You decided to take the plunge into recording. Congratulations! There has never been a better time to start. We’re living in a golden age of recording technology with access to more affordable, incredible-sounding equipment than ever before! You’re probably starting to put together a wish list of microphones, instruments, MIDI controllers, and all the other tools to make great music at home or in a project studio.
But, arguably, no piece of gear is more important than the audio interface you choose. It is the bridge between you and your digital audio workstation (DAW), providing the inputs you need to plug in your microphones, guitars, and other instruments as well as the outputs to run to your headphones and studio monitors. Like the large-format consoles of yore, an audio interface is the command center of your music production environment. And they can come in all shapes and sizes — from humble single-channel units that will fit in your pocket, perfect for solo artists or for travel, to complex rackmounted devices made for capturing full-band live performances.
Deciding on your first (or next!) audio interface can seem daunting — there are a lot of options, each tailored to different workflows. In this article, we will address some of the questions you might ask while shopping for an interface and hopefully demystify some of the terms you’ll come across when reading product descriptions. And, throughout the article, we’ve peppered some links to articles that go into further detail on this topic. Without further ado, let’s dive in and explore the audio interface!
What Type of Audio Interface Should I Choose — USB, Thunderbolt, or Ethernet?
Currently, there are three primary interface types — USB, Thunderbolt, and Ethernet — and selecting the right interface starts with your computer. For PC users, USB interfaces are the main choice since those interfaces will almost universally work with Windows-based machines. Current Mac systems are generally equipped with Thunderbolt, and most manufacturers offer both affordable and high-end interfaces with Thunderbolt connectivity. It should be noted, however, that some high-performance PCs now come equipped with Thunderbolt connections, too. Ethernet interfaces featuring technology such as Dante and AVB are more specialized, but they are becoming a popular option due to their scalability and network routing that can help streamline complicated recording setups. In terms of performance, each type of interface is capable of professional results.
Do Bit Depth and Sample Rate Matter?
While checking out the numerous audio interfaces available, you’ll undoubtedly come across information related to bit depth and sample rate. Currently, most interfaces will feature, at minimum, a bit depth of 24 bits and a sample rate of 48kHz or greater — which is higher than the CD standard of 16-bit/44.1kHz — and may offer 32-bit floating-point bit depth and sample rates as high as 192kHz (or even 384kHz). But what do these numbers mean, and are higher values necessary?
Well, first, let’s break down bit depth and sample rate. In the article “What Is a Digital-to-Analog Converter and How Does It Work?,” Craig Anderton describes analog-to-digital conversion (via the ADC — analog-to-digital converter) as the process in which a waveform is sampled at a consistent rate (technically the sampling frequency) and has a numerical value assigned to each level change. The frequency at which the waveform is sampled is commonly called the “sample rate.”
So, if your interface has a sample rate of 48kHz, then that means it takes 48,000 samples for every second of audio. More samples over a given period of time (higher sampling frequency) create a smoother, more analog-like waveform, which arguably creates a more natural sound, particularly in the high frequencies. Why are higher frequencies more impacted? Without getting overly technical (like delving into the Nyquist Theorem, which states (f) = d/2, where f is the sampling frequency and d is the highest frequency you wish to record — whew!), filtering out aliasing artifacts (another big word) becomes easier (and sounds better) as you increase the sampling frequency.
So, the CD-standard sample rate of 44.1kHz is adequate to capture and reproduce frequencies up to 20kHz but with very little margin. Half of 44,100 is 22,050, which is just slightly higher than the 20kHz target bandwidth. Higher sample rates like 48kHz (with a net bandwidth of about 22kHz), 96kHz (netting above 40kHz bandwidth), and so on, are capable of capturing frequencies beyond the realm of human hearing. Whether we can hear frequencies that high (above 20kHz) is not debatable (we can’t), but there is harmonic content that is generated by live music in that frequency range. Whether it is discernable depends on the listener, but having the ability to capture it is a good thing. For more information on this, check out Sweetwater’s “Audio Interface Buying Guide.”
Bit depth is different in that it relates to the dynamic range of an audio interface. For every one bit, there is an available 6dB of dynamic range. Therefore, 16-bit audio processing has a 96dB dynamic range; 24-bit has 144dB; and so on. As the bit depth increases, the available resolution for dynamic range also increases, meaning that 16-bit recordings have less absolute dynamic range available than 24-bit recordings. At Sweetwater, we recommend a minimum of 24-bit/44.1kHz when recording music.
What Causes Latency, and How Do I Minimize It?
When audio travels into an interface, through a computer, and back out to your monitors, there’s an inherent delay, or latency, that is produced. That is due to the processing time required for the A/D or D/A stage, which can range from minimal (unnoticeable) to unusable (especially for musicians, whose timing is paramount). Sometimes latency can be significant enough to distract artists during a performance, especially when attempting to monitor through plug-in effects and processors such as reverb, compression, and EQ. However, more powerful computers and interfaces with faster processors — found even in affordable units — have become much more efficient, allowing artists to monitor with effects that can help give them confidence while tracking.
Yet, as you get deeper into a session and plug-ins start to add up, it’s inevitable that you’ll begin to tax your system and introduce latency. One way to mitigate that is to adjust your hardware buffer size within your DAW or your interface’s control software. Buffer sizes generally range from 32 samples to 2,048 samples. Lower buffer sizes mean lower latency but can tax your computer, causing clicks or dropouts during playback. While higher buffer sizes reduce the demand on your computer, they also result in higher latency, which means that they can make it impossible to play in time due to the delay. Generally, we recommend recording at the lowest buffer size your system can handle and switching to higher buffer sizes during mixdown.
Some interfaces work around the issue of latency by providing direct monitoring, permitting you to monitor the input right from the input before the signal makes the trip through the A/D > Computer > D/A (digital-to-analog converter) path. The most basic direct-monitoring setups only let you hear the dry input signal with no option for monitoring through effects and other processors. But some interfaces with onboard DSP (which we’ll discuss later) give you the option of monitoring with effects. The Universal Audio Apollo Twin X DUO and Apogee Symphony Desktop are two examples.
How Many Inputs and Outputs Do I Need?
When selecting an audio interface, it can be helpful to think ahead to how you envision recording your music. For instance, it’s common for artists today to build songs track by track using a combination of real instruments and virtual instruments. If that’s you, then an audio interface with just one or two built-in preamps (or direct inputs) may be enough to bring your music to life. However, if you plan on recording ensembles or multi-miked drums, then you’ll want to make sure you have enough inputs to accommodate all those mics. For instance, it can be very easy to use eight or more inputs for miking a drum kit alone. And if you are using condenser mics, then you’ll need to make sure your interface has phantom power.
Of course, adding inputs adds to the cost of an interface. Some interfaces give you the option to expand the number of available inputs, such as the Audient iD14, a two-channel USB interface that can be expanded to 10 inputs by connecting a device like the Audient ASP800 8-channel microphone preamp to its ADAT input. Expandable interfaces are a great option for slowly increasing the capabilities of your home studio as you progress in your craft. Check out Craig Anderton’s article about “How to Add More Inputs to Your Audio Interface.”
Selecting an interface with the right number of outputs is also important. While nearly every interface will feature a stereo monitor output and at least one headphone output, there are situations where you may want additional outputs for more advanced setups. Let’s look at recording a full band, for example. In that situation, each band member may want a slightly different monitor mix. Providing separate mixes requires additional outputs that can be routed to external headphone amplifiers or fed through a snake box. We provide a walkthrough on how to accomplish this using a Universal Audio Apollo in “How to Create Headphones Mixes with a UA Apollo,” but the process is similar for other interfaces.
You’ll also want more outputs if you intend to integrate hardware devices into your DAW. Sending multiple tracks in a session through different analog compressors, EQs, rackmounted digital effects, or even through guitar pedals can add extra dimension to a mix. This blend of a DAW and hardware processors is referred to as a hybrid studio setup, and it’s becoming extremely popular among Sweetwater’s customers, providing the sonic character of analog gear with the flexibility and reliability of digital audio.
Should I Choose an Audio Interface with MIDI I/O?
If MIDI is an important part of your production workflow, then you’ll need to choose an interface that includes MIDI I/O. (Yes, there are interfaces without MIDI I/O.) If you’re into synths or Eurorack modular gear, then having the traditional 5-pin MIDI I/O on your interface is a handy way to integrate those devices into your DAW without having to purchase a separate MIDI interface. The Focusrite Scarlett 4i4 3rd Gen is one of the more affordable USB interfaces to include dedicated MIDI I/O.
What Does It Mean When an Interface Has Built-in DSP?
Interfaces with built-in digital signal processing (DSP) relieve some of the burden plug-ins place on your computer’s system by providing separate processing power for certain plug-in effects, typically associated with the interface. Universal Audio’s popular Apollo series is an excellent example of DSP-powered interfaces. Apollo interfaces, from the 2-in/4-out Apollo Solo to the 18-in/20-out Apollo x16, are equipped with cutting-edge SHARC processors, which give you the ability to track through any of Universal Audio’s exemplary emulations of analog gear in real time, latency-free, as well as to use more plug-ins during mixdown than your computer can capably handle on its own. Other manufacturers, including Apogee, PreSonus, and Audient, also feature built-in DSP. DSP-powered interfaces are generally more expensive than their non-DSP-powered counterparts, but they can help you maximize your system’s available resources.
Are There Sonic Differences That I Can Hear Between Interfaces?
Can you hear any difference between audio interfaces? Considering that’s the critical role of an audio interface — converting your mic or instrument signals into data you can manipulate on your computer — then it makes sense that the sound of an interface is a crucial consideration. If you’re interested in comparing the sound of USB interfaces under $500, Lynn Fuston, our informal “Director of Shootouts,” compared nine different interfaces on a variety of typical sources (voice, guitars, piano) and allows you to listen to how they compare in this article: “9 Best Audio Interfaces Under $500 Shootout – Take a Listen!“
Conclusion
We hope this article answered some of your burning questions about audio interfaces. But if you’re still looking for guidance, then please reach out to our knowledgeable Sales Engineers at (800) 222-4700. They’ve helped thousands of artists just like you find the perfect gear to bring their music to life!