Call Us: 01202 597180
We're open: Monday - Saturday 10am - 6pm
Sundays and Bank Holidays 10am - 4pm.

CHOOSING AN AUDIO INTERFACE

Posted on May 9, 2011 by Joe Stachowiak There have been 2 comment(s)

Alesis IO2 Audio InterfaceINTRODUCTION

So, you're new to the world of computer music and audio recording are you? And you're looking to invest in an audio interface, or simply wondering what one is, and why you might need one? Well my friend, you have come to the right place! In fact, I remember being majorly confused about this whole subject when I first became interested in music production in the hazy days of my early teenage years! So if you're just as confused as I was and want to learn more, then you'd better put seatbelts on your ears, because I'm about to take them for the ride of their lives! Our handy guide helps you choose the audio interface that is best for you, and also explains terms such as 'sample rate', 'bit depth' and 'latency'.

CONTENTS

1. Introduction and Contents
2. What Is An Audio Interface?
3. Why do I Need One?
4. What Causes Latency and Why is it an Issue?
5. Buying an Audio Interface - First Steps
6. If You Are Not Going to be Recording...
7. How May Inputs Will I Need?
8. How May Outputs Will I Need?
9. Recording Quality - Bit Depth and Sample Rate
10. Will I Need to Route MIDI Through The Interface?
11. Firewire or USB?
12. Audio Interfaces for Digital DJs
13. Audio Interfaces for Live Mixing
14. The Look
15. Software
16. Extending the Functionality
17. Summary

2. What Is An Audio Interface?

WHAT IS AN AUDIO INTERFACE?

The term 'audio interface' is really nothing to be confused about, as it is essentially just an external soundcard. And if you are wondering what a soundcard is, this is just the specialised group of components that deal with getting audio in and out of your computer. For example, if you need to record some sound into your computer, the chances are your computer's soundcard comes with a small microphone connection. This will allow you to plug in a computer microphone, speak into it, and the clever electronics of the soundcard will turn your voice into data within the computer. This is achieved by a device within the soundcard called an Analogue-to-Digital (AD) convertor... i.e. the microphone converts your voice into a voltage (which is in an analogue form), and the AD convertor then converts this voltage into digital data (that the computer can store).

If you want to play your recording back, the soundcard will take the digital data stored on the computer, and turn it back into an analogue voltage, which can be passed as sound out of speakers or a set of headphones that are connected to the output of your computer's built-in soundcard. It performs this task using it's... yes, you guessed it... Digital-to-Analogue (DA) convertor (the reverse of the Analogue-to-Digital convertor). Note that the speaker within your computer is not actually part of the soundcard... it is just connected to it.

3. Why Do I Need One?

WHY DO I NEED ONE?

So you may now be wondering, if your computer already has a built-in soundcard, why would you need to buy an external one? Well, the truth is, you don't necessarily 'need' to buy one, but if you are serious about music production, then it is highly recommended that you do, as the soundcard that comes with your computer isn't designed as a professional piece of audio equipment, and so it won't offer you the quality, performance, and flexibility of a dedicated audio interface.

In more detail, an audio interface offers you:

1. Improved recording quality.

Standard computer soundcards are limited to recording audio with a certain sample rate and bit depth. What does this mean? For now all you need to know is that the higher the sample rate and bit depth, the more detail you will capture in your recordings. CDs have a sample rate of 44.1kHz, and a bit depth of 16, and this will probably be what your standard computer soundcard is rated as. However, if you are producing a professional recording, it is likely that you will want to record sounds in much more detail, even if you ultimately plan to convert your final tracks to CD quality after you have finished mixing. The general rule is that the higher the quality of the original recording, the better it will sound when it is converted to a lower quality.

Another thing to note is that audio interfaces generally introduce less noise into your recordings. For example, if you are recording a source with a microphone, audio interfaces tend to supply professional, low-noise preamps. These are devices used to bring the recording up to a special level called 'line level' whilst introducing as little noise as possible, and they will offer a significant improvement in quality over recording with the standard soundcard supplied with your computer.

2. Improved output quality.

Standard soundcards are housed within the computer, and are therefore subject to interference from neighboring electronics, which will become apparent as noise in connected speakers/headphones. Audio interfaces are separate from the computer, and are therefore not at risk from such interference, giving you a crisper, cleaner sound when you listen back to your music.

3. Decreased Latency.

Latency when recording is a big problem with standard computer soundcards. When your computer receives some audio information, it processes it before storing it and/or passing it out to the speakers or a pair of connected headphones. This naturally takes a little bit of time, both for the signals to travel to and from the soundcard, and for the computer to perform its processing. The time that it takes for all this to happen is called 'latency'... it is essentially a delay in the signal.

For more information on latency, please refer to the next page (4. What Causes Latency and Why is it an Issue?).

4. More connection flexibility.

What if you want to plug in a professional microphone? Or multiple microphones? Maybe you need to supply a condenser microphone with phantom power? Or what if you want to set up a secondary pair of reference monitors, or have the ability to route a click track to a pair of headphones whilst playing music out of the main monitors? Or maybe you want to record to two sources at once? What if you want to record a guitar? What if you need to connect something into your set-up using standard 5-pin MIDI connections? Audio interfaces (or audio/MIDI interfaces) allow you to do all this with extreme ease. All you need to do is ensure you purchase an audio interface with all the connections you need, as different models offer different types and numbers of connections.

Hopefully you can now see why audio interfaces are so important to the serious music enthusiast! Now read on if you want some tips on the different types of interfaces that exist...
4. What Causes Latency and Why is it an Issue?

WHAT CAUSES LATENCY AND WHY IS IT AN ISSUE?

So, why is latency an issue? Imagine you have a MIDI keyboard hooked up to your computer that is triggering either a software or hardware synthesiser to output some sound. If your system has a high latency, then it will introduce a noticeable delay between when you press the keyboard note, and when you hear the sound come out of your speakers/headphones. In a similar way, if you are recording and monitoring a vocal performance, latency will cause a delay in the signal between you speaking down the microphone, and the sound coming out of the speakers. Situations like this are VERY annoying and are completely off-putting!

So what causes latency? In order to record and output some audio information, the computer must firstly covert the analogue ‘sound’ into digital data, before processing and storing it, then turn the recorded data back into analogue information before passing it out of the speakers. However, due to computer speed and power limitations, it cannot do this all in real time… instead it uses something called buffers (which are essentially just allocated portions of computer memory). A buffer allows the computer to read in a certain amount of audio information and store it until it is ready to process it. So for example, if you had a buffer size that could store 10ms of audio data, when you start recording, the buffer would fill up with 10ms of audio data, and then at the end of that 10ms period, the computer would read out the information in the buffer and process the 10ms of audio all at once! This would then free up the buffer to record the next 10ms of sound, which would then get read out and processed, which would free up the buffer again, and so on and so on! In a similar way, if the computer is playing audio, it will load 10ms of audio into a buffer to play, then once the 10ms has played it will load in another 10ms of audio, and so on! By processing chunks of audio at once, the computers CPU acts more efficiently and is less burdened… essentially it has time where it is not processing audio (and loading it into buffers) that it can dedicate to doing something else!

That’s all good, but what does this have to do with latency? Well, let’s imagine we are playing some audio that is routed through a software reverb plug-in, and that in this situation our computer has a buffer that stores 1 second of audio… this is an unusually large buffer but it highlights the problem of latency well.

Initially we do not have the reverb plug-in turned on, and so when we press play, our buffer fills up with one second of unprocessed audio, then plays the audio within the buffer. Every second, the buffer re-fills with audio to play, creating a constant stream of sound. However, what happens if we suddenly decide to turn on the reverb effect? The answer is that you are likely to experience a delay, as the buffer only ever updates after every second. So, for example, if you turn the reverb effect on after 3.5 seconds, you will not hear the reverb effect for another 0.5 seconds, when the buffer has had chance to fill up with the processed audio data. If you then switch the reverb ‘off’ after 6.1 seconds, you won’t hear the effect of this for a whole 0.9 seconds, as your computer has already loaded the buffer with processed audio (representing the portion of the song between 6 to 7 seconds).

If you are recording, then the buffer will need to fill up with a second of audio before the computer empties it to process it… in which case, if you are monitoring what you are recording (listening back to it), you won’t hear any sound until it has been converted to digital data, the buffer has filled up, been processed, made a return journey through the output buffer, and then been converted back to analogue ‘sound’, hence you will get a rather substantial and annoying delay with a large buffer size. Hopefully you can see that the larger the buffer size, the more latency you are likely to experience.

So how do we stop this unwanted phenomenon? Well, the truth is that it can’t be eliminated completely, but it can be reduced. You may have noticed that your recording program has a way to adjust the computer's buffer size in its preferences window…

Hooray! So I can just make the buffer size smaller if my computer’s soundcard is introducing noticeable latency? Well, yes you can... however, the smaller the buffer size, the harder your computer will have to work to process audio quickly, so it's resources will soon become drained, and you may find that your computer becomes really slow, or in some cases introduces some unwanted artifacts into the sound as it can't keep up with your demands! In fact, if your computer has an extremely small buffer size and it does not have enough resources to cope, it is likely that you will experience gaps in your sound as the computer cannot empty or refill the buffer in time with your demands! For this reason you will always need to find a balance between latency and CPU load, and the exact values will depend on your computer.

But if the computer’s CPU is always affected by the buffer size, how could an audio interface solve this? Well, you may have noticed that most audio interfaces offer something called ‘zero-latency monitoring’. This technology allows you to record with extremely low latency whilst not heaping loads of work on your CPU.

In fact, recording and monitoring audio is where you are most at risk of latency issues. As I mentioned earlier, this is because audio data has to pass through two sets of buffers… once as the sound is recorded to the computer, and once when it is output from the computer!

Zero-latency monitoring eliminates this issue, and works by routing the input directly to the output, meaning that the sound doesn’t have to pass through any buffers at all! In this case the main latency that gets introduced into the signal is by the AD and DA convertors, although the combined delay from both convertors is generally less than 2ms, which will be unnoticeable even to the most acute listening ear! This is brilliant for recording situations where the performer wants to listen to their work as they perform it. However, because zero-latency monitoring bypasses the computer, you cannot apply any plug-in effects to the signal, so it is not ideal in every situation… unless you’re interface features on-board DSP effects! You could also route an external hardware unit into the signal path, so you aren’t completely lost if you are a vocalist who likes to monitor with a bit of reverb, for example. However, do bare in mind that the more you do with the audio signal, the more latency you will introduce… but the methods mentioned here should be significantly quicker than routing audio through a computer.
5. Buying an Audio Interface - First Steps

BUYING AN AUDIO INTERFACE - FIRST STEPS

Ok, so you’re now pretty sure that you need an audio interface, but you're unsure which one to buy. The first thing you need to do is to think about what you are going to need to do in your projects. You may want to ask yourself a number of questions, such as:

Am I going to be recording? If so, what am I going to be recording (e.g. vocals, guitar, etc)?

What is the maximum number of things I will need to record at once? E.g. will you only ever be recording your voice, or will you be undertaking multitrack recordings of entire bands with fully mic'd drum kits?

Will I require phantom power to use condenser microphones?

What quality do I want to make my recordings at? E.g. are you satisfied with creating recordings at 44.1kHz (CD quality), or do you want to make recordings in more detail? If so, how much more detail do you want to capture your recordings with?

How many different outputs will I need? E.g. will you only be running a single pair of studio monitors, or do you have a number of pairs of reference speakers? Is it likely that you will need to route a click track to a pair of headphones, whilst playing music out of your main speakers?

Will I need to route any MIDI through the interface?

Will I be using any hardware synthesisers?

Will I be using any external audio effects?

Do I want to connect it to my computer via Firewire or USB?

Where will I be using it? E.g. Are you going to be using it in the studio, on the road, for DJing, or for a mixture of these scenarios?

How much immediate feedback do I want it to give me? E.g. Do you want it to have detailed LED meters to monitor recording levels?

Would I prefer to have the option of setting up the interface with software as well as the hardware controls?

Is it likely that I will need to extend the functionality and features of the interface in the future?

As you can see, there is a lot to consider when purchasing an audio interface, and if you are new to all this you may now be feeling even more daunted and confused! But hey there, don't worry little fella! I'll talk you through it all, and together we can make it through!
6. If You Are Not Going to be Recording...

IF YOU ARE NOT GOING TO BE RECORDING...

The chances are, that if you are running a small home studio, at some point you will want to record something, or have some way of getting audio into your system. Situations where you may require this kind of functionality include recording vocals (or an instrument) through a microphone, recording the direct signal from an electric guitar, recording music from a vinyl turntable or a tape recorder, or routing audio from a hardware synthesiser back into your system so that you can hear it through your monitor speakers (and of course record its output onto your computer).

However, if you are NOT planning on EVER recording anything as you only EVER work with pre-recorded samples and software synths, then I would assume you are either after:

a) Something to supply a higher quality audio signal (with lower noise) to your (two) studio speakers, in which case, check out these products:

M-Audio Pro Tools Recording Studio – This budget USB interface doesn’t offer all the features in the world, but it provides you with two RCA outputs. However, please note that RCA connections are unbalanced, and so if you are running long cables, or simply want noise reduction technology to deliver even cleaner signals to your speakers, then you may want to look elsewhere.

Alesis IO2 – a little more expensive than the M-Audio Pro Tools Recording Studio, but offers a lot more features as well as those all-important balanced outputs with noise reduction technology, which is essential when running longer cables to carry your audio information. Again, the Alesis IO2 connects to your computer via USB. You may also want to check the Alesis IO2 Express, which is almost identical to the Alesis IO2, although it doesn't feature any S/PDIF connectivity... although it is cheaper! :)

Echo Audio Audiofire 2 – if you’re after something that connects to your computer via Firewire rather then USB, the Audiofire 2 may be exactly what you are after, offering 2 balanced outputs! However, the Firewire connectivity comes at an increased price compared to the slower USB devices that I have already mentioned.

Focusrite VRM Box – if you only ever mix your projects through headphones, the Focusrite VRM Box gives you excellent sonic detail, whilst also supplying you with some intuitive software that allows you to hear audio as if it were coming from a set of speakers in front of you. On top of this it also allows you to choose from a selection of speakers and recording environments so you can reference your mix in a number of situations! In fact, the Focusrite VRM Box is a handy piece of kit to own even if you only sometimes mix through headphones, and you can connect it to an existing audio interface that has a S/PDIF connection (more on this in a bit). Just make sure that you have a decent pair of headphones if you opt for the VRM Box, as the better the headphones, the more accurate your mixes will be.

 

b) You are searching for a more hands on way to control your speaker and headphone outputs, in which case, check out these products:

M-Audio Pro Tools Recording Studio – If this is all you require an audio interface for, then there is no point at all in shelling out loads of money, and so this budget audio interface would be perfect for you as long as you don't need the headphones and speakers to be capable of playing different things at the same time (i.e. you won't need to route a click track to the headphones whilst your speakers play something different) or you want to control multiple sets of speakers. If this is the case, you will need to look for a product with more than 2 outputs, so skip to the section entitled 'How Many Outputs Will I Need?'

c) You need to connect a MIDI device into your system using standard 5-pin MIDI cables (i.e. a MIDI device that does NOT communicate data via USB or Firewire) , in which case, check out these products:

… If this is the case, please refer to the section entitled ‘Will I Need to Route MIDI Through The Interface?’

d) You need to route audio out of more than two outputs:

… (e.g. you are running a 5.1 surround sound set-up, you have additional pairs of speakers to reference your mix, or you want to record to a separate device whilst listening through your main monitors). Again, if this is the case, skip to the section entitled 'How Many Outputs Will I Need?'

e) You are a digital DJ and need a way of routing audio from two (or more) separate decks to a single stereo output, whilst also running a separate headphone mix:

… If this is the case, skip to the section entitled ‘Audio Interfaces for Digital DJs’.

You may have noticed that some of the interfaces I recommended in this section have inputs, so have the capability to record even though you are not going to utilise it... this is because most audio interfaces (even budget ones) offer at least two inputs, but they are useful things to have at your disposal just incase the situation arises where you do ever need to make a recording.
7. How Many Inputs Will I Need?

HOW MANY INPUTS WILL I NEED?

Right, we've covered appropriate interfaces for you if you DON'T need to record, but what if you do need to record? The key here is to determine what you are going to be recording, and how many things you will need to record simultaneously.

In the simplest scenario, you will just want to record your voice, in which case you will need an audio interface with one microphone input, and if you are using a condenser microphone, you will also need your interface to be capable of providing 48V phantom power (this is what condenser microphones require to work).

If you do not require phantom power, then you may want to consider these products:

M-Audio Pro Tools Recording Studio – Offers one microphone input, and a guitar/instrument input just in case, and it comes at a great price.

However, if you DO require phantom power, or think that you will require it in the future, and you are still only working with a simple recording set-up, then you may want to consider the following products:

Alesis IO2 – Provides a 48V phantom power switch, along with 2 inputs, both of which can either be used to connect a microphone or a guitar/instrument. Plus it provides LED meters so you can see straight from the interface whether your recording is set at an adequate level, or whether it is clipping... basically, if you see the LED meter go into the ‘red’ on your audio interface, then this is bad, and you need to turn your recording levels down! You may also want to consider the Alesis IO2 Express if you do not need digital S/PDIF connectivity.

Mackie Onyx Blackjack – This budget USB interface features an exceptional build quality with its all-metal chassis, and it features exceptional quality pre-amps for extremely clear recordings. With its two balanced output connections and zero-latency analogue monitoring path, this interface provides you with everything you need for simple, high-quality recording scenarios. However, it does not feature any MIDI connections, so ensure that you don’t require this before you buy!

M-Audio Fast Track Pro – A popular budget USB audio/MIDI interface with 2 mic/instrument inputs, balanced and unbalanced outputs and a number of hands on controls!

Apogee ONE – This audio interface is perfect for both portable and studio work and it looks fantastic! It allows you to record one channel of audio at a time (mic, instrument or guitar) and offers extremely high quality inputs and outputs. However, it is only compatible with Macs, so unfortunately Windows users will have to miss out. You may also want to look at the Apogee Duet if you want a high-quality, portable interface capable of recording up to 2 channels of audio at once.

Steinberg CI2 – This dedicated audio interface comes with 2 mic/line inputs (one of which can also be specially to set with electric guitar signals) and 2 balanced speaker outputs, as well as latency free monitoring. It does not feature any MIDI connections, although it does come with a specialized AI knob that can be used to control the included Cubase AI 5 software, which is a fantastic tool to speed up your workflow if you don’t already own some sort of control surface. Or check out the Steinberg CI2+ for advanced control features!

Focusrite Saffire 6 – This quality USB audio/MIDI interface offers exceptional quality and a number of hands on controls with 2 mic/instrument/guitar inputs and 4 outputs!

You may be wondering why I am recommending interfaces with two inputs when this situation only requires one (for a microphone). The truth is that most interfaces offer an even number of inputs, so you would be hard pushed to find something that just offers the 'one' you are after. However, it's always handy to have a spare, just incase!

If you are planning on recording more than one thing at a time, then you will need to search for an audio interface that satisfies your particular needs. Think:

1. How many microphones do I need to record with at once?

… then search for an interface that offers at least that many microphone inputs with preamps. You will usually find that microphone inputs come in the form of XLR/1/4” jack combo connections, or dedicated microphone XLR connections.

XLR/1/4” jack combo connection:

XLR/1/4

Switchable 1/4” jack connection – the connections in this picture are labeled ‘Guitar’ and so are suitable for recording an electric guitar, as long as the switch is set to ‘Guitar’:

1/4

3. How many line level inputs will I need?

Line level inputs will be required for routing the audio you receive from devices such as hardware synthesisers, audio amplifiers and mixers. For example, if you are running one hardware synthesiser and you want to record a stereo signal from it, you will need at least two separate line level inputs (one for the left channel and one for the right) on your interface. Line inputs come in the form of 1/4” jack connections (see above).

4. Will you need anything else?

For example, some audio interfaces offer S/PDIF input connections, which can be used to record a digital stereo audio signal (e.g. from a MIDI sound module). These come in the form RCA connections.

S/PDIF connections:

S/PDIF input and output RCA connections

That's probably all you will need to consider in terms of inputs when purchasing an interface for recording audio. Some specialised high-end interfaces offer features such as optical inputs for recording audio from a digital system, but in all honesty it is highly unlikely that you will require such things, unless you are working with an extremely complex set-up.

However, some audio interfaces also offer something called ‘virtual inputs’. These types of inputs don’t have any physical connections on the interface, but are useful for recording audio within the computer. For example, if you hear a sound on the internet that you simply have to sample, then just use your virtual inputs to record it!

One important point to be aware of is that some audio interfaces may appear to have more inputs than they actually possess, so it is always important to read the product information before you make a purchase. For example, if you look at the front panel of the Alesis IO2, you will see that it has two microphone inputs and two Guitar/Line inputs.

Diagram showing how many inputs may be split between fewer channels.

However, this does NOT mean that you can record and balance 2 microphones and 2 guitars all at the same time! If you read the product information, you will see that the Alesis IO2 is specified as having 2 inputs... this means that it will only let you record up to two simultaneous things at once, and with the connections that it offers, you would be able to record any combination of up to two microphone/guitar/line sources (one on it’s first input channel, and another on it’s second input channel).

Compare this with the M-Audio Pro Tools Recording Studio, and you will see that despite both offering two inputs, the M-Audio Pro Tools Recording Studio only lets you plug a microphone into the first input, and a guitar/line level source into the second, so you couldn't record from two microphones at once, for example.

Guitar and microphone inputs of the M-Audio Pro Tools Recording Studio.

Hopefully this illustrates the need to check the connections and the number of inputs on an audio interface before you buy it!

If you require an audio interface with more than 2 inputs, then there are loads of products out there, each with different types and combinations of connections. If you are going to need to make a more complex recording then you may want to consider one of the following products:

Focusrite Saffire Pro 14 – An excellent value Firewire audio/MIDI interface with a fantastic 8 high-quality inputs (2 Mic/Inst, 2 Line, 2 S/PDIF, and 2 Virtual). Note that the virtual connections let you record audio from a source within your computer, so are useless if you need to record any outboard equipment, but are excellent if you want to do something such as sample audio from online, etc. With phantom power, and a total of 6 outputs, this modestly priced interface offers features that mean it punches way above its price tag.

Tascam US-600 – Modestly priced USB audio/MIDI interface featuring 3 mic/line inputs, one mic/instrument input, and a stereo S/PDIF input! However, it does only feature unbalanced RCA outputs, so if you need balanced outputs, this interface will not suit your needs. You may also want to consider the Tascam US-800, which is exactly the same but offers additional Mic, Line and Instrument inputs.

MOTU Audio Express – This high-quality audio/MIDI interface can connect to your computer via either a Firewire 400 or high-speed USB 2.0. It offers 2 Mic/Instrument inputs, 2 line inputs, and stereo S/PDIF inputs, as well as 4 line outputs and 2 stereo S/PDIF inputs.

Focusrite Saffire Pro 40 – offers an amazing 20 inputs and 20 outputs at an amazing price! With 2 Mic/Line/Inst inputs, 6 Mic/Line inputs, 2 S/PDIF inputs, 8 optical inputs, and 2 virtual inputs, this could well be the interface you are after if you need to produce complex, high-quality recordings without breaking the bank.

8. How Many Outputs Will I Need?

HOW MANY OUTPUTS WILL I NEED?

So, you're sorted with your inputs, but now you need to consider your outputs!

If you are running a small bedroom studio, it is likely that you will only require two main outputs; one for the left speaker and one for the right. If this is the case, then you should be fine with most audio interfaces. Just be aware that different audio interfaces may use different connections for their outputs. Most audio interfaces will use line1/4" balanced jack connections for their outputs, although some feature unbalanced RCA output connections instead.

Line 1/4” balanced jack main output connections:

Line 1/4” balanced jack main output connections.

RCA main output connections.

Unbalanced connections are fine if you are running short cable lengths, but balanced output connections are always preferable if your speakers/studio monitors feature balanced connections, as balanced connections feature noise reduction technology that ensures the signal you hear is as clear as possible... balanced connections are especially important when routing a signal over longer distances, as the longer the cable, the more noise is likely to be introduced into the original sound. Just be aware that you will need to use a balanced cable to run a balanced signal – if you plug in an unbalanced cable into a balanced connection it won’t matter, you just won’t get a balanced signal! Click HERE if you want more information on the difference between balanced and unbalanced audio signals.

So, why might you want more outputs? One of the most common reasons for requiring extra outputs would be if you want the capability to route a click track to a pair of headphones whilst playing the main music out of your studio monitors. Yes, most interfaces with 2 outputs will also feature a headphone output, but the headphones will always be sent the same signal that your speakers are sent. If you require the headphones to be sent a different signal to the main speaker (e.g. a click track), you will require an interface with the capability to route independent channels to the headphones. In practice, this means that you will need 4 independent outputs: outputs 1 and 2 for the main speakers, and outputs 3 and 4 for the stereo headphone signal. Now an audio interface with this capability will probably not look much different from a standard 2 channel interface, as the extra outputs are featured on the headphone connection, so it is important to read the products specifications before you buy to make sure that the interface features separate headphone outputs. Also don't worry if you want the flexibility of routing the same signal to your headphones as your speakers AND the option to route different audio to each. Audio interfaces that offer this functionality let you switch between the two!

Another reason why you may need more outputs? If you have a selection of speakers that you use to reference a mix, then you may want to connect a number of pairs into your set-up, and switch between them to hear your mix through different systems. Or you may be running a 5.1 surround sound set-up. Or if you are working in a live situation, you may want to route the music to a number of different PA speakers, some angled towards the crowd and others used for on-stage monitors. In any situation where you require more than two speakers, you will need an interface with more outputs. These will usually appear in the form of more 1/4" balance jack Line Out connections. Your first 2 outputs will usually be labeled something like 'Main 1 and 2', and then further outputs will be numerically labeled in sequence, e.g. 3, 4 , 5, 6, etc.

So for example, if you want to have a primary and secondary pair of studio monitors connected into your system, you will connect your main pair of speakers to outputs 1 and 2, and your second pair to outputs 3 and 4, and you will then be able to use your recording software, or the interface itself to select which speakers the sound comes out of.

Line out connections are not just useful for connecting extra speakers... you can also use them to create send paths for processing your audio with external hardware effects units. Of course you will then also need two spare line inputs to route the retuning processed audio back into your mix. Just remember that stereo signals require two connections, so to create a stereo send/return path you will need at least 2 free line outputs AND 2 free line inputs.

Again, you may notice that some interfaces offer different types of outputs as well as standard line outs. The most common of these is probably a S/PDIF connection. These carry a stereo signal, and are useful if you want to hook up to a piece of digital equipment, for example to record your audio on a different system.

The other type of output connection you may see on audio interfaces is an optical output (or TOSLINK connection). Again, this is offers another method for connecting to digital audio devices, and can even carry multiple channels at once... however, it is unlikely you will need this type of connectivity if you are only working on fairly simplistic projects.

For more information on different connection and cable types, click HERE.

If you require more than 2 standard speaker outputs, then you may want to consider the following products:

Focusrite Saffire PRO 14 – An awesome Firewire audio/MIDI interface an even more awesome price! The Focusrite Saffire PRO 14 offers 4 line outputs and 2 S/PDIF outputs, so is the perfect choice for hooking up an extra pair of monitors into your system, and is also perfect for recording to another bit of electronic gear.

Focusrite Saffire PRO 24 DSP – If the Saffire PRO 14 doesn’t quite fulfill your output needs, then this Firewire interface offers an additional 2 line outputs (6 in total) alongside the 2 S/PDIF outputs and also comes with the added bonus of VRM technology, which allows you to mix through your headphones just as if you were mixing through a pair of speakers in front of you! Also check out the standard Focusrite Saffire PRO 24 if you just want the extra connections, but are not bothered about having VRM.

Focusrite Saffire PRO 40 – This Firewire interface provides you with an amazing 20 outputs for an excellent price – that’s 10 line outputs, 2 S/PDIF outputs and 8 optical outputs!

MOTU 828 Mk3 – This audio/MIDI interface can be powered via either Firewire or USB 2.0 and provides you with a host of connectivity and features including 8 pristine quality line outputs, 2 main XLR outputs, S/PDIF outputs and optical outs.

MOTU Audio Express – Provides you with 4 balanced line and a stereo S/PDIF output, and can be powered via either Firewire 400 or USB 2.0.

Focusrite Saffire 6 – fantastically priced USB audio/MIDI interface with 4 unbalanced RCA outputs.

9. Recording Quality - Bit Depth and Sample Rate

RECORDING QUALITY - BIT DEPTH AND SAMPLE RATE

Once you have decided how many inputs and outputs your audio interface will need, you should probably start to think about how detailed you want your recordings to be, and this involves thinking about those terms that I mentioned earlier: sample rates and bit depths.

If you are unsure about what either of these terms means, then I will give you a little introduction...

The terms 'sample rate' and 'bit depth' are specific to digital audio. When audio is stored in a digital format, it is stored as a stream of values, and the more values you store (or SAMPLE) from a piece of audio within a given timeframe, the more accurate your reproduction will be. For example, lets say you are recording a piece of audio that is one second long. To store it in a digital format, you would need to choose points within the waveform to convert into a value and store as digital data. Lets say you have the waveform as shown below:

One second waveform.

… and you decide to take five samples each second at equally spaced intervals:

One second waveform sampled 5 times.

When you store the values, this would recreate the following waveform:

One second waveform sampled 5 times - resulting waveform.

As you can see, it is not the same as the original! In fact, we have missed some details of the original sound because we haven't stored enough samples. If we increase the sample rate to ten samples a second, this would give us the following reproduction of the sound:

One second waveform sampled 10 times and resulting waveform.

It's better, but it's still not right – the basic shape is still a little incorrect and we have missed out the smaller details altogether! Hopefully you can see that the more we increase the sample rate, the more accurate our recordings become, as they allow us to capture smaller and smaller details within the sound. So how many samples per second do you need to take to create an accurate recording? A number of years ago, some science boffins discovered that the minimum sample rate required to produce an accurate recording was 44.1kHz (that's 44,100 samples per second), and this became standard for CD quality. However, this is the MINIMUM sample rate required for an accurate recording, and so the more samples you process/record a second, the more accurate your recording will be! As I have already mentioned, it is highly likely that you will eventually convert your track to CD quality anyway, but the general rule is, the more accurate your original recording, the better your converted track will sound.

If recording quality is not that important to you, then an interface that can record at 44.1kHz would suit you just fine... the chances are, most people will not be able to tell the difference if your tracks are just getting played on consumer electronic systems such as home or car stereos.

If recording is mildly important to you, then many budget audio interfaces also allow you to record up to sample rates of 48kHz. This is better than CD quality, and will probably be adequate for most small home studios.

However, if you want to be more professional, a number of audio interfaces exist that allow you to record at even higher sample rates! I personally prefer to work at a sample rate of 96kHz as I believe that this gives exceptionally clear detail, and once you venture above this to higher sample rates, only those with the most acute listening ear can tell the difference, although you will find many professional audio interfaces offering recording sample rates up to 192kHz! However, one thing to note is that storing sounds at higher sample rates will take up more memory, so it's always a balance between performance and practicality.

And bit depth? Bit depth works in a similar way to the sample rate, but instead of working within the time domain, it concerns itself with amplitude. Essentially, the higher the bit depth, the more variations in amplitude you will be able to capture. For example, in a simplistic situation where you had a system that was only capable of distinguishing audio as 'minimum', 'middle' and 'maximum', this would not give you a very accurate reproduction of the original audio signal.

For example, if our computer only has enough memory to store each sample as one of three depth values and we have this original waveshape:

Waveform and 3 amplitude levels.

… when we store it in digital form, our computer will have to determine which ‘depth’ each sample is:

Waveform split into 3 amplitude levels.

… and so we will end up with a sound that is not the same as the original, and has less dynamic detail:

Resulting waveform split into 3 amplitude levels.

If you had a system that could distinguish audio at 5 different levels ('minimum', 'mid-low', 'middle', 'mid-high', and 'maximum'), then you would get a better reproduction of the audio signal, with a much more dynamic feel (variation of different amplitudes):

Resulting waveform split into 5 amplitude levels.

Again, the more levels you can distinguish audio at, the more natural your recording will sound, and the more 'depth' it will possess. 16 bit signal (CD quality) can distinguish audio at 65,536 different levels of depth. 24 bit audio (which is the standard for professional recordings) contains a massively increased 16,777,216 different levels of depth. If you are serious about recording, you really should look for an interface that can record at a bit depth of 24, although be aware again, that the higher the bit depth you record at, the more memory you will need to store each sample.

Again, different audio interfaces offer different sampling rates and bit depths. Some even offer different sample rates depending on the input you are using to record (S/PDIF inputs commonly offer higher sampling rates than the analogue line inputs on budget interfaces for example), so make sure to read the products specifications before you buy to ensure that you get a product that suits your individual needs.

I could now give you a list of recommended audio interfaces to choose from all with different sample rates and bit depths (although most modern audio interfaces provide 24-bit recording), but the truth is, the list could go on forever! The best way to select an interface with the appropriate sound quality is to firstly narrow down your choices depending on how many inputs, outputs and other features you need, and then examine each interfaces specifications to determine which one best suits your needs.
10. Will I Need to Route MIDI Through The Interface?

WILL I NEED TO ROUTE MIDI THROUGH THE INTERFACE?

In other words, will you need to connect any 5-pin MIDI cables into your set-up? If you just own a MIDI keyboard, the chances are that it communicates MIDI data through a USB cable, in which case you will not need to use any MIDI connections... just use the supplied USB cable running directly from the controller keyboard to your computer.

However, there may be situations where you are using a piece of MIDI equipment that does not feature MIDI USB connectivity. For example, if you are using an older hardware synthesizer and you need both your computer to trigger its output (e.g. from MIDI events within a DAW) and you want to be able to record MIDI information from the synth in your computer, then the best way to do this would be to connect a MIDI interface up to your computer via USB or Firewire, and then connect your synthesiser to your interface with standard MIDI cables via the MIDI In and Out connections on each device! Simples!

Most interfaces nowadays also come with MIDI connectivity, so it is again best to base your choice of interface on other factors first (e.g. number of inputs, number of outputs and maximum sample rate), and then check that it also features MIDI connections. If you are simply looking for an interface to handle MIDI connectivity, and are not worried about anything else, then you may want to consider one of the following products:

Alesis IO2 – A budget USB audio/MIDI interface, but with a solid build and those all-important MIDI In and Out connections. This small interface also features input connections for recording, and outputs for hooking up a pair of studio monitors. You may even prefer the Alesis IO2 Express, which is exactly the same as the standard IO2, but doesn't provide any S/PDIF connectivity (pictured below).

M-Audio MIDISORT – If you aren’t bothered about anything else (e.g. you don’t need to connect a pair of speakers to your interface), then you may want to consider a pure MIDI interface. This budget piece of kit attaches to your computer via USB, and simply provides you with 5-pin MIDI In and Out connections for linking a MIDI device without USB connectivity into your set-up.

EMU XMIDI 1x1 – cheap and cheerful plug-and-play MIDI interface that gives you instant MIDI input and output from your computer with one USB connection. Also check out the EMU XMIDI 2x2 if you require 2 MIDI Ins and Outs.


11. Firewire or USB?

FIREWIRE OR USB?

The first thing to do is to check your computer. Does it have any spare Firewire connections (or indeed ANY Firewire connections)? If not, then your mind has been made up for you and you will need a USB interface! Although you now have to decide whether you would prefer a standard USB interface or a USB 2.0 interface! And if you also have an available Firewire connection, then you also need to decide whether you would prefer this instead! And if you have a Firewire 800 connection, would you prefer a Firewire 400 or a Firewire 800 interface? But what is the difference between them all?

All these connections are used to carry data at high speeds, bi-directionally (i.e. they can pass data from object A to object B, and pass data in the other direction, from object B to object A, all down the same wire). The main difference between each type of connection is the speed that each communicates data. Standard USB (or USB 1.1 to be more precise) is the slowest at communicating data, and hence is implemented on real budget interfaces. With simple set-ups, a USB 1.1 audio interface should be adequate, and you should not have any problems with latency. However, if you are working with professional audio, or with more complex set-ups, you will probably want a device that communicates data mush faster, and hence minimise latency.

USB 2.0 communicates data at a much higher speed (480 Megabits per second) than USB 1.1 (12 Mbps), and it is now becoming the USB standard. Now, Firewire 400 offers a slightly reduced communication speed (400 Mbps) compared to USB 2.0. However, this does not necessarily mean that USB 2.0 is better. For one thing, these ratings are maximum speeds, ad whilst Firewire can contain a continuous data transfer rate of 400 Mbps, USB 2.0 cannot sustain its 480 Mbps constantly, and will keep speeding up and slowing down. In addition to this, USB 2.0 data has to travel through the computers CPU, which slows down the data communication and puts a heavier load on your computer... Firewire does not.

However, you should not have any trouble running USB 2.0 or Firewire 400 interfaces... both are extremely fast and should guard against any latency issues resulting from communication speeds. Some interfaces even feature Firewire 800 connections, which communicates data at 800 Mbps, but this is usually only implemented on real top end products, and in all honesty is not really necessary as USB 2.0 and Firewire 400 are generally more than fast enough.

So to sum up... if you are on a tight budget and are running a simple bedroom set-up (e.g. computer, MIDI keyboard, and two speakers), then a standard USB device will suit you just fine. If you have a little more money to spend then it is a good idea to go for a USB 2.0 of Firewire device though as this will offer you more protection from latency, and generally give your system a better performance. Just ensure that your computer has the right connections for the specific audio interface you want to buy, and check the system requirements of the audio interface to check that it is fully compatible with your computer. And also don't worry if you own a Mac and only have Firewire 800 connections available... you can connect a Firewire 400 device to a Firewire 800 connection, you just might have to buy an extra cable to handle this. And be aware that just because you have connected a Firewire 400 device to a Firewire 800 input, it will not work any faster - it will still communicate data at Firewire 400 speeds.

In fact, this is something that you should be thinking about before you begin to decide how many inputs and outputs you need. You can then use the handy search function on our website to only search for USB or only search for Firewire interfaces!
12. Audio Interfaces for Digital DJs

AUDIO INTERFACES FOR DIGITAL DJS

If you require an interface for digital DJing, then the first thing I would recommend you to do would be to refer to the website of your favoured DJ software and see what they recommend.For example, Traktor software is especially designed to work with Native Instruments’ Audio DJ interfaces (different models exist for different set-ups), and Rane SL interfaces are purpose-made for Serato Scratch.

However, you don’t necessarily have to use the hardware recommended by the developers, and a number of other interfaces also exist that would be suitable for digital DJing purposes. Just make sure that your interface has enough stereo inputs and outputs to match the number of decks/channels that you want to run (i.e. if you want to run two decks, your interface will need two sets of left and right inputs and outputs), a headphone output to monitor your channels (preferably with an easily accessible gain control), and you may also require a microphone connection (or two) if you are planning on using MCs or vocalists. Plus, you may also need MIDI In and Out connections if you are planning on incorporating any MIDI devices into your sets.

Other audio interfaces that you may want to consider for digital DJing purposes include:

Numark DJ|IO – if you only need no run 2 decks/outputs, then this simple budget interface will provide you with everything you need, with 4 mono RCA inputs (2 stereo), and stereo jack outputs!

MOTU Ultralite Mk3 – If you require more outputs (for additional decks), then this portable interface is perfect. It even gives you 2 mic/instrument connections for adding a vocalists or MCs into your set, or incorporating a live instrument, as well as a number of other features including a whole host of outputs.

13. Audio Interfaces for Live Mixing

AUDIO INTERFACES FOR LIVE MIXING

Sure, audio interfaces are essential for pro studios and digital DJing, but they can also be used for live mixing to balance the levels between all your instruments. If you are a playing in large/medium sized venues then it is likely that they will provide a mixer for you, and quite possibly a sound technician to make sure your performance all sounds amazing. However, if you are just starting your live musical journey, playing in venues such as local pubs and small clubs, then it is possible that you will need to provide your own mixer/interface if you want to get the best out of your sound.

Generally, the same rules apply for buying a live audio interface as they do for buying a studio interface, i.e. make sure the interface has enough dedicated inputs and outputs for the purpose of your live performance. However, there are also a few other things that you should consider when purchasing an audio interface for use in live situations. The first is the build of the interface. If you are going to be taking this thing on the road to multiple gigs, the chances are it is going to get knocked about a bit! Therefore it is wise to spend a little more money on an interface with a solid build, as you don't want to drop it on the floor and see it's cheap plastic casing smashed to pieces, nor do you want it's various knobs and switches to start falling off in your hand because it can't take the pace of life on the road!

The second thing to consider is practicality and ease of use. Presumably, if you are mixing live, you want an easy way to control the level of each individual input, so you should look for an interface with a dedicated level control for each input. After all, you don't want to be scrolling through loads of deep menus to set levels!

If you are really serious about live performance, it is probably best to purchase a dedicated mixer with a built in audio interface. This will give you a dedicated fader for each input, along with panorama controls, and more often then not, EQ, which will allow you to control the frequency content of each input signal, to make your whole mix gel better together.

If you are purchasing a mixer for live performance, then you may want to consider one of the following:

MOTU Audio Express – This highly versatile interface is a fantastic option if you are looking for something to use both in the studio and as a live mixer for small performances. As well as giving you a choice of USB 2.0 and Firewire 400 connectivity, it provides 2 mic/guitar inputs, 2 line inputs, a stereo S/PDIF input and 4 line outputs, as well as MIDI connectivity and a pedal connection. Whilst it’s size, shape and features make ideal for use in the studio, the fact that each of it’s inputs has a dedicated level dial on the front, coupled with it’s excellent LED feedback means it is also highly suited to live mixing if you are a solo performer or in a small band!

Peavey PV6 USB – Budget live mixer with 6 channels. The first two channels are monophonic, and allow you to hook up a microphone or line device. The final four channels come in stereo pairs (3/4 and 5/6), and allow you to either hook up either a pair of line level signals or a microphone. Each of the four strips on the mixer (relating to inputs 1, 2, 3/4, and 5/6 respectively) comes with individual EQ (3-band on the first 2 strips and 2-band on the last 2 strips) and pan, level and EFX controls, and the mixer even comes with a USB connection so you can record performances straight to your computer! You may also want to check out the PV 14 USB and PV 20 USB if you need more inputs.

Mackie Pro FX8 – With it’s rugged build quality, this live mixer gives you 8 channels (2 mono and 6 stereo) to play about with, offering 3-band EQ, level, pan, FX sends, and a fader on each, plus a load of other features such as inbuilt effects and a graphic equaliser. Plus, it gives you a USB connection to record performances! You may also want to check the Mackie Pro FX12 if you require more inputs, but similar functionality.

Again, I could go on for pages and pages suggesting live mixers, so instead I would suggest you look through the Live Mixer section of our website and see what else we have to offer…
14. The Look

THE LOOK

Obviously the design, colour scheme, and in some way the layout will be down to personal preference, so I can't really advise you with that. But there are a few things to consider about the look that I can help you with. For example, some audio interfaces feature more visual indicators than others. If you are recording, do you want the interface to have meters on that display the levels of the incoming audio signals to help you see when your recordings are in danger of clipping? If so, would you prefer these were displayed on LED meters, or on a more accurate LCD screen? Would you like any LEDs to indicate when your interface is receiving and sending MIDI data? Do you want it to display the sample rate of your current project? There are loads of little features like this that can be found on certain interfaces, and they are useful as quick indicators, preventing you from looking at the computer screen too often, and speeding up your workflow.

As an example of what is out there, you may want to look at the following interfaces:

Focusrite Saffire 6 – This budget USB interface offers excellent quality, but minimum visual feedback, with just a few LEDs to indicate variaous states of the interface.

MOTU Audio Express – The front panel of this audio interface offers excellent LED feedback, including level meters, MIDI In/Out, Pad, Phantom power and sample rate indicators.

Apogee Duet 2 – This portable audio interface only offers 2 inputs and 4 outputs, but it offers excellent audio quality, and a detailed OLED screen to give you accurate level feedback.

15. Software

SOFTWARE

You will find that a lot of audio interfaces also come with included software. This does not generally include simple budget interfaces, but with interfaces that offer more features, the software often allows you to perform certain functions quicker and more easily, rather than having to scroll though multiple menus on the hardware interface itself. For example, some audio interfaces will come with a software mixer, that allows you do things like set the levels of each individual output, or route signals to different places (e.g. allow you to specify which output the headphone mirrors).

Generally, if you are working with a budget interface, you will not have the need to use a piece of software as you should be able to do everything that the interface offers on the hardware interface with ease.

Some interfaces also come with extra bits and pieces such as royalty free loops, or DAW softare (such as Ableton Lite or Cubase LE), so if this is something that interests you, then it is worth checking the specifications of the product extra carefully to check exactly what it comes with.

For some examples of audio interfaces that come with software, you may want to check the following products, but please don't take this as an extensive list! These are just examples, and lots of audio interfaces come with their own software packages:

Apogee Duet - Comes with Maestro software for advanced control over the interface. The updated Apogee Duet 2 also comes with updated Maestro 2 software, allowing you to do things such as assign the interfaces' touchscreen button to carry out specific tasks.

M-Audio Fast Track Pro - Comes bundled with inTone Express software, giving you a broad range of tools from guitar and bass stomp boxes to virtual mixers and much more! The interface also comes with Pro Tools SE!

MOTU Audio Express - Comes complete with CueMix FX software (for Mac and Windows), which gives you graphic, on-screen control of the interfaces on-board mixer, allowing you to set levels and control signal routings from within your computer. This interface also comes with Audiodesk, a professional DAW (for Mac ONLY).

16. Extending the Functionality

EXTENDING THE FUNCTIONALITY

Certain audio interfaces offer a useful expansion option in that they allow you to connect certain other interfaces to them to extend their functionality. This is a brilliant option if you know, or think that your projects will grow in complexity over the coming years, but do not currently have the budget to spend on an interface with a huge amount of input and output connections. For example, when you first start out, you may only require two mic inputs and two line outputs, so you purchase an audio interface that offers these connections. However, after a year, you suddenly find that you need to start working on products that require 3 mic inputs, a guitar input, two line inputs, and four line outputs. If you own an expandable device, then you can just purchase an additional compatible interface with an extra mic input, a guitar input, two line inputs, and two line outputs, connect them both together, and your two devices will now act as a one device with all the connections that you need! This prevents you from needing to purchase a completely new interface every time you need more inputs and outputs, and so is an extremely handy feature to have.

Most MOTU interfaces are particularly versatile in this area, but they aren’t the only ones, so check the product specifications before making a purchase if this is important to you! Your computer may also give you the option of creating an Aggregate Device, which essentially allows you to virtually link multiple interfaces together to create something that your computer will view as a larger interface! So for example, you could create an Aggregate Device with a 2 input interface and a 3 input interface, to create a 5 input interface! Search online or in your computers help files if you are unsure of how to do this.
17. Summary

SUMMARY

Whether you read this whole guide, or just picked out the sections you were interested in, hopefully you now have a much better idea of why you need an audio interface, and how to choose one based on your project needs.

Although we have suggested a number of audio interfaces in this guide, it is certainly recommended that you have a look about on our website for yourself. The best way to begin your search is to navigate to the 'Shop' section of our website, select the 'Computer Music' section (down the left hand side), select 'Hardware' and then choose either 'Firewire Interfaces' or 'USB Interfaces' depending on what type of interface connection you require. If you have a budget, it may then be a good idea to use our 'Sort By Price' feature. To do this, look for the menu displaying the word 'Name' underneath the STAFF PICK section and to the right. Click on this menu and select 'Price', then click the 'Sort' button next to it. The page will then reload, but will have sorted all the interfaces in your search in terms of price, from low-to-high. You can then use the page navigation buttons to search through all our items to find the product that best suits your need. Also, don't forget to check the STAFF PICK product! This product will be a product that we feel gives high performance and represents excellent value for money.

If you see a product that you like, the click on it and read the product description. Here you should be able to find out the important details of the interface such as how many inputs and outputs it has, what types of inputs and outputs it has, the recording quality of the interface, etc. If the product description has a 'Features Summary' or 'Specifications' section then this is probably the easiest place to look. It may also help to select the 'Images/Media' tab below the product picture. If any images or videos of the product exist then they will show up in here, so will allow you to examine the interface in more detail to gain a visual idea of how the inputs and outputs are laid out, etc.

Finally, although every attempt is made to keep this guide up to date, you may occasionally find that information about products or product availability has changed - after all, we are only human! - in which case it is still important to read the product description of one of our recommendations if you are interested in buying it. And if you still have questions, please feel free to contact us either by telephone (01202 597180), via our Live Chat service, or pop into our Poole store.

Thanks for reading and happy interface shopping!


This post was posted in Computer Music, How To Guides, Magazine, Product News and was tagged with choosing, interface, midi

2 Responses to CHOOSING AN AUDIO INTERFACE

  • [...] there that knowing which one is right for you is a near-impossible task without sufficient advice (click here to read my in-depth guide). However, if you are after an interface that offers the most amount of [...]

    Posted on February 9, 2012 at 5:56 pm

  • [...] can click here to read our guide to purchasing an audio interface, although if you want some up-to-date [...]

    Posted on July 25, 2012 at 5:56 pm

Comments