Digital sound mixers have replaced analogue models in many recording studios and live stages. The versatility, features and improved sound of digital mixers were once the exclusive preserve of a few studios, though lower prices have been leading them to into the mainstream. Analogue mixers still sell well, however, with virtues of simplicity, reliability and low cost.
Traditional mixers combine signals using analogue techniques. On an analogue mixer, each of several inputs--for microphones, keyboards, and other signals--has a fader, or volume control, that feeds into a master amplifier. The master amplifier also has a fader that controls overall loudness. Sounds are combined, routed and modified as electrical signals.
A digital mixer takes each sound signal input and converts it to a rapid stream of numbers. This is called analog-to-digital conversion (ADC). The mixer combines, routes and processes the numbers with computer software. At its output, the digital mixer converts the numeric information back to standard electrical signals. Engineers call this digital-to-analog conversion (DAC). Digital mixers have many of the physical features of analog models, including faders, knobs and switches, but internally the circuits are very different.
The circuits that convert sound signals to numbers in a digital mixer produce a small amount of signal delay, called latency. The delay time depends on the equipment and its settings, usually amounting to 10 milliseconds (thousandths of a second) or more. While this doesn't sound like much, it interferes with the musical beat. Musicians trying to play while hearing this delay can become confused. Analog mixing consoles process sound immediately and doesn't suffer from latency.
Analog circuits must be carefully designed and used to avoid noise. All circuits create a small amount of hiss that creeps into the sound. More analog circuits means more chances for noise to build up. They can also pick up electrical interference from computers, cell phones and other sources. Digital circuits are less susceptible to this kind of noise, as signals are handled as numbers, save for the mixer's inputs and outputs.
Many of a digital mixer's features are done as software programs, so its capability is less dictated by its physical hardware than an analog's. Designers can create hundreds of sound effects, filters and ways to control the dynamics of the sound's loudness. It's much easier to automate a digital mixer than an analog one, so a sound engineer can store, recall and fine-tune entire mixing sessions. Many digital mixers have virtual controls that let the user route and mix sounds in ways that would be otherwise impossible.
In 2010, digital mixers continue to command a premium price over their analog counterparts. The high-quality digital to analog converters, computers and hard disks cost money, and the mixer needs analog and digital parts. Analog mixers enjoy a strong following in the medium and low end of the price range, such as small convenience mixers for live performance.
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