more complete sound without latency to a whole new level.

So Which Audio Interface Sounds The Best?

That debate rages on musical forums across the Internet and in music shops around the world. The truth is as with almost anything, you will get what you pay for.

In terms of quality of sound and features the more you pay the better quality of audio interface you will get. But it is worthwhile investigating by hearing the differences in quality if you can, because you may be surprised how small the difference in quality is between what can be quite a wide difference in price.

It's best not to get to hung up on things like sample rate. For standard music, like if you're planning to release a demo CD, then working with, or mixing down to 16 bit audio will be more than enough. But if you record a jazz band, then you may want to look at 24 bit.

The trade off is not just about quality with bitrate either, you have to remember that the higher the sample rate, the faster it it will need to be processed and the more disk space you'll need. So there's no point in spending a lot of money on a high sample rate if your computer can't cope.

What's important is that you get the audio interface that perfectly fits the type of recordings you are going to make. So everything we have talked about in terms of the type of connectors and the number and type of interfaces is important, as is understanding the negative around potential connection problems using USB.

Have a look at some of our guides on audio interfaces!