The Phonograph reference article from the English Wikipedia on 24-Apr-2004
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Phonograph

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The phonograph, or gramophone, was the most common devices for playing recorded sound from the 1870s through the 1980s. Usage of these terms is somewhat different in British English and American English; see usage note below. In more modern usage, this device is often called the turntable or record player. In the late 19th and early 20th century, the alternative term talking machine was sometimes used. The phonograph was the first device for recording and replaying sound.

The term phonograph means "writing sound", a term coined from Greek roots. Similar related terms gramophone and graphophone mean the same thing. Arguably, any device used to record sound or reproduce recorded sound could be called a type of "phonograph", but in common practice it is usually only used to refer to certain historic technologies of sound recording.

Image:EdisonPhonograph.jpg
Edison cylinder phonograph from c. 1899

Table of contents
1 History
2 British and American language usage differences
3 Discs versus cylinders on the marketplace
4 The dominance of the disc phonograph
5 Turntable technology
6 The phonograph in the 21st century
7 External links

History

The earliest known invention of a phonographic recording device was the phonautograph, invented by Leon Scott and patented on March 25, 1857. It could transcribe sound to a visible medium, but it apparently had no means to play back the sound after it was recorded. The device consisted of a horn that focused sound waves onto a membrane to which a hog's bristle was attached, causing the bristle to move and enabling it to inscribe a visual medium. Initially, the phonautograph made recordings onto a lamp-blackened glass plate. A later version used a medium of lamp-blackened paper on a drum or cylinder—an arrangement to which Thomas Edison's later invention would bear striking resemblance.

Thomas Alva Edison announced his invention of the first phonograph, a device for recording and replaying sound, on November 21, 1877 and he demonstrated the device for the first time on November 29 (he patented it on February 19, 1878; US Pat. No. 200,521). Edison's early phonographs recorded on a cylinder using up-down (vertical) motion of the stylus. Edison's early patents show that he also considered that sound could also be recorded as a spiral on a disc, but Edison concentrated his efforts on cylinders, since the groove on the outside of a rotating cylinder provides a constant velocity to the stylus in the groove, which Edison considered more "scientifically correct". See also: phonograph cylinder

Emile Berliner invented what he called the Gramophone, another device for recording and replaying sound, and patented it in on November 8,1887 (US Pat. No 372,786). It recorded on a disk using side-to-side (lateral) motion of the stylus.

British and American language usage differences

In British English "gramophone" came to refer to any sound reproducing machine using disc records, as disc records were popularized in the UK by the Gramophone Company. The term "phonograph" is usually restricted to devices playing cylinder records

In American English, "phonograph" was the most common generic term for any early sound reproducing machine. Berliner's Gramophone was considered a type of phonograph. "Gramophone" was a brand name, and as such in the same category as "Victrola," "Zon-o-phone," and "Graphonola" referring to specific brands of sound reproducing machines.

The brand "Gramophone" was not used in the USA after 1901, and the word fell out of use there. In contemporary American usage "phonograph" most usually refers to disc record machines or turntables, the most common type of analogue recording from the 1910s on. The word has survived in America based on its nickname form, "Grammy", in the Grammy Awards.

Discs versus cylinders on the marketplace

Disc recording is inherently neither better nor worse than cylinder recording in potential audio fidelity. However Berliner's disc technique had commercial advantages over the Edison cylinder system:

After years of experimentation, in 1895 Berliner decided he had perfected his "gramophone" system to begin commercial production of his disc records and "gramophones" or "talking-machines" to play them on. These were the first analogue disc records to be offered to the public. From the mid 1890s until the late 1910s both phonograph cylinder and disc recordings and machines to play them on were widely mass marketed and sold. The disc system gradually became more popular due to its cheaper price and better marketing by disc record companies.

The dominance of the disc phonograph

Berliner's lateral disc record was the ancestor of the 78rpm, 45rpm, Long Play, and all other analogue disc records popular for use in sound recording through the 20th century. See analogue disc record and vinyl record.

The "phonograph", or "gramophone" or "turntable", remained a common element of home audio systems well after the introduction of other media such as audio tape and even the early years of the compact disc. They were not uncommon in home audio systems into the early 1990s.

Turntable technology

Drive systems: direct and belt

The technology of the modern turntable is generally very simple, with either belt drive or direct drive dominating. Earlier designs also used an indirect drive system using rubber-tyred wheels, but this fell out of favour since these have poor rumble performance. These systems generally used a synchronous motor which ran at a fixed speed, locked to the frequency of the mains supply. Different speeds were engaged by bringing different diameter transfer wheels into play between the motor and the platter.

The belt drive system improved on this by creating greater isolation between the motor and the platter, so the transfer of noise (usually heard as low frequency rumble) was much reduced. Since it is difficult to make synchronous motors to give multiple speeds, the use of DC motors gained favour, with additional electronics for speed control. On the most sophisticated designs, feedback from the platter itself, in the form of a series of pulses, was used to ensure that the speed of the platter remained locked and absolutely stable. (Many platters have a continuous series of reflective markings machined around their edge to provide these pulses). A drawback of basic DC motors is that of cogging, where the motor tends to rotate in steps rather than smoothly. This effect can be transmitted to the platter and hence add unwanted noise to the playback. Special motors such as those with helical armatures can be used to overcome this.

In a direct drive system, the motor drives the platter directly, without any intermediate wheels or belts. In fact, the platter itself can form part of the armature of the motor. This approach requires very careful and sophisticated design, with a considerable amount of electronics for starting and speed control. However, it has been made to work very successfully, and some of the most renowned designs use this approach.

Pickup systems

The other main area of interest is the arm and pickup. Early electronic turntables made use of a crystal or piezo-electric pickup, where the mechanical movement of the stylus in the groove applied pressure to a crystal of quartz, which generates an electrical voltage proportional to the applied pressure. Such crystal pickups are relatively robust, and yield a good level of signal which requires only a normal amount of amplification. The drawback of this approach is that the crystal's output tends not to be very linear, that is, it introduces unwanted distortion into the signal. In addition, it is difficult to make a crystal pickup suitable for stereo reproduction, and the close coupling between the crystal and the stylus leads to a certain degree of stiffness in the pickup which is detrimental to good reproduction. It also tends to increase wear on the record.

In all high-fidelity systems, the crystal pickup has been replaced by the magnetic cartridge. In this system, the stylus carries a tiny permanent magnet, which is positioned between a series of fixed coils. As the magnet moves in response to the mechanical stimulation of the grooves, it induces a tiny current in the coils. This signal is then fed to an amplifier. Because the magnet is so light, and is not coupled mechanically to the coils, the system follows the grooves far more faithfully and lightly. In addition, stereo reproduction is possible simply by suitable arrangement of the pickup coils, and the system has far lower distortion. There are two main drawbacks. One is that the signal level is very much lower than with a crystal pickup, requiring much greater amplification. This makes it more prone to noise such as thermal noise, and interference from external sources. Also, the magnetic induction approach means that the signal increases in level with increasing frequency, so low frequencies are attenuated, and frequency correction is required. Both of these problems are addressed using a special preamplifier that implements the RIAA equalization curve. Such preamplifiers were a standard part of most stereo systems sold prior to the dominance of the compact disk, which does not require this.

Arm systems

Arm technology has changed relatively little. Originally, even though the arm was light, the full weight of it rested on the record. With the early forms of pickup, right through to the crystal pickup, this was required to create sufficient tracking force to follow the grooves adequately with the relatively stiff styli. Naturally, record wear was not given great consideration. With the advent of the magnetic cartridge, far lighter tracking forces could be realised, and the balanced arm came into use. This uses a counterweight to offset the majority of the weight of the arm, and usually this incorporates a calibrated dial that allows a specific tracking weight to be dialled in. Weights of just 1 or 2 grams are typical. The arm itself still has to be reasonably light overall so that it does not create sideways drag on the record as the grooves spiral inward, and indeed most arms include a spring-loaded bias which attempts to offset this small force, so that the stylus itself is left with no net force on it. Many audiophiles subscribe to the view that the arm is the most important component of the transcription process, and will often pay a very high premium for top quality arms. One problem with a swinging arm is that it must necessarily present the stylus to the record at a slightly different angle as it sweeps across from beginning to end in an arc. This change in angle, albeit tiny, is claimed by many to have an audible effect. Simply making the arm longer so that the change in angle is minimised is the usual solution, but more a more radical approach is that of the linear tracking turntable. In this system, the arm is not pivoted at a fixed point, but travels along a track parallel to the diameter of the disc. The arm must be driven along the track by a motor, since the force available from the record itself would be insufficient. A servomechanism constantly tracks the required position of the arm, and drives it into position accordingly. Very sophisticated design is needed to make this work well, and to isolate the arm from extraneous noise caused by the tracking system. In practice the system was not widely used, and the very best audiophile turntables still generally use the simpler fixed arm approach.

Front-loading systems

A brief mention could be made of one attempt to make the use of records more convenient, in the dawning age of the compact disk. In the early 1980s, one manufacturer designed an upright (front loading) record playing stereo system, in which the record was placed in a door which hinged downwards to accept it. The door retracted automatically and the record was spun in the vertical plane. A pair of linear-tracking arms traversed the disk, one on each side, meaning that the whole record could be played without stopping and turning it over. The whole system was mechanically and electronically exceedingly complex, and while it worked, the system as a whole was aimed at the mass market and had only mediocre sound quality. The large physical size of the hinged door made it vulnerable to damage, and the retraction motor was barely able to lift its weight, especially after some years of use.

The phonograph in the 21st century

Phonographs or disc record turntables continue to be manufactured and sold into the 21st century, although in much smaller numbers.

Image:TurntablesWWOZ.jpg
Phonograph turntables at a radio station, 2003

Technics were largely responsible for the reinvention of turntables in the late 1960s when they created the first direct drive turntable, the SP-10. Turntables and vinyl records remain popular in techno music, where they allow great latitude for physical manipulation of the music by the DJ. The turntable is also useful in "scratching" in hip hop or rap music, though for recording use it has largely been replaced by the sampler (musical instrument).

The laser turntable - using a laser as the pickup, rather than a stylus in physical contact with the disc - was conceived of in the late 1980s, although the first examples were not of usable audio quality. Practical laser turntables are now being manufactured by ELPJ. They are favoured by record libraries and audiophiles.

Experimentation is in progress in retrieving the audio from a record by scanning the disc and analysing the scanned image, rather than using any sort of turntable, by Ofer Springer at the Hebrew University of Jerusalem.

See also: Audio signal processing, Sound recording, Sound reproduction, DJ.

External links