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GLOSSARY OF TECHNICAL TERMS--22 Micro- is a prefix meaning one millionth, as in a microvolt (millionth of a volt). A micron is a millionth of a meter. Mil, milli- both mean one thousandth. A mil is one thousandth of an inch-a familiar unit in specifications of tape thickness and phono-stylus dimensions. The prefix milli- (millisecond, millivolt) designates one thousandth of whatever unit of measure it is attached to. Mix (or mixdown) is the process of combining two or more audio signals in carefully chosen proportions to create a single signal with the desired instrumental and frequency balance. The device usually used for mixing-as well as the person doing it--is called a mixer. Mixer, an audio control unit whose basic function is to combine two or more audio signals into a single composite signal, is most familiar to audiophiles in the form of a microphone mixer. Such a unit permits the outputs of a number of microphones to be adjusted in level and combined (mixed) for recording on one or two (or four) channels. The simplest mixers are small, passive (that is, not powered) units; the most elaborate are the large mixing consoles, used in sound studios, which can reduce sixteen or more inputs to two or four channels, adding equalization and artificial reverberation to each input when desired. Modulation is the imposing of a signal on some type of transmission or storage medium-a radio carrier, record groove, magnetic tape, etc. Occasionally you'll encounter references to an unmodulated record groove (meaning simply a straight, smooth groove with no audio information inscribed in it) or an unmodulated radio signal (meaning that the carrier embodies no audio signal in the form of frequency or amplitude modulation). On the other hand, 100 percent modulation means that the medium is carrying the strongest signal it is capable of handling or, in the case of radio, the strongest signal legally allowed. (Modulation also has a specific musical meaning: a change of key within a piece of music.) Mono is a word freely used as a substitute for monaural, which is unacceptable to careful users of language, and monophonic, which is correct but some what unfamiliar to many readers. In either case it means single-channel sound, in contrast to stereophonic (two-channel) and quadraphonic (four-channel). Moving coil, moving iron, moving magnet are all designations for different types of transduction systems used in generating the electrical output of a magnetic phono cartridge. All magnetic cartridges derive their outputs from the relative motion of a magnetic field and a coil of wire. Sometimes the stylus moves the magnet, sometimes it moves the coils, and sometimes it moves a soft-iron "armature" that varies the magnetic flux impinging on the coils. Multipath refers to the reception of the same radio signal (by a receiving antenna) from several different sources at the same time. Typically, one source is the direct broadcast from the transmit ting antenna, which follows a straight line path to the reception site. The other sources are reflections of the signal, usually caused by large natural objects or structures in the vicinity, and frequently arriving from other directions. Thus a single broadcast can find its way to the receiver via multiple paths. Multipath reception is undesirable because the reflections, having traveled a longer distance than the direct signal, arrive "late" at the receiver and interact with the direct signal in ways that cause noise, distortion, and loss of stereo separation. Practical cures for multipath include use of a directional receiving antenna, a reception site free of reflection-causing objects, and a tuner with good interference rejection.
Also see: TAPE HORIZONS: Tape Backings, CRAIG STARK NEW PRODUCTS: A roundup of the latest in high-fidelity equipment
Source: Stereo Review (USA magazine) |
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