Audio interfaces are vital to any digital-audio-workstation-based recording system. These interfaces connect microphones to computers to speaker monitors. Audio interfaces are the central hub of practically all all DAW-based recording studios, providing inputs, outputs, and analog-digital and digital analog converters. They also provide many additional, non-essential, functions that's we'll get into in this article.
Like any I/O system, choosing the “best microphone audio interface” is largely dependent on your unique recording needs. If you're only planning on recording with one microphone, a bare bones AI would work well for you (or a digital mic like the Blue Yeti USB that effectively has a built-in audio interface). Conversely, when recording full bands with full drum kits, a much bigger and advanced audio interface will be required.
But the question remains, what are the best microphone audio interfaces? From my research and professional experience, I would recommend the following 2 audio interfaces:
- Universal Audio Apollo 8 Quad: The Universal Audio Apollo 8 Quad (link to check the price on Amazon) is one model in UAD's ultra-impressive Apollo line of audio interfaces. Whether you're running Windows or Mac, 4 Apollo interfaces and 6 UAD-2 devices are capable of simultaneous connection over Thunderbolt. The Apollo 8 Quad also comes with and runs a plethora of high-quality plug-ins to capture that “analog sound” you want without engaging extra CPU.
- Focusrite Scarlett 2i2: The Focusrite Scarlett 2i2 (link to check the price on Amazon) is perhaps the most popular Scarlett model from Focusrite. It's my top recommendation as a simple audio interface for small project studios. At a very reasonable price, the 2i2 sounds great and easily
connects two inputs and two outputs to your computer.
We'll get into each of these in a moment, but first, let's discuss some points that make for a superb microphone audio interface.
Related reading:
• How To Connect A Microphone To A Computer.
• Are Microphones Input Or Output Devices?
• Do Microphones Output Mic, Line, Or Instrument Level Signals?
• Microphone Impedance: What Is It And Why Is It Important?
• Are Microphones Analog Or Digital Devices? (Mic Output Designs)
What Makes A Great Audio Interface?
- Type and number of inputs and outputs: Select an audio interface that has the right number of mic inputs and audio outputs for your specific or ideal situation. Bigger isn't always better with interfaces, but the interface you select should be able to cover the largest sessions you plan on running.
- Preamplifier quality/input gain: Choose a microphone audio interface with quality mic inputs that have clean gain. Mic level signals need amplification for use in digital audio workstations. If we're using an audio interface to boost these signals, we should use one that has high-quality preamps. Phantom powering is another very useful asset to look for in the preamp section of the interface.
- A-D and D-A converter quality: Pick an audio interface that works effectively when converting audio from analog to digital (inputs) and from digital to audio (outputs). Ensure the bit depth and sample rates are industry standard and the latency ratings are low.
- Versatility: Versatility is important if you'll be professionally recording with your audio interface. When tasked with varying numbers of microphones, audio inputs, headphone sends, the monitor sends, etc. it's critical that you have an audio interface that can be set up to accommodate the clients' needs. Versatile audio interfaces will typically come with standalone routing software.
- Frequency Response: Buy an audio interface with as flat and neutral a frequency response as possible. The last thing we want is a coloured audio interface that will output a false representation of the audio in our DAW or inside the interface itself.
- Digital I/Os: Though often unneeded, having various digital I/Os in an audio interface may benefit the audio professional. If necessary, look for audio interfaces that provide S/PDIF, ADAT, World Clock, and other digital I/Os.
Now that we know what we're looking for in an audio interface, let's discuss each of my recommendations in detail.
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The Universal Audio Apollo 8 Quad
The Universal Audio Apollo 8 is “the world’s most acclaimed professional recording interface for Mac and Windows” according to UAD's website.
Universal Audio is featured in the following My New Microphone articles:
• Top Best Audio Interface Brands In The World
• Top Best Microphone Preamplifier Brands In The World
• Top Best Audio Plugin (VST/AU/AAX) Brands In The World
The “Quad” in the Apollo 8 Quad refers to its onboard UAD-2 QUAD Core DSP Acceleration which allows this amazing audio interface to run legendary UAD plug-ins independently from the connected computer and digital audio workstation.
This audio interface gets my top recommendation for both project and commercial studios. It has superior A/D and D/A conversion, acting as a high-end digital interface with all the benefits, and sound, of high-end analog equipment.
The UAD Apollo 8 Quad comes with a powerful software controller and works with both Windows and Mac via Thunderbolt connection.
Let's get into the UAD Apollo 8 Quad with more detail.
Inputs And Outputs Of The Universal Audio Apollo 8 Quad
The Universal Audio Apollo 8 Quad has the following I/O complement (8 inputs and 14 outputs):
- 4 Mic/Line Combo Inputs: When set to mic input, each of these 4 inputs has unison-enabled mic preamps, allowing for tracking with mic preamp sounds from Neve, API, and Universal Audio.
- 2 High-Impedance Instrument Inputs.
- 4 Analog Line Inputs (8 when counting the other 4 in the combo inputs).
- 8 Analog Line Outputs (10 including Monitor outputs).
- 2 Analog Monitor Outputs (one stereo pair).
- 2 Headphone Outputs (stereo).
- Up to 8 ADAT channels via dual I/O ports with S/MUX.
- 1 stereo input and 1 stereo output S/PDIF.
- 2 Thunderbolt 2 connections (Thunderbolt 1 compatible): One to connect to the computer and the other to link other compatible Universal Audio interfaces.
- 1 Word Clock input and 1 Word Clock output.
The Thunderbolt 2 Apollo/computer interface will send 18 x 24 simultaneous input/output channels. This is excellent for combining multiple UAD interfaces together for larger sessions. The UAD Console 2.0 software will help to route the I/O to your liking with the additional benefit of configuring latency-free plug-ins.
With a single Apollo 8, we can run 8 inputs (via mic, line, or high-impedance inputs) along with 14 outputs (via 8 mono line outputs, stereo monitor outputs, and 2 stereo headphone outputs).
The I/O of this audio interface is excellent and is further enhanced by its software. Depending on your requirements, one or more UAD Apollo 8 Quads would be an amazing enhancement to your studio.
The impedance values are as follows:
- Mic inputs (1-4): 5.4 kΩ (variable via Unison plug-ins)
- Line inputs (1-2): 10 kΩ
- Instrument inputs (1-8): 1 MΩ (variable via Unison plug-ins)
- Line outputs (1-8): 100 Ω
- Monitor line outputs (L+R): 100 Ω
Preamplifiers Of The Universal Audio Apollo 8 Quad
The Universal Audio Apollo 8 Quad mic preamplifiers provide extremely clean gain to their mic signals.
But UAD takes it a few steps further than having uncoloured preamps.
First, the built-in UAD-2 QUAD Core allows Realtime UAD Processing. This means we can record a mic input through any of UAD's preamp emulation plugins. This is all done with the processing power of the Apollo 8 Quad itself for near-zero latency, without draining CPU.
On top of that, the 4 Unison-enabled mic preamps allow for recording through exacting preamp emulations from Neve, API, Manley, and Universal Audio. This means that the mic input's specs will actually change (notably the input impedance and pad) to emulate classic preamps in both analog and digital fashions.
All the inputs of the Universal Audio Apollo 8 Quad are of extraordinary quality. The mic preamps take it even further with their near-spot-on emulation of highly sought after mic preamplifiers.
And if that wasn't enough, each preamp has a switchable high-pass filter, 48V phantom power, pad, phase invert, and stereo linking capabilities.
For more info on high-pass filters, check out the following My New Microphone articles:
• What Is A Microphone High-Pass Filter And Why Use One?
• Audio EQ: What Is A High-Pass Filter & How Do HPFs Work?
The available gain range for the preamp channels is 10 dB to 65 dB for the mic, line, and Hi-Z (instrument) inputs.
A-D And D-A Converters Of The Universal Audio Apollo 8 Quad
The Universal Audio Apollo 8 Quad features next-generation 24-bit/192 kHz Apollo A/D and D/A conversion. Advanced analog circuitry allows for the optimal signal path and amazing conversion.
The A-D conversion handles 8 channels simultaneously while the D-A conversion handles 14 channels simultaneously. Supported sample rates are 44.1, 48, 88.2, 96, 176.4, 192 kHz with 24-bit bit depth.
The roundtrip latency of the Apollo 8 Quad is a negligible 1.1 ms at a 96 kHz sample rate. This spec does not change with up to four serial UAD plug-ins via a Console application.
Although the Apollo8 Quad does a fantastic job in colouring the sound of its channels in musical ways, the D-A converter ensures a clean accurate output from the Apollo 8. Whatever is outputted from the digital audio workstation or other digital playback system is practically uncoloured when sent through the Apollo 8 Quad's outputs.
The result is a clean sound with little to no latency. This is exactly what we want from the A-D and D-A converters in a high-end audio interface.
Versatility Of The Universal Audio Apollo 8 Quad
The Universal Audio Apollo 8 Quad is a very versatile audio interface.
Much of its versatility is configurable inside its console software, where the user can pick between numerous digital audio plugins to affect the sound of the channel without affecting the CPU of the connected computer at all. With the plugins, each input of the Apollo 8 Quad has practically limitless parameters to affect the sound of the channel. UAD's trademarked Unison technology even alters the physical analog circuitry of the mic inputs to emulate various preamps.
Routing within the software adds even more versatility to this unit. The options are plentiful with the Apollo 8.
On top of that, the Apollo 8 has mic, instrument, and line inputs as well as 14 different outputs including multiple monitor and headphone mixes.
The Apollo 8 Quad also includes the Realtime Analog Classics Plus plug-in bundle. This bundle gives us access to legendary compressors such as the Fairchild® 670 and EQs like the Pultec® EQP-1A. It also has stunning guitar and bass amp emulations from Softube, and UA’s landmark 610-B Tube Preamp and EQ plug-in. All plugins run on the Quad processor and do not in the slightest bit affect the computer's CPU.
Pultec is featured in My New Microphone's Top Best Audio Equalizer Brands In The World.
The list of versatile aspects could go on and on. And if you happen to reach your limit with a single UAD Apollo 8 Quad, the Thunderbolt connections allow you to cascade up to 4 Apollo interfaces and 6 UAD-2 devices, adding DSP and I/O as your studio grows. That's hard to beat.
Frequency Response Of The Universal Audio Apollo 8 Quad
The Universal Audio Apollo 8 Quad outputs a crystal clear sound with a flat frequency response across the range of human hearing.
Digital I/O Of The Universal Audio Apollo 8 Quad
As mentioned, the Universal Audio Apollo 8 Quad has many options when it comes to digital I/O
One Apollo 8 Quad unit is designed with:
- Up to 8 ADAT channels via dual I/O ports (Digital Lightpipe) with S/MUX
- 1 stereo input S/PDIF
- 1 stereo output S/PDIF
- 2 Thunderbolt 2 (Thunderbolt 1 compatible)
- 1 Word Clock input (SDI/BNC)
- 1 Word Clock out (SDI/BNC)
These digital I/O options allow the Apollo 8 to “play nicely” with many other pieces of gear as a flexible unit in most studio configurations.
The Focusrite Scarlett 2i2
The Focusrite Scarlett 2i2 is always my first recommendation when it comes to aspiring talents in tiny project or bedroom studios. In fact, I run a 2i2 at my home audio workstation.
Focusrite is featured in the following My New Microphone articles:
• Top Best Microphone Preamplifier Brands In The World
• Top Best DAW Control Surface Brands In The World
• Top Best Audio Interface Brands In The World
This simply designed and inexpensive audio interface is excellent for beginners and professionals alike. It's great in small studio spaces and even on the road.
Let's talk a bit more about why the Focusrite Scarlett 2i2 gets my recommendation as an audio interface.
Inputs And Outputs Of The Focusrite Scarlett 2i2
As the name suggests, the Focusrite Scarlett 2i2 has 2 inputs and 2 outputs.
Each of the inputs is a combination jack that will accept mic level, line level, or instrument level. When an XLR is connected, the 2i2 will know to accept mic level. When a TRS or TS is connected, there's a toggle switch for each of the inputs to choose between line or instrument.
As for outputs, the 2i2 routes its analog line-level outputs through both an unbalanced stereo headphone out and two mono (left and right channel) monitor outs.
The impedance values are as follows:
- Mic inputs: 3 kΩ
- Line inputs: 52 kΩ
- Instrument inputs: 1 MΩ
- Headphone line output: 10 Ω
- Monitor line outputs: 94 Ω (Balanced)
Preamplifiers Of The Focusrite Scarlett 2i2
The preamplifiers in each of the Focusrite Scarlett 2i2's inputs provide up to 50 dB of gain.
This gain is not the cleanest and will introduce some noise and colouration to the signal. That being said, this colouration isn't necessarily a terrible occurrence and often times it's not even noticeable.
A-D And D-A Converters Of The Focusrite Scarlett 2i2
The A-D and D-A converters of the Focusrite Scarlett 2i2 are near the top of their class (project “prosumer” gear).
The 2i2 converts at a bit depth of 24-bit and supports the following sample rates: 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz, 192 kHz.
Innovative driver and conversion design give the Scarlett 2i2 a round-trip latency as low as 2.74ms. This is practically unnoticeable and any additional latency would be caused within the digital audio workstation.
Versatility Of The Focusrite Scarlett 2i2
The Focusrite Scarlett 2i2 is not overly versatile, but with only 2 inputs and 2 outputs, that's to be expected.
The phantom powering of the 2i2 is not channel-specific. It's either on for both the mic inputs or off for both inputs.
The headphone output is also a replica of the monitor out, only condensed into an unbalanced stereo output rather than two balanced mono outputs (left and right channels). That being said, the headphone out has its own volume control separate from the monitor out volume control.
There's also a direct monitor switch. With the direct monitor engaged, the input signals route directly to the 2i2's headphone and monitor outputs. This enables monitoring with zero latency without affecting the input signals that are sent to the computer.
Frequency Response Of The Focusrite Scarlett 2i2
The inputs and outputs of the Focusrite Scarlett 2i2 are nearly perfectly flat. The 0.25 dB variation of the mic inputs is the greatest variation in response of all the inputs and outputs on the 2i2. This 0.25 dB variation between the 20 Hz and 20,000 Hz limits of human hearing is practically negligible. This is what we want in an audio interface.
Digital I/O Of The Focusrite Scarlett 2i2
The only digital I/O of the Focusrite Scarlett 2i2 is the USB 2.0 output. This allows for quick connection to a computer which is exactly when this audio interface is designed for.
The Recap
Again, choosing the right audio interface depends on your specific situation. These recommendations are for fairly common setups I've been a part of in my profession, but may not suit you perfectly. For this reason, I've gone through a discussed what to look for in an audio interface. Please think of this article as a buyer's guide as well as a recommended gear page.
Once again, my top 3 recommended audio interfaces are:
- Universal Audio Apollo 8 Quad: Top recommended audio interface.
- Focusrite Scarlett 2i2: Top recommended beginner/budget/small studio audio interface.
For all the My New Microphone mic/gear recommendations, please check out my page Recommended Microphones And Accessories.