The Computer Audio Interface Guide

Face it, your computer's built-in speakers and sound jacks are weak! One simple, inexpensive change will make everything sound MUCH better.

A/D converters (Analog-to-Digital input) and D/A converters (Digital-to-Analog output) are the chips that handle audio Input and Output (I/O). The mini-jacks built into top-of-the-line Macs and PCs use the same junky converters found in the cheapest computers. There are dozens of outboard interfaces available which have better quality A/D/A converters, more I/O channels and extras like a volume knob. The physical unit with input/output jacks is usually referred to as an "interface" (or sometimes an "I/O" or "breakout box"). The old term "soundcard" was used back when our only choice was a circuit board which had to be installed in your computer's PCI slot. Many new computers don't have PCI slots, so these days PCI soundcards are an unnecessary pain. Go for a FireWire or USB interface instead, for "hot-swap" flexibility and for use with laptops. Technically these are not "soundcards," a term which really only applies to PCI card interfaces.

Be careful to note the actual number of physical analog inputs/outputs that an interface has. Many manufacturers advertise "6 inputs" but some are digital (S/PDIF, ADAT optical). If you need more microphone preamps, get an interface with an ADAT input. Then you can add an external mic pre with an ADAT output, such as the Focusrite OctoPre (with ADAT Interface card) or the Presonus Digimax. For audio recording, plan for the price of additional hard drive storage and a viable backup method.

When deciding on the best protocol to connect with, FireWire (400 MB/sec) is much faster than USB 1.1 (12 MB/sec), which can choke on just a few channels. FireWire 800 (800 MB/sec) was promising but did not last long in the marketplace. USB 2 (480 MB/sec) is much faster than USB 1, so don't bother with a USB 1 interface.

Make sure that an interface is compatible with your OS, and check that your software will "see" the interface. All recent Macs have both FireWire (IEEE 1394) and USB; some have USB 2. All recent PCs have USB1 or USB2. Add FireWire with a PCI card in your dektop or a cardbus (PCMCIA) card in your laptop, but be careful regarding card compatibility.

No matter what you have, connect to your amplifier (stereo system, receiver, etc) with the right cable. Most consumer amplifiers use RCA input jacks. If your audio output jack is a small round jack (1/8" mini), get a 1/8"-to-RCA adapter cable like the Radio Shack 6' right-angle 42-2483, 3' gold 42-2550 or 6' gold 42-2551. Many models listed below use RCA or 1/4" jacks. Pro models have 3-pin XLR jacks. For more check cables at zZounds.com.

If your amp is too far away (or if you don't have one), consider USB powered speakers, such as the Harman Kardon SoundSticks, which plug into your USB port and don't require an amplifier. Or try the non-USB SoundSticks 2 or other small non-USB speakers from Polk Audio or Bose. Get shielded speakers if you have a CRT monitor. Mac users, get Apple's Airport Express, and AirFoil to send any audio to it.

• For very high bandwidth tasks such as 32+ track audio or hi-res video recording, you might need to spread the data in/out and hard drive read/write load over two busses. This can be done by putting your audio I/O on FireWire and your hard drive on USB 2.0. Or, add a SECOND FireWire bus to a desktop computer with a PCI card. For example, I got 44+ 24bit tracks out of my 867 PowerBook by adding a FireWire card in the Cardbus slot. I got even more out of my G5 iMac by using the built-in FW and USB 2.0.
• For an opinion on USB vrs FireWire, see this Sweetwater article (3/26/02). For a FireWire interface shootout see this 2003 Electronic Musician article.
• What's mLAN? Read this.
• See MacInTouch for reports on using some USB interfaces with Mac OS 9.
• If you are adding USB or FireWire to a PC by means of a card, make sure that the card is compatible with the audio interface.
• Keep all your various computer volume settings (at the player application, your system sound output volume, etc) as high as they will go without clipping. Then, control your listening volume from the LAST stage of the chain, such as your stereo amp. This will give you the best resolution from your digital-to-analog converters and the lowest noise. And if you can't afford an external interface, at least use this tip to bypass a PC's CDROM D/A converters.
• For more on recent Mac audio input/output jacks, see this article.