They settled on the average or possibly the median of these tests, which turned out to be 78 rpm. Other companies adopted this, but the process was not complete until the early s. After standardization problems still occurred. Because of electrical mains frequencies differences on opposite sides of the Atlantic, stroboscopic speed testers and synchronous motors meant a nominal speed of These were later fixed in national but not international standards.
A inch 78 with Berliner-type grooves could hold between 4 and 5 minutes per side. The first practical sound films produced in the US in the late s had their sound on separate disc records and it was more important for the sound to be continuous. A reel of film might run for 11 minutes, so a rotational speed of about 32 rpm was required to make the sound match the picture. It seems CBS engineers who developed the first LPs in , simply experimented with one of the old machines hanging around in their workshop.
They then developed new groove dimensions which gave an acceptable signal-to-noise ratio with the new plastic material "vinyl". The 45 rpm speed was the only one to be decided by a precise optimization procedure by RCA Victor in Calculus was used to show that the optimum use of a disc record of constant rotational speed occurs when the innermost recorded diameter is half the outermost recorded diameter.
Given the CBS vinyl groove dimensions and certain assumptions about the bandwidth and tolerable distortion, a speed of 45 rpm comes out of the formula.
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The standard of 78 rpm arrived by default, although the actual speed depended on the electrical mains frequency. Constant linear speed, or varying the rpm, was commercialized but did not prove to be a success until the arrival of the CD. Maxfield of Bell Laboratories for sound films produced on the Vitaphone system.
And it was a professional de facto standard before it became commercialized by CBS in The 7-inch discs lasted a minute or so and had low sound quality. Berliner and his assistant Fred Gaisberg realized that unless the speed was governed, the gramophone would never be more than a novelty. Gaisberg visited a young mechanic who was making clockwork machinery in hoping to use it for sewing machines.
This machinery was never successful in sewing machines, but was ideal for gramophones, and it rotated at 78 rpm. The mechanic, Eldridge Johnson, became a millionaire. Columbia made all its discs to run at 80 and HMV had its pioneer recordings produced between 68 and 92 rpm with the key of the piece marked on the label. You then tuned it on your own piano, using the gramophone's governor.
These speeds all gradually settled into the standard of In parts of the world that used 50 Hz current, the standard was Thus these records became known as 78s or "seventy-eights". This term did not come into use until after World War II when a need developed to distinguish the 78 from other newer disc record formats, an example of a retronym.
Earlier they were just called records, or when there was a need to distinguish them from cylinders, disc records. Standard records was also used, although the same term had also been used earlier for two-minute cylinders.
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Columbia and RCA's competition extended to equipment. Some turntables included spindle size adapters, but other turntables required snap-in inserts like this one to adapt RCA's larger 45 rpm spindle size to the smaller spindle size available on nearly all turntables. After World War II, two new competing formats came on to the market and gradually replaced the standard "78": the 33?
The 33? RCA Victor developed the 45 rpm format and marketed it in , in response to Columbia.
Both types of new disc used narrower grooves, intended to be played with a smaller stylus—typically 0. In the mids all record companies agreed to a common recording standard called RIAA equalization. Prior to the establishment of the standard each company used its own preferred standard, requiring discriminating listeners to use preamplifier with multiple selectable equalization curves. A number of recordings were pressed at 16?
RPM, but these were mostly used for radio transcription discs or narrated publications for the blind and visually impaired, and were never widely commercially available, although it was still common to see turntables with a 16 RPM speed setting produced as late as the s. The older 78 music record format continued to be mass produced alongside the newer formats into the s, and in a few countries, such as India, into the s.
As late as the s, some children's records were released at the 78 rpm speed. For a two-year period from to , record companies and consumers faced uncertainty over which of these formats would ultimately prevail in what was known as the "War of the Speeds". Eventually the 12" mm 33? The 45 rpm discs typically emulated the playing time of the former 78 rpm discs, while the LP discs provided up to one half hour of time per side though typically 15 to 20 minutes.
The 45 rpm discs also came in a variety known as Extended play EP which achieved up to minutes play at the expense of attenuating and possibly compressing the sound to reduce the width required by the groove. From the mids through the s, in the U.
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The large center hole on 45s allows for easier handling by jukebox mechanisms. RCA 45s can also be adapted to the smaller spindle of an LP player with a plastic snap-in insert known as a "spider"; such inserts were prevalent starting in the s. While the stylus moves horizontally when reproducing a monophonic disc recording, on stereo music records the stylus moves vertically as well as horizontally. In the Westrex system, each channel drives the cutting head at a 45 degree angle to the vertical.
LP and 45 RPM Records
During playback the combined signal is sensed by a left channel coil mounted diagonally opposite the inner side of the groove, and a right channel coil mounted diagonally opposite the outer side of the groove. It is helpful to think of the combined stylus motion in terms of the vector sum and difference of the two stereo channels. A monophonic cartridge will reproduce an equal blend of the left and right channels instead of reproducing only one channel.
Conversely, a stereo cartridge reproduces the lateral grooves of monophonic recording equally through both channels, rather than one channel. EMI cut the first stereo test discs using the system in It was not used commercially until a quarter of a century later. Stereo sound provides a more natural listening experience where the spatial location of the source of a sound is, at least in part, reproduced. In Mercury began three-channel stereo recordings, still based on the principle of the single microphone. The center single microphone was of paramount importance, with the two side mics adding depth and space.
Record masters were cut directly from a three-track to two-track mixdown console, with all editing of the master tapes done on the original three-tracks. In Mercury enhanced this technique with three-microphone stereo recordings using 35mm magnetic film instead of half-inch tape for recording.
The greater thickness and width of 35mm magnetic film prevented tape layer print-through and pre-echo and gained extended frequency range and transient response. The Mercury Living Presence recordings were remastered to CD in the s by the original producer, using the same method of 3-to-2 mix directly to the master recorder. The development of quadraphonic music records was announced in These recorded four separate sound signals.
This was achieved on the two stereo channels by electronic matrixing, where the additional channels were combined into the main signal. When the records were played, phase-detection circuits in the amplifiers were able to decode the signals into four separate channels. They proved commercially unsuccessful, but were an important precursor to later "surround sound" systems, as seen in SACD and home cinema today. Typically the high frequency information inscribed onto these LPs wore off after only a few playings, and CD-4 was even less successful than the two matrixed formats.
In the late s and s, a method to improve the dynamic range of mass produced records involved highly advanced disc cutting equipment. Also in the late s, "direct-to-disc" records were produced, aimed at an audiophile niche market. These completely bypassed the use of magnetic tape in favor of a "purist" transcription directly to the master lacquer disc. Also during this period, "half-speed mastered" and "original master" records were released, using expensive state-of-the-art technology.
A further late s development was the Disco Eye-Cued TM system used mainly on Motown 12" singles released between and The introduction, drum-breaks or choruses of a track were indicated by widely separated grooves, giving a visual clue to DJs mixing the records. The appearance of these music records is similar to an LP, but they only contain one track each side.
The history and resurgence of vinyl records - Stevens Point News
The early s saw the introduction of "dbx-encoded" music records, again for the audiophile niche market. ELPJ, a Japanese-based company, has developed a player that uses a laser instead of a stylus to read vinyl discs. In theory the laser turntable eliminates the possibility of scratches and attendant degradation of the sound, but its expense limits use primarily to digital archiving of analog records.
Various other laser-based turntables were tried during the s, but while a laser reads the groove very accurately, since it does not touch the record, the dust that vinyl naturally attracts due to static charge is not cleaned from the groove, worsening sound quality in casual use compared to conventional stylus playback. The normal commercial disc is engraved with two sound bearing concentric spiral grooves, one on each side of the disc, running from the outside edge towards the centre.
Since the late s, both sides of the record have been used to carry the grooves. The recording is played back by rotating the disc clockwise at a constant rotational speed with a stylus needle placed in the groove, converting the vibrations of the stylus into an electric signal see magnetic cartridge , and sending this signal through an amplifier to loudspeakers. The majority of music records are pressed on black vinyl.
The colouring material used to blacken the transparent PVC plastic mix is carbon black, the generic name for the finely divided carbon particles produced by the incomplete burning of a mineral oil based hydrocarbon. Carbon black increases the strength of the disc and renders it opaque.
Some music records are pressed on coloured vinyl or with paper pictures embedded in them "picture discs". These discs can become collectors' items in some cases.
During the s there was a trend for releasing singles on coloured vinyl — sometimes with large inserts that could be used as posters. This trend has been revived recently and has succeeded in keeping 7" singles a viable format. The inch dimensions are nominal, not precise diameters. The actual dimension of a 12 inch record is mm Records made in other countries are standardized by different organizations, but are very similar in size. The record diameters are typically mm, mm and mm.
There is an area about 6 mm 0. This section allows the stylus to be dropped at the start of the record groove, without damaging the recorded section of the groove. Between each track on the recorded section of an LP record, there is usually a short gap of around 1 mm 0. This space is clearly visible, making it easy to find a particular track. Towards the label centre, at the end of the groove, there is another wide-pitched section known as the lead-out.