The audio input/output (I/O) that's built into your computer is fine for playing games and maybe for watching movies. But once you begin to produce your own music on a computer, you'll soon want to step up to a better-quality audio interface. At that point, you'll probably face a bewildering number of options in a market that's overflowing with competing products. In this column, I'll sort through the confusion and start you off on the right path. Note that I will discuss only interfaces — the peripheral components that convert analog audio into digital audio and back. Your computer might also have built-in speakers, but studio monitors are a topic for another column.
First off, what's wrong with your computer's current built-in audio hardware? Well, it might not have enough inputs and outputs to meet your growing needs. Furthermore, it's likely to be a bit noisy, because the manufacturer probably didn't spend much on the audio components. A little noise on playback is bearable, but any that is added to the audio signal on input will be recorded into the track. You'd have to spend hundreds of dollars on noise-removal software to get rid of that noise, and it makes more sense to spend your money on a better audio interface and get lots of other features in the bargain.
Manufacturers love to toss out impressive-sounding specs when they introduce audio interfaces. But what do the numbers really mean?
FIG. 1: The Edirol UA-1EX costs less than $100 and provides stereo input and output at up to 24-bit, 96 kHz. It connects to the computer via USB.
When a stream of analog audio (such as a signal from your mixer) enters the interface, it's digitized — that is, it's converted to a stream of numbers. The sampling rate determines how many numbers are generated each second, and the bit resolution (also called the bit depth) determines how accurate each number is. More is better with both of those specs — up to a point.
Audio CDs store audio with 16-bit resolution, and their sampling rate is 44,100 samples per second, or 44.1 kHz (sometimes these specs are shortened to “16/44.1”). All audio interfaces on the market today record and play back audio with those CD-quality specs, and most offer 24-bit, 96 kHz operation. A 24-bit signal will be slightly cleaner, and a recording made at 88.2 or 96 kHz will have a more sparkling high end.
Although 32-bit, 192 kHz interfaces are available, when you record audio at a higher rate and resolution, your computer has to work harder and you'll quickly eat up space on your hard drive. If you have an older computer or are interested mainly in doing home demos and honing your craft, 16-bit, 44.1 kHz is more than adequate, even though your interface might be capable of more.
Other reasons to upgrade your computer audio hardware include having more inputs and outputs and having the kind you need. Interfaces with 4, 8, or more ins and outs are readily available. Unless you're planning to record a full band and capture each instrument on a separate track, a basic 2-in, 2-out interface such as the Edirol UA-1EX will be more than sufficient to get you started (see Fig. 1).
Many interfaces have built-in microphone preamps (or mic pres), which are usually associated with 3-hole XLR jacks. The purpose of a mic pre is to boost the low-level signal coming from the mic to the same level as the rest of your audio. Professionals often use dedicated hardware mic pres because they also impart a subtle but pleasing quality to the sound. When you're initially building a computer audio system, though, you should be able to get by with an interface that has its own mic pres.
Many interfaces have dedicated headphone outputs. If you're planning to record with other musicians, having two headphone outs, each with its own volume knob, may be desirable.
FIG. 2: The E-mu 0404 is an affordable 2-in, 2-out interface that has zero-latency monitoring and onboard DSP.
Also desirable is zero-latency monitoring. If you're listening to your own performance while you record (as opposed to listening to already-recorded backing tracks, which all interfaces will allow), and if the audio signal you're generating passes through the computer before coming back out to the headphones, you'll become aware of a small time lag. A time lag of this sort is called latency. Latency is less of an issue today than it was a few years ago, but even when using newer gear, some musicians find it distracting. An interface that passes its input(s) directly back to the headphone/monitor outputs at the same time it's being sent to the computer will remove the distraction caused by latency.
In addition to analog I/O suitable for connection to a mixer, most interfaces include some form of digital audio I/O. This is usually in the form of stereo S/PDIF connectors (either optical or coaxial). Some interfaces have 8-channel ADAT digital audio I/O. Digital audio connectors are used for noise-free signal routing to other digital devices.
Many audio interfaces have one or more MIDI In and Out jacks. You can use these jacks to connect your computer to a keyboard or some other type of MIDI controller for sequencing. If you plan to do any MIDI sequencing and don't have a MIDI interface yet, an audio interface that has MIDI will be very useful.
The Computer Hookup
Ten years ago, audio interfaces usually connected to the computer via a circuit board that was plugged into a PCI or NuBus slot inside the computer. Some manufacturers still build PCI-based interfaces, but the more common ways to connect an interface to a computer today are via USB and FireWire. Yet another connector, the PC Card slot, is gaining in popularity.
FIG. 3: The Mackie Onyx 1220 mixer connects to your computer via an optional FireWire card that installs inside the mixer''s chassis.
USB and FireWire interfaces tend to be 1-box solutions. An interface that uses the PC Card slot has a second box or a breakout cable, which connects to the card that slides into the slot. The same is true of most PCI interfaces (see Fig. 2).
All of these hookups work fine for audio, as long as the manufacturer's driver software is solid. A driver is a small program that you install when you buy the interface. The driver is required for the computer to “see” the interface as an audio device. How can you tell whether the driver is trouble-free? Check the manufacturer's user forums for discussions of problems and solutions, and then cross your fingers and hope for the best.
Some interfaces can receive electrical power via the USB or FireWire connection. That is convenient, especially if you're carrying a laptop around to various recording locations and don't want the hassle of plugging in an extra power supply. If you do this, keep the laptop plugged in, because an audio interface will drain the battery quickly. Also, not all laptops provide power to their connectors. Before you buy, check with the interface manufacturer to learn about compatibility with laptops. And if you need multichannel audio, stay away from USB 1.1 — it's slower than the others (many older laptops have USB 1.1).
Many manufacturers have started building audio interfaces into other types of hardware. If you shop around, you'll be able to find MIDI keyboards, mixers (such as the Mackie Onyx 1220; see Fig. 3), and control surfaces that supply their own computer audio I/O. Depending on your needs, this type of all-in-one product may be a great option. At present, most of the audio I/O found on MIDI keyboards is basic, with no frills. You can buy a mixer, however, with many channels for conventional mixing and also many simultaneous channels of audio streaming to and from the computer.
Speaking of bundles, you'll often find free software extras included with some interfaces. These might include digital audio sequencers such as Steinberg Cubase LE or Ableton Live, audio editors, and other types of music software. The bundled software can be a terrific incentive if you're just getting started, but be aware that the versions of well-known programs that are often bundled with hardware are older or limited in some way.
There's never been a better time to upgrade your computer's audio I/O. If you do a little online research and read EM faithfully, you'll have no trouble finding the interface that's right for you.
Jim Aikin is a music-technology expert, a cello teacher, and a hobbyist computer programmer. You can visit him online atwww.musicwords.net.