CHOOSING AN AUDIO INTERFACE BY MITCH GALLAGHER
Last month’s column [“How to Build A Recording Rig, Pt. 2,” April 2012]
was the third chapter on choosing the right
equipment for your recording studio. We’ve
looked at strategies for narrowing down the
options, discussed how to choose a recording
centerpiece, and began exploring the possibilities for audio interfaces. Evaluating these
things will help you narrow down your audio
interface choices, but there is more to examine in order to solve this part of the puzzle.
Software Compatibility. The interface
you choose has to work with the software
you will be using. Fortunately, most interfaces support ASIO, CoreAudio, or other
protocols that allow them to work with
most audio software packages. This also
applies to Pro Tools, which for years was a
closed system when it came to audio interfaces, but is now open and can work with
just about any unit on the market.
That said, some interfaces are more compatible than others. That means in some
cases, there is tight integration between a
particular interface and a particular piece of
software. For example, some of Steinberg’s
audio interfaces provide access to features in
the company’s Cubase and Nuendo software
that aren’t available when using audio interfaces from other manufacturers. It works the
other way as well. Avid’s high-end Pro Tools
audio interfaces have extra features available
when using Pro Tools software. The Pro Tools
interfaces will work with other software packages, but you can’t take advantage of those
extra features if you’re not running Pro Tools.
Connectivity. The next factor we need
to look at is connectivity—inputs and
outputs. This is one of the most important
things to think about when choosing an
interface, and there are several different
types of I/O connections.
Analog inputs are where the audio signals
get routed into the interface from various
devices such as keyboards, drum machines,
external mic preamps, and more. An input
doesn’t necessarily mean there is a microphone preamp built into the interface.
Many analog inputs only accept line level,
which is a higher level than a microphone
puts out (we’ll talk more about mic preamps later in an upcoming column).
There are two types of analog inputs—
balanced and unbalanced. Unbalanced
connectors used to be considered “
semi-pro-fessional,” though this designation has faded.
1. The 2-channel Roland Duo-Capture offers a surprising amount of connectivity with a mic preamp and line input, stereo outputs, and headphone outs for around $80 street. 2. A higher-end
audio interface like the MOTU 896mk3 Hybrid can connect via Firewire or USB. 3. Introduced at
the 2012 NAMM Show, the Universal Audio Apollo combines a full-featured audio interface with
18 inputs and 24 outputs, along with onboard DSP processing chips for running the company’s
acclaimed UAD- 2 plug-ins, many of which emulate vintage studio gear.
Unbalanced connectors use a single conductor for the signal and a second conductor for
the ground/shield. For example, guitars and
keyboards are unbalanced devices. Balanced
gear utilizes XLR or TRS connectors, which
have two conductors for the signal and a
third for the ground/shield. With this, balanced connections are much more immune
to picking up airborne noise and the signal
can be run for longer distances. Typically,
“pro” equipment will have balanced connections, including most studio gear like mic
preamps, compressors, EQs, and mixers.
The two operating levels for analog inputs
are - 10 dBV and + 4 dBu. The differences
aren’t really important, as long as you match
the levels of all the devices you are connecting. That means connecting - 10 gear to - 10
inputs and + 4 gear to + 4 inputs for best
results, unless you are using some sort of lev-el-matching device. In most cases, + 4 will be
balanced, while - 10 gear will be unbalanced.
Like analog inputs, analog outputs can be
balanced (+ 4) or unbalanced (- 10). Analog
outputs are used to feed the signal to external components such as compressors, limiters, EQs, effects boxes, mixers, and more.
Unless you’re planning to use these types
of external gear in your studio during mixdown, you may not need that many outputs.
Digital I/O allows the routing of digital
signals into and out of the interface. This is
useful for connecting certain preamps, key-
boards, effects processors, and some digital
mixers. And having digital I/O can help the
interface be more flexible when hooking up
external gear. A digital connection can also
be the “cleanest” way to get a signal in and
out, since the signal doesn’t have to be recon-
verted to and from analog multiple times.
MITCH GALLAGHER is the former
Editor in Chief of EQ magazine. His book is
Guitar Tone: Pursuing the Ultimate Guitar
Sound. In addition to being a writer, he is
a freelance recording engineer/producer/
mastering engineer, teaches music business and audio recording at Indiana
University/Purdue University, and is Sweetwater’s Editorial