NAC Audio Cassette Glossary

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A

AC Bias: The alternating current, usually of frequency several times higher than the highest signal frequency, that is fed to a record head in addition to the signal current. AC bias serves to linearize the recording process and is universally used in analog recording. Generally, a large AC bias is necessary to achieve maximum long wavelength output and linearity, but a lower value of bias is required to obtain maximum short-wave!ength output. The mechanism of AC bias can best be explained in terms of anhysteresis.

Aliasing: When reconstructing an analog signal from its sampled data representation, false lower frequency components can result from an insufficient sampling rate, i.e., less than required by the sampling theorem. This undesirable result is called aliasing.

Alignment: Most commonly, Head Alignment, but also used to describe the process of adjusting a recorder’s Bias and Equalization for optimum results from a specific tape.

Analog: Refers to the historic method of recording an audio signal in the same manner in which it is heard.

ANRS, Super ANRS: A noise reduction system u sed by JVC. ANRS operates on principles similar to those used by the Dolby system. Therefore, there is a degree of compatibility between recordings made with either system.

Azimuth: The angle of a tape head’s recording gap relative to the tape.

Azimuth Alignment: Alignment of the recording and reproducing gaps so that their centerlines lie parallel with one another and at right angles to the direction of head/tape motion. Misalignment of the gaps causes a loss in output at short wavelengths. For example, using a track width of 50 mils, a misalignment of only 0.05 degrees will cause a 3 dB loss at a wavelength of 0.1 mil.

Azimuth Loss: High frequency losses caused by head misalignment.

B

Base Film: The plastic substrate that supports the coating. The base film of most precision magnetic tape is made of polyester.

Base Film Thickness: The thickness of the polyester material used for magnetic tape, varying from 0.24 mil in C120 cassette tape to 1.5 mil for audio mastering tape and instrumentation tape.

Bias: A steady-state signal applied to the tape (usually by a high frequency oscillation of 50-100,000 Hz or more) to minimize distortion and noise and increase frequency response and efficiency in recording. Every tape formulation has slightly different bias requirements.

Bias Adj.: The control which regulates the amount of bias mixed in with the signal to be recorded.

Bias Cal.: A control which calibrates the VU meter on a recorder so it reads 0 VU in the bias position of the output selector switch when bias is properly set.

Bias Switch: Switch used on cassette recorder to change the amount of bias current required for different types of tapes.

Blocking: The tendency for adjacent layers of tape in a roll to adhere, particularly after prolonged storage under conditions of high temperature and/or humidity.

Break Elongation: The relative elongation of a specimen of magnetic tape or base film at the instant of breaking when it has been stretched at a given rate.

Brown Stain: A non-magnetic substance that forms on that area of a magnetic head’s surface over which tape passes. Its origin is not well understood but it is known to occur primarily in the presence of low humidity.

Built-in Reference Tones: Refers to adjustment tones which are available within the recorder for adjusting record level and bias.
Bulk Eraser: A device used to erase an entire tape at one time. Bulk erasers are usually more effective than recorders’ erase heads.

C

Capstan: The driven spindle or shaft in a tape recorder – sometimes the motor shaft itself which rotates against the tape (which is backed up by a rubber pressure or pinchroller), pulling it through the machine at constant speed during recording and playback modes of operation.

Capstan Idler: A rubber wheel which presses the magnetic tape against the capstan so that the capstan can move the tape.

Cassette: A tape cartridge in which the tape passes from one hub to another. Most commonly applied to the Compact Cassette developed by Philips, but also to a variety of Micro and Mini Cassette systems that are not mutually compatible.

Cassingle: A short two-sided cassette single, usually containing one or two songs. Cassingles were popular in the 70s and 80s and usually packaged in O-Cards.

Channel: An independent signal path. Stereo recorders have two, such channels. Quadraphonic ones have four.

Chrome: Called Type 2 – This is “chrome” or CrO2 tape. The ferric-oxide particles are mixed with chromium dioxide. Recommended for music with a higher range of frequency.

Chrome Plus: An expansion on the chrome format to capture a broader range of sound.

Chromium Dioxide (Cr02): A modern magnetic particle oxide of the high energy type. Chromium dioxide is a highly acicular particle with the crystal structure of rutile. Tapes made with Cr02 exhibit a coercivity of 425 to 475 Oersteds.

Coating: The magnetic layer of a magnetic tape, consisting of oxide particles held in a binder that is applied to the base film.

Coating Thickness: The thickness of the magnetic coating applied to the base film. Modern tape coatings range in thickness from 170 to 650 microinches. Coating thickness is normally optimized for the intended application. In general, thin coatings give good resolution at the expense of reduced output at long wavelengths; thick coatings give a high output at long wavelengths at the expense of degraded resolution.

Cobalt Doped Oxide: This is normally a gamma ferric oxide particle which has been doped with cobalt to achieve a higher coercivity. Modern forms of this oxide are acicular and have been used to make tapes with coercivities in excess of 1000 Oersteds.

Coercivity: Measured in Oersteds, the measurement of a magnetic characteristic. The demagnetizing force required to reduce the magnetic induction in a magnetic material to zero from its saturated condition.

Compact Cassette: A small (4 x 2-1/2 x 1/2″) tape cartridge developed by Philips, containing tape about 1/7″ wide, running at 1-7/8 ips. Recordings are bidirectional, with both stereo tracks adjacent for compatibility with monophonic cassette recorders, whose heads scan both stereo tracks at once.

Crosstalk: Undesired signal leakage from one sound channel or track to another.

Cycle: An alternation of a waveform which begins at a point, passes through the zero line and ends at a point with the same value and moving in the same direction as the starting point.

Cycle Per Second: A measure of frequency, equivalent to Hertz.

D

De-esser: A compressor which reduces sibi- by triggering compression when it senses the presence of high frequency signals above the compression threshold.

Decibel: Abbreviated “dB” or “db”, it is a relative measure of signal or sound intensity or “volume.” It expresses the ratio of one intensity to another. One dB is about the smallest change in sound volume that the human ear can detect. (Can also express voltage and power ratios logarithmically.)

Deck (Tape): A tape recorder that does not include power amplifiers or speakers.

Degaussing: A process by which a unidirectional magnetic field is removed from such transport parts as heads and guides. The presence of such a field causes noise and a loss of high frequencies.

Digital Audio Recording: A system which converts audio signals into digital words which are stored on magnetic tape for later reconversion to audio, in such a manner that dropouts, noise, distortion and other poor tape qualities are eliminated.

Digital Recording: A method of recording in which the information is first coded in a digital form. Most commonly, a binary code is used and recording takes place in terms of two discrete values of residual flux.

Distortion:

3rd Harmonic: The introduction of an unwanted 3rd harmonic of the fundamental signal (3 octaves higher than the fundamental signal).

Intermodulation (IM): Distortion that results when two or more pure tones produce new tones with frequencies representing the sums and differences of the original tones and their harmonics.

Dolby: A proprietary electronic device or circuit that reduces the amount of noise (principally tape hiss) introduced during the recording process by boosting – in carefully controlled amounts – the strength of weak high frequency signals before they are recorded. During playback the signals (and the noise) are cut back by an exactly equivalent amount. The original dynamics are restored, but the noise is reduced by 10 dB.

Dropout: The momentary loss of a recorded signal.

Dropout Count: The number of dropouts detected in a given length of magnetic tape.

Duplication: The reproduction of your music on a run of duplicate cassettes. At NAC, tapes are manufactured to custom length with your preferred tape type

E

Equalization: The selective amplification or attenuation of certain frequencies. Also refers to recognized industry standards for recording and reproducing “characteristics” (such as the NAB Standard).

Equalizer: A device which is designed to change the frequency balance of a signal.

Erase Head: A device used to remove recorded signals from magnetic tape.

Erasure: A process by which a signal recorded on a tape is removed and the tape made ready for rerecording.

F

Ferric: The tape inside the shell consists of a thin plastic base material, with a bonded coating of ferric oxide powder. The oxide is normally mixed with a binder to attach it to the plastic, and a dry lubricant to avoid wearing out the recorder. FERRIC is standard ferric-oxide tape –  called Type 1 and also referred to as “normal bias.”

Flutter: Distortion which occurs in sound reproduction as a result of undesired speed variations during recording or reproducing. Flutter occurring at frequencies below approximately 6 Hz is termed “wow.”

Four-Track or Quarter-Track Recording: The arrangement by which four different channels of sound may be recorded on quarter-inch-wide audio tape. These may be recorded as four separate and distinct tracks (monophonic) or two stereo pairs of tracks. Tracks 1 and 3 are recorded in the “forward” direction of a given reel, and Tracks 2 and 4 are recorded in the 11 reverse” direction.

Frequency: The rate of vibration of an electrical 0 or mechanical oscillation. Measured by the number of complete cycles executed in 1 second. In audio terminology, frequency range is considered to be from 20 cycles per second, or 20 Hertz, up to 20,000 cycles per second, or 20 Kilohertz.

Frequency Response: The variation of response with respect to signal frequency. Usually, the frequency response of a tape is given in dB relative to that of a reference tape measured under the same conditions.

Frequency Response Curve: The curve relating the variation in output with frequency of a piece of equipment or magnetic tape when the input is kept constant.

Fringing: The Pickup of extra bass frequency signals by a playback head when reproducing a signal recorded by a head with a wider track configuration, such as playing a full track tape with a half-track head.

FullTrack Recording: Recording monophonically on one track whose width is essentially the same as the tape’s.

G

Gain: The ratio of output power to the input power for a system or component. Usually expressed in decibels.

Gamma Ferric Oxide: The common magnetic constituent of magnetic tapes in the form of a dispersion of fine acicular particles within the coating.

Gap: The space between the pole pieces of a tape head.

Gap Depth: The dimension of the gap measured in the direction perpendicular to the surface of a head.

Gap Length: The dimension of the gap of a head measured from one pole face to the other. In longitudinal record recording, the gap length can be defined as the dimension of the gap in the direction of tape travel.

Gap Loss: The loss in output attributable to the finite gap length of the reproduce head. The loss increases as the wavelength decreases.

Gap Width: The dimension of the gap measured in the direction parallel to the head surface and pole faces. The gap width of the record head governs the track width. The gap widths of reproduce heads are sometimes made appreciably less than those of the record heads to minimize tracking errors.

Gauss: The metric unit I of magnetic flux density equal to one Maxwell per square centimeter.

Generation Loss: The ‘increase in noise level which occurs each time a signal is recorded on tape.

Graphic Equalizer: An equalizer which indicates its frequency response graphically through the position of its controls. When the controls are in a straight line at the 0 position, the response is flat.

H

Head: Ina magnetic recorder, the generally ringshaped electromagnet across which the tape is drawn. Depending on its function, it either (a) erases a previous recording, (b) converts an electrical signal to a corresponding magnetic pattern and records it on the tape, or (c) picks up a magnetic pattern already on the tape and converts it to an electrical playback signal.

2 Head: The system used on most cassette recorders, requiring that playback occur after the recording has been made.

3 Head: Refers to the recording/playback head configuration within the recorder. A 3-head system allows simultaneous playback of recorded material.

Head Alignment: Mechanical adjustment of the spatial relationships between the head gaps and the tape.

Head Block: An assembly holding an erase, record and playback head in a certain physical alignment.

Head Demagnetizer or Degausser: A device used to neutralize possible residual or induced magnetism in heads or tape guides.

Head-to-Tape Contact: The degree to which the surface of the magnetic coating approaches the surface of the record or replay heads during normal operation of a recorder. Good head-totape contact minimizes separation loss and is essential in obtaining high resolution.

Headroom: The number dB increase possible above the operating level (0 VU) before unacceptable distortion occurs.

Hertz (Hz): The unit of frequency. Equivalent to cycles per second.
High Energy Oxide: Any magnetic oxide particle exhibiting a BsHc product higher than that of gamma ferric oxide. Chromium dioxide and cobalt doped oxide are the two most common examples at the present time.

High Energy Tape: A tape made with a high energy oxide.

High, Cr02: bias position required for high bias tapes, including both chromium dioxide and cobalt modified.
Intrinsic Coercive Force: The magnetizing field strength needed to reduce flux density from saturation to zero.

I

Imprinting: The process of printing your design on the surface of the cassette shell with ink. Imprinting has similar limitations to silk-screen printing for shirts and promotional products. It is available from NAC as single-color printing on any color shell.

Intrinsic Coercivity: The maximum value of the intrinsic coercive force. The intrinsic coercivity is a basic magnetic parameter for the material and requires complete saturation of the sample for its measurement as does the saturation flux density.

Iron Oxide/Gamma Ferric Oxide: The most popular oxide particle produced from an oxide of pure iron.

J

J-Card
The folded printed insert for the Norelco box. It serves the purpose of “Album Art”.

K

KHz: Abbreviation for kilohertz, or one thousand cycles per second.

L

Layer-to-Layer Adhesion: The tendency for adjacent layers of tape in a roll to adhere to one another.

Layer-to-Layer Signal Transfer: The magnetization of a layer of tape in a roll by the field from a nearby recorded layer, sometimes referred to as “print-thru.”

Leader: Special non-magnetic tape that can be spliced to either end of a magnetic tape to prevent damage and possible loss of recorded material and to indicate visually where the recorded portion of the tape begins and ends.

M

M.O.L. (Maximum Output Level): In audio tape, that record level which produces a 3rd harmonic distortion component at 3.0%.

Magnetic Tape: With a few exceptions, magnetic tape consists of a base film coated with magnetic particles held in a binder. The magnetic particles are usually of acircular shape and approach single domain size. See gamma ferric oxide, chromium dioxide and cobalt doped oxide.

Modulation Noise: Noise which results from the agitation of the oxide molecules through the recording process. The modulation noise level increases as record level increases and disappears when no signal is present.

Mylar: A registered trademark of E.I. dupont de Nemours & Co., designating their polyester film.

N

Noise: Any unwanted electrical disturbances, other than crosstalk or distortion components, that occur at the output of the reproduce amplifier. System noise is the total noise produced by the whole recording system, including the tape. Equipment noise is the noise produced by all the components of the system, with the exception of the tape. Tape noise is the noise that can be specifically ascribed to the tape. Typical sources of tape noise are: 1) Bulk Erased Noise – the noise arising when reproducing a bulk erased tape with the erase and record heads completely deenergized, 2) Zero Modulation Noise – the noise arising when reproducing an erased tape with the erase and record heads energized as they would be in normal operation, but with zero input signal. This noise is usually 3-4 dB higher than the bulk erased noise. The difference between bulk erased and zero modulation noise is sometimes termed bias induced noise-, 3) Saturation Noise -the noise arising when reproducing a uniformly saturated tape. This is often some 15 dB higher than the bulk erased noise and is associated with imperfect particle dispersion; 4) DC Noise – the noise arising when reproducing a tape which has been non-uniformly mag- _ magnetized by energizing the record head with DC, either in the presence or absence of bias. This noise has pronounced long wavelength components which can be as much as 20 dB higher than those obtained from a bulk erased tape. At very high values of DC, the DC noise approaches the saturation noise; 5) Modulation Noise – the noise arising when reproducing a tape which has been recorded with a given signal, and which is a function of the instantaneous amplitude of the signal. This is related to DC noise and arises from the same causes.
Noise Reduction: The amount in dB that the noise added to a signal by transmission or storage chain, especially a tape recorder, is reduced from the level at which it would be if no noise reduction devices were used.

Noise Reduction Systems: Refers to electronic circuits designed to minimize hiss level in magnetic recording.

O

O-Card: A printed card stock sleeve package for the cassette tape. Often associated with “Cassingles.”

Output: The magnitude of the reproduced signal voltage, usually measured at the output of the reproduce amplifier. The output of an audio or instrumentation tape is normally specified in terms of the maximum output that can be obtained for a given amount of harmonic distortion, and is expressed in dB relative to the output that can be obtained from a reference tape under the same conditions.

Oxide (Magnetic Oxide): The magnetizable particle used in the manufacture of magnetic tape.

Oxide Buildup: The accumulation of oxide or, more generally, wear products in the form of deposits on the surface of heads and guides.

Oxide Coating: The magnetic material coated on base film.

Oxide Shed: The loosening of particles of oxide from the tape coating during use.

P

Pinchroller: A rubber or neoprene wheel which presses the tape against the capstan during recording or play.

Playback: The reproduction of sound previously recorded on a tape.

Playback Head: A transducer which converts magnetic flux into electrical current.

Polyester: An abbreviation for polyethylene terephthalate, the material most commonly used as a base film for precision magnetic tape. The chief advantages of polyester over other base film materials lie in its humidity and time stability, its solvent resistance and its mechanical strength.

Prerecorded Tape: A commercially available recorded tape.

Pressure Pad: A device that forces tape into intimate contact with the head gap, usually by direct pressure at the head assembly.

Print-thru: The effect of signals being magnetically impressed on adjacent portions of tape. This is the effect of magnetic induction and its cause can be excessive spooling or heat. Factors affecting spurious printing are principally heat, tape thickness and recording level and, to a lesser extent, time. Print-through increases linearly with the logarithm of the time of contact, other factors being constant.

Q

R

Record Level: The amount of energy level delivered to the recording head and to the magnetic tape. Indicated by the VU meter and measured in Nanowebers per meter.

Record Tabs: Those plastic tabs seen in the back edge of a cassette. When removed, sensing fingers prevent the record button from being depressed.

Recording Speed (IPS): Refers to the number of inches per second, or centimeters per second, of tape movement.

Recording-Level Meter: An indicator on a tape recorder that provides some idea of the signal levels being applied to the tape from moment to moment. It is intended as an aid in setting the recording levels.

Reel: The flanged hub, made of metal, glass or plastic, on which magnetic tape is wound.

Re-Mastering: Most music received from NAC customers is mixed and delivered to us on digital media. Our audio engineers optimize the range of sound to be as full and possible, but distortion-free, for the recording on the cassette tape. Analog audio originals are also filtered and tagged to make the best cassette duplication.

Reverberation: The persistence of a sound after the source stops emitting it, caused by many discrete echoes arriving at the ear so closely spaced in time that the ear cannot separate them.

S

Saturation: The condition reached in magnetic tape recording where output does not increase with increased input and hence distortion increases significantly.

Sensitivity: The magnitude of the output when reproducing a tape recorded with a signal of given magnitude and frequency. The sensitivity of an audio or Instrumentation tape is normally expressed in dB relative to the sensitivity of a reference tape measured under the same recording conditions.

Shell: The cassette shell is the plastic exterior of the tape itself. They come in a variety of colors and style variations. Since the shift by the industry to CDs, the manufacture of shell types is limited.

Shell Liner: Clear and tinted cassette shells are commonly lined with a protective foil. It can be a color element for the tape design.

Separation: The degree to which two stereo signals are kept apart.

Shedding: A tape’s giving off of oxide or other particles from its coating or backing, usually causing contamination of the tape transport and, by redeposit, of the tape itself.

Signal-to-Noise Ratio: The ratio, usually expressed in decibels, between the loudest undistorted tone a system can handle and the noise remaining when the signal is reduced to zero.

Sonic Welded Assembly: Refers to the joining of the two plastic parts of a cassette by the use of a sonic weld, actually melting the plastic at the point of joining.

Splice: A physical join between pieces of tape.

Splicing Tape: A special pressure-sensitive, non-magnetic tape used for joining two lengths of Magnetic tape.

Squeal: Audible tape vibrations, primarily in the longitudinal mode, caused by frictional excitation at heads and guides.

Stiction: A term loosely used to describe the phenomenon of tape adhering to transport components such as heads or guides.

T

Tape Guides: Grooved pins or rollers mounted between and at both sides of the tape head assembly to position the magnetic tape correctly on the head as it is being recorded or played.

THD: Total Harmonic Distortion.

Total Thickness: Normally, the sum of the thicknesses of the base film and the magnetic coating. The total thickness governs the length of tape that can be wound on a given reel.

Track: An area of tape surface that coincides with the location of the recorded magnetization produced by one record gap.

Track Spacing: The distance between the center lines of adjacent tracks.

Track Width: The width of the track corresponding to a given record gap.

Two-Track Recording: On 1/4″ wide tape, 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).

U

Ultimate Tensile Strength: The force per unit cross-sectional area required to break a tape or length of base film, usually given in pounds per square inch (psi). Ultimate tensile strength is also quoted in terms of pounds per tape sample of given width and base thickness.

V

VU Meter: A type of recording level indicator which shows average signal levels in decibels relative to a fixed reference level (and, often, in percent of maximum recommended modulation). While the term is frequently used for any level meter using this scale, it applies most strictly to meters having a specified, standard degree of damping.

W

Width: Refers to the width of the tape, varying from 0.150″ in cassette tape to 2.0″ for video, mastering and instrumentation tapes. The size of the picture in a horizontal direction.

Wow: Slow, periodic variations in the speed of the tape, characterized by its effect on pitch. A measure of non-uniform movement of magnetic tape or other recording parts.

Wrap: The length of the path along which tape and head are in intimate physical contact.

X

Y

Yield Strength: The minimum force per unit cross-sectional area at which the tape or base film deforms without further increase in the load. Units are pounds per square inch (psi) or pounds per tape sample of given width and base film thickness.

Z

Zenith: The tilt of the head in the direction perpendicular to the tape travel.