Recording - March 2016 - 62

carries two channels of audio via an RCA-tipped cable or a fiber optic cable,
but these days it's usually available as a "value-added" extra port on the back
of an audio interface (see below) rather than on dedicated converters.
It used to be commonplace for a particular DAW program to work only when
the manufacturer's own hardware converter box was connected to the computer;
most notably, in earlier years Pro Tools wouldn't work unless a converter from
Digidesign/Avid was hooked up. Happily, a few years ago the makers of Pro
Tools realized that there was a big audience for their products that already owned
A/D converters, and they made their programs compatible with any hardware.
Figure 1 is a block diagram of a line-only interface box; the blue lines represent analog signals, the red lines digital. Why would you need multiple
analog line outputs? Well, channels 1 & 2 might be allocated to your main
monitor system, 3 & 4 to your cheap'n'cheerful speakers used as check monitors, and 5 & 6 to a headphone amplifier.

inputs (though newer models offer more, sometimes a lot more); professional studios often
need to use more mics than two-for example,
in a multi-miked drum setup. (Heck, for my ultrasimple Ottoman Underground recording that
this series is organized around, I used six mics
and a mic-level DI signal.)
Another reason is that pro studio engineers like
to choose mic preamps that make synergistic combinations with the mics being used and the instruments being recorded, such as the way Nevepedigree preamps work on drums. Then there
were the forces of habit and economics; pro studios already had external A/D and D/A converters and rackmounted or console-incorporated mic
preamps, and didn't feel like buying them again
in an all-in-one interface.
Finally, there was a matter of quality; early generations of all-in-one boxes used fairly low-grade mic
preamps, often built onto a single IC chip.
Remember when I said, back in the second preamp
article (Recording, October 2015): "Though most

It slices! It dices!
A decade or so ago, with the home-studio movement gaining steam, manufacturers realized they could combine an external A/D and D/A converter
with a mic preamp and create an all-in-one box that would simplify life for
the many project-studio owners who didn't need to record more than a couple of channels at once, because they were building their recordings one or
two tracks at a time. Combining a preamp with a converter that could connect to the computer via USB or FireWire offered a compact, all-in-one solution that has proved enormously popular, with far too many models on the
market to list here: we call them audio interfaces.
Manufacturers soon included switching (usually software-driven) that could
take the computer's digital output and feed it to a pair of monitor speakers or
headphones with the requisite knob to control volume. The output switching
became quite elaborate, enabling users who were overdubbing to feed a headphone mix of previously-recorded tracks and the new material coming through
the mic preamps (we'll talk about that in another article); some boxes incorporated digital signal processing (DSP) to add effects like echo to the monitor mix.
Once DSP was in the interface box, the sky was the limit; users could, for
example, add processing like compression or EQ to the signal on the way
into the computer. The software mixers that controlled monitoring got more
and more elaborate, until they were almost mini-DAWs. Why is that a good
idea? Here I'm going to unabashedly lift a quote from a manufacturer
(PreSonus), because they expressed the idea well: "Adding just the right
amount of compression, EQ and reverb can make a huge difference in [musicians'] ability to hear themselves clearly...The result is a better performance
and ultimately a better recording."
This all sounds wonderful, but audio interfaces incorporating mic preamps
and DSP are seldom found in professional studios. Why not? Several reasons. First off, the typical outboard interface box has two mic/instrument
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RECORDING March 2016

inexpensive mic preamps aspire to neutrality, some
of them have a characteristic 'cheap' sound that
imposes itself-thin, bright, and one-dimensional."
Unfortunately, that limitation carried over to the mic
preamps in low-budget all-in-one interfaces, especially when they were relatively new on the market.
Alas, you still get what you pay for.
The preamps in some interfaces have gotten
better; companies like Universal Audio, with a
long history of building high-quality gear, have
moved into the field, while newer makers are
putting out interfaces with better-quality mic preamp circuits. For example, Check out Paul Vnuk
Jr.'s review of the Antelope Zen Studio, a multichannel all-in-one interface, in Recording's
October 2014 issue. He found that while its
preamps weren't quite comparable to his best
separate rackmounted units, they compared in
quality to the mic inputs on a good professional
console. And that's no small potatoes.
What about the quality of the A/D and D/A
conversion? There again, you get what you pay
for; a higher-budget interface gets you a box
with a better-quality internal clock (most interfaces won't let you use an external one, though
there are exceptions), a more robust power supply, and better performance from the analog
input and output sections. You also get better isolation between the digital and analog sections,

Table of Contents for the Digital Edition of Recording - March 2016