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A guide to choosing the right audio interface

June 02, 2016 10 translation missing: en.blogs.article.read_time 2 Comments

Audio Interfaces Guide


There are so many Audio Interfaces on the market nowadays.  With such a wide variety of features and configurations available, it’s not unusual that things can get a little confusing when trying to make the right purchase decision. Below is a guide that will hopefully make this choice a little easier for you!

What is an audio interface?

What we once called a “Sound Card” is now typically referred to as an Audio Interface. Even though this piece of Audio Hardware has had a name change, it is still essentially doing the same thing - acting as an ‘interface’ between what you want to record, and your computer. This is perhaps an oversimplification of what is actually possible from an audio interface, as it is also responsible for processing a number of different audio related tasks.  However, in the interest of keeping things simple and to-the-point, an audio interface essentially allows analogue and digital connectivity of microphones, speakers, headphones, hardware synthesisers, MIDI and signal processors to be channelled directly into and out of your computer via a dedicated protocol such as USB, Firewire or Thunderbolt.  Thanks to today’s high-speed data transfer capabilities, audio interfaces are now most commonly seen in the form of an external box, which connects to the computer via cable.  PCIe and PCI sound cards which connect directly to the computer’s motherboard (hence where the name “Sound Card” originally came from) are still available, but are slowly being phased out as more people adopt non-configurable computers such as laptops and iMacs.

Do you really need an audio interface?

All computers (Mac or PC) should already have some type of audio interface already built in, so you may be wondering if you really need another one.  These built-in audio interfaces are generally only designed to deal with basic audio tasks, so they will suffer from very high latency issues (we will explain this later) and typically won’t exhibit a very good quality of sound.

So, if you want to record an external sound source such as a synthesizer, keyboard, guitar or microphone and want your recordings to be in any way professional, the answer is yes - you’ll need to get yourself a dedicated Audio Interface!  Luckily, technology has come a long way over the years, and features that used to be considered premium are now becoming standard (and therefore much more affordable).

What type of features and configuration will I need?

Audio interfaces come in many shapes and sizes, however the most basic interface will have 2 analogue inputs for recording into the computer, 2 analog outputs to connect to your speakers, a headphone output and a volume knob to control the loudness. Some will also come with MIDI ports to connect MIDI-equipped devices likekeyboards,drum machines, orMIDI Controllers.  A basic interface such as this should be relatively inexpensive (around $200) - thePresonus iTwo is a great-value interface for anyone looking to start recording.  

If you’re looking for portable recording, theRoland UA-22 Duo-Capture has all of the above, and you can power it from batteries!  

Before investing in any type of audio interface you should really first be asking yourself what type recording you intend to do, and where your money will best be spent.  For example, you can think about investing in more inputs/outputs available for simultaneous recording, better microphone preamps, faster connection types for lower latency, or investing in better quality AD converters for better overall sound quality.

Perhaps you’re a singer and wish to record your vocals and guitar simultaneously.  In this case, a 2-channel audio interface such as theApogee One or Mac,Apogee One for iPad and Mac,Audient iD14, or theAudient iD22 will provide excellent sound quality through world-class converters and pre-amps.  Maybe you need a couple of extra inputs for a drum machine or synth?  In this case, theNative Instruments Komplete Audio 6 is pretty hard to beat for value.  Or, for the ultimate in sound quality, theApogee Quartet will provide world-class converters for your recordings.

Or, maybe you want to record your whole band, or a drum kit? In this case, you’ll need more inputs – maybe 8 or more.  If you want to record with microphones, you’ll need a separate preamp for each microphone you wish to record with.  TheRoland Octa-Capture,Motu 8Pre, orPresonus Studio 192 are all great options for this task.  

If you only need to record line-level signals (such as from a keyboard, drum machine, or synthesizer), or if you already have external preamps, you could perhaps choose an audio interface with multiple line-level inputs instead of spending extra money on pre-amps that you may not use.  For lots of line-level inputs and a ton of extra functionality, all from a german company that is renowned for creating stunning hardware, theRME Fireface UCX is an amazing choice!  

In reality, when you start adding more inputs and outputs to an audio interface, you invariably start spending more dollars. Whatever you do, don’t buy an 8 I/O interface if you’re only going to record yourself at home - spend that extra money on better quality conversion, or preamps!

What other qualities should I look for in an audio interface?

The price of an audio interface should generally be determined by the quality of the internal circuitry, the various added features that may be included, and how many inputs/outputs are available on the unit. The most common audio interfaces allow 2-4 analogue inputs and outputs - giving you simultaneous connectivity of a microphone(s), direct input for guitar, and outputs for speakers and headphones.

In terms of physical components that one can look for when buying a new audio interface, it’s probably good to be aware that sometimes the ‘sum of the parts’ can equate to more than the whole.  What is meant by this is that the overall performance of an audio interface may come down to more than simply having high quality components alone.  For example, the drivers (custom-built software that allows the computer to communicate with the hardware) are an integral part of any audio interface - if the drivers are not functioning correctly, nothing else will!  Some brands such asRME, have gained an industry reputation for having extremely reliable drivers to accompany their high quality hardware systems.

However, when it comes to sound quality in general, the most significant hardware components involved are the A/D and D/A convertors, and the microphone preamps – the quality of these components should definitely be something to consider when buying a new interface.

What does AD/DA stand for and why is it important?

AD (Analog to Digital) and DA (Digital to Analog) conversion is a fundamental component of any audio interface.  For example, when analog sound is fed into the interface via a microphone or external instrument, this sound is converted into a digital form that can be recognised by the computer.  In DA conversion the process is reversed, meaning that the computer is processing a digital signal and converting it into analog (i.e the signal that is sent to your studio monitor speakers).  The end result of the AD/DA conversion relies heavily on the quality of the digital converters that are used.  For example, brands such as Apogee Electronics have gained a strong reputation for having world-class converters, and are generally considered industry leaders in this respect.

Understanding some important technical specifications

It’s easy to feel intimidated by that long list of technical specifications that accompany an audio interface.  The main two factors to consider when looking at this list are bit depth, and sample rate.  Firstly, bit depth refers to the number of bits of information or ‘resolution’ in a sample of music, which in real terms is interpreted as the amount of ‘dynamic range’ available.  1 bit provides a total of 6dB of dynamic range.  All standard CD’s read at 16-bit, therefore a 16 bit recording provides a total dynamic range of 96dB (16x6).  Luckily most audio interfaces these days now record at 24-bit which provides a total of 144dB of dynamic range.  24bit is now considered a standard for recording, and you should make sure your interface has at least this amount of bit depth.  Some high-end audio interfaces have the ability to record at 32-bit - this is usually a standard found in professional recording studios.

Sample rate is also an important consideration, and again refers to the volume of data contained within a second of incoming audio.  The CD standard is 44.1kHz, meaning that 44,100 digital ‘snapshots’ are taken every second to measure and interpret a piece of incoming audio.  Most audio interfaces are now capable of recording at sample rates of between 44.1 kHz to 192 kHz.

Connection Type and Latency

Audio interfaces in today’s market are predominantly utilising the USB protocol for connection to your Mac or Windows PC. USB offers the greatest flexibility across both major computing platforms, and now (with the introduction of USB 3.0) we are starting to see the kinds of performance that only used to be seen from PCIe.  USB has the added advantage of being able to power your audio interface too - eliminating the need for an external power supply.  Not all USB audio interfaces are bus-powered however, or they will have limited features when self powered, so be sure to check exactly how your USB interface will function when bus-powered. For most audio applications USB 2.0 will be more than enough bandwidth to successfully function as the protocol for your audio interface. TheRME UFX for example, is a USB 2.0 device, and it can handle 60 channels of audio at very low latencies. USB 1.0 however, is not an acceptable protocol for an audio interface - it is too slow with minimal bandwidth, and will quickly result in pops and clicks when running multiple audio tracks. Many mid-range mixers will have a USB 1.0 audio interface as an extra feature, but they are really only capable of transmitting stereo I/O.  

For Mac users, Thunderbolt is comparable to both USB 3.0 and PCIe - in fact, Thunderbolt technology has grown from the need to provide the same performance specs on offer from PCIe systems in an external protocol. Thunderbolt also has the added advantage of being able to daisy-chain other Thunderbolt devices together (such as hard-drives) and DSP systems such as the the UAD-2 Thunderbolt Satellite. Thunderbolt is also capable of connecting 4K monitors, given its wide bandwidth for data transfer and inter-connectivity with the mini display port. Whilst Thunderbolt is current, it has in a way replaced Firewire ports on current Mac computers. Apple have a nasty history of introducing specific connector types and protocols that become industry standard, only for them to be tossed away with future updates and hardware models.  Anyone who owns an iPhone will understand this phenomenon! There are Firewire-to-Thunderbolt adaptors that enable you to connect a Firewire audio device to your Thunderbolt equipped Mac. However, this does not enable you to take advantage of the Thunderbolt protocol - your audio device will still function at Firewire speeds.

The issue of latency is closely related to the type of audio-interface you choose. In a nutshell - latency is the time delay that results from the digital-to-analog and analogue-to-digital conversion process, and is only a matter of milliseconds. Too high a latency is noticeable to the ear, and is of particular concern when tracking large ensembles that require dozens of microphone inputs and headphone sends simultaneously. This is one of the key reasons thatAVID HD and HDX systems are so expensive. They address this issue by processing the audio I/O streaming entirely on the hardware itself, eliminating both the computer and DAW from the equation. However, there are other systems that have addressed this problem too. TheApogee Symphony MKII Thunderbolt systems can achieve similar results - you also have the added advantage of Apogee’s supreme convertor and clocking technology. Basically, protocols such as Thunderbolt, USB 3.0 and PCIe will be much more apt at handling high track counts due to the higher bandwidth available to their data transfer.    

Analog and Digital Connections

The Analogue and digital connectivity will often determine which model of a particular brand you have decided to go with. These connectors are referred to as I/O or “inputs and outputs”. Inputs would include microphones, hardware synthesizers/keyboards or external preamps. Your outputs are connected to speakers, headphones, headphone amps and summing mixers or external recorders, and you only need as much I/O as you have gear to be simultaneously connected to your interface.

Common analogue connectors on an audio interface are microphone inputs - XLR three pin connector, and line-level inputs and outputs. Line inputs and outputs are usually TRS (Tip/Ring/Sleeve), although some interfaces will use XLR connectors for balanced line level connection also. Other analogue connectors include RCA (Radio Corporation of America) - the consumer red and white plugs for unbalanced devices and headphone sockets. Headphone jacks are most commonly a 6.5 TRS connector, although they have a different impedance to accommodate headphones.

The difference between analogue and digital connections, is that any external hardware that is connected digitally (via an optical/lightpipe cable for example) to an audio interface will have already taken care of the digital-to-analogue conversion process.  This can be an advantage if you have a boutique top quality pre-amp with a digital output, such as theAudient ASP800, orUniversal Audio 4-710D.  In this scenario, you don’t need to rely so much on the quality of your audio interface’s A-D converters, and you can simply connect a preamp digitally.

Digital connections also offer practical solutions. Most notably, you can send multiple channels along a single cable. ADAT (Alesis Digital Audio Interface), for example can send 8 channels of audio (at 44.1 or 48kHz) along a single fiber optic, or Lightpipe cable.  It’s important not to get terms confused when discussing digital audio. ADAT is the protocol. It generally uses TOSLINK connectors, and travels on a Lightpipe (fiber optic) cable.

However, the most significant component in your studio when working with digital audio devices will be your clocking system. In short, a quality digital audio clock will synchronize the various digital devices and create a much clearer audio signal. Higher quality audio interfaces such asApogee,Universal Audio,Lynx andRME will have much better internal clocks in comparison to cheaper alternatives.

Onboard DSP

Digital Signal Processing (DSP) provides a huge advantage when recording with an audio interface. Universal Audio have probably best ‘popularised’ this feature by including their UAD-2 DSP cards inside theirApollo audio interfaces, allowing them to host and run the Universal Audio plugins with near-zero latency.. The newer series of Apollo’s are available as Thunderbolt and USB 3.0 devices, therefore maximising the potential of multi-tracking with plugins. This technology is not limited to UA, and in fact many audio interface manufacturers now incorporate DSP features into their devices. RME runs Total-Mix FX - it’s own software GUI that allows audio to be processed through the hardware itself (reducing CPU load on the computer). The Apollo does stand out however, as it allows you to actually monitor Universal Audio plugin effects in real-time.

Click HERE to see all the Audio Interfaces we sell. And use the code AIBLOG at our checkout to get an extra special discount if you buy before June 30th. 

To summarise - we all need an audio interface if we want to produce music on a computer. The question is how many I/O do you need, do you need microphone preamps, onboard DSP or high quality converters. What kind of connection works best for you and will it work on Mac, PC or both. Hopefully you've gained enough knowledge from this blog to feel confident that you've settled on the right device. If you have any questions, feel free to contact us and we'll be happy to get back to you.

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2 Responses

Jamie Reid
Jamie Reid

June 06, 2016

Hi David, yes this is a great feature of the Universal Audio Apollo hardware! While there are similar examples of ‘console’ style software that’s included with some other audio interface hardware (such as RME’s TotalMix and MOTU’s CueMix), the quality and versatility of the UAD plug-ins are pretty hard to beat!

David McCarroll
David McCarroll

June 03, 2016

I think one of the other things worth noting is that the UAD Apollo series also feature their own software interface (cunningly referred to as “Console” – mainly because it pretty much mimics a traditional mixing console) which allows you to record and monitor material using the UAD plug in essentially in real time with zero latency (I believe it is about 2 ms), and to either print the tracks dry or with the UAD plugins added to the recording – in this way fpr example, a vocalist can monitor their voice with a bit of compression, decent preamp emulation and reverb to sweeten up their voice in the headphones, which is always an encouraging thing. Other interfaces may offer a similar feature, I am not sure, but it certainly is a cool thing about the Apollo (which is of course also a very good interface to boot).

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