Glossary – T
A three-element fixed attenuator.
Recording of whole or part of a musical item. Thus a long work or one which is difficult to perform might consist of many 'takes to be edited together.
A reel on a tape recorder that winds the tape after it passes the heads.
On a tape recorder, the motor that is used, to supply take-up tension to the tape on the take-up reel and for fast forward operation.
A circuit enabling spoken directions to be given from a studio control cubicle or television control room, or from a production panel to a studio, or other program source, for the purpose of directing a performance or rehearsal.
The tangential relationship of the tape with the convex surface of the head, as measured at the location of the head gap.
A tape unit without a power supply or speaker.
A delay system using an auxiliary tape recorder. The delay is a function of the tape transit time as it travels from the record head to the playback head.
A low level, wide spectrum noise heard when a recorded tape is played back.
A tape machine that provides both recording and playback facilities.
The torque applied by the supply reel motor to keep the tape from freely spilling off the supply reel, and to maintain good tape-to-head contact.
On a tape recorder, a two position switch which changes the torque applied by the reel motor(s).
The torque applied by the take-up reel motor, to maintain a smooth wind as the tape leaves the capstan and capstan idler assembly.
A group of acoustic screens, arranged to trap (and usually to absorb) sound in the region of the microphone.
Electrical connection point.
A tape containing a series of test tones at a standard reference fluxivity. The test tape is used to verify the performance of the tape recorder's playback system.
A few initial pressings are first made and sound checked. Faults common to all must be due to an earlier process. Only when all are traced and rectified is production started. Each disc is visually inspected after pressing, but some clicks and pops can get by.
The level above which a compressor begins functioning.
The level below which an expander begins functioning.
The level above which a limiter begins functioning.
The lowest level sound that an average listener with good hearing can detect.
The sound level at which the listener begins to experience physical pain.
The opening at the narrow end of a horn, where it is attached to a compression driver. Also, the small diameter opening of a compression driver, where it is attached to a horn.
Subjective expression, describing the sound picked up by a microphone placed very close to an instrument.
A misalignment of a tape recorder head, around its vertical axis.
Also termed tone color. The distinguishing quality of a sound that depends primarily upon harmonic content and secondarily upon volume.
Shorthand method of specifying the values of resistor and capacitor to be used in a frequency correction network by reference to the time taken for the voltage across the capacitor to fall to 37% (approx.) of its original value through the resistor.
Any signal processing device, in which there is a time delay between input and output.
The fundamental frequency or pitch of a musical note.
A pivoted arm on a turntable that houses the pickup cartridge.
Lightweight construction is necessary to reduce mass, yet rigidity is also essential. Tubular aluminium, magnesium, and wood have been used, and the shells skeletonised. Low friction pivots require forces of no more than 2-50 mg maximum applied at the stylus, to move the arm horizontally or vertically. Unipivots are often used to achieve this.
Vibration from the stylus spreads from the cartridge through the shell and the arm, but at each interface there is a reflection which eventually arrives back at the stylus in similar manner to sound reverberation. A system of energy shunts to bridge the intersections has been devised to counteract this effect. These are fine brass wires that are bridged across physical interfaces such as the head to conduct vibrational energy across the interface and prevent it being reflected back to the stylus. They are not commonly used or well known.
The arm resonant frequency depends on its mass and its support springiness, which is the cartridge compliance. Output drops rapidly below resonance, so it should be pitched high enough to reduce lower frequency rumble, disc warps and ripples which can otherwise produce large amplitude subsonic signals that could overload the amplifier and even damage the speakers. Rumble and flutter can produce intermodulation sidebands at audio frequencies. Their amplitude depends on the resonant frequency, decreasing as it rises. So a high resonant frequency is desirable, yet it must also be below the lowest recorded audio frequency of 20 Hz. A frequency only just below is therefore the optimum; 10 Hz was once recommended, but 16 Hz is now the preferred figure. A quick check is that the product of the mass and compliance should equal 100 for a resonant frequency of 16 Hz. For a frequency of 10 Hz the product is 250 which is the upper limit. High compliance is clearly undesirable unless mated with an arm of low mass. In addition to the mass/compliance resonance, there is a self resonance that falls usually within 10-250 Hz. The main effect of this is a considerable increase in crosstalk between channels. It can be minimized by viscous fluid arm-damping and flexible decoupling of counterweights.
Rotary friction pulls the stylus toward the centre of the disc even when it is blank. In the groove this means extra pressure on the inner wall. To offset this, bias compensation in the form of a small weight which is lifted on a string or pivoted lever by the inward arm travel, or by attraction from a weak magnet, is provided.
A counter weight is slid along the rear arm extension, and clamped when the arm is in balance. Then a spring tension is adjusted to add the required tracking weight. The tension control may be calibrated in grams, or an external balance may be required.
A test signal comprising short sequences of sine-wave energy.
Also termed timbre. Classified as diapason, pure, string, or reed.
A control that provides variation of an amplifier's frequency
Non-linear distortion due to the different shapes of the cutting and reproducing styli.
1. The path of a phono stylus within the grooves of a disc. 2. The ability of a meter movement, or other dynamic device, to precisely follow the envelope of the applied waveform. 3. The process of completing a recording session, track by track, as in a Sel-Sync session.
1. The difference between the curved path followed by a pivoted pickup and the straight radial path of the cutter. 2. An unwanted error introduced in an audio system, when the output level or frequency response of the system deviates from the input signal. 3. A straight arm forms a tangent at one point in the groove, but if an offset is formed by bending it near the cartridge, two tangential points can be obtained at which tracking error is zero. Some designs equally space the zero points from the start and finish of the groove to equalize maximum tracking error either side of and in between the two points. However, distortion for a given tracking error increases as the groove velocity decreases, and so is at a maximum near the centre of the disc. It is better, therefore, to arrange the second point to be nearer the disc centre so that the distortion is equalized rather than the tracking error. For a 12 inch disc which starts at 145 mm and finishes at 60 mm the optimum distances are 120 mm and 65.6 mm.
Violent oscillations of the groove walls tend to throw the stylus out, so downward force is required to retain it. This must overcome the maximum acceleration (1000 g) of the stylus mass multiplied by a factor of 1.4 due to the 45 dedgree groove wall angle. So for a mass of 0.5 mg, a force of 0.5 x 1000 x 1.4 = 0.7 g is needed to equal the stylus force. As this must be overcome with a safety margin, plus allowance for mechanical resistance, arm friction and side-thrust, it must be multiplied further. A factor of x2 would be appropriate. Excessive weight causes wear on the groove walls, but insufficient weight is worse as the stylus can lose contact then scrape the wall when it re-connects. Weight should therefore be adjusted toward the upper limit of the maker' s specified range, but should not be exceeded.
Regions of the tape of specified width scanned by the tape heads.
A device that converts one form of energy into another form. A loudspeaker is an electro-acoustical transducer.
Any curve on a graph which is a plot of input vs. output.
Copying by re-recording on a different medium.
Component having two coils of wire, the primary and secondary, whose lengths (number of turns) are in a fixed ratio to permit voltages to be stepped up or down and circuit impedances to be matched for maximum power transfer.
A transformer used to match the impedance of one line or network with another.
1. An electrical surge. 2. A phenomenon which occurs during the change of a system from one steady state to another. 3. A relatively high amplitude, suddenly decaying. 4. peak signal level.
A measure of an audio system's ability to accurately reproduce transients.
Equipment for converting the audio-frequency electric currents corresponding to a program into a modulated carrier wave which can be radiated by an aerial.
In a tape recorder, the system of motors, tape guides, etc., used to move tape past the head assembly.
Convenient method of tabulating the output condition of a gate or system for every combination of inputs.
In a shelving equalizer, the frequency at which the equalizer begins to flatten out, or shelve. Defined as the frequency at which the level is 3 dB above (or below) the shelving level.
A high frequency loudspeaker.