by Arthur Shifrin
"The Columbia process of recording, as developed especially during the last two years, produces a naturalness and roundness and perfection of tone that is positively unequalled in any other. The singing voice, as recorded in the Columbia laboratory is the living voice of the artist: clear; flawless; and natural ... "
- from a Columbia demo record circa 1911
THERE'S A LOT of interesting and entertaining stuff on those old discs and cylinders; to some collectors their contents are no less than sacred. Be they ordinary commercially pressed discs, privately recorded, or those legendary old broadcasts, there is widespread interest in listening to, collecting, and improving them. One of the frequently printed inquiries to Herman Burstein's informative "Tape Guide" column concerns this highly specialized aspect of recording. The usual presumption is that this process of improvement, or restoration as I prefer to call it, is made through the taping process. The recommendations often proposed, in the hope of diminishing highs and thereby reducing noise and distortion, include: taping at slow speeds; deliberate mis-biasing; playing back a tape of the noisy discs on a wide-gapped or worn head; recording from outputs which are affected by an amplifier's tone controls and filters; shunting capacitors to ground at the phono preamp's inputs; and utilizing any of the recently marketed consumer-oriented equalizers within recording or playback lines.
Unfortunately, there are common misconceptions about the causes and characteristics of 78 noise, and these make the above suggestions, at best, inadequate. I certainly don't intend to cast any aspersions upon Mr. Burstein; but because the field of restoration is such a narrow area of the audio engineering profession, few enthusiasts, even few professional engineers, know how to contend with the challenges presented by old, noisy discs.
Before I describe some restoration techniques, I'm going to give a primer course about the ways in which pre-tape and pre-L.P. era recordings were mastered and manufactured.
Knowing why the techniques are used should help you get the most effective results and, I hope, provide a firm foundation upon which you can experiment with your own procedures. Everybody knows that old records sound terrible; the crucial question is "why?" They can be noisy and distorted because they are dirty, worn and mutilated, mastered ineptly, manufactured out of inferior materials or played with the wrong stylus. Additionally, the presence or lack of fidelity is mostly due to the means of mastering and not those of mass production. Aside from a few photo-optical and magnetic experiments, the primary way to record sound prior to the 1920s was a purely mechanical process. Records were recorded precisely the same way in which "Little Nipper" listened to "his master's voice"--through a horn. One or several cones would collect sound waves in the studio and transmit them to a diaphragm which modulated a cutting stylus. Since the only full range diaphragm is the living eardrum, this "acoustical" process of recording could produce a dynamic range, at best, ranging from approximately 200 Hz to 3 kHz. "Mechanically" mastered records are easily distinguished by their washed-out tonality. Subsequent to 1925, most discs' were recorded electrically, as all are today. By 1924, the Western Electric process which had originally been developed to pre -record orchestrations for silent films enabled a useful frequency range from 50 Hz to 4 kHz, a substantial improvement as perceived by the ear, even when such discs were played back on acoustical mechanisms. Marketed as "Viva-Tonal" and "Orthophonic" recordings by Columbia and Victor respectively, frequencies up to 10 kHz could be mastered in wax by 1928. Unfortunately, those ultra high frequencies could not be effectively transferred to pressings. Those which were, would be quickly eradicated by playings of the gougingly heavy steel needles used in those days.
All old records are not alike. There is an obvious difference between cylinders and discs, the former being cut vertically (up and down undulations) and supposedly recorded at 160 rpm. Most commercially released discs were laterally cut (horizontal vibrations), some were vertical, and others with a hybrid characteristic which ostensibly enabled them to be played upon either kind of pick-up (in the old lexicon, re producers). Some old commercial releases, such as those first issued by Victor in 1931, were played at 33 1/2. Speeds other than 78 (actually, 78.26) were either standard for same firms such as Columbia and OKeh (that is the way the firm spelled its name) which cut their discs at 80, or occurred due to, perhaps, a lack of quality control. For example, referencing reproduction to the known pitch of certain artists such as Caruso, the ostensibly correct speeds of many discs have been determined to range from the low 70s to low 80s. Some Pathés and early Berliner records are said to have been recorded in the 90s rpm! Speed variances, especially prior to the use of hysteresis-synchronous motors in cutting lathes, leave little choice but to render this point to subjective analysis.
The rigid tar-like substances out of which most "78s" were pressed were not the only materials used in manufacturing discs. Some outfits such as the Durium Corporation pressed its "Hit of the Week" releases upon terrific sounding laminated cardboard bases. Aluminum (both uncoated and sprayed over with acetate), plastics, and glass comprised other kinds of discs of varying sizes and thicknesses. 78 pressings are the most commonly found old records because they were mass produced for public consumption. Most frequently issued in 10- and 1-inch diameters, they are occasionally found in odd sizes ranging from 5 1/2 to 20 inches wide.
Prior to Emil Berliner's development of the mass manufacturing technology, which remains essentially unchanged today, each disc produced was indeed an original. The artist would be encompassed by as many recording machines as would permit proximity to the recording horns and perhaps a dozen discs could be manufactured simultaneously. These coarsely surfaced, brittle platters were inevitably noisy because the materials, techniques, and equipment simply did not yet exist which would enable etching or impressing of grooves into a surface which could be smooth yet capable of withstanding destruction by the forcefully tracked steel needles used in gramophones.' The Berliner process revolutionized the re cording industry. By mastering upon impeccably smooth bees wax and then electroplating the originals, the capability of mass production was realized. A flawless, oppositely impressed metal copy of the master could be used to press playable duplicates out of whatever material was then available for that purpose. Consequently, it is a mistake to assume that most or all of the noise on old records is due to the mastering process. Under optimum conditions, the wax masters and their subsequent metal parts (mothers and stampers) are by today's standards, incredibly quiet. That is, a metal part which is neither tarnished nor mutilated will be substantially noiseless when played with a modern cartridge equipped with an appropriate stylus and without any filters! The problem was to maintain the integrity of the grooves when the final discs were stamped. The technology of plastics was embryonic and shellac was apparently the only economically (perhaps the only) feasible material out of which an adequately smooth disc could be produced. Unfortunately, a disc made of this substance would be too brittle to withstand the rigors of every day use, let alone handling on the assembly lines. Obversely, the tar-like materials which enabled a disc's durability precluded silent surfaces and accurate reproduction of the grooves in the pressing process. The coarseness of these substances meant that minute protrusions would be present within the grooves and these would produce noises running the gamut from hiss, through scratching, to popping and clicking.
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Vector Switch for Pick Ups
You might protest that the circuit between the phono cartridge and preamp's inputs is "hands off" territory and for good reason. Excessively long leads will introduce hum and cause loss of highs to the precarious, unamplified signal. This switch can be added to your system without jeopardizing its integrity. A miniature rotary switch, such as Centralab's PA 1026 or PA 2026, should be mounted as closely as possible to the base of the tone arm. Since most tone arm boards are too thick for standard switch and pot mounting shafts, you will probably have to countersink the hole' so that the switch can be mounted securely to the base. A hex driver for the 1/2-in. nuts which can be used on these switches is usually about 3/4 -in, wide: a wood drill bit of that width is the least costly and neatest way to make this kind of hole. The dull black Mallory dial plate #373 or gloss black Centralab P-178 are marked 1-2-3 and will clearly indicate the three positions as well as conceal the mounting hole.
If the turntable's base is too shallow to accommodate these four wafer switches which protrude about two inches, then the three wafer PA 2028 or subminiature PSA 228 will be required. Exact dimensions for these are detailed in their Industrial Distributor Components Catalog.
The wires leading out of the tone arm and into the shielded phono cables must be interrupted so that they can be fed into the four input poles of the switch. This would necessitate cutting open the leads to the kind of multi -conductor cables which plug directly into the base of the arm. So that this circuitry cannot be damaged by accidental tensioning of the cables leading to the preamp, provide strain relief. An additional safety precaution is the installation of RCA type phono connectors so that moving the unit will, at most, disconnect the cables harmlessly at the turntable's jacks. Should the switch induce hum, mount a small can over the underside of the assembly and ground it.
For the less adventuresome who prefer not to operate on their hard-earned equipment, the same switch can be externally mounted. Its placement within a metal cabinet is recommended because, when grounded, the enclosure tends to act as a shield. For vertical vectors, the two ground leads of the cartridge must be isolated from each other on the input side of the switch, so on the cables leading from the turntable to the box, use connectors (e.g. microphone type) which will not lead the two grounds into conversion on the switch's chassis.
Conventional RCA or phone jacks can be used on the box's outputs because the two channels' grounds are common at that point. (Refer to the text about the suitability of your arm's wiring.) Proximity of the box to both the turntable and preamp is crucial: it must be placed so that the total run of cable between the cartridge and preamp does not exceed the pickup's requirements for capacitance. If possible, sever the tone arm's original leads and insert the four new connectors so that the phono cables' lengths are not increased.
Should either project seem too complex, the author's services are available commercially!
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The most common solution to these two mutually exclusive problems was to press into "solid stock," an homogeneous mixture of the two or more elements responsible for both characteristics. Naturally, their being mixed compromised each other's function. The qualities of pressings varied slightly or drastically, even amongst discs issued by the same company. Factors influencing this lack of continuity included plant location, availability of materials, and business conditions. A disc containing a greater proportion of shellac was better sounding and more costly. The best solid-stock discs I have heard are Brunswicks pressed by that firm after 1931, when ownership passed from Warner Brothers to The American Record Corporation, which also owned Columbia.
Interestingly, both before and after its acquisition by RCA in 1928, Victor sanctimoniously discriminated against its customers of the popular Black label discs: its classical "Red Seal" pressings were usually quieter despite identical pricing schedules. Expectedly, the budget-priced labels, such as Decca and Perfect, were noisier and more distorted than the almost twice-as-costly Victor’s, Columbia’s, and Brunswick’s. There were, of course, exceptions to this rule. Small independent companies, such as Musicraft and Black and White, either could not or would not use superior materials in their full-priced products. However, pre-CBS Columbia's budget labels, such as Diva, OKeh, Clarion, and Harmony; Victor's Blue birds, and Brunswick's Melotones, usually had as fine quality as their more costly counterparts. Regardless of label, most discs pressed during World War II were inferior to their predecessors because the supply of shellac was terminated by the Japanese embargo of India. Scrap drives were instituted to collect any old solid -stock discs which were mixed in with whatever pure shellac was still on hand. As time progressed and the supply of shellac became depleted, the discs became progressively worse. They are amongst the most difficult types of discs to restore.
Another facet of the early recording technology was responsible for the noisy surfaces. Carborundum, a mineral almost as hard as diamond, was deliberately introduced into the record mixtures so that the needles would be ground down to conform to the geometry of each discs' grooves. Even with the advent of electrical recording, it was not economically feasible to market a lightweight magnetic cartridge with a semi -permanent stylus as we know them today. Other than Edison's enduring diamond styli which could not be used for lateral discs, all phonographs utilized a reproducing mechanism which required the insertion of a new needle for each playing. As you'll see later on, the concept of customized needles was in fact precocious. If a 78 from that era is not virgin, then it will contain the ground remnants of the needles which had previously played it. These obviously contribute to the disc's noise and even if a method were developed to remove them, the impressions they made within the grooves would still add to the noise problem.
Prior to its acquisition by CBS in 1938, Columbia undoubtedly made the most superior mass-produced discs.
Around 1910, the firm pursued technological advances to offset the marketing blitzkrieg achieved by Victor, then the world's largest recording company. One of these was the two sided record which had the advantage of two selections for the price of one--a concept which Victor at first steadfastly resisted. The other was probably the world's first flexible and almost non-breakable record. Marketed as the "Marconi Velvetone" line', these were shellac laminated upon some kind of paper base. They were only slightly abrasive and, despite their superiority to any other discs at that time, failed in the marketplace. Sales resistance might have been due to their thin, flimsy appearance and relative lack of durability.
In mid 1923, Columbia again attempted to market a superior "New Process" record which was a conventionally thick, lavishly manufactured platter. Essentially two "Marconi Velvetone" discs mounted upon a common tar base, these five layered discs outperformed any others in their day.
Whether pressed as 78s or 33 1/3 radio transcriptions and film soundtracks, their easy superiority is conspicuous as soon as they are heard.
If your fields of interest extend to working with recordings of old broadcasts, and you succeed in gaining access to the actual discs, then you will encounter those which may differ radically from the 78s with which most people are familiar.
"Electrical Transcription" described a pre-recorded commercial or program. "Air-check" denoted a recording whose source was an actual broadcast signal picked out of the air. "Line-check" indicated that the recording was made from a point on the studio or network line prior to the transmitter. Eventually, the three terms became synonymous, and I mention this because the labels on many of these discs might not accurately indicate the nature of the recordings' origins. A broadcast recording might be pressed or an instantaneous disc. A pressed transcription was manufactured as were commercial releases, except that few were usually made due to a limited number of possible customers. Manufactured out of plastics, solid or laminated stocks, these could be cut outside -in or inside -out (i. e. the first groove being the inner-most one). Their speeds and sizes were often determined by program formats. For example, a 16-in. side cut at 33.333 could contain 15 minutes of programming. Both sides could contain two quarter-hour shows or one half-hour show, with pre-recorded provisions for a locally made live announcement while the disc was being turned over and cued. If sequential sides were pressed on two different discs, then a segue was possible without any live-miking. Contrary to popular belief, most radio stations in those days depended upon pre-recorded programming; live entertainment originated mostly from the networks. Interestingly, the people credited with creating the syndication business are Freeman Gosden and Charles Correll, creators of Amos 'N Andy. In the late 1920s their NBC shows were heard from discs in certain markets. 12-in. wide and recorded at 78, each side could hold up to five minutes of material. Locally originated openings, closings, and mid-show breaks enabled the simulation of a complete 15 minute program.
By contrast, the "instantaneous" disc was analogous to present day tape and designed for the capability of playback with out having to resort to the time and expense of the pressing process. The first such discs were highly polished aluminum platters into which the grooves were directly inscribed. They were improved upon by the late Cecil Watts by the addition of acetate coatings into which the grooves were cut. Higher frequencies could be recorded with less noise on the more modern blanks. Ironically, the older uncoated ones are today easier to restore than those acetates used during the transition period from about 1932 to 1935. Given that an unmutilated samples of both types is available, the acetate, due to chemical deterioration, will sound worse despite its originally having a wider dynamic range. The early coated blanks were poorly manufactured; they had relatively bumpy surfaces and excessive instability. If it has been stored properly, without exposure to excessive heat or humidity, an acetate dating back to the middle thirties has the potential for impressive, brilliant sound.
During World War II, recording blanks as well as pressings, were affected by changes in the availability of materials.
Defense priorities included aluminum, so most of the blanks produced from 1941 through 1945 had glass bases. Yes, fragile, easily-destroyed glass! These are extremely difficult to work with and, even if not already cracked, might be so delicate that merely carrying them to the turntable results in their destruction. They are usually stamped "glass" and should obviously be handled with extreme care. Never carry them with support from only one point and never subject them to stress by weight: they should be stored vertically and not permitted to lie diagonally within shelves amongst other discs. As a precaution, I "criss-cross" the backs of single sided ones with masking tape. Additional support is thus provided and should a crack occur, breakage does not result.
Cracked glass discs can be salvaged if the acetate layers are still intact. Should you observe a crack beginning to form, a narrow piece of masking tape placed over it at the rim and corresponding area between the label and innermost groove will usually hold the disc together-at least long enough to withstand handling while you're trying to get it on tape! If a disc has fallen apart, only the most enduring patience might reclaim it. If you suspect that a disc might be glass, its base type can be determined safely by scraping the insides of the center or eccentric stabilizing holes. The centers of many glass discs had cardboard inserts which prevented the formation of cracks by missing the spindle when placing the disc on the turntable. Consequently, when any paper from the labels is scraped away, you will observe either glass or cardboard surrounding those holes. Additionally, you can see a strong light through the blue, red or green acetate coatings.
The most extraordinary equipment requirements will occur if you intend to tape cylinders because (I assume!) there's just no audio dealer who stocks state-of-the-art cylinder players. The least effective way to transfer them is to place a microphone in front of an old phonograph's reproducing horn. Remember that in those days, the technology of recording was always superior to that of playback and you'd be restricting the results to the primitive capabilities of the device. What is required is a player which enables use of modern stereo cartridges. There are two ways that this can be accomplished, building a completely new mechanism or cannibalizing an old one. What results is probably the most curious-looking sound instrument which any reader of AUDIO has ever seen.
A straight tracking arm such as the one made by Rabco can be mounted in place of the old reproducing head. Whether or not this can be affected without permanently mutilating the old mechanism depends upon your mechanical talents.
Prior to making the investment, the arm's manufacturer should be consulted to verify that the mechanism will permit the cartridge to travel across the length of your longest cylinder.
A possibly less expensive alternative is to use a conventional tone arm, preferably the longer ones used for 16-in. discs.
Minimal tracking error will be achieved by mounting the arm so that at the record's center grooves, the rear-front axis of the cartridge is perpendicular to the length-wise axis of the cylinder.
A turntable with the 78 speed is obviously required for most old commercial discs. Automatic changers will often jam up due to inconsistent hole diameters and prove very trying when you're attempting to play an inside start platter. The tedium of easing the arm into that first groove without it defiantly flying back up can tax the most patient personality. Discs larger than 12 in. require an oversized turntable and arm.
Geometry dictates that optimal tracking can only be achieved with the longer arm. Variable speed control is necessary for old discs because the heavier, larger ones can slow down some turntables. Stylus drag, a slowing down due to the friction produced by exceptionally heavy tracking, also requires speed correction capabilities. Turntables which enable limited or infinitely variable speed adjustments are widely available and can be selected to fulfill the requirements dictated by the kinds of discs you collect. Units such as my semi -fixed Thorens TD-124II can be internally adjusted to achieve radical speeds, so an occasional off-best disc might not necessitate the borrowing or purchasing of another machine. Should a disc cover a turntable's built-in strobe device, the only way to verify a correct playing speed is to place a strobe disc over the record and check it while the stylus is actually tracking the grooves.
Different surfaces produce varying degrees of friction and this technique eliminates any guesswork.
You might occasionally be able to acquire an old, massive studio turntable, such as those once made by Gates and RCA.
If you are mechanically inclined and feel that you can service it and shrewdly dress the inevitable holes from its previous arm(s), then buying it would be worthwhile. They are less susceptible to slowing down effects due to their great inertia, and the giant platters eliminate overhang with 16 -in. discs and afford more protection to the large glass discs. The old arms, frequently without variable tracking force and always lacking anti -skating facilities, should be replaced. If you're curious, I use a Thorens TD-124-II turntable equipped with a Shure SME 3012 arm.
The initial step in restoration of discs and cylinders is cleaning those which might be dirty. We all know that styli interpret dirt as unnecessary noise and distortion, non-abrasive, non-ammoniated soaps and warm (not hot) water will suffice for both pressings and acetates. A forceful, diffused flow of water will wash out any soap and lint which should have been rubbed ONLY in circular motions corresponding to the groove patterns. Once acetates have been washed, they should be played while still wet. In some cases, substantial noise reductions will be observed. If an acetate is so chemically deteriorated that it is covered with a white, frost-like coating, residue buildups will occur so quickly that within minutes the stylus will be incapable of tracking the grooves properly. Only in such cases should you resort to full-strength ammoniated cleaning liquids which will eliminate the troublesome coating temporarily. Unfortunately, these chemicals also have the capacity to jar the acetate layers from their base. Only experience will enable you to predict the advisability of this measure.
If you have developed a talent for editing, a more conservative way to attack this problem is to track the disc in short sections, cleaning the stylus at frequent intervals and then splicing out the interruptions. Uncoated aluminum discs can be effectively cleaned by a remarkable substance known as Aluminum Jelly.
(It is not to be confused with Naval Jelly.) Both are non abrasive and the former makes aluminum oxides and dirt, such as those which mar old storm doors, water soluble. If you are concerned about the possibility of ruining labels, there is usually enough ungrooved area around the centers to mask them with waterproof adhesive tape and any household plastic wrap.
Other treatments which you might have to perform upon old discs are de -warping, groove scraping, and hole centering. Creased acetate -coated discs whose surfaces have peeled away from the base are usually impossible to repair. Bent ones can be straightened out by the continual application of weight over long periods of time. Pressed records are most easily flattened out by heating them uniformly.(in an oven) to NO MORE than 200° Fahrenheit. The plyability of the warming discs can be tested at their rims. Once in this state, they should be removed at least as carefully as you would extract a prize winning pizza from its oven! Clean, non-textured Formica sheets, which extend over the total area of the disc, will protect the softened record from damage. The heated disc should be carefully slid onto the face-up bottom piece, covered with the second, and then weighted down long enough to permit gradual cooling.
Hole eccentricities, which are usually due to manufacturing errors should be corrected to minimize wow. Discs may be reamed, filed or even drilled to establish their centers. Should locked grooves or loud clicks be encountered, they might be due to coagulated foreign substances which could possibly be scraped out manually with the assistance of a powerful magnifying lens and steel needle. Practice these techniques on unimportant discs before performing them on the irreplaceable ones!
Phasing Out Noise
Vector isolation with magnetic stereo cartridges is the first electronic step in noise reduction of records. From a stylus' eye view, the surfaces of all old records are rough and produce movement in unwanted and irrelevant directions. Vertical grooves will have lateral noise and lateral grooves will have vertical noise. By phasing out the unwanted signals, an optimal S/N can be obtained (minimal noise prior to any filtering or expanding). With selective wiring, a magnetic stereo cartridge can play four kinds of grooves: stereo, lateral, vertical, and hybrid. A pure lateral vector is produced by wiring both channels in parallel; the two hots are jumped together and these become the hot leads into the phono preamp's inputs and the two grounds are jumped together, becoming the shields. A pure vertical vector is extracted by jumping the left hot to the right ground, this pair becoming the hot leads into the phono preamp's inputs. Similarly, the right hot and left ground are tied together and these become the shields. Hybrid grooves are neither vertical nor lateral. Supposedly cut at 45°, discs such as these will require some experimentation for each case.
A characteristic that is a perfect 45° should be played out of either side (but not both) of the cartridge. A groove cut more towards the lateral characteristic will play better with lateral wiring. Similarly, a characteristic resting between 45° and 90° might play better with the vertically wired configuration.
Additionally, an arm, such as the SME 3012, which enables the cartridge shell to be rotated about its axis can be immensely valuable. Turning the stylus towards the rim or center of the disc can also improve the tracking of these peculiar grooves.
Vertical vectoring requires isolation of the two ground leads coming from the cartridge. An arm whose wiring provides common grounding of the left and right shields will short out when vertical circuitry is introduced. Therefore, a check with an ohm-meter or consulting the arm's manufacturer would be in order prior to making any wiring alterations.
The thin, delicate leads in tone arms and cartridge shells can obviously not withstand continual changes; sometimes they don't even survive original installation! A mechanically efficient and safe way to provide a choice of isolated vectors is to set up individually wired shells and cartridges, three of which could handle any kind of groove: stereo and hybrids, lateral and vertical. Fitted with a microgroove stylus, the lateral shell would improve S/N on monaural LPs and 45s. Similarly, the stereo shell would serve the dual functions of playing both old and the most modern discs. If your tone arm does not pro vide interchangeable shells or you wish to work with only one cartridge, then a switched circuit which would enable all three wiring configurations can be inserted between the cartridge and the phono preamp's inputs. The functional advantage of this switch is that it enables instantaneous comparisons against the three possibilities without tedious cartridge or shell changes.
Styli Considerations If 60 years ago it was recognized that the customizing of styli was necessary, then the drastically increased transparency of modern equipment intensifies the importance of that approach. No filters, equalizers, noise gates or other signal treating devices can compensate for less than perfect tracking. Not only are the discs' grooves sized differently from the 2.5 mil "standard," but justifications exist for using styli which barely conform to them at all! For example, if in a lateral groove mutilation has occurred towards or at its bottom, then a stylus which has the capacity to ignore that region would presumably produce better results and, in fact, it does! Analogous to trying to avoid potholes when driving, the idea is to select a stylus which can offer a smoother ride through those spiral-shaped Grand Prix courses we call old records.
There are two kinds of stylus alterations which are effective for improving the tracking of grooves: truncation and extraordinary sizing. For these techniques I am in debt to Robert B. Carneal, Acting Chief Engineer of the Record Music Di vision of The Library of Congress, and Martin L. Kite of Woodbridge, Virginia. The ensuing recommendations are based upon Kite's assiduous research into original technical data and Carnéal's stereo-microscopic evaluation of grooves.
The Library, having had the budget to purchase the necessary experimental equipment and expensively priced (e.g. $80 per stylus!) customized Stanton styli, proved the importance of this aspect of restoration.
A truncated stylus is one with its tip ground down so that its height is disproportionately shorter than its diameter. As if a ball having a given diameter were placed in a slightly narrower hole, a truncated stylus which perfectly fits a lateral groove will not reach the bottom. Resultantly, less offensive information is fed into the system. An obverse demonstration of this effect can be evaluated with most 78s by comparing their sound when played with both microgroove and "standard" styli. The former, due to their small size, will emphasize lower altitude information and produce more distorted, noisier, and lower level signals. (With a small number of discs, the microgroove stylus will produce a better sound.) On vertical grooves, a truncated stylus will function as a noise gate by tending to ignore the more minute indentations which cause high frequency noises. Careful observation of this effect must be made to insure that an incorrectly chosen stylus is not ignoring low level passages as well! Extraordinary sizing further enables the audio archaeologist to discriminate against parts of grooves and to contend with unusually wide, narrow or mutilated ones. For example, the most useful parts of a particular groove might be so close to the surface that even normally sized truncated tips will not produce optimal results. Returning to that ball in the hole, given that the ground rules induce us not to alter the size of the opening, the only' alternative is to change the sphere. Some discs' grooves are so wide that normal styli play too much of their floors: these are over-modulated (too loudly recorded) signals made by conventional sized cutter heads and correctly leveled signals inscribed by abnormally large cutter heads.
Over -modulated discs rarely occur among commercial pressings and abnormally wide grooves seem to be most common amongst acoustical discs. Exceptionally narrow grooves are usually found amongst transcriptions, including Victor's notoriously noisy long playing records issued in the 1930s.
Contrary to most collectors' assumptions, they were not cut with the conventionally wide grooves of that era and will sound unnecessarily noisy when played with "standard" styli because too much of the usually mutilated groove ceilings are picked up by them. Edison discs and cylinders, especially those elusive 12-in., 20-minute high speed Diamond Discs also have particularly narrow grooves.
A variety of styli is often necessary to play one recording.
Mutilation, over-modulation, or sub-velocity grooving' will mean that as the recording is played, the characteristics of the grooves are changing. The object of having a choice of styli, whether to play one disc or an entire collection, is to establish a compromise amongst noises, distortions, and signals. International Observatory Instruments' sells special styli from stock on Shure assemblies for the M44 cartridge body (they seem to work equally well on the M90 series). I.O.I.'s offerings include a truncated Shure N44-3 2.5 mil diamond as well as assemblies for Edison vertical grooves and the "ball cut" Pathés which have wide, shallow modulations. Their workmanship is impeccable, but I question the advisability of supplying these useful styli in assemblies which start to collapse as tracking forces are set to exceed three grams. Perhaps heavy by contemporary standards, this weight is too light to resist the inertia developed by styli speeding along those bumpy grooves at about 78 rpm. What results is continual launching of the stylus not out of, but just enough above the grooves' correct playing altitude to cause inconsistent noise.
Due to psychoacoustic reasons which prevent us from adjusting to rapid and continual noise fluctuations, this kind of interference is, at least to me, unbearable.
The Stanton 500 cartridge fitted with their D5127 stylus assembly is a stereo unit which tracks satisfactorily up to 7 grams. Splendid for playing new or old discs, its only draw back is that the 2.7 mil stylus produces too much noise on every kind of old groove on which I have tested it. Similarly, G.E.'s monaural VRII9 cartridges have heavy tracking capabilities which extend up to 30 grams. The intimate tracking capabilities at such high weights produce spectacular results with older acetate recordings and are required in cases which dictate manual manipulation of the arm through and past points where grooves have become locked due to mutilation.
No other stylus assemblies I have worked with can withstand that kind of abuse. Additionally, the G.E. 4G-02D and 4G-03D 2.5 and 3.0 mil diamonds are particularly useful in both conventional and truncated formats. The terrific aspect about the G.E. single or dual stylus cartridges is that they are so inexpensive. Priced at about $5.00 without styli, their cost makes feasible a truly professional cartridge set-up: one stylus assembly per cartridge per shell . I have learned the painful lesson that even with cartridges designed for this capacity, continually changing stylus assemblies jeopardizes their delicate structures and wears out the cradle parts into which they are inserted.
Since no cartridge manufacturer I know of will cooperate to the extent of supplying stylusless assemblies, we are required to pay an expensive premium for the ability to order customized styli. The Stanton 2.7 mil assembly (the last time I purchased one) costs $12.00. G.E. assemblies can be purchased for about $2.00 by ordering the cheapest sapphire points; G.E. or Recoton replacements are equally acceptable.
For vertical and lateral discs, the minimum library of sizes should be 2.5, 3.0, and 3.5 mil truncated. Should you work with transcriptions, then a 2.0 mil truncated will often be useful. Frequent encounters with old acousticals will probably warrant styli ranging from 4.0 to 5.0 mil. Increments in size by tenth mils, instead of half mils, conceivably would be justified but economics of cash and time leave me inclined to settle for the sizes I have listed. Vertical discs which are not mutilated might require non-truncated versions of the indicated sizes. Custom mounting and grinding of all the styli I have discussed is available from either I.O.I. or Expert Pickups Ltd. [11] I suggest that prior to placing any orders, you obtain comparative estimates for the same items. The costs for these services are reasonable. Expert Pickups charges approximately $9.00 for a first-class diamond installed in a customer's assembly. I believe that both firms' rates are competitive.
above: Conceptual drawings showing various commonly found filter curves.
Signal Treatment
Whether working from your own originals or taped duplicates from other sources, equalizing and filtering are the least difficult aspects of restoration. The results you achieve at these stages are predicated upon what you have first done to prevent noise and distortion (i.e. optimal tracking). Additionally, factors such as the effectiveness of your signal treating equipment, the transparency of your playback equipment, the listening environment in which you work, and the state of your hearing will affect the caliber of your endeavors. Psycho-acoustic factors such as masking and phase re-enforcement also affect your perception of signals.
Interestingly, when high frequency noises are superimposed upon programs, the recordings sound more crisp. Resultantly, their removal unnecessarily accentuates muffling effects.
Similarly, noise is not so easily perceived in a noisy environment and there are days when due to illness or attitude, you find yourself "not hearing right" and unable to make qualitative audio evaluations.
Broad and narrow band noises are the two fundamental categories into which most sonic disturbances fall. Unfortunately, most occur (are loud enough to be heard) amongst the same frequencies which contain the recorded sound. Clicks, scratching, rumbling, and multiple harmonic distortion are broadband noises. Hums and whistles are usually very narrowly banded. Regardless of their type, the objective is to diminish them with as few adverse side effects as possible. With varying results, both equalizers and filters can be used to reduce broadband noises. The distinctions between these two kinds of devices are conceptual and, I think, subjective. When their characteristics are plotted, filters are usually identified by straight graphs as compared to the curved ones of equalizers.
Indeed, some devices are capable of producing either kind of pattern. The terminologies used to describe filter and equalizer effects are derived from geometric descriptions of their response curves. An equalized characteristic is also defined by the frequency at which it is most pronounced. Curiously, much of the industry labels filter coordinates by the frequencies at which they are down 3 dB from a reference level: rather anachronistic considering the 50 dB attenuation capabilities of the new generation of filters! A slope of X dB/ octave is also a vague means of reference: I think that filtering functions are more easily understood by citing the attenuation achieved at the frequencies with which one is concerned.
The diagrams demonstrate the kinds of frequency effects which are produced by filters and equalizers.
Theoretically, the device most ideally suited for contending with any kind of noise and equalization problems is a third-octave equalizer which is actually a set of narrow band-pass filters whose effectiveness can be individually adjusted. The third-octave-wide bands are approximately the most subtle frequency widths whose changes can be detected by the human ear [12]. When devices such as these are manufactured with adjacently mounted sliding potentiometers, they are often called graphic equalizers because the control's knobs simulate a graphic representation of the response curve produced by the unit. Certainly more glamorous, interesting and expensive than units with rotary pots, their only advantage is the instantaneous plotting capability. A graphic equalizer is not necessarily more effective or desirable simply because of its mode of operation. The value of such a device depends upon the filtering capabilities of its filters and the durability of the pots used in its construction. The functional depth of a notch is measured from its bottom to the system's reference level, so each filter's output should be set to maximum. Resultantly, the greatest possible filtering effect will occur. Once an optimal set of adjustments for all noises and distortions has been made (these will usually be narrow notches for hums and whistles, and severe low passing after certain frequencies), then additional corrections for tonality should be attempted.
Most of the tonal adjustments you will find necessary are due to the old discs having been recorded with curves which do not correspond to modern RIAA standards. Depending upon the characteristics of noise and signal, some settings for optimal noise reduction will preclude correct tonality and some kind of compromise will have to be established. For example, bumping the curve on the left side of a notch or prior to a low pass slope will help to minimize muffling when contending with severe amounts of noise in the 5-10 kHz range. Narrow band disturbances can usually be eliminated by this kind of device without affecting tonality. A newly touted application for these units is the flattening out of the response characteristics of listening environments. That kind of adjustment is made very infrequently; after original installation it is only necessary when the environment has been changed. The caliber of pots used in some of these units acknowledges the fact that you don't redecorate your room as frequently as you change recordings. Thus, units marketed for this application rarely hold up under the continual use to which they'd be subjected in daily restoration. One -third -octave graphic equalizers capable of 50 dB attenuations, such as B&K's [13] luscious model 124, cost over $2,000 per channel. Units which are not equivalently priced usually contain less durable pots but are perfectly acceptable for environmental equalization.
Now that you've fallen off your seats, I can assure you that you don't have to sell the family's jewels, or your car (with the gasoline shortage, maybe you should!) in order to accomplish such extensive noise reduction. In fact, the myriad of possibilities offered by such sophisticated devices are often impediments to efficient operation because too much experimental time per recording is required. Segregation of filtering and equalization functions are easier to adjust. Equalizers whose controls are less selective (e.g. one octave) are more useful, especially when taping performances which occupy more than one side of a disc. Be they inside or outside start records, equalization must be continually adjusted as the disc is playing so that when juxtaposed, the tonality of one's outer grooves matches that of the other's inner ones. Formerly marketed as "record compensators," new, more sophisticated equalizers with rolloff, shelving, and selective boosting and attenuation are now readily available to consumers. Usually with ± 10 dB ranges, they are satisfactory for most purposes, although not as versatile or effective as the very costly "professional" units such as those manufactured by Pultec [14], Lang Electronics [15] and Martin Audio [16]. Cost and effectiveness considered, the most precious instrument you can acquire for restoration is Universal Audio's Little Dipper filter set. Priced at about $425, this remarkable device is so versatile and so effective that my first exposure to it was a revelation. A single -channel unit, it consists of continuously variable high- and low-pass filters, both with 18 dB/octave slopes. More spectacularly, there are two independently operable, frequency-selected filters, each with six functions. Functional from 20 to 22 kHz, these can act as narrow-, medium- or wide-notch or bandpass filters [18]. Additionally, the entire unit can be used as a selectively boosting equalizer. Tuning out obnoxious frequencies is as easy as tuning a radio; the notch controls are adjusted until the disturbances are least conspicuous. Capable of attenuation down 40 dB from reference levels, one Little Dipper can provide two of the same or different notches simultaneously.
Although two are frequently inadequate, terrific results can be obtained by a simple technique. For example, I prefer not to rely upon tape encoding systems. Therefore, the records intended for restoration are taped in anticipation of filtering the master upon playback. Resultantly, those frequencies amongst which both tape hiss and 78 noise predominate are not filtered when the disc is recorded. Instead, the first pass through the unit contends with narrow band noises and, in the case of severely scratchy surfaces, middle highs. When the tape is subsequently played back, after re-patching, the rest of the noises are then treated and with them, any tape hiss. The tape master's S/N is then so low, that hiss in any silent sections cannot be distinguished from a tape which is not moving at all! Expectedly, this two-stage filtering technique enables first generation quality on any dubs made from the tape master. If due to that perennial problem of money, you are compelled to choose between any equalizer and this device, sacrifice the equalizer. Once you have heard a whistle or hum disappear with no adverse effect upon tonality, you will agree that my enthusiasm is justified.
Given that you might not be able to indulge in a Little Dipper, I respectfully suggest that the less expensive consumer equalizers alone are not useful compromises, good as they are for room and speaker equalization, because they lack a range of effectiveness necessary for dealing with 78 noise. Prior to my becoming "professional" and not being able to afford studio caliber equipment, I experimented with filter and equalizer circuits and developed the Sonic Attenuator. A passive device containing a severe low-pass filter (i.e. calibrated in 2 dB steps down to minus 22 at 5 kHz), the unit has an insertion loss of about 16 dB due to the inclusion of an equalizer circuit. Adjustments for 100, 1k and 10 k curves are independent of the filter, and I am convinced that for restoration, it is disproportionately effective for its price. Its price, you collectors, leaves you free to continue purchasing those old discs! The two-step taping technique which I described earlier is equally applicable. The equalizer section is used to make the master tape, and the low-pass filter is used to play it back. Should you already have made an investment in an equalizer such as those sold by Soundcraftsmen, JVC, Frazier, Metrotech and Allied -Radio Shack, then their value in restoration can be greatly enhanced by a steep low- and high-pass filter set. I even use these to supplement my "professional" equipment and would like to have a chance to sell you one. A full -track demo tape containing before/after comparisons and commentary is available for $2.00, cost deductible from any purchase. Hope to hear from you! Editing is an effective but tedious, expensive and often painful way to eliminate skipping, locked grooves, and the loud pops and clicks which persist despite applications of all other techniques. It can be done either by cutting the tape or removing sections of oxide. Both approaches have serious disadvantages. While removal of oxide maintains the integrity of pace, the trial and error nature of this procedure can be very costly in time and material. Should a mistake be made, the tape cannot be reused to re-record that section of the program. Obversely, cutting into the tape can jeopardize timing. I prefer the latter technique because removed sections can be reinstated. With painstaking shaving of the open splices, they can usually be made undetectable upon playback.
Whichever technique you prefer, this sort of complex work must be performed at no slower than 15 ips because quarter-track or narrower spliced signals usually "blip" when they pass over their playback heads. Additionally, the taped signals must be sufficiently dispersed throughout the tape so that the sections to be eliminated can be exactly isolated. I personally cannot envision a serious recordist editing within sounds at speeds less than 15 ips. The consumption of tape in this process is extreme, and it is often necessary to duplicate a playing copy to avoid jeopardizing a master which might have hundreds of splices in it.
There are a few techniques which you might want to try that are indigenously tied in to the taping process. Since most 78 noise predominates the same frequencies which modern tape machines easily record even on cassettes, slow speed taping is not one of them. Similarly, misbiasing is not desirable because a severe reduction of highs will be accompanied by inadequately low levels. Substantial high-end rolloff can be achieved when recording by deliberately misaligning the record head's azimuth. Since the performance of the playback head is the criterion against which the recording functions of a machine are evaluated, it is prudent to restrict this practice to the record head. By feeding a high frequency (e.g. 10k or higher) tone into a recorder, the head can then be easily reset to produce the highest possible levels as read by the untampered-with playback head.
Frequent performance of this operation is not advisable because most head hardware is not designed to withstand the stresses of continual adjustment. It should be conducted only as a last resort.
Some tape machines incorporate a completely safe and effective way to roll off highs. If their controls separately adjust motor speeds and recording equalizations, then all that is necessary is to record a tape with an equalization in tended for a higher speed. Tapes recorded with 15 ips equalization will be down 10 and 20 dB respectively at 7.5 and 3.75 ips. Obversely, a tape recorded with a lower speed's equalization will have an accentuation of highs. Of course.
there are internal adjustments for recording equalization on any recorder, but as with the head hardware, the delicate coils, capacitors, and pots cannot survive frequent adjustments.
Mastering at less than 7.5 ips on track widths narrower than 1/2-track is ill-advised because sound dropouts abound on slow -speed, narrow tape tracks.
Most collectors consider the addition of echo or reverberation as an inexcusable travesty of good taste and integrity. With out getting involved in the philosophical aspects of the matter, I would like to at least suggest a correct way to do it. If a tape has not been thoroughly de-clicked, then all of these singular noises will be accentuated by such effects. Therefore, it is advisable to treat only the middle and lower frequencies.
Echo circuits built into tape decks cannot be so selectively operated. Some units, such as Fisher's "Spacexpander," are easily switched to act in that manner. Should your echo unit (an auxiliary tape machine with separate playback and record heads can be considered to be an echo unit in this application) not have this capability, then you can achieve this effect even without a mixer.
The remaining electronic techniques which are useful for restoration involve the manipulation of dynamic range. From simple riding of gain to the most expensively designed limiters, compressors, and expanders, this is an important aspect not only because it helps produce correctly leveled tapes, but also contributes to improved S/N. A volume expander (which makes loud passages even louder) will reduce background noise because overall listening levels have to be diminished.
Using these to record tapes is quite difficult because volume peaks become frequent and intense. When used in playback circuits either directly from an original source or a tape, an expander operating at about 8 dB will reduce background noise by that much. If the restored recording contains substantial levels of background noise which, due to any consideration, is clearly heard, then the breathing or "swooshing" effect of that noise being pumped in and out of audibility will be particularly obnoxious. The expandability of a recording is determined only by trying it. An expander which operates in the area of 40 dB is a noise gate which ignores signals whose levels fall below that, or any other preset threshold. Unless a restoration has background noise levels comparable to modern recordings, noise gates will produce peculiar and undesirable effects with them.
Whereas most electronic recordings will benefit from expansion, most acousticals require compression or limiting.
Recording artists' proximities to the recording horns were adjusted according to the volume they produced so as to avoid overloading the cutting mechanism and breaking the groove walls. Vocalists and soloists would lean towards and away from the cones as a further means of dynamic control.
Despite those primitive efforts at volume control, these old records frequently have peaks which should be diminished for correct taping levels and listening comfort. DBX's 117 "decilinear" system not only enables expansion and compression, but tape noise reduction as well. One other device I should mention is the old Fairchild "Compander," which requires an auxiliary amplifier to drive its sensing circuits.
It can be driven by your monitor amplifier, but that would make its efficacy dependent upon your listening levels.
I hope that I have shown the feasibility of more sophisticated technical approaches to playing old recordings. Too often collectors do not derive full enjoyment from their discs and even more frequently, the old radio buff is saddled with pathetic, inept transfers. Depending upon your available time and funds, there are obviously many ways in which restorations can be pursued and I think that this information can help anyone interested in the subject.
Footnotes
1. "L.P." denotes Columbia's microgroove process and is not synonymous with "long playing records" (e.g. Victor catalogues began listing 33 1/3 "long playing records" in 1931).
2. Firms which specialized in "budget" labels recorded acoustically until the late 1920's.
3. In their original contexts, "gramophones" played discs and "phonographs" played cylinders.
4. At the time of this writing, I have not yet been able to determine if "The Father of Radio" actually participated in the development of this kind of record or simply leased his prestige to the company.
5. Coated and uncoated aluminum discs were not designed to be played with steel needles which, due to their hardness, would grind down the playing surfaces. Many of these were subjected to that kind of abuse.
6. Technicians, i.e. artisans, used to hand polish wax masters and metal parts to reduce noise. The discs with which we work could conceivably be so treated, but only at great expense of time and considerable possibility of ruining them.
7. Innermost grooves of a disc have a slower velocity than those at the rim and therefore have more restricted dynamic range; grooves cut too close to the center will have substandard characteristics.
8. International Observatory Instruments, Inc., 5401 Wakefield Drive, Nashville, Tennessee 37220.
9. According to Martin Kite, the G.E. stereo VRII cartridges have unacceptably high distortion characteristics.
10. The G.E. "dual" cartridges can accommodate two styli and this makes them even more economical to use. Most cartridge shells will have to be drilled to allow use of the turn knob.
11. Expert Pickups Ltd., P. O. Box 3, Ashtead, Surrey KT21 2QD, England.
12. I.S.O. center frequencies for these component filters are, in Hz,: 20, 25, 31.5, 40, 50, 63, 80, 100, 125, 160, 200, 250, 315, 400, 500, 630. 800, 1k, 1.25k, 1.6k, 2k, 2.5k, 3.15k, 4k, 5k, 6.3k, 8k, 10k, 12.5k, 16k, and 20k.
13. B&K Instruments Inc., 5111 West 164 Street, Cleveland, Ohio 44142.
14. Pulse Techniques Inc., 1411 Palisades Avenue, Teaneck, New Jersey 07666.
15. Lang Electronics Inc., 14 East 39 Street, New York 10016.
16. Martin Audio Inc., 320 West 46 Street, New York 10036.
17. United Recording Electronics Industries, 11922 Valerio Street, North Hollywood, California 91605.
18. Defined by UREI as 3 dB down at 5%, 10%, and 50% of the center frequencies of each notch or bandpass configuration.
(Source: Audio magazine, April 1974)
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