Whether you’ve researched production and engineering in magazines (we recommend Tape Op) or on the web, you’re well aware of the ongoing debate between the virtues of analog and digital recording. Eventually, Phil and I will discuss the merits and limitations of both, but for now I will define the two terms in order to lay the foundation for future articles including next week’s Producer Speak: “Bit Depth, Bit Rate, and Sample Rate.”
Digital audio relies on a series of points (called samples) and works similarly to film. A reel of film is comprised of a series of still photos which, when projected at high speed, gives the illusion of fluid motion to the naked eye. Your brain “connects the dots” from one image to the next. Digital audio works like film in that sound is captured via a series of samples (which could be thought of as snapshots of sound pressure levels). These dots are then connected to form waveforms:
The scale is very different, however. Though film could theoretically run at an unlimited rate of frames (images) per second, we only need to capture and play back about 30 frames per second to give the appearance of realism. A CD, on the other hand, plays back at a rate of over 44 thousand samples per second.
Analog audio does not rely on samples at all. Analog is so called because when sound is captured to an analog medium, the waveform that is created is analogous with the sound wave being captured. This means that an analog audio signal has a higher potential for quality, although analog signal decreases in fidelity (quality of exactness) each time it is copied or transferred, whereas a digital signal will retain its quality no matter how many times it is copied.
Things that are analog: reel-to-reel tape, cassettes, microphones, preamps (not including built-in analog-to-digital converters).
Things that are digital: Protools, CDs, DAT, MP3s, WAVs, DVDs, anything on a computer.
Analog to Digital converters such as the Digidesign 192 bridge the two formats together. These are sometimes called A2D or simply “converters” when also referring to Digital to Analog conversion devices.
Next week’s Producer Speak: “Bit Depth, Bit Rate, and Sample Rate.”
