Why You Need An Audio Interface
An audio interface is one of the most integral parts to your setup, whether you’re building a home studio or portable recording outfit. While you might mix and match a range of instruments and microphones, your audio interface is the constant piece of kit you will use to record. It is the central hub to all of your audio, converting your instrument’s sound from analogue to digital for your PC digital audio workstation (DAW) to process. It’s important you get the right one to suit your needs.
Before audio interfaces existed, everything used to be recorded in analogue on tape. By converting music to a digital format, it became easier to distribute via CDs and transfer from PC to PC.
There's huge scope for recording interfaces to suit a range of applications. This beginner’s guide is here to remove the guesswork and help you find the best audio interface for your dream recording setup.
Choosing your audio interface
In order to find the best I/O interface to suit your needs, you’ll need to consider a few things that'll quickly narrow your choices to a few options:
Audio Interface Size
The First thing to establish when choosing an I/O interface is the environment you are planning to record in. Are you hoping to set up an established project studio/producer setup in the spare room? Maybe you're after a desktop interface you can keep next to your computer. If you need something truly portable, you might be happy with a simple all in one device that’s discrete so that you can record at the press of a few buttons. Let's take a look at the different size interfaces on the market.
The desktop audio interface is the perfect choice for a small project studio. Most desktop interfaces have a good range of inputs and the essential features you’ll need to record without going overboard on inputs.
Rackmount interfaces are designed to fit into an audio rack so that you can combine lots of outboard gear without taking up too much space. The larger format provides room for more inputs and preamps. Ideal for larger studios.
Interfaces contain a variety of connections. You need to make sure you can plug your interfaces into your laptop or PC. Simply check what inputs your device has before buying a new audio interface.
- USB - The standard connection every PC uses. Most modern wired gadgets connect to your computer this way, including phones, cameras and tablets. USB 2.0 has been out for a long time and has a relatively average connection speed - otherwise known as latency. However, new computers and the latest interfaces have USB 3.0 (USB-C) connections that offers wider bandwidth.
- Thunderbolt - Created by Apple, Thunderbolt is the fastest easily obtainable audio interface connection. There are now a number of Thunderbolt Interfaces out on the market, which offer ultra-low latency and unparalleled performance. All the latest Macs come equipped with Thunderbolt inputs, but if you’ve got a Windows PC you might need to get an input specifically installed. This is the successor to Firewire.
- PCI Express - An internal card-based computer connection platform primarily found in desktop computers. Since these cards are plugged directly into the PC motherboard, they require an available PCIe slot for installation, which some computers may lack.The PCIe connection provides high data bandwidth and low latency, allowing audio interfaces that use it the ability to handle many simultaneous inputs and outputs.
- Ethernet - Extremely high-end. It's not needed for home use as the quality doesn't justify the cost. But it's the best option for professional studios and broadcast facilities that have tens of thousands to spend on recording equipment.
The converters in your interface are another key element to the quality of your recordings. There are two different types:
- Analogue to Digital Converters (A/D) - this type of converter takes the analogue waveform coming from your preamp and converts it into a digital signal that the computer will understand and feed into your recording programme (DAW). It’s a key element of your recording path.
- Digital to analogue Converters (D/A) - these do the opposite to A/D converters. They take the Digital signal and convert it back to an analogue waveform that can be sent to your monitor speakers. This conversion doesn’t directly affect your recordings but it does affect playback, i.e. what you hear.
Inputs and outputs
Sound can be captured in a variety of different ways so it’s important to work out the quantity and type of inputs you'll need. Recording instruments or vocals through a microphone requires an XLR connection. These carry analogue signals. They're easily recognisable because they are the largest slots you'll see on the interface. You can alternatively plug your instrument straight into the interface to design sound using PC plug-ins, providing the interface has 1/4 jack inputs. An interface has TRS outputs so you can plug your headphones and speakers in to listen back to what you're recording.
If you’re a singer-songwriter you may only need a small interface with a couple of inputs for overdubbing. However, if you’re looking to record a 5 piece band all at the same time, you’ll need a mixture of inputs; including a number of microphone inputs for the drums alone. Listed below are the types of inputs available and what they're used for.
- Jack - Inputs used for guitars, bass, keyboards, synths and external gear. Stereo instruments like Keyboards will need 2 jack inputs for the right and left channels. Outputs are used for connection to monitor speakers and any analogue effects and other gear that you want to feed through an effects channel (bus).
- XLR - Balanced Microphone inputs. XLR mic inputs are combined with a microphone preamp that boosts the signal to a usable level. Each preamp comes with a gain knob so you can set the level of boost on the signal.
- Combo Jack XLR Inputs - Audio interfaces usually have a combination of jack and XLR so that you have the option of plugging in easily without having to reach to the back of the unit.
- 3.5mm Jack - Allows you to hear what you're recording through headphones or speakers. If you want an accurate representation of the sound you're producing, get some good full range FRFR monitors.
- S/PDIF (Sony/Philips Digital Interface) - This is the main input/output for any digital sources. Whether it’s a digital effects module, a sound box or a keyboard arranger, the digital input saves you from any noise that might come into the signal through an analogue input. S/PDIF comes in 2 different formats; Coaxial or Optical. Make sure that any devices plugged in have the right connection!
- MIDI - Used to plug in peripherals that can control the software in your computer. For example, a keyboard can be hooked up so to play software instruments hosted on the computer. Some modern dedicated controller peripherals have USB connections that plug directly into your computer. However with most keyboards, MIDI will be your only option.
- ADAT - An optical connection that allows you to transfer digital audio between different equipment. It can transfer up to 8 channels at 48 kHz/24bit.
"Your signal chain is only as strong as your weakest link!"
There are a number of key elements in an audio interface that will determine the overall quality of your system.
The journey from microphone to computer (your ‘signal chain’), is only as strong as your weakest link. You may have the most expensive and legendary microphone that captures sound in incredible detail , only for it to run through a bad cable or into a poor interface. All that gorgeous detail can be lost or drowned out by background noise.
When recording with microphones, the preamp is the first element in your interface that will affect your sound. A microphone naturally captures sound at a relatively low volume level, so it’s the job of the preamp to boost it back up to its original level. Most I/O interfaces have in-built preamps so you can plug in and record straight away. However, external preamps contain more features and provide better quality in the vast majority of cases.
A decent pre-amp will boost the sound with superb clarity, whereas a lower quality preamp will also bring in background noise and unwanted imperfections. Although some imperfections can be good. Top preamps aren’t just clear and crisp. They bring unique colouring to a recording. Whether it’s a bit of analogue warmth or what producers call “air”, the best mic preamps have their own signature sound and are highly sought after.
An interface may also provide phantom power. This is needed for condenser microphones that won't work without an external XLR compatible power supply. Most I/O interfaces have a switch to turn it on and off. It'll run through the standard XLR chain the microphone uses to deliver the sound.
Sample Rate and Bit Depth
The converters on most good quality audio interfaces are capable of excellent sound. The main factors to take into account are the Sample rate and bit depth. In a nutshell, sample rate can be described as the amount of sound detail, and bit depth as the representation of the dynamic range (how many different volume levels between your quietest sound and loudest sound).
Sample rates on interfaces can reach up to 192khz and to a bit depth of 24-bit, however it’s worth noting that standard CD quality is much lower at 44.1khz/16Bit. Part of the reason they're now outdated is because they don't provide an accurate representation of sound. When buying an I/O interface, it's worth thinking about what you are going to do with your music once created. Does it need to be the pinnacle of quality?
Today, a good benchmark for “high resolution” audio is considered at 96kHz/24bit upwards. Better circuitry and more accurate clocking leads to a more precise, focused sound. The benefits of high end conversion are subtle and need high-end speakers to fully appreciate.
Latency used to be a bigger issue than it is today, but still worth recognising. If you have ever recorded before, you may have noticed some lag between playing something and hearing it through your speakers/headphones, and the recording also appearing on your DAW. There is a small delay of a few milliseconds as it passes through the audio interface.
This will never be completely eradicated, but USB3 and Thunderbolt's processing is so good, it's not really noticeable. The only downside is that these interfaces are pricier than USB and Firewire. But it makes such a difference to temper levels, it's probably worth it.
Most audio interfaces will work with all types of digital audio workstation, or DAW software. These are an essential part of recording music. A DAW is a PC suite that lets you edit your instrument tracks. If you're buying an interface for the first time, they will usually provide a DAW download to work with it anyway. Just in case, check the compatibility between the two. It's usually safer to pick a brand and stick with it, as you will also learn how to use the software as you go. Although they all look similar, recognising functionalities will save you a lot of time working out unfamiliar workstations.
Some of the big names on the scene include Steinberg Cubase, Ableton Live, Presonus Studio 1, Cakewalk Sonar, Propellerhead Reason, FL Studio, Apple Logic Pro and Avid Pro Tools. Some are well-suited to electronic and virtual instrument musicians because of their built-in VST plug-ins like FL and Reason, while others are great for live instruments such as Ableton and Cubase. It's difficult to say any are suited to beginners, as the more you get to know them, the more familiar they become. However, the free DAW you get with most interfaces is a good place to start for the basics.
There are a lot of companies making audio interfaces, so it can be a bit difficult to work out who makes the best. Here are a few of the biggest names you should know and will probably see as you research what one you’re after.
- Focusrite – one of the most popular brands at an entry level price range. Pretty much everyone has used the Scarlett USB interface at some point. Cheap, does a clean job, reliable and looks sleek on your desk. But that’s not all Focusrite do. They have a mid-priced Clarett range with MIDI connections and newer Pro models that comfortably challenge the very best in the world.
- Universal Audio - if you’re looking to splash some cash UA are worth a look. Their entry level interface comes in over £400. However, these guys offer great plug-ins and great preamps. Not much comes close to their Apollo series of rackmount interfaces. Every type of I/O you could want, top A/D D/A conversion and Thunderbolt connection.
- Native Instruments – have a higher reputation for DJ controllers, plug-ins and the Komplete production suite, but make one interface that’s all-encompassing on a budget. Also named the Komplete, this desktop box has two mic inputs, MIDI compatibility and four analogue outputs. The biggest draw the included production package and the excellent and essential Cubase DAW.
- M-audio – a company focused on making beginner interfaces. The M-Track series comes with the Ableton Live DAW and the AIR Creative Collection FX, a popular plug-in package most known for its use on Pro Tools. At 24bit/192kHz you’ll have great recording quality at a cheap price.
- PreSonus – one of Focusrite’s biggest rivals. They also offer a very cheap entry level point called the AudioBox that benefits from its simplicity. Naturally, as you move up the range they offer loads more I/O’s, talkback features, Class A preamps and the PreSonus Studio One DAW.
In an ideal world, we would all love to get the biggest and best audio interface out there for our studio. Unfortunately, high-end recording gear can easily run into the thousands, and won't bring you the leaps in quality you might expect.
Generally, within the various price bands, the more you spend the higher the quality of interface. However, there is a delicate balance between better sound and number of inputs.
That's why it’s important to consider how many inputs you’re realistically going to need, because if you’re a solo musician who records instruments one at a time, avoid buying an audio interface with loads of inputs and instead invest in a good preamp or converter.
Most interfaces allow you to expand the number of inputs anyway, so your recording setup can grow when you’re ready.
The best audio interface for you is one that has all the functionality you need within your budget. Choosing the right interface for you may seem daunting at first, but by carefully considering your requirements, you can very quickly narrow down your choices.
What is MIDI?
MIDI or Musical Instrument Digital Interface is a way of controlling an aspect of your instrument (synth/keyboard/sequencer/DAW) through separate controller hardware.
What is a Combo Jack?
A combo jack combines both an audio signal directed to your headphones and the ability to send audio into an interface or PC. Ideal for headset use.
Do different preamps have different sounds?
Yes. Preamps from various manufacturers add slightly different characteristics to your microphone recordings. For example, some produce warmth, others create transparency.
What counts as an I/O?
Anything that receives analogue signal from an instrument, and anything that relays it to a PC, speaker, or headphones, respectively.
What is latency?
The delay between playing an instrument and a DAW recognising the digital source. Can be reduced easily through updating drivers.
Why do I need an XLR or TS cable?
Microphones require XLR cables to connect to a preamp. Plug your TS cable from guitar to interface to record direct into the DAW with plug-ins.
What is phantom power?
Phantom power allows your condenser microphones to function. Most preamps provide phantom power so simply plug in as usual.