The Input Side

One major drawback to this approach was that the audio hardware on PCs and laptops was universally poor and didn't begin to approach professional standards. As a workaround, recording engineers use external audio interfaces, typically connected by PCI cards or FireWire, to obtain acceptable input quality. Meanwhile, audio chipsets on PCs and laptops have begun to improve, partly driven by the home cinema market; it's not uncommon to find a digital audio output on an ordinary PC now.

The results you can achieve from digital, computer-based recording still depend greatly on the analog signal you put into the machine. When you record acoustic instruments and the human voice, a better-quality microphone and interface make an obvious difference. The cheap plastic microphones that are bundled with PCs and domestic hi-fi's aren't much good for audio recording projects, because they reproduce the audible frequency range unevenly and generate obvious noise in the signal.

For the last 50 years or so, professional recording studios have relied on a microphone design that hasn't changed much over time. Indeed, the original Neumann and Telefunken branded condenser microphones, devised in Berlin in the late 1940s and early 1950s, are highly sought after by contemporary studios. In more recent decades, millions of Neumann copies have been turned out by Russian and Chinese factories at a tiny fraction of the price of the originals (see Figure 9-2).

Figure 9-2. The Oktava MK-319, a Russian condenser microphone based on the classic German designs of the 1940s and 1950s. Photo by Gregory Maxwell, GNU FDL

The typical large-diaphragm condenser microphone has a circular capsule about an inch across, suspended inside a wire basket to protect it from damage. The circuit inside the main body of the microphone is powered using voltage across the conductors of the microphone cable, instead of a separate power lead; this arrangement is known by audio engineers as phantom power. If you have a microphone that needs phantom power, which by convention is usually 48 volts, then you also need equipment that can provide that power in the cable. Not all equipment that has the standard three-pin XLR socket has phantom power, and some battery-powered condensers and vintage ribbon microphones can be damaged by the voltage, so this is something to watch out for. Dynamic microphones, which don't require phantom or battery power, are generally safe to be plugged into a powered socket—but if you aren't sure, check the manufacturer's documentation.

■ Tip Phantom-powered microphones shouldn't be plugged in or unplugged while the mixer or other equipment they're connected to is switched on. This can make a loud, nasty bang noise in your speakers or headphones, and probably isn't good for the microphone either. Instead, connect the microphone first, then power up the mixer or push the phantom power button, and finally, turn up the speaker or headphone level control. Preferably, do this half an hour before recording begins, so the microphone can warm up; this dries out any moisture that has collected in the condenser capsule. Moisture in a phantom-powered microphone can add random spikes of noise to your recording. This is why new microphones are often packaged with sachets of silica gel.

For recording one voice or instrument at a time, you can now buy a low-cost condenser microphone with a USB interface built in. Instead of the traditional analog interface with a three-pin XLR plug (see Figure 9-3), these newer microphones feature an analog-to-digital convertor chipset that is often USB

class-compliant, advertised under the misleading slogan "works without a driver." In fact, these interfaces use a generic USB audio driver, which is provided on GNU/Linux systems by ALSA. The great thing about these USB condenser microphones is that they bypass the need for a separate hardware interface with XLR sockets, which is particularly advantageous in a laptop or mobile recording situation. They aren't so useful if you already have a collection of analog condenser microphones or need to use several of them at once. In that case, you need a separate audio interface and possibly an analog mixer with phantom power, too.

Figure 9-3. Decent analog microphones standardized on the three-pin XLR connector, shown here in female and male variants, many years ago. Some newer microphones connect via USB instead. Photo by Michael Piotrowski, GNU FDL

However, to get started, any microphone that works enables you to begin learning the techniques of sound recording and editing. Particularly if you're using a condenser microphone, it's a good idea to buy or make a pop filter for recording speech or vocal tracks. This is a simple circular wire or plastic frame about five or six inches in diameter with a covering of mesh fabric, attached to the microphone stand. You can make a pretty good one out of a wire coat-hanger and a nylon stocking! The function of this device is to sit between the sensitive microphone capsule and the human mouth, in order to disperse excess energy from plosive sounds like the letter P. Otherwise, these sounds can sometimes be too loud on a recording, because of the rush of air hitting the microphone capsule.

The podcasting phenomenon means that more people than ever before have the ability to produce and distribute audio content worldwide. You don't need a broadcast license or to be affiliated with an established media outlet, and the equipment is very affordable and accessible.

The name podcasting is misleading, because an Apple iPod has never been required to make or listen to podcasts. This name caught on after web developers began to offer automated syndication of audio files over the Internet in the early 2000s. Audio files had been shared through simple web links for years before that, but podcasting used the power of the Web's emerging Really Simple Syndication (RSS) standard to alert subscribers to fresh content. RSS enabled podcast producers to build a regular audience quickly and at minimal cost, to the consternation of traditional broadcasters who had millions of dollars invested in infrastructure and government licenses.

One of the most popular tools for creating podcasts is Audacity (GNU/Linux, Windows, Mac), which is both an easy to use multitrack recorder and a fast editor (see Figure 9-4). Audacity is probably the most widely used of all Free Software multimedia applications, having enjoyed more than 60 million direct downloads from the web site by mid 2009.

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