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A BRIEF HISTORY OF RECORDING
For the first 50 years of recorded sound, starting with Thomas Alva Edison’s playback of “Mary Had a Little Lamb,” all recordings were acoustic. Absolutely no electronic equipment was involved at any stage— unless you want to count in the light bulbs used to see what was going on. Recording relied entirely on the acoustic energy of a performer’s voice or musical instrument going directly into the microphone. One lone microphone, responding to this very close voice or instrument, caused a stylus to etch the physical track of the sound waves directly onto a hard wax record as the performance was actually occurring. Back then, all recordings occurred only in real time. Performers had to play vigorously or sing directly into the microphone to be loud enough to make the recording—hence the numerous operatic recordings from that time.
Because there was no electronic amplification, much instrumental music could not be recorded and symphonic music was out of the question, as the instruments could not all be crowded close enough around the lone mike. Unique instruments that have never been heard from since were specially created during this brief era just to provide accompaniment to voices. Playback volume depended on the power of the performer’s voice or instrument, as well as on the type of playback needle used (cactus provided less volume than steel), and on whether the doors of the Gramophone cabinet were left open or closed.
This was truly direct-to-disc recording (tape did not exist) because the discs or wax cylinders being engraved with the performance could not be duplicated—each record was unique, like an original handwritten manuscript. Duplication of a very limited sort was achieved by setting up a battery of recording machines, as many as 20 at a time, each with its immense horn pointing at the performer. Of course, the nearer horns produced the better records. Recording artists often had to repeat the same performance 60 times a day to meet demand.
If a performer made a mistake, that mistake (if not too gross) remained recorded for posterity. Nowadays musicians, having grown up with tape recording, assume a recorded performance must be “perfect”—unlike a live performance. A flaw on a recording that one anticipates and waits for each time the recording is played can be potentially annoying, but on the other hand, the degradation in sound quality as bits of tape are dubbed and spliced and remixed is also irritating, as are the sometimes rather sterile or mechanical performances that can also result.
From the time of Edison’s first experimental talking machine in 1877 to the turn of the century, the “recording industry” flourished. But competition and rivalry also flourished, with Emile Berliner’s disc and Edison’s cylinder presenting alternative methods of recording and playback, each with advantages and each produced by a company holding patents that left the other without some element necessary to improve its product. In 1901, the rivalry reached a head—the entire industry was shut down by the courts and all recording ceased. In 1902, the major interests arranged an agreement pooling the patents. The advantages of the disc were combined with the advantages of the cylinder’s engraving process and literally millions of records were sold over the next 20-odd years—until the arrival of radio, which nearly killed off the phonograph but which also provided its means of survival.
In 1925, electronically amplified recordings were introduced, with characteristic hoopla and overblown claims. In acoustic recording, the microphone mechanically controlled a cutting stylus. But in electronic recording, the mike converted the energy of the airwaves into a minute electric current. This tiny electrical signal was then electronically amplified many thousands of times to control a cutting head, which, just as in the earlier acoustic method, etched a physical representation of the sound waves directly into a hard wax platter. Here again, the recording process had to take place while the performance was actually occur ring—direct to disc. There was no convenient way to make a test recording first, listen to it, and make revisions before doing the “real take.”
These electronic recordings were made possible through the development of a unique amplification devise: the vacuum tube, or valve as the English call it, developed earlier in the century for radio amplification. A tiny electric current fed into the tube could be made to control a much larger current that would take on the pattern of the smaller. Now, instead of requiring performers to stand close to the mike and sing loudly or play directly into it, recordings could be made from a distance and capture quieter sounds. Fidelity was greatly improved. In addition, by removing major sections of the recording and playback process from mechanical form into the electrical form of vibration, electronic techniques avoided many of the distortions of forced mechanical vibration. With no mass or weight or substance, electricity could respond extremely accurately to the mechanical signals of the mike and record groove. Electronic recording and playback unfortunately also introduced four new sources of distortion in the form of transducers—the mike, cutting head, playback cartridge, and speakers. All recordings still remained direct to disc until after World War II.
During the 1930s, a heated controversy developed over which was preferable, the single-mike technique, which some considered gave the most natural results, or the use of several mikes set up around the orchestra and singer, their electrical output then mixed together before being fed to the cutting head. This controversy has never been effectively settled and is still being actively debated today. Curiously, the advent of digital recording may settle this debate—it is being found that simpler miking techniques produce better results.
The next revolution came with the ability to record onto tape and then transfer the taped performance onto a disc. Developed by the Ger mans during World War II to facilitate propaganda, tape recorders had advantages that were quickly recognized and seized upon by recording studios. Tape recorders rapidly replaced direct-to-disc cutting equipment after the war. The great advantage of tape was that it was a semi-permanent storage medium that could be replayed immediately without damage and could be readily cut and edited. This opened up enormous versatility. Instead of having to be satisfied with choosing from among at most a few takes of a performance, which were all that were normally commercially feasible on direct to disc, now engineers found that many experimental takes could be run on tape, listened to, altered slightly, and done again. The engineer could even take parts from one tape and splice them together with the good parts from another tape, creating a composite of the best of several versions of the performance.
Two-track recording equipment was introduced in the 1950s, and so stereo recording, which had already been partly worked out back in the 1930s, now became commercially feasible. Multitrack arrived in the early 1 960s with the introduction of three and four-track machines capable of “sync” recording, meaning that as the tape was played back, a new track of music could be recorded alongside it. Eight-, 16-, and 24-track recorders followed. Forty-six tracks can be created by bridging two 24-track machines together, using 1 track from each for the bridging. And so today we have the Cuisinart approach to recording.
Digital recording and playback methods were pushed to center stage with the introduction of the compact disc in 1982—1983. Digital sound has been steadily improving since then, but some would say it’s only improved from the unbearable to the tolerable; others feel it’s a distinct improvement over what they’re used to hearing. That may sum it up best, for now at least—digital is an improvement over much run-of-the- mill mid-fl equipment but not as yet an overall improvement over really good analog, though some CD players are beginning to be able to compete with some high-end systems.
All recording is inherently imperfect—in that none perfectly captures reality—and each form of recording, from 78s to CDs, has had its different imperfections. It is a question of which imperfections are preferred and what other tradeoffs and compromises are required.
A breakthrough occurred in digital techniques in 1986, one just as important as the development of digital itself—it was shown that digital could sound good, good enough even to compare with analog.
This advance came not from the research labs of Sony or Philips but, in the tradition of most significant audio developments, from the small labs of audio designers whose pursuit of technology is guided by their passion for music.
However, and this must be stressed, the work done by Theta, Distech, Mod Squad, CAL, and a few others has as yet been incorporated into very few CD players. For the moment, unless you buy one of the few high-end players, analog remains the preferred recording/playback medium for music.
The introduction of digital is comparable to other historic changes in recording techniques: the switchover from acoustic to electric recording in the late 1920s, the postwar change from 78s to 33 1/3 microgroove, the conversion from mono to stereo in the 1950s. At all these points (as well as the introduction of the tape recorder, solid state, and multi- track,), the reception has been divided—one group recognizing the very real losses incurred by the new technology, another group hailing its benefits and overlooking the drawbacks. Each new format is proclaimed by some to be “indistinguishable” from the live performance. This began with Edison’s recording of “Mary Had a Little Lamb” and continues to this day with digital. For all the advantages of each new format, there have also been definite tradeoffs.
A new technology is not ipso facto better than the now “old-fashioned” technology. Digital is a major change but it is not, or certainly not as yet, necessarily a change for the better in terms of music. It is natural that listeners admire all the things the new medium does better than the old. And, initially at least, they pay little attention to those areas where the new technology is less good than the old because they take for granted from long experience with the old that these aspects are OK. It takes some listening time to adjust the ears and recognize that while the new does offer advantages, there are also disadvantages com pared to what came before. Digital, whether better or worse than analog, is just another way to make a recording.
Digital sound, as currently available, presents a different mix of strengths and weaknesses than analog. The important issue is to com pare and balance these strengths and weaknesses. Instead, the common attitude has been to proclaim digital obviously superior to analog simply because it is superior in certain areas where analog is relatively weak, while minimizing or ignoring those areas in which digital is inferior to analog’s many strengths. It is important to identify what you want and should expect from recorded sound—if you’ve never heard a good analog recording played back on a good system, you may be easily impressed by digital sound, just as you can be impressed by a “frozen gourmet entrée” if you’ve never enjoyed the taste of a well-prepared meal.
It would have been informative, when first digital came out, if LPs had been released in both the digital and analog formats to demonstrate the clear superiority of digital—a method of demonstration used effectively during the switchover from mono. Audiophiles urged this, but unfortunately it was not done.
The trouble is that digital is being sold to the public not for what it actually is but for its highly promoted name. Sooner or later, people catch on that all is not as it’s being represented, and there may be a backlash against a fashion that claims more than it delivers.
Take the proclamation “Perfect sound forever.” Now consider that in the four years following the CD’s introduction in late 1982, the players have gone through a number of different generations (is perfection perfectible?) and that all players sound different. There’s a mismatch there somewhere between promise and reality.
However, the work of Mike Moffat (Theta) and others has demonstrated that digital has a sonic as well as a commercial future. If Sony and Philips had had more interest in quality sound, then instead of costing the CD its credibility among high-end listeners, they could have done a lot better than the mass-fl results that they labeled “perfection” in a classic rerun of the emperor’s new clothes.
Digital recording is based on a theorem developed by Harry Nyquist in the 1920s, which states that if two points on a wave form are identified, then the wave’s entire shape can be defined. This theorem in turn is based on theories developed by an 18th-century French physicist and politician, Jean Baptiste Fourier. Digital was first commercially used in 1978 to produce digitally recorded LPs. In 1982 - 1983, the compact disc was released by Sony and Philips, giving digital its own unique format.
For the past 100 years of recorded sound, sound waves have been stored in their “natural” analog form. In digital recording, by means of an analog-to-digital converter inserted between the live sound source and the recording tape recorder, the music is converted from its normal analog wave form into a series of digital numbers. This circuit takes a series of “sonic snapshots” of the audio signal—about 44,000 times per second—which are then translated into a binary code of 1’s and 0’s. Sampling of the wave form occurs at a frequency—44. 1 kHz—roughly twice that of the highest audio frequency recorded, to ensure each wave form is sampled at two points. It is this code of binary numbers and not the original wave form that is preserved on tape and then encoded as microscopic pits and smooth places on a compact disc.
In order to be made audible again, the code numbers must be converted back into analog during playback. The numbers instruct the CD player’s digital-to-analog decoder how to “reconstruct” the encoded sound. Unlike analog, the sound one hears is not what is on the tape itself (if this were so, all one heard would be electronic gibberish) but is the synthetic result of the D-to-A circuitry carrying out the encoded instructions.
The chain from live analog music to digital encoding and back again to analog is immensely complex. Nearly all of it involves new or recent technology and there are numerous opportunities for things to go wrong.
As it stands, no evidence has yet come to light either that digital is inherently unsuited for music recording or that it will be superior to analog. It is simply another approach that, while the technology is so new, offers at least as many problems as advantages. The technology is still not fully understood even by those whose job it is to use it.
Digital is promoted as an excellent storage medium because it’s so stable. Once whatever’s being recorded has been converted into numbers, those numbers remain unchanged until they need to be converted back into their original form. At least in theory, a number recorded onto tape is not subject to the same degradation as an analog signal recorded onto tape. In practice, this does, not appear to be the case. Engineers and designers have heard degradation from one generation to the next. In addition, the digital master tapes store far less well than analog master tapes and, for safety, need to be copied over every year. If sonic degradation occurs between generations, as has been heard, this is not an encouraging prospect.
Digital in theory also benefits by eliminating two of the transduction points required with analog—the playback cartridge and the cutting lathe’s cutting head. Wherever energy is converted from one form to another (for example, the cartridge transduces the mechanical energy of the LP groove into electrical energy) there is a major source of distortion, so reducing the number of transduction points is a clear advantage. On the other hand, as there are no digital recording microphones or digital speakers, the conversion of the live analog waveform into digital at the recording session, and then back again to analog during playback, introduces an entirely new realm of sonic problems.
It becomes irrelevant that the numbers can’t be distorted during recording and reproduction, or that extraneous noise is greatly reduced (the CD’s vaunted silent background), if the digital recording process captures only an approximation of the music signal and then plays back another “approximation” of the analog music signal. One of the more disturbing aspects of digital sound is that quiet musical passages in dig ital are the most distorted, while the loud ones are very clean. This is the direct opposite of analog and has made a large contribution to the CD’s reputation. Analog is quiet in the soft passages, where distortion is actually most disturbing, but more distorted in loud passages, where the distortion is less harmful to the music.
Analog is an open-ended format—its limitations are basically those of the recording and playback equipment and of the artistry of the recording engineers. Those old recordings from the 1950s, so well regarded then, still challenge most recordings made today.
Digital, on the other hand, is a closed format, limited not just by the equipment and recording artistry but also by the format itself. A standard of limited resolution was designed into the digital medium and internationally agreed upon. (Such industry-wide agreement is in itself remarkable. The last time that occurred was when the LP’s RIAA standard was finally established back in 1953 after years when each recording company used its own individual standard. The previous industry- wide agreement was back in 1902, when the flat LP was chosen over the cylinder.) The limits set by digital are permanent, whereas better playback of an analog recording will reveal more of the information contained in the recording. While it is true that digital playback systems are improving, there is a limit to how much “more” is available to be revealed on a digital recording—as the old saying goes, the numbers tell it all.
The present digital format could be improved by raising the sampling standard. In fact, this has already been done since digital’s introduction—it’s been raised from a 14- to a 16-bit sampling rate and oversampling has been introduced. Unfortunately, those recordings made under the old standard cannot be improved or upgraded to the new one. So those who sang their hearts out on. 14 bits are going to stay entombed there. What’s criminal is that great art is being recorded for history using a medium that is still incompletely developed, when an excellent recording medium exists in analog. Nonetheless, digital recording has taken over much of audio, at least among the big labels. No major orchestra now has a long-term analog recording contract. No major label is now releasing new recordings in anything other than digital.
Digital has also been steadily improving since its commercial release, in terms of both the recordings and the compact disc players. We hope this improvement will continue until digital is truly as good as or (could it be?) even better than analog. We hope digital will not rest on its commercial success and accept the popular response of “good” to mean “good enough.”
THE RECORDING CHAIN
Recording and playback are mirror images, with the recording itself representing the plane of the mirror. The scale of the music signal ranges from full-size at the live performance to not quite life-size coming out of the speakers. In between, it is microsonic. The goal is to “unrecord” the recording so as to gain the illusion that the original live performance is occurring in your living room.
The acoustic energy produced by the performer’s voice and/or instrument is converted by the microphone into electrical energy that can be used by the engineer in the control room. The mike’s diaphragm, as it vibrates in response to the sound waves, produces a variable voltage. This is the reverse of the playback speakers, in which the speaker diaphragms vibrate in response to a variable current from the amp, and produce in turn acoustic energy analogous to the sound waves of the original live performance.
The mixing console usually comes between the mike and tape recorder so the engineer can fiddle with the sound before it’s laid down on the master tape. The signal may pass through the mixing console more than once. Here the sound is equalized or “EQed,” which achieves the engineer’s desired balance in the frequency spectrum, increases or decreases the presence of certain bands, and alters the output or gain. The signal also travels through mixers, faders, compressors, limiters, reverb, overdubbing, remixing; is sliced, diced, and otherwise reconstituted—all with the goal of “improving” the sound.
In minimalist recordings, the mixing console may be totally eliminated, the sound being recorded straight onto the tape, or at least the mixing console is put to minimal use. Often, the studio’s “monster” is replaced by a portable “mike mixer,” which is a simple mike preamp with minimal EQ. In direct-to-disc recording, the sound goes directly to the master disc, eliminating even the tape stage.
The tape mix (except in the case of direct-to-disc) that is finally approved by the engineers, producers, and anyone else involved is called the master tape. From this master tape is made the reproduction master; and from this, copies are made by the thousands. This sequence of steps is essentially the same for LPs, CDs, and cassette tapes.
Since the ascendance of digital and the compact disc, many people have mistakenly come to believe the LP is the equivalent of the dodo. Unwittingly, they are blaming the faults of their playable equipment on the record. Ignorant of how to select and correctly set up a good “record player,” most people never hear the extraordinary amount of detail waiting to be revealed on an LP.
Ironically, despite its mass-market decline the LP is steadily gaining new status beyond connoisseur circles as more thoughtful listeners begin to compare carefully the sonic qualities of CD and LP. Many are opting for the musical strengths of the LP over the strengths of the CD. (Digital LPs seem to combine the disadvantages of both worlds with the benefits of neither.)
In the earlier years of CDs, audio enthusiasts generally consigned it to the mid-fl regions, giving the analog LP unmistakable sonic top place. But as CDs improve their sonic quality in response to the com plaints of the audiophile community and as LPs improve their pressing quality in response to the CD “cleanness” challenge, the two may come to represent simply alternative media of comparable sonic worth. The main argument against this occurrence is a practical one: Neither retailer nor manufacturer will be eager to stock two inventories. One medium will almost assuredly have to eradicate the other, just as LPs wiped out 78s in a short time and stereo instantly antiquated mono.
A note of caution: In your first frenzy of excitement over CDs, do NOT dump your LPs. (Or if you must, please dump them into welcoming arms.) Even as the vinyl disc is superseded, the enormous and irreplaceable repertoire of artists and performances on LP will continue to be in high demand. Even if the analog recording is rereleased in digital, the sound of the digitally re-mastered recording can never be as good as in its original analog form.
The LP is also one of the more durable of storage media, contrary to its reputation. A CD even slightly damaged (which is far easier to do than has been advertised) loses large amounts of information, which, while covered over by the error correction circuit, results in very nasty distortions. Cassette tape fades, bleeds through, and generally deteriorates much faster than LPs. If the tape jams or breaks, as can happen quite easily, then the whole tape is unusable. LPs, in contrast, if scratched will make a nasty tick, but this lasts only a moment. If one side is seriously damaged in an accident, you still have the other side.
In order to reveal better all of the music on an LP — to be a better “unrecorder” — it helps to understand a little about how an LP is made. Recording techniques for the analog LP are essentially the same as for any other format. Whether an LP is manufactured from an analog or a digital tape, the production process is essentially identical. The only difference is that the digital tape must be retranslated by computer back into analog form before going to the cutting head.
The four steps of manufacturing that critically affect quality are (1) the disc cutting or lacquer mastering, (2) plating, also called matrixing, (3) pressing, and (4) packaging. Pressing and packaging are completed in the same facility; mastering and plating are often each performed by a separate company. -
The master tape represents the best the record can be—whether it sounds as if it were recorded on an answering machine or transports you to the original performance. Then each additional processing step adds its own layer of distortion.
The master disc, or master lacquer, is like the original engraving of the live music from which all the copies will be made. A separate master is made for each record side from the two-track stereo master tape (analog or digital). How many minutes of music to fit on each side is an important question. (Of course, in symphonic works, length of side is largely determined by where the music permits of a natural break.) In general, the wider the music’s dynamic range, the greater its bass, and the faster the tape-mastering speed, the more room the music will take up—and, in both cases, the less music will fit on a side.
Trying to squeeze in more music results in a clear degradation of sound quality—cramming the grooves closer together requires com pressing the dynamic range so the grooves can be narrower; and distortion increases the closer the grooves come to the spindle, called end of side, because cartridge/groove alignment becomes progressively worse toward the center. If the music stops some distance away from the spindle, i.e., if there’s a wide run-out of blank grooves, then the music will be subjected to less distortion. When buying a record, look for a total playing time for each side of about 20 minutes or less—this at least suggests some attention to good sound.
Incidentally, the numbers and letters you see engraved in the run- out next to the label are the matrix numbers assigned to the master tape for each side and used for identification throughout the manufacturing process.
To make the master lacquer, an aluminum disc prepared with a thick coating of lacquer is engraved by a cutting lathe with a physical analog of the original sound waves. The cutting lathe is like a big, extremely heavy-duty turntable. In fact, it’s the direct counterpart of your turntable at home, with the cutting head being the mirror image of the playback phono cartridge. Instead of following a groove and producing an electrical signal, as does the playback cartridge, the cutting head follows an electrical signal (from the master tape) and produces a physical groove. To more easily cut the continuous spiral groove into the disc in as, exact an analog of the live sound waves as attainable, the cutting stylus is heated.
Every motion of the cutting lathe head is guided by a special disc mastering console through which the master tape is played. The RIAA equalization (see below) and any special treatments such as noise reduction, equalization, speed alterations, and the amount of “land” or space between the grooves can all be specified at the console immediately before the cutting of the master lacquer. Wow, flutter, and rumble, if any of these problems are present in the cutting lathe, may be cut into the record right along with the music. Rumble from the lathe certainly can often be heard on a good playback system.
Quality recordings are mastered in “real time,” meaning the same length of time taken by the original musical performance is required to make the master. Speeding up the tape in order to hasten the mastering process makes production cheaper, but at a high cost in fidelity.
Some engineers can “read” the lacquers and tell the kind of music by the grooves’ width, depth, and pitch. You too can “read” the LP grooves at home and tell something about the quality of the mastering job before you ever hear the record. Large grooves indicate that the music was not unduly compressed in order to squeeze more onto each side—you can expect the dynamic range to be good. If the inner grooves, which are always more distorted, stop well away from the label leaving at the very least an inch of run-out, this also indicates mastering care. With a little observation and experimentation of your own, you can also pick up a feel for sound quality by the particular sheen on the record— some have a rainbowlike gloss suggestive of careful cutting and clean pressing quality.
Mastering, when done properly, is at once art, craft, and labor of love. Though learning the basics of how to operate the cutting equipment takes only a couple of weeks, disc masterers are generally apprenticed for several years. Some never really learn the art, despite calling themselves professional disc masterers. Also, no matter how accomplished a masterer, adjustments in the mastering room cannot improve a poorly engineered tape or mediocre music, despite the forlorn efforts of cutting room impressarios.
Before the final master lacquer is cut, acetates, or reference lacquers, are made, which can be played only a few times. These are used for final approval by musicians, producer, and others involved. Because these acetates have a tendency to sound somewhat duller than the final vinyl version, they can sometimes lead inexperienced or indifferent listeners astray—requesting the disc masterer to “brighten up” the sound on the acetate may result in a finished record that sounds overly bright.
The master lacquer obviously can’t be used to press records directly, so a copy is made. Plating is the first step in converting the master lacquer into the molds or stampers used for mass-pressing the vinyl records. Lacquers should be plated within 24 to 48 hours of being made and must be kept under refrigeration until they are plated.
The lacquer is coated with a thin film of silver and electroplated in a nickel bath. The nickel plating now bears an exact negative impression of the lacquer, which is peeled away and discarded. A positive “mother” is formed from this negative metal mold, by again electro plating the mold to provide a positive impres identical to the original lacquer. This is the mother or pressing master from which all the stampers that actually mold the records are made. Mothers can be stored safely for 20 years. From the mothers, the final negative molds are made, producing stampers strong enough to sustain the force of pressing the records. Each generation of negative-to-positive-to-negative transfer increases the presence of imperfections and adds further distortions, causing a slight loss of sonic transparency.
A stamper can make only a few thousand pressings before becoming worn. The earlier in the pressing run, the better the LP’s pressing quality. The producers of excellent-quality recordings may allow far fewer pressings to be made before the stamper is discarded. Obviously, unless a special edition of only 1,000 or so LPs is being made, numerous stampers have to be used for each recording and each one will come out a little different. One pressing may therefore sound better than another of seemingly the same recording; even though the master tape through to the mother were identical, the stampers were different and also undoubtedly reached different stages of wear.
To press the records, the stamper for each side of the record is placed in a molding machine (distantly related to a waffle iron). A hot biscuit of vinyl, sandwiched between two labels like an Oreo cookie or ice cream sandwich, is placed between the stampers and then hydraulically compressed. Bingo!—a record. This is repeated every 30 seconds, producing 120 records an hour. The method is called compression molding. Vinyl temperature, room temperature, and humidity all affect the quality of the pressing. Improper cooling, or curing, results in warped records.
The polyvinyl chloride used may be virgin vinyl (unused and the best grade) or a mix of virgin and regrind, which is made of ground-up and melted-down defective records and flash, the raw edges trimmed off after pressing. In some records, you may even find actual chunks of old record label—you can imagine what this would do to your stylus, let alone your ears. The better the quality of the vinyl, the less the surface noise—pops, ticks, clicks, and the notorious “record fart.” This burping noise is caused by no-fill, a tiny pinhole in the groove caused by a bubble or speck of dust in the vinyl or a defect in the stamper.
Premium virgin vinyls, such as Teldec, can be half again to double the price of the standard mixed grade. One way of identifying virgin vinyls is that they are commonly translucent (hold them up to the light), being colored with ink rather than the carbon black used for nonvirgins. Carbon black, unfortunately, is granular and adds to surface noise. Radio stations often receive special pressings of virgin vinyl to keep surface noise off the airwaves.
Forty-fives are often made by a cheaper pressing method, called injection molding. This uses polystyrene, a harder and more brittle plastic than vinyl. Hot liquid styrene is poured into the mold, then quickly baked and cooled, much the same way that cheap plastic toys are made. This method is twice as fast as the compression method and the styrene is cheaper than vinyl. However, the records wear out faster and tend to register greater background noise.
The RIAA Curve
Record manufacturers are forced by purely mechanical difficulties to distort the recording deliberately. The ideal record would store in its grooves a precise analog of the sound from the live performance. However, this would mean the grooves would have a large amplitude at bass frequencies, restricting playing time, and a low amplitude at high frequencies, causing signal-to-noise problems. So in practice, the music signal is first passed through an equalization network that cuts the bass and boosts the treble. This equalization, standardized in 1953 as the RIAA (Recording Industry Association of America) curve, is reversed during playback, in the preamp’s phono stage. (Tape deck, tuner, and CD, which don’t require the RIAA curve, are connected to the preamp after this phono stage.) How precisely the preamp corrects the RIAA curve is, of course, critical to how your music sounds.
The treble is boosted because of record surface noise, most of which is in the upper midrange and up. By increasing the strength of the higher musical tones in a recording before the disc is made, you can reduce background noise during playback. When the preamp’s phono stage equalizes the signal and cuts back on the treble, it also cuts back on the surface noise. The treble is brought to its correct original level while the surface noise, which started at “normal,” is reduced to below normal, improving signal-to-noise ratio.