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 system used mainly on Motown inch singles released between and The introduction, drum-breaks, or choruses of a track were indicated by widely separated grooves, giving a visual cue to DJs mixing the records.
The appearance of these records is similar to an LP, but they only contain one track each side. The mids saw the introduction of dbx-encoded records, again for the audiophile niche market. ELPJ , a Japanese-based company, sells a laser turntable that uses a laser to read vinyl discs optically, without physical contact. The laser turntable eliminates record wear and the possibility of accidental scratches, which degrade the sound, but its expense limits use primarily to digital archiving of analog records, and the laser does not play back colored vinyl or picture discs.
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 attracts due to static electric charge is not mechanically pushed out of the groove, worsening sound quality in casual use compared to conventional stylus playback.
In some ways similar to the laser turntable is the IRENE scanning machine for disc records, which images with microphotography, invented by a team of physicists at Lawrence Berkeley Laboratories. In order to convert to a digital sound file, this is then played by a version of the same 'virtual stylus' program developed by the research team in real-time, converted to digital and, if desired, processed through sound-restoration programs.
Terms such as "long-play" LP and "extended-play" EP describe multi-track records that play much longer than the single-item-per-side records, which typically do not go much past four minutes per side. An LP can play for up to 30 minutes per side, though most played for about 22 minutes per side, bringing the total playing time of a typical LP recording to about forty-five minutes.
Many pre LPs, however, played for about 15 minutes per side. The term EP is still used for a release that is longer than a single but shorter than an album, even if it is not on vinyl format.
The usual diameters of the holes are 0. Many 7" singles pressed outside the US come with the smaller spindle hole size, and are occasionally pressed with notches to allow the center part to be "punched out" for playing on larger spindles. Sizes of records in the United States and the UK are generally measured in inches, e. LPs were inch records at first, but soon the inch size became by far the most common. Flexi discs were thin flexible records that were distributed with magazines and as promotional gifts from the s to the s.
This format was soon dropped as it became clear that the RCA 45 was the single of choice and the Columbia inch LP would be the album of choice. Most colors were soon dropped in favor of black because of production problems. However, yellow and deep red were continued until about Price, plant manager. In the s, the government of Bhutan produced now-collectible postage stamps on playable vinyl mini-discs. The normal commercial disc is engraved with two sound-bearing concentric spiral grooves, one on each side, running from the outside edge towards the center.
The last part of the spiral meets an earlier part to form a circle. The sound is encoded by fine variations in the edges of the groove that cause a stylus needle placed in it to vibrate at acoustic frequencies when the disc is rotated at the correct speed. Generally, the outer and inner parts of the groove bear no intended sound exceptions include the Beatles ' Sgt.
Increasingly from the early 20th century,  and almost exclusively since the s, both sides of the record have been used to carry the grooves. Occasional records have been issued since then with a recording on only one side.
The coloring material used to blacken the transparent PVC plastic mix is carbon black , which increases the strength of the disc and makes it opaque. Some records are pressed on colored vinyl or with paper pictures embedded in them "picture discs".
During the s there was a trend for releasing singles on colored vinyl—sometimes with large inserts that could be used as posters. This trend has been revived recently with 7-inch singles. Records made in other countries are standardized by different organizations, but are very similar in size.
The stylus is lowered onto the lead-in, without damaging the recorded section of the groove. This space is clearly visible, making it easy to find a particular track. Towards the center, at the end of the groove, there is another wide-pitched section known as the lead-out. At the very end of this section the groove joins itself to form a complete circle, called the lock groove ; when the stylus reaches this point, it circles repeatedly until lifted from the record.
On some recordings for example Sgt. Automatic turntables rely on the position or angular velocity of the arm, as it reaches the wider spacing in the groove, to trigger a mechanism that lifts the arm off the record. Precisely because of this mechanism, most automatic turntables are incapable of playing any audio in the lock groove, since they will lift the arm before it reaches that groove.
The catalog number and stamper ID is written or stamped in the space between the groove in the lead-out on the master disc, resulting in visible recessed writing on the final version of a record. Sometimes the cutting engineer might add handwritten comments or their signature, if they are particularly pleased with the quality of the cut. These are generally referred to as "run-out etchings". When auto-changing turntables were commonplace, records were typically pressed with a raised or ridged outer edge and a raised label area, allowing records to be stacked onto each other without the delicate grooves coming into contact, reducing the risk of damage.
Auto-changers included a mechanism to support a stack of several records above the turntable itself, dropping them one at a time onto the active turntable to be played in order. Many longer sound recordings, such as complete operas, were interleaved across several inch or inch discs for use with auto-changing mechanisms, so that the first disk of a three-disk recording would carry sides 1 and 6 of the program, while the second disk would carry sides 2 and 5, and the third, sides 3 and 4, allowing sides 1, 2, and 3 to be played automatically; then the whole stack reversed to play sides 4, 5, and 6.
The sound quality and durability of vinyl records is highly dependent on the quality of the vinyl. During the early s, as a cost-cutting move, much of the industry began reducing the thickness and quality of vinyl used in mass-market manufacturing. Many collectors prefer to have heavyweight vinyl albums, which have been reported to have better sound than normal vinyl because of their higher tolerance against deformation caused by normal play.
Manufacturing processes are identical regardless of weight. In fact, pressing lightweight records requires more care. This flaw causes a grinding or scratching sound at the non-fill point.
Virgin vinyl means that the album is not from recycled plastic, and will theoretically be devoid of these impurities. In practice, this depends on the manufacturer's quality control.
The " orange peel " effect on vinyl records is caused by worn molds. Rather than having the proper mirror-like finish, the surface of the record will have a texture that looks like orange peel. This introduces noise into the record, particularly in the lower frequency range. With direct metal mastering DMM , the master disc is cut on a copper-coated disc, which can also have a minor "orange peel" effect on the disc itself. As this "orange peel" originates in the master rather than being introduced in the pressing stage, there is no ill effect as there is no physical distortion of the groove.
Original master discs are created by lathe-cutting: a lathe is used to cut a modulated groove into a blank record. The blank records for cutting used to be cooked up, as needed, by the cutting engineer, using what Robert K. Morrison describes as a "metallic soap", containing lead litharge, ozokerite, barium sulfate, montan wax, stearin and paraffin, among other ingredients. Cut "wax" sound discs would be placed in a vacuum chamber and gold-sputtered to make them electrically conductive for use as mandrels in an electroforming bath, where pressing stamper parts were made.
Later, the French company Pyral invented a ready-made blank disc having a thin nitro-cellulose lacquer coating approximately 7 mils thickness on both sides that was applied to an aluminum substrate. Lacquer cuts result in an immediately playable, or processable, master record. If vinyl pressings are wanted, the still-unplayed sound disc is used as a mandrel for electroforming nickel records that are used for manufacturing pressing stampers. The electroformed nickel records are mechanically separated from their respective mandrels.
This is done with relative ease because no actual "plating" of the mandrel occurs in the type of electrodeposition known as electroforming, unlike with electroplating, in which the adhesion of the new phase of metal is chemical and relatively permanent. The one-molecule-thick coating of silver that was sprayed onto the processed lacquer sound disc in order to make its surface electrically conductive reverse-plates onto the nickel record's face.
This negative impression disc having ridges in place of grooves is known as a nickel master, "matrix" or "father". The "father" is then used as a mandrel to electroform a positive disc known as a "mother". Many mothers can be grown on a single "father" before ridges deteriorate beyond effective use. The "mothers" are then used as mandrels for electroforming more negative discs known as "sons".
Each "mother" can be used to make many "sons" before deteriorating. The "sons" are then converted into "stampers" by center-punching a spindle hole which was lost from the lacquer sound disc during initial electroforming of the "father" , and by custom-forming the target pressing profile. This allows them to be placed in the dies of the target make and model record press and, by center-roughing, to facilitate the adhesion of the label, which gets stuck onto the vinyl pressing without any glue.
In this way, several million vinyl discs can be produced from a single lacquer sound disc. When only a few hundred discs are required, instead of electroforming a "son" for each side , the "father" is removed of its silver and converted into a stamper.
Production by this latter method, known as the "two-step process" as it does not entail creation of "sons" but does involve creation of "mothers", which are used for test playing and kept as "safeties" for electroforming future "sons" is limited to a few hundred vinyl pressings.
The pressing count can increase if the stamper holds out and the quality of the vinyl is high. The "sons" made during a "three-step" electroforming make better stampers since they don't require silver removal which reduces some high fidelity because of etching erasing part of the smallest groove modulations and also because they have a stronger metal structure than "fathers". Shellac 78s are fragile, and must be handled carefully. In the event of a 78 breaking, the pieces might remain loosely connected by the label and still be playable if the label holds them together, although there is a loud pop with each pass over the crack, and breaking of the stylus is likely.
Breakage was very common in the shellac era. He wanted to cry but could not. Salinger 's novel The Catcher in the Rye occurs after the adolescent protagonist buys a record for his younger sister but drops it and "it broke into pieces I damn-near cried, it made me feel so terrible. Another problem with shellac was that the size of the disks tended to be larger because it was limited to 80— groove walls per inch before the risk of groove collapse became too high, whereas vinyl could have up to groove walls per inch.
By the time World War II began, major labels were experimenting with laminated records. As stated above, and in several record advertisements of the period, the materials that make for a quiet surface shellac are notoriously weak and fragile. Conversely the materials that make for a strong disc cardboard and other fiber products are not those known for allowing a quiet noise-free surface. Although vinyl records are strong and don't break easily, they scratch due to its soft material sometimes resulting in ruining the record.
Vinyl readily acquires a static charge, attracting dust that is difficult to remove completely. Dust and scratches cause audio clicks and pops. In extreme cases, they can cause the needle to skip over a series of grooves, or worse yet, cause the needle to skip backwards, creating a "locked groove" that repeats over and over.
This is the origin of the phrase " like a broken record " or "like a scratched record", which is often used to describe a person or thing that continually repeats itself. Locked grooves are not uncommon and were even heard occasionally in radio broadcasts. Vinyl records can be warped by heat , improper storage, exposure to sunlight, or manufacturing defects such as excessively tight plastic shrinkwrap on the album cover.
A small degree of warp was common, and allowing for it was part of the art of turntable and tonearm design. Standard practice for LPs was to place the LP in a paper or plastic inner cover.
This, if placed within the outer cardboard cover so that the opening was entirely within the outer cover, was said to reduce ingress of dust onto the record surface. Singles, with rare exceptions, had simple paper covers with no inner cover. A further limitation of the gramophone record is that fidelity steadily declines as playback progresses; there is more vinyl per second available for fine reproduction of high frequencies at the large-diameter beginning of the groove than exist at the smaller-diameters close to the end of the side.
Another problem arises because of the geometry of the tonearm. Master recordings are cut on a recording lathe where a sapphire stylus moves radially across the blank, suspended on a straight track and driven by a lead screw.
Most turntables use a pivoting tonearm, introducing side forces and pitch and azimuth errors, and thus distortion in the playback signal. Various mechanisms were devised in attempts to compensate, with varying degrees of success. See more at phonograph. There is controversy about the relative quality of CD sound and LP sound when the latter is heard under the very best conditions see Analog vs.
It is notable, however, that one technical advantage with vinyl compared to the optical CD is that if correctly handled and stored, the vinyl record will be playable for decades and possibly centuries,  which is longer than some versions of the optical CD. Guidelines for proper vinyl storage include not stacking records on top of each other, avoiding heat or direct sunlight and placing them in a temperature controlled area which will help prevent vinyl records from warping and scratching.
Collectors store their records in a variety of boxes, cubes, shelves and racks. Even so, these early electronically recorded records used the exponential-horn phonograph see Orthophonic Victrola for reproduction. CD-4 LPs contain two sub-carriers, one in the left groove wall and one in the right groove wall. CD-4 sub-carriers could be played with any type stylus as long as the pickup cartridge had CD-4 frequency response.
The recommended stylus for CD-4 as well as regular stereo records was a line contact or Shibata type. Equipment of modest quality is relatively unaffected by these issues, as the amplifier and speaker will not reproduce such low frequencies, but high-fidelity turntable assemblies need careful design to minimize audible rumble. Tonearm skating forces and other perturbations are also picked up by the stylus. This is a form of frequency multiplexing as the control signal restoring force used to keep the stylus in the groove is carried by the same mechanism as the sound itself.
High fidelity sound equipment can reproduce tracking noise and rumble. During a quiet passage, woofer speaker cones can sometimes be seen to vibrate with the subsonic tracking of the stylus, at frequencies as low as just above 0. Another reason for very low frequency material can be a warped disk: its undulations produce frequencies of only a few hertz and present day amplifiers have large power bandwidths.
For this reason, many stereo receivers contained a switchable subsonic filter. Some subsonic content is directly out of phase in each channel. If played back on a mono subwoofer system, the noise will cancel, significantly reducing the amount of rumble that is reproduced. High frequency hiss is generated as the stylus rubs against the vinyl, and dirt and dust on the vinyl produces popping and ticking sounds. The latter can be reduced somewhat by cleaning the record before playback.
Due to recording mastering and manufacturing limitations, both high and low frequencies were removed from the first recorded signals by various formulae. With low frequencies, the stylus must swing a long way from side to side, requiring the groove to be wide, taking up more space and limiting the playing time of the record.
At high frequencies, hiss, pops, and ticks are significant. These problems can be reduced by using equalization to an agreed standard.
During recording the amplitude of low frequencies is reduced, thus reducing the groove width required, and the amplitude at high frequencies is increased.
The playback equipment boosts bass and cuts treble so as to restore the tonal balance in the original signal; this also reduces the high frequency noise. Thus more music will fit on the record, and noise is reduced. The current standard is called RIAA equalization. It was agreed upon in and implemented in the United States in ; it was not widely used in other countries until the s. Before that, especially from , some different formulae were used by the record manufacturers.
In Joseph P. Maxwell and Henry C. Harrison from Bell Telephone Laboratories disclosed that the recording pattern of the Western Electric "rubber line" magnetic disc cutter had a constant velocity characteristic. This meant that as frequency increased in the treble, recording amplitude decreased. Conversely, in the bass as frequency decreased, recording amplitude increased. Otherwise, bass modulation became excessive and overcutting took place into the next record groove.
When played back electrically with a magnetic pickup having a smooth response in the bass region, a complementary boost in amplitude at the bass turnover point was necessary. Miller in reported that when complementary boost at the turnover point was used in radio broadcasts of records, the reproduction was more realistic and many of the musical instruments stood out in their true form. West in and later P. This meant that the electrical recording characteristics of Western Electric licensees such as Columbia Records and Victor Talking Machine Company in the era had a higher amplitude in the midrange region.
Brilliance such as this compensated for dullness in many early magnetic pickups having drooping midrange and treble response. Over the years a variety of record equalization practices emerged and there was no industry standard. Evidence from the early technical literature concerning electrical recording suggests that it wasn't until the — period that there were serious efforts to standardize recording characteristics within an industry. The atomic mass of an atom is usually within 0.
The number of protons an atom has determines what element it is. However, most elements in nature consist of atoms with different numbers of neutrons. Both isotopes of chlorine have 17 protons, but chlorine has 20 neutrons, 2 more neutrons than chlorine, which has In the case of chlorine, chlorine has a mass of around 35 u, and chlorine around 37 u. As mentioned above, note that the atomic mass of an atom is not the same as its mass number. The mass number symbol: A of an atom is the sum of the number of protons and the number of neutrons in the nucleus.
The following equation:. Since counting individual atoms or molecules is a little difficult, quantitative aspects of chemistry rely on knowing the masses of the compounds involved. Atoms of different elements have different masses. Early work on the separation of water into its constituent elements hydrogen and oxygen indicated that grams of water contained Later, scientists discovered that water was composed of two atoms of hydrogen for each atom of oxygen.
Therefore, in the above analysis, in the Therefore, an oxygen atom must weigh about 16 times as much as a hydrogen atom:. Hydrogen, the lightest element, was assigned a relative mass of '1', and the other elements were assigned 'atomic masses' relative to this value for hydrogen.
Thus, oxygen was assigned an atomic mass of We now know that a hydrogen atom has a mass of 1. As we saw earlier, it is convenient to use a reference unit when dealing with such small numbers: the atomic mass unit. Thus, the mass of the hydrogen atom 1 H is 1. Once the masses of atoms were determined, the amu could be assigned an actual value:.
Although the masses of the electron, the proton, and the neutron are known to a high degree of precision Table 2. For example, the ratio of the masses of 1 H hydrogen and 2 H deuterium is actually 0. Notify me of new comments via email.
Notify me of new posts via email. Homework for this evening: Read Lesson 12 in the textbook. Remember to include the dash between s and. Password: S- the S must be capitalized Work through the homework problems at the end of Lesson 12 and then verify accuracy with the Lesson 12 Homework Answers.
Come to class tomorrow prepared to ask questions about anything of the homework problems from lesson 12 you did not understand.British guitarist Allan Holdsworth’s album has only ever been reissued on vinyl as part of a limited edition 12 LP until now. The bonus track on this RSD release has never been on vinyl before. SIDE 1: 1. “Three Sheets To The Wind” 2. “Road Games” 3. Water On The Brain” SIDE 2: 1. “Tokyo Dream” 2. “Was There?” 3.