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Posted on June 28, 2013 by Joe Stachowiak There have been 0 comments

Focusrite Scarlett 18i8If you're new to the world of audio recording and production then the prospect of choosing an audio interface can often be a daunting one. What do all those specifications mean? How do you know which interface has the correct number of inputs and outputs for your needs? Indeed, what even is an audio interface? Thankfully, Focusrite have made comparing specifications a whole let easier in their handy reference chart: CLICK HERE to view it or read on to find out more about audio interfaces.

Focusrite Interfaces


Once you're in the know, there really is no need to fear the term 'audio interface'. An audio interface is simply a soundcard that deals with getting sound into and out of your computer; something that is essential for recording and production projects. Professional audio interfaces offer a way of working with higher-quality audio compared to your computer's built-in soundcard and they often provide specialist connections and features for working with professional audio equipment. For example, most audio interfaces will have at least one specialised microphone input (called a microphone preamp) with a phantom power switch, which is needed for working with condenser microphones.


The number of inputs and outputs that you require will depend entirely on the size of your projects. If you are never going to record anything, you don't actually need any inputs at all, but you will find that most interfaces offer at least a couple of inputs just in case.

When deciding how many inputs you need, you will need to consider the maximum number of things that you will ever need to record at one time. If you are a solo performer that will only ever be recording a miked guitar and your vocals through a separate microphone, then you will only really require 2 microphone inputs. If you sometimes plan on switching the miked acoustic guitar for an electric guitar plugged directly into the interface then you will also need to make sure that at least one of the inputs doubles as an 'Instrument' input. If you are a duo and you plan on using two microphones alongside a keyboard (which usually has a stereo output; one output for the left channel and one for the right), then you will need an interface with at least two microphone inputs and two separate analogue line inputs, i.e. 4 inputs in total. Of course, if you are heavily miking up a whole drum kit then you will require even more microphone inputs.

The main things to be aware of are that you will need enough separate inputs for everything that you plan on recording simultaneously and that the inputs are of the correct type to deal with the equipment that you will be using (i.e. microphone inputs for microphones, Instrument inputs for electric guitars and basses and analogue line inputs for things like keyboards and synths). If you are using any hardware effects in a send/return configuration then you will also need spare inputs to connect to. If you are unsure of what you will require then please feel free to call our sales team on 01202 597180 and we will be more than happy to advise you.

There are a a few quick additional things to note with regards to inputs...

If you only have a two input device and you want to record, for example, two microphones and a keyboard (totalling 4 signals if the keyboard has a stereo output), then this is still possible. In this scenario you would have to record two of the signals first (e.g. the two microphone signals) and then the second two signals on top of the original recordings afterwards (e.g. the keyboard). This process is known as overdubbing and whilst it is obviously more time-consuming, it does offer a workaround when you have too few inputs.

Secondly, you will notice that some interfaces have digital inputs. If you are new to recording or only undertaking basic projects then you will probably not need to worry about these. Digital inputs are mainly used for connecting to other devices with digital connections or for linking multiple interfaces together.

Finally, you may notice that some interfaces have 'virtual' inputs. These do not provide any physical inputs on the interface itself, but instead allow you to route audio signals from other programs within your computer and record them.

So, moving onto outputs and for basic projects, you will only need 2 outputs: one to connect to one speaker and another to connect to a second speaker. If you plan on using multiple sets of speakers (e.g. for reference purposes) then you will of course need enough outputs to connect to all of your speakers.

In some cases, although you will only be using one set of speakers, you may want to route a different set of signals to your headphones than you are hearing out of the main speakers. This can be useful if, for example, you are working with a vocalist that just wants to hear a click track along with their performance with a bit of reverb, whilst you track their performance alongside the rest of the track. In this case you will need an interface with at least 4 analogue outputs because you will be sending one mix to your left and right speakers (2 outputs) and a second mix to the left and right ears of the headphones (another 2 outputs).

Again, as with the inputs, if you are planning on using hardware effects in a send/return configuration then you will need enough inputs to satisfy this. The send/return configuration means that you route a signal out of the interface (via its outputs), through an effects unit and then back into the interface (via the interface's inputs).

You will also notice that some interfaces have digital outputs as well as inputs. Again, these are used for connecting to other digital hardware (e.g. a digital recorder) or for linking multiple interfaces together.


MIDI connections on an interface have become less and less important as most modern MIDI controllers and synths now connect to your computer via USB. However, if you are working with a MIDI device that does not have this functionality (e.g. an old synth or hardware effect with MIDI connections) or you would simply rather save your USB ports on your computer for other things, then you should look for an interface with MIDI connections.


The first thing to check here is what connections your computer has. For example, if you only have USB connections then your decision is made: get a USB interface! In fact, even if you have a PC with both connections, I would still recommend getting a USB interface unless you have a specialist Firewire card as Firewire is notorious for being unreliable on PCs. If you have a Mac then it does not really matter what you get.

In the past, Firewire was a much faster protocol than USB, but with USB advances (i.e. USB 2.0), you shouldn't really notice much difference between the two. Technically speaking, if you are using a Mac computer, Firewire will probably be slightly faster than USB 2.0, but it's really not going to be anything significant and so shouldn't be your primary concern.


Sample rate determines how often a sample of a sound is taken in order to reproduce it digitally. Whilst analogue signals are continuous, digital signals are comprised of individual pieces of data that are played back so quickly so as to sound like a continuous signal. For example, with a 44.1kHz signal, 44100 pieces of data are used to represent one second of audio. With a 96kHz signal, 96000 data samples will represent one second of audio and hence should be able to pick up more intricate details in a sound.

With this in mind, technically speaking, the higher the sample rate, the better quality recordings you will get. However, CD quality is 44.1kHz and theoretically, this should be more than enough to cover the entire frequency range of human hearing. However, there are people that claim that they can hear an increase in quality when the sample rate is increased and so most producers tend to work at 48kHz or 96kHz. Some interfaces let you work at even higher sample rates than this!

However, there is a trade-off. The higher the sample rate that you work with, the more storage space you will need to save your files. As a general rule you should work at the highest sample rate possible whilst not compromising storage for your particular system.

Personally, I used to work at 96kHz but have recently cut down to 48kHz to save memory. Critically listening, I think that I can hear a slight difference between a 48kHz and 96kHz sound, although it is extremely subtle and could well just be down to the fact that I know that one is of a higher quality. At the end of the day though, my tracks are all going to be bounced down to 44.1kHz CD quality or compressed into mp3 format so I really doubt in its final form that anyone is going to notice whether the track was originally at 48kHz or 96kHz! If you think that you can hear a significant difference between sample rates then I would suggest working with as higher sample-rate as possible even if your tracks are going to get converted to CD/mp3 though as it will allow you to make more informed decisions at the mixing stage.

Bit-depth is similar to sample rate but it deals with the dynamics (volume levels) of a sound. The higher the bit-dept, the more intricate level differences the interface will be able to pick up. You should work using the highest bit-depth possible as this does make a noticeable difference. Most interfaces now offer a 24-bit mode and whilst CDs only use 16-bits, it is advisable to work using as higher bit-depth as possible to allow you to make more accurate decisions at the mixing stage.


In this article we have covered the basic things that you should be looking for when buying an audio interface. There are many other features that an interface can have though, including the ability to connect and record to an iPad, built-in effects, included software, advanced routing options and much more!

If you require further advice on buying an interface of any kind then please give us a call on 01202 597180 and we will be happy to help.

CLICK HERE to view our range of Focusrite USB interfaces

CLICK HERE to view our range of Focusrite Firewire interfaces

This post was posted in Blog entries, Computer Music, General News, How To Guides, Product News, Recording and was tagged with audio interface, focusrite