With constant advances in technology, looking for the best audio interface can feel like aiming for a moving target. Interfaces all share a central task—converting audio between analog and digital formats—but there are important differences. They vary in form factor, processing, inputs and outputs, software, price, compatibility and more. Desktop models like the Focusrite Scarlett 2i2 let singer/songwriters and DJs lay down tracks in their bedrooms at very low cost. Portable interfaces like the Universal Audio Apollo Solo are great for sliding into a bag on the way to a studio session, podcast recording or live show. And thanks to recent advancements, consumers can get capabilities previously available only to recording professionals. Take the Universal Audio Apollo x8 Gen 2, which has enough I/O to power a full home studio right out of the box.

All these audio interfaces can seem like a lot to keep straight. But look on the bright side: diversity means that no matter your needs, there is an interface tailored perfectly for you. We’re here to help you find it. This guide is your one-stop shop to how these devices work, what you can do with them, and what all those specs really mean.

Table of Contents

Why Do I Need an Audio Interface?
The Essential Components of an Audio Interface
   Microphone Preamps
       Understanding Mic Preamps: Transparent vs. Color
       Color Preamps by Manufacturer
   Instrument, Line and Digital Inputs
   Converters
   Monitoring
   MIDI Connectivity
   Onboard DSP
How Do I Find the Best Audio Interface for Me?
   What are you recording?
   Are you recording at home?
   What about mobile recording?
   Are you building a permanent studio?
   Do you need expandability?
   Connectivity
Additional Resources

Why Do I Need an Audio Interface?

Simply put, if you have an analog sound you want to record on your computer, you’re going to need a digital audio interface. Some gear will have one built-in (like USB microphones), but the more you record and as your I/O needs evolve, chances are you'll want to pick up a dedicated audio interface sooner or later.

Luckily, there are models for musicians and content creators at every budget. Some are perfect for making a demo with one instrument. Others are powerful enough to record an entire band at once—vocals, electric guitars, MIDI keyboards, drums, you name it. DJs need interfaces to record digital and analog gear side-by-side while keeping the levels nice and even. Podcasters use audio interfaces to record dialogue and monitor the sound through studio headphones. If you record and edit audio, there's an interface out there with exactly what you need. It all comes down to making sure it has the right components.

The Essential Components of an Audio Interface

Analog-to-digital conversion is a complex undertaking that involves a lot of moving parts, but the right interface can streamline your process so you don't have to think about it. Some users may not even be interested in the finer details, and that’s okay. If you’re a podcaster or a singer/songwriter who plays acoustic guitar, you can grab a simple interface like a Focusrite Scarlett Solo (one mic input) or Scarlett 2i2 (two mic inputs), hook up your gear, open up GarageBand, and be good to go without breaking the bank. Seriously, it can be that easy if you want.

Pictured: Focusrite Scarlett 2i2 Gen 4 Audio Interface

But if you’re looking to get the most out of your interface, or if you have greater needs, you’ll want to know the components that come into play. That's why we're going to break down the essential ones for you.

Microphone Preamps

If you're planning to record voices or acoustic instruments, you will need at least one microphone input. Many of the most popular desktop interfaces will have two, like the UA Apollo Twin X DUO Gen 2.

A microphone input fits the standard XLR cable used for analog microphones. Most of these inputs will be combo jacks, meaning they also accommodate the 1/4" connections most commonly used with instrument and line-level sources. Each of these inputs will have a preamplifier, also known as a preamp or pre. Preamps are necessary because the signal from a microphone is weak, so it needs to be boosted to line level before it’s strong enough to record effectively. Preamps will have corresponding gain controls, which can be used to adjust how much the signal is being boosted. So, when we talk about how many preamps an audio interface has, we’re talking about mic inputs.

Pictured: Universal Audio Apollo Twin X DUO Gen 2 Audio Interface

Another component of a mic preamp is phantom power. Phantom power is necessary for using condenser microphones, which require up to 48V of power to function properly. When utilizing phantom power with a condenser microphone, be sure not to turn it on until after you've connected your microphone to the preamp.

If you want to add more mics than the number of preamps in your interface, you’ll need to resort to external preamps, or else you’ll need to upgrade to a larger interface. It’s not a fun problem to have, which is why it's important to verify the number of microphone preamps an interface has, versus its number of line or instrument inputs.

Note: Some of the most popular dynamic and ribbon microphones require a bit more gain than a typical condenser microphone. For example, the Shure SM7b dynamic, a first-choice for podcasting and vocal recording, and the Royer R-121 ribbon, a go-to for recording guitar amps, both require more gain. Your preferred interface might not supply the gain needed to power these mics alone. Devices like the Cloud Cloudlifter or Royer's dBooster can be used to give your mics the boost they need.

Understanding Mic Preamps: Transparent vs. Color

There are obvious differences from one preamp design to another. Consider the amount of gain they provide, how noisy they are, the quality of their connectors, etc. But one of the key considerations is how they affect the overall sound: are they transparent, or do they color the signal?

Transparent preamps are designed to boost the signal level of the mic while altering the sound as little as possible. Think of it like a photo with no filter added. These are great for drawing out the specific characteristics of your favorite mic and source audio without embellishment. Common examples of transparent preamps are the ones inside the Focusrite Scarlett and portable Apogee units.

Transparent preamps are all about simplicity, but don’t mistake them for a limitation. The transparency only applies to the analog signal as it comes out of the preamp. Once it's been recorded into your DAW, you can apply digital plug-ins and whatever else your heart desires. Transparency just means you start with a clean slate.

Other preamps add color, which is where things get interesting. Think of these like photographs where the exposure, saturation and other aspects have been tweaked. That doesn’t mean the change is artificial—vintage tube amplifiers are as authentic as it gets, and they’re known for the warm color they add to countless recordings. While you can still buy standalone mic preamps such as the Universal Audio SOLO/610 to color your recordings, many audio interfaces offer features to emulate classic preamps. And because they can typically be toggled off, you still have transparency mode as an option. However, keep in mind that these are hardware effects. Once your audio is recorded, it'll be difficult to remove those tonal qualities later.

Pictured: Universal Audio SOLO/610 Microphone Preamplifier 

Color Preamps by Manufacturer

Below is a quick rundown on interfaces with preamps that will color your sound. These examples come from four of the most popular manufacturers: Focusrite, Steinberg, Solid State Logic and Universal Audio.

In the 1980s, one of Focusrite's most important products was the transformer-based ISA 110 mic preamp designed by legendary recording equipment designer Rupert Neve. This module was known for the bright, airy sound it added to vocal recordings. Focusrite brought that color to their audio interfaces with Air mode, a preamp setting that was first available for Clarett+ interfaces like the 2Pre. It's now built into third-generation Scarlett interfaces as well. When toggled on with the dedicated button (one for each mic input), Air mode emulates the sound that made the ISA preamp famous.

The Steinberg UR-RT2 interface is another option if you want some color, this time with transformers from Rupert Neve Designs. The UR-RT2 has two preamps, with buttons to toggle the transformers for each one. Steinberg describes the transformed sound as richer, with enhanced harmonics.

Solid State Logic offers switchable color preamps on their SSL 2 MKII and SSL 2+ MKII desktop interfaces with the Legacy 4K button. This name is a reference to SSL’s legendary 4000 series consoles, used in some of the biggest recording studios in the world. Legacy 4K is designed to emulate the sparkly analog sound that those consoles are famous for. These highly affordable interfaces are an appealing way to get a classic sound from even the most barebones recording rig.

Pictured: Solid State Logic SSL 2+ MKII Audio Interface 

If you’re looking to explore the world of "color" preamps even further, Universal Audio interfaces use a platform called Unison. Instead of just one button, Unison offers a variety of plug-ins that emulate classic mic preamps from UA, Neve, API and more. These plug-ins are applied within the unit, so the sound enters your DAW with the color added, just like it would with a hardware preamp, as seen below in our video with musician BlankFor.ms.

UA Apollo interfaces, like the popular Apollo Twin X DUO Gen 2, also include Unison compatibility on their instrument inputs, letting you play electric guitars and keyboards through emulated signal paths as well. Many of the Unison plug-ins are sold separately, and some are not cheap, but they have been praised for remarkable accuracy and ease of use.

Note: The tonal qualities of "color" can be highly subjective. Many professionals are impressed with how authentic the plug-ins can sound, while others swear by external hardware only. Listen to samples, read the customer reviews on our website—but in the end, you’ll have to trust your own ears.

Instrument, Line and Digital Inputs

In addition to the mic inputs and preamps, interfaces can have any combination of other I/O, all useful for different purposes. Here’s a quick rundown on each type.

Instrument inputs, also called Hi-Z inputs, are for signals stronger than the ones that come from mics, but weak enough that they still need some boosting. Z stands for ohms, which measure impedance. The most common use for a Hi-Z input is connecting an electric or acoustic/electric guitar directly into the interface.

Line inputs, or line ins, are for signals with voltage high enough that they don’t need extra boosting. If you have an electric guitar already running through a preamp, you can use the line output to connect the preamp to your audio interface. It's also the right input for a DJ console, or pretty much any gear with a line-level output. Line ins can also help future-proof your rig. If you run out of mic inputs, for instance, you can connect an external mic preamp through a line-level connection. Many new synths and electronic drum kits offer digital output over USB or S/PDIF, but for those that don't, you can connect to the analog line inputs of your interface.

Line outputs can output line-level analog signals at high voltage. If you want to use pedals and rack effects while mixing, these will come in handy. You can output the sound as an analog signal (re-converted from digital), run it though your external processing gear, then send it back to the interface with the line input. You can also use these line outs to connect to powered studio monitors or amplifiers.

The above connectors are analog, but interfaces can have digital inputs and outputs as well. These come in the form of S/PDIF or ADAT connectors. The S/PDIF connections usually run through pairs of RCA-like cables. ADAT connections run through optical cables. The main benefit of digital inputs is that they let you expand the total number of audio channels you can record at once. External mic pres often have their own analog-to-digital converters, so they can output the digital signal to your interface through these specialized connectors. A S/PDIF input can accommodate up to two more channels, and an ADAT connection can add up to eight—as long as you have the external gear with the proper I/O. Luckily, with options like the Focusrite Scarlett OctoPre, maxing out your interface with up to eight more mic pres can be surprisingly cost effective.

Pictured: Focusrite Scarlett OctoPre 

Converters

Like with the inputs and outputs, you don't necessarily have to get into the weeds on converters if you don't want to. Every audio interface in this article has a capable converter. There are options under $200 with 24-bit/192 kHz resolution, and even the absolute lowest-cost desktop option runs at 16-bit/48 kHz, slightly above CD quality. We’ll explain what the numbers mean, but just know 24-bit/96 kHz resolution is more than enough for almost everyone. It wasn’t too long ago that those numbers were found only in high-end studio interfaces. Thanks to advances in computer chips, good converters have become more affordable than ever.

However, elite-level converters do make a difference. To see why, we’ll have to talk a bit about how they work. If you're not looking to get into the weeds, skip ahead.

Analog signals look a lot like sound waves, with changes in frequency, wavelength, magnitude, etc. The converter captures an image of the wave over time by taking a series of quick snapshots at high resolution. The frequency of the snapshots is called the sample rate, and the resolution is the bit depth. In the early days of digital recording, 16-bit was the standard resolution and 24-bit was high definition. At 24-bit resolution, the signal-to-noise ratio allows a theoretical 144 dB of dynamic range with minimal noise. It’s rare to find deeper resolution than this, because the hardware usually won't have any use for all that extra headroom.

The bigger leaps have come in the area of sample rate. Early converter design operated under the Nyquist Theorem. Roughly put, the Nyquist Theorem states that you could get a perfect reconstruction of the sound wave if you took samples at twice the highest frequency humans can hear. So, early converters sampled at 44.1 kHz, theoretically more than double what our ears could sense. It was later discovered that using even higher sample rates, called oversampling, could improve the quality of the recording even more. Long story short, converters started sampling at a higher rate of 48 kHz, with elite interfaces running at 96 kHz or 192 kHz. Flash forward to today, and even affordable desktop interfaces like the PreSonus Quantum ES 2, Focusrite Scarlett 2i2, and the UA Volt 2 can operate at 192 kHz.

Pictured: PreSonus Quantum ES 2 Audio Interface 

However, conversion doesn't begin and end with sample rate and bit depth. Converter design is complex. As you spend more and start looking at higher-end brands like Apogee, UA, RME and others, you'll find even higher quality converters that, due to their superior designs, will sample your audio better.

In addition to analog-to-digital conversion, audio converters also do the reverse. Digital-to-analog conversion is especially important while mixing, for two reasons: (1) you’ll need to monitor the audio while editing it, and (2) you might need to run the signal through analog processing gear with line outs and ins. A professional interface makes sure you get high-quality conversion in both directions.

Monitoring

You'll need to monitor your audio while it’s in the process of being recorded and mixed. That’s why interfaces always have a monitoring output to let you listen to the audio live through headphones or speakers. The better the design of these output stages, the easier it will be to make good decisions while recording and mixing.

MIDI Connectivity

These days, the majority of new MIDI instruments connect through USB. These DJ controllers, synths and electronic drum kits can record straight to the DAW with no need for an interface. However, older MIDI instruments may connect with older DIN connectors. While many audio interfaces have followed the trend away from DIN, ones that have this input will make it easy to incorporate vintage gear into your rig.

Onboard DSP

A more recent trend is to include digital signal processing (DSP) inside the interface. These built-in processors let you add plug-ins during the recording and mixing stages without taxing your computer's CPU. If you’ve ever tried to run too may plug-ins on a computer that can’t handle it, you’ll know how helpful this can be.

A primary example of DSPs in action is the Universal Audio Apollo line. In addition to the Unison preamps that can run plug-ins, Apollo models include two-, four- and six-core processors that run the Universal Audio Digital (UAD) plug-ins. When shopping for Apollo interfaces, consider how may plug-ins you might want to run simultaneously and choose the best Apollo for the job.

For more information on the current Apollo lineup, be sure to check out Universal Audio Apollo Gen 2 Audio Interfaces | Creative Upgrades.

How Do I Find the Best Audio Interface for Me?

Now you know pretty much all the essential information about audio interfaces. Take a breath—it’s time to make your choice. With all the above info covered, picking an interface is as simple as making a list of your needs. If your choice has all the components necessary to cover your list, you can buy with confidence.

What are you recording?

Start by making an inventory of everything you want to record. Begin with all the audio sources, including vocals, instruments, ambient sounds and whatever else you can see yourself wanting to capture. Then consider how many mics and inputs each of the sources will need. Are you recording your electric guitar straight into the interface with a Hi-Z instrument input, or are you going to put a mic on the amp? How many mics are you using for drums? Don’t forget synths and drum machines—if you want to record some of these at the same time, look for multiple line inputs. And then there’s mixing. Do you want to use any pedals or rack gear? Make sure you’ll have enough outs and ins to get them all incorporated into your analog signal path.

Once you’ve got everything listed, determine how many of each input you’ll need to have available simultaneously. That’s your minimum. Depending how extensive your needs are, you might be able to get an interface that fits all the necessary I/O in one desktop box. If your input needs are greater, consider external gear in addition to larger interfaces. An external preamp with two to eight mic inputs can be cheaper and more efficient than multiple interfaces with a bunch of extra I/O you don’t need.

Are you recording at home?

The next thing to consider is the space. One of the most exciting things about audio interfaces is that they let people record at high quality from the convenience of their bedroom. The most popular models are mostly desktop units with one to four input channels, ideal for singer/songwriters, beatmakers and content creators.

Three popular desktop models are the aforementioned Focusrite Scarlett 2i2, Apogee Duet 3 and PreSonus Quantum ES 2 all of which have two mic pres and convert audio at 24-bit/192 kHz quality. The Duet is the most expensive of the three, but in return you get excellent preamps, a sleek build and intuitive operation. A fourth desktop option is the affordable PreSonus Quantum HD 2, which sports a few features that are rare for this tier. It has DIN input/output for old-school MIDI devices, DSP onboard processing and, in a first for this guide, 32-bit sample depth.

Pictured: PreSonus Quantum HD 2 Audio Interface 

What about mobile recording?

Of the four above, both the Apogee and Steinberg work with iOS devices. The Apogee is built for extra portability, with a form factor small enough to slide into a backpack pocket. But there are even more specialized iOS-compatible options. These mobile units are great for podcasters and musicians who need simple, portable operation.

Pictured: IK Multimedia iRig HD X USB-C Audio Interface 

Apogee makes the JAM+, a handheld interface with one instrument input and iOS compatibility. IK Multimedia produces a nice selection of ultraportable, pocket-sized interfaces that work with iOS, Mac and Windows—some with single inputs. Vocalists, DJs, podcasters, livestreamers and field recorders alike will love the iRig Stream, with a stereo RCA input, level knob, and mic gain and headphone volume control. For electric guitarists and bassists who want to record straight to their phone, there’s the iRig HD X. Capable of sample rates up to 96kHz, this model has an instrument input, tuner, headphone monitoring, AmpliTube 5 SE and TONEX SE compatibility, as well as amplifier output and gain knobs—all in one tiny package. The iRig Pro I/O has an XLR/1/4" combo jack, MIDI in/out, plus the ability to charge your iOS device if you’re ever in a pinch.

Are you building a permanent studio?

For more established studio spaces with racks and other storage, there are high-end professional interfaces. These can handle many inputs at once, with up to eight simultaneous mic channels and any number of line, instrument, MIDI and digital I/O.

On the affordable end, the Focusrite Scarlett 18i20 and PreSonus Studio 1824c both have eight mic pres and a bunch of other I/O. For those looking for the elite experience, there are prestige models like the Universal Audio Apollo x8p Gen 2, with eight Unison preamps and six processing cores for running proprietary UAD plug-ins. You pay for what you get with the x8p, but what you get is a single interface that can power a full studio.

Pictured: Universal Audio Apollo x8p Gen 2 Audio Interface 

Do you need expandability?

While you may only need a couple mic pres right now, keep in mind that your needs may change in the future. There are ways to leave room to expand. Remember: digital connectors, especially ADAT inputs over optical cables, leave tons of room for external mic pres. And for expanding into more diverse sources, there’s always the line in, which can handle any line-level signal you throw at it.

If you have small needs now but want expandability, consider the Universal Audio Apollo Twin X QUAD or the Focusrite Clarett+ 2Pre. These are two-preamp desktop models, but they have ADAT inputs, meaning you can connect up to eight additional mic pres for up to quadruple the mic I/O. They have minor price bumps compared to barebones units, but that ADAT input could end up saving you down the line.

Pictured: Focusrite Clarett+ 2Pre Audio Interface 

If you’re building a permanent studio rig with lots of channels, cabling can become a big problem. To prevent tangling and clutter, some advanced interfaces use DB25 cabling for line-level I/O. These cables bundle connectors into groupings of eight. The bundling lets engineers run batches of signals between important pieces of gear. DA25 line inputs and outputs are essential for very large professional interfaces like the Universal Audio Apollo x16 Gen 2, which is designed to fit into complex studio setups with ease.

Connectivity

Modern interfaces connect to computers via USB ports. Smaller units are powered by the port, while larger ones just use it to transfer data. Not all of these connections are made equal. The USB standard has been updated over the years, with increases in performance each time. You might see specs like USB 2.0, 3.0 and 3.1—all significant jumps in the maximum data transfer rate. USB became roughly ten times as fast in the switch from 2 to 3, then doubled again for 3.1. These specs matter, especially if you’re planning to work your interface hard. USB connectors also come in multiple shapes, usually the classic rectangular USB-A or the newer, reversible USB-C. These shapes can both technically run at USB 2.0, 3.0 or 3.1 speeds, so make sure to check both the shape and the speed rating. They're not the same thing.

For the most advanced interfaces, there’s another tier of connector called Thunderbolt. The most recent version is Thunderbolt 3, which is four times faster than where USB 3.1 maxes out. Thunderbolt connectors are prominent for interfaces that rely on DSPs, like Universal Audio Apollo. It makes sense, since running all those native plug-ins requires serious communication between the computer and the onboard processor cores. Thunderbolt has also allowed Universal Audio to develop their own DAW called LUNA, which will work natively with the in-unit processors and Unison preamps during the editing process. Other high-end Thunderbolt interfaces include the Apogee Symphony series and PreSonus Quantum, both designed for permanent studio use.

Two legacy connectors you should know are FireWire and PCIe. They're no longer relevant for new interfaces, but you might come across them. FireWire was a connector found primarily on Mac computers. It improved on the average speeds of the time, but it’s slower than modern USB and Thunderbolt, so it's only mentioned with respect to older products. PCIe had speed improvements as well, but these connectors needed to be plugged directly into a computer motherboard with an open PCIe slot. Unless you have a specific legacy reason to want either of these connectors, avoid them and go for something with USB or Thunderbolt 3.

Additional Resources

Now that you know all the fundamentals, you can shop for an audio interface with confidence. We also have additional articles with more info to help you start a podcast or record from a home studio. And as always, you can contact Guitar Center by phone, online or in-store for help finding whatever you need.