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A Glossaru of HiFidelity, r continuad fr...

A Glossaru of HiFidelity, r continuad fr... image A Glossaru of HiFidelity, r continuad fr... image A Glossaru of HiFidelity, r continuad fr... image
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A Glossaru of HiFidelity, r continuad from page 1 7 f INTERMODULATION DISTORTION - Distortion which results when two or more pure tones are non-linearly combined to produce new tones with frequencies representing the sums and differences of the original tones and their harmonies. IPS- Abbreviation for tape speed in "inches-per-second." JACK- Receptacle for a plug connector leading to the input or output of a tape recorder or other piece of equipment. KHz-Abbreviation for thousands of cycles-per-second. LEADER AND TIMING TAPE-Special tough non-magnetic tape which can be spliced to either end of a magnetic tape to prevent its damage and possible loss of recorded material. White or in color, it features a mark every Tt inches. Used as a timing tape, therefore, it can be spliced between musical selections to provide desired pauses upon playback. LEVEL INDICATOR-A device on a tape recorder primarily to indícate the level at which the recording is being made, and which serves as a warning against under or over-recording. It may be a neon bulb, a "magie eye," or a VU meter. See also VU METER. LOUDNESS-Sound level as detected by the average human ear. The ear is more sensitive to "middle" frequencies than to low or high extremes especially at low levéis. LOW NOISE TAPE-Magnetic tape with signal-to-noise ratio three to five db better than conventional tapes, accomplished by noise reductions rather than increased low frequency output, making it possible to record sound (especially wide frequency-range music) at reduced tape speeds without objectionable background noise (hiss) and without compromising fidelity. MAGNETIC TAPE-A high quality tape which has been precision-coated by the manufacturer with a layer of magnetized metal oxide partiële. The result is a recording medium which can be erased and re-used, and which offers the highest fidelity of reproduction possible today. MICROPHONE-A sound transducer or device for converting sound waves into electrical energy of the same frequency. MIL- One-thousandth of an inch. Tape thickness is usually measured in mils. MIXER- Device by which signáis from two or more sources can be blended and fed simultaneously into a tape recorder at the proper level and balance. MONAURAL RECORDER-Uterally, a tape recorder intended for listening with one ear only, however, in popular usage refers to single channel recorders, as distinguished from multi-channel (stereophonic.binaural, etc.) types. More correctly, but less universally called "monophonic" recorder. MONOPHONIC RECORDER-See MONAURAL RECORDER. NAB CURVE-Standard playback equalization curve set by National Association of Broadcasters. (See EQUALIZATION). NOISE- Unwanted random sound created in small amounts by electronic equipment, heads, and also by rough or non-homogeneous oxide coatings on magnetic tape. Mostly confined to ƒ the extremes of the audible frequency Jl b j# spectrum where it occurs as hum and or hiss. May be reduced to negligible levéis by good machine and tape design. NOISE WEIGHTED-The noise measured within the audio-frequency pass band using a measuring instrument which has a frequency selective characteristic. The sensitivity is usually greatest in the frequency range where the ear is most sensitive. OCTAVE-The interval between two frequencies of sound or electrical energy ha ving a ratio of 2 : 1 . OPEN REEL-Designates reel-to-reel machines, as opposed to quick-loading types such as cassette machines. OUTPUT-Also MAXIMUM UNDISTORTED OUTPUT-The useful power delivered by a recorder using a particular type of tape, usually at an High-Fcilutin' Jargon ily fixed level of harmonie distortion (1% or 3%) and relative to the performance of a Standard reference tape. OXIDE- The ferro-magnetic partiële which, when properly dispersed in a plastic binder and coated on a base, form the magnetic portion of magnetic tape. Conventional oxide partióles chemically known as gamma ferric oxide, are brown in color, acicular or needle-like in shape, and of micron length. All oxides used in magnetic tape are magnetically "hard", maintaining magnetism induced in them til demagnetized by external magnetic fields of approximately 50 oersteds intensity or more. PATCH CORD-Sometimes called "attachment cord." A short cord, or cable, with a plug on either end (or with a pair of clips on one end) for conveniently connecting together two Y pieces of sound equipment such as a phonograph and tape recorder, an amplifier and speaker, etc. PAUSE CONTROL-Feature on some tape recorders making it possible to stop the movement of tape temporarily without switching the machine from "play" or "record" positions. Essential for a tape recorder used for dictation and generally helpful for editing I purposes. PEAK-The maximum instantaneous volume of a quantity such as sound, but most frequently as electrical voltage or power. PHASING-In stereo applications, the establishment of the correct relative polarity in the connection between amplifier output and löudspeakers so that one speaker tends to reinforce rather than cancel the output of the other (particularly evident at low frequenties). PINCH ROLLER-See PRESSURE ROLLER. PLAYBACK HEAD-Magnetic head used to piek up signal from a tape. Often the same head as is used for recording, but with circuitry changed by means of a switch. See also HEAD. PLUG- A circuit connector which is inserted into a jack. POLYESTER BASE-Plastic film base for magnetic tape. It provides strength and resistance to temperature and humidity change. POST EMPHASIS-That portion of the equalization which is applied in the reproducer. POWER An amplifier producing sufficient power to opérate a loudspeaker. POWER CORD-Cord for connecting the tape recorder to an external power source, such as 1 17 volt a.c. current. PRE-AMPLIFIER-Also PRE-AMPAn amplifier that raises extremely weak signal levéis such as those from a microphone, magnetic playback head or a phonograph pickup to a level sufficient to drive a power amplifier. Some tape recorders combine the pre-amp and the power amplifier. PRE-EMPHASIS-(PRE-EQUALIZATION)- That portion of the equalization which is applied during recording. PRE-RECORDED TAPE-Tape recordings that are commercially available. PRESSURE PAD-A device which forces tape into intímate contact with the head gap; usually by direct pressure at the head assembly. Feit or similar material occasionally protected with self-lubricating plastic is used to apply pressure uniformly and with a minimum of drag to the base-side of the tape. PRESSURE ROLLER-Also called "pinch roller", "puck" or "capstan idler". A spring-loaded rubber-tired roller which holds the magnetic tape tightly against the capstan, permitting the latter to draw the tape off the stock reel and past the heads at a constant speed. PRINT THROUGH-Transfer of the magnetic field from layer to layer of tape on the reel. Print through can be a problem when an over-modulated recording is stored for long periods at high room temperatures. REMANENCE-The induction in lines I l of flux per unit width of tape, which JJJl continued on page 26 JJIJ A Glossary of HiFidelitij, Iligh-Falutin' Jargon continued from page 23 remains when the magnetizing Field is reduced to zero from a level producing saturation. A figure of merit for magnetic tape indicative of relative output, distortion, and response at low frequencies (long wave lengths). RELUCTANCE MICROPHONE-Inex pensive electro-magnetic (variable reluctance) type microphone supplied with many tape recorders which is extremely rugged and durable but generally not as high quality as crystal or ceramic types. Employs a metal "wand "wand" which moves in a magnetic field to produce varying voltages. RESPONSE-See FREQUENCY RESPONSE. RETENTIVITY-Equivalent to REMANENCE except expressed in terms of flux density or flux per unit of cross sectional área. A figure of merit for coating despersions, independent of coating thickness, and thereby useful for estimating coating sensitivity at short wave lengths. REWIND CONTROL-Button or level for rapidly rewinding tape from the take-up reel to the stock reel. RF- Abbreviation for radio frequency, which refers to that part of the general frequency spectrum between audible sound and infrared light (about lOk Hzto 10,000,000 M Hz). RUMBLE- A disagreeable noise of very low pitch or frequency peculiar to the turntables and associated drive mechanisms of disc recording and player systems. Rare to non-existent in tape systems unless present in'pre-recorded tapes and reproduced by the tape recorder. SATURATION-The condition reached in magnetic tape recording where output does not increase with increased input. Useful for defining reference output levéis, since it is independent of bias current. SENSITIVITY-As used to describe the capabilities of recording tape, indicates the relative output for a given input in the linear (low) distortion portion of a tape's magnetic transfer characteristic. Sensitivity data plotted as function of frequency (or wave length) gives frequency response, usually relative to a standard reference tape. SEPARATION-The degree to which two stereo signáis are kept apart. Stereo realism is dependent on the successU ful prevention of their mixture before XVreaching the output terminals of the power amplifier. Tape systems have separation capability inherently far superior to that of disc system. SIGNALS-TO-NOISE RATIO-The voltage ratio, usually in db, between the loudest undistorted tone recorded and reproduced by a recorder, and the noise reproduced when the signal (but not the bias) is reduced to zero. SINGLE TRACK RECORDER-A tape recorder which records or plays only one track at a time on or from the tape. See also MONAURAL RECORDER. SPLICING BLOCK-Metal or plastic device incorporating a groove within which ends of the tape to be spliced are held. An additional diagonal groove provides a path for a razor blade to follow in cutting the tape. SPLICING TAPE-A special pressuresensitive, non-magnetic tape used for splicing magnetic tape. lts "hard" adhesive will not ooze, and consequently will not gum up the recording head, or cause adjacent Iayers of tape to stick together. SQUEAL- The audible noise caused by altérnate sticking and release of tape. May occur at heads, pressure pads, or guides where friction develops with face or back side of magnetic tape. Largely eliminated by regular cleaning of suspected surfaces or using a tape employing a built-in dry silicone lubricant. STEREOPHONIC SOUND-'Dimen sional" or "directional" sound reproduction achieved through use of two or more sound tracks, or channels, heard simultaneously through speakers arranged in the same relative positions as were the microphones during recording. TAPE DECK-Tape recorder designed for use in a high fïdelity music system. Usually consists of drive mechanism and does not include power amplifier, speaker or case. TAPE GUIDES-Grooved pins or rollers mounted at each side of the recording tape head assembly to position the magnetic correctly on the head as it is being recorded or played. TAPE A system of movable guides which automatically diverts tape from contact with the recorder's heads during fast forward or rewinding modes of operation. TAPE PLAYER-A unit capable of playing pre-recorded tape. TWEETER-A loudspeaker designed to reproduce only the treble or high frequencies of the audible spectrum. TWO TRACK RECORDING-The arrangement by which only two channels of sound may be recorded, either as a stereo pair in one direction or as separate monophonic tracks (usually in opposite directions). UNIFORMITY-In terms of magnetic tape properties, a figure of merit relating to the tape's ability to deliver a steady and consistent output level upon being recorded with a constant input. Usually expressed in db variation from average to mid-range frequency. VOLUME-An acoustical, rather than _ an electrical measurement. Refers to the pressure of sound waves in terms of dynes per square centimeter. The louder the sound, the greater the pressure. Most technicians prefer to talk in terms of decibels. VU METER-A "volume-unit" meter which indicates audio frequency power levéis in decibels relative to a fixed reference level. The meter movement differs from those of ordinary voltmeters in that it has a specified ballistic response adapted to monitoring speech and music. Used in many homes and most professional recorders to monitor recording levéis and maintain them within distortion limits of the tape. WAVE LENGTH-In tape recording and rëferring specifically to the tape magnetization created by pure single tone recording, the shortest physical distance between two points of the same magnetic polarity and intensity, also when expressed in mils, the ratio of tape speed (in ips) to recorded frequency (in k Hz per second). WEIGHTING CHARACTERISTICThe shaped response-frequency characteristic of a measuring device used to produce more realistic indications of the subjective effects than are obtained with unweighted (flat) measurements. WOOFER-A loudspeaker designed specifically to reproduce the bass or low frequencies of the audible spectrum. WOW- A form of distortion in sound reproducing systems caused by periodic variation in the speed of the medium (such as tape), and characterized by its effect on pitch. WRAP-The length of the tape's path along which tape and head are in intimate physical contact. Sometimes measured as the angle of arrival and departure of the tape of respect to the head. See also HEAD ALIGNMENT. JJ J