The Complete Guide to Computer Music - Part 2

Audio Interfaces

T.J. Glover | 31 July 2006

The computer is central to the way we all work in the studio. Future and Computer Music magazine's T.J Glover gives you the lowdown on every component you'll need for the ideal set-up. This month: audio interfaces...

Last month I gave you a heads-up on the very basics of getting a computer-based music production system up and running, introducing you to the various bits and pieces you need to turn your unassuming Mac or PC into a fully fledged, genuinely professional-quality music production studio. For the next few installments of this series, I'll be zooming in on some of those fundamental bits of hardware and software in order to help you figure out your personal computer music needs and spend your money wisely in the right areas. First up, audio interfaces.

The need to expand

Your computer almost certainly comes with audio input and output capabilities built in, but this will generally be in the shape of a multimedia soundcard or motherboard-integrated system designed for gaming, playing back DVDs, CDs and MP3s, and hooking up a microphone for speech recording or online communications. Connections will probably be of the minijack variety, the highest supported bit-rate may well be only 16-bit (CD quality), the drivers aren't likely to be optimized for music production, and the noise floor will be intolerably high for serious recording. Bad, bad, bad - what you need is an audio interface with pro-spec inputs and outputs, fast drivers and high quality analogue-to-digital (and vice versa) converters.

An audio interface will connect to your computer in one of three different ways: PCI, USB or FireWire. A PCI (Peripheral Component Interconnect) interface - AKA soundcard - goes inside your computer in one of those slots that also play host to such things as network cards and internal modems. Since the backplane of a PCI card isn't big enough to house 1/4" jack or XLR sockets, a soundcard will usually come with a cabled 'breakout box' into which instruments and microphones are plugged. PCI interfaces offer the lowest latencies of the three standards (see below), but it's worth noting that they're only a viable option for desktop computers, as laptops don't have PCI slots or anything like the space needed to hold them.

USB and FireWire interfaces connect just like any other USB and FireWire devices, via a single cable that plugs into the relevant port somewhere on the outside of your computer. In most cases, this cable even carries the power required for the interface to operate, enabling laptop users to record 'on the move' without having to plug into the mains. The interface itself is a high-tech looking box with up to eight analogue inputs and eight outputs (and occasionally more) on 1/4" or XLR sockets, a couple of the inputs usually featuring preamps for boosting mic- and guitar-level signals. If you're planning on working with a band, you're going to want as many inputs as possible for multitrack recording, but if you're a one-man outfit, a single stereo pair may well be enough. Similarly, unless you're working with a hardware mixer and outboard effects units, you probably only need enough outputs to hook up your speakers - i.e., two.

Many audio interfaces also boast digital ADAT and S/PDIF connectivity, but this is by no means an essential consideration for most - it's the analogue I/O you need to be most concerned with, and these days just a couple of hundred quid will get you surprisingly high quality converters. Spend over ????500 and you're very much in professional territory.

Designated driver

Just as important as the hardware is the driver. This is a piece of system-level software that forms the link between your audio interface, operating system and music applications, and it needs to be fast and stable. The need for stability is obvious - you don't want your system crashing in the middle of a perfect take - but how can an audio interface be 'fast' or 'slow' Well, when monitoring a live input via your DAW or sequencer, there's a delay between the signal entering the interface, being sent through the software and passing back through the interface to the speakers. The same happens with MIDI and software instruments, the delay in this case occurring between a MIDI keyboard key being pressed and the software generating the sound and sending it to the interface outputs. This delay is called latency, and it's a fact of life for computer musicians. In the old days, we had to put up with very noticeable latency values (50 milliseconds and up), but today's interface drivers are so well tuned that they can go as low as 2-3ms, although 7-10 is average, which is still faster than most people are ever going to notice. There's no getting around this with MIDI instruments, but most interfaces now offer 'direct monitoring' of audio, whereby the input is passed straight to the output, resulting in effectively zero latency. The drawback is that because your music software is being bypassed, you can't monitor with effects in this way. Oh, and I should point out that this ONLY applies to recording: for playback and purely 'internal' work, latency is in no way an issue.

And that's basically it for audio interfaces! There are loads of them on the market, so set yourself a budget, get a few copies of Computer Music in and read some reviews, and prepare to be amazed at what you can get for your money quality-wise.