Home | Audio | DIY | Guitar | iPods | Music | Brain/Problem Solving | Links| Site Map
This work is licensed under a Creative Commons License.
Turntables and Cartridges
History of Turntables and How They Work | History of Turntable Cartridges | Cartridges | Turntable Tools
In reproducing a phonograph record, the aim is to take out of the groove exactly the intelligence that was pressed into them. And the wiggles in the groove are meaningless in themselves. They have to induce exactly the right physical motion in a stylus before they make sense---which means that they must move under the stylus at the right speed and that the stylus itself must track the groove accurately, wigwagging as the wiggles demand. A turntable spins the grooves; a tone arm holds pickup and stylus in place. What we want from the turntable sounds simple, but it isn't. In the first place, there are three speeds: 78.26 rpm for the old-fashioned standard shellac records, 45 rpm for the little seven-inchers with the big center holes, and 33 1/3 rpm for long-playing discs. The speed must be exact in every case. If the turntable is slow, the pitch drops; if fast, the pitch rises.
Moreover, the speed must be exact at every instant of playing. A turntable that alternately slows down and speeds up will ruin musical enjoyment even though its average in each rotation is an exact 78.26, 45 or 33 1/3 rpm. The phenomenon produced is called "wow," a very expressive word denoting the alternating rise and fall of musical pitch which results from fluctuations in turntable speed. When these fluctuations are rapid, the term is "flutter."
How Turntables Work
The ordinary shaded-pole motor, which runs your electric drill or power saw, is no good for such precision work because any variation in the voltage of your house current will change its speed. Most turntables use a specially designed "induction" motor which is fairly stable in feed, though extreme changes in line voltage may disturb it (look for a tag stating its requirements: "95-130 volts" means disaster-proof). Even this isn't absolutely steady. The 60-cycle alternation of AC electric supply, however, is invariable (an electric clock practically never goes wrong), and thus a "synchronous" motor, which decides its speed by the frequency of alternating current, can keep a constant rpm unless a complete power failure occurs. It also eliminated the dangers of turntable rumble and extruded "hum." Getting this constant speed of the motor up to the turntable (in three different varieties) takes considerable ingenuity. Today's best and most expensive turntables use one of five methods to translate motor speed into turntable rotation.
On the Rek-O-Kut and the Garrard the power gets to the turntable by means of a "rim drive"; that is, the final agent is a bard-rubber drive wheel which locks into position between the motor's axle spindle and the inside rim of the turntable. This is the most common way of making a turntable spin. Usually the spindle, the upward-protruding end of the motor shaft, is cut in "steps" to three different diameters. The speed-control knob locks the wheel against one of the three steps. When the wheel locks against the part of the shaft with the greatest diameter, the turntable spins most swiftly, and so on. A conical or tapered spindle may be used to give continuously variable speed---anywhere from 15, say, to 100 revolutions per minute. There are several variations on this procedure. Rek-O-Kut, for example, locks wheels of different diameter against a one-size spindle; the new Weathers uses a ceramic disc instead of a rubber drive wheel, and attaches the disc directly to the motor shaft. The D & R applies to the drive wheel to the outer rather than the inner rim of the turntable. On the Scott the turntable drive is direct: that is, the drive shaft of the motor locks into one of three gears on another drive shaft, which in turn is geared to the center of the turntable. The Components Corporation uses a linen belt which fits directly onto the drive shaft (at one of three diameters) and then fits around the circumference of the turntable. The Fairchild runs the belt inside, to a cast-iron flywheel below the table. There are arguments for and against each of these methods. The Components Corporation gets the motor farthest from the turntable and the pickup, thus minimizing the danger of noise from the motor. For the same reason, though, it is rather bulky and unattractive, and requires the most elaborate mounting. Direct drive uses metal parts only and can thus be machined to the closest tolerances. It also lasts longest, at least in theory---but not necessarily in practice. And when something goes wrong, the repair may be expensive. Rim drive requires occasional replacement of the rubber-tired idler wheels and drive spindle-tops. It is, however, the easiest to repair.
A turntable does not become a record player until you add a tone arm, which must be separately purchased and mounted. Like the custom turntable, the separate tone arm solves a multitude of problems. You will recall that the cutting stylus rides across the record on a bar from circumference to spindle, following a true radial path always at right angles to the line of motion of the groove. For accurate reproduction, the playback cartridge, too, should always point straight down the groove, so to speak. But we bold the playback stylus in a tone arm, which pivots, making a curved rather than a straight track across the record. In a really bad tone arm, the playback stylus will sometimes be off as much as 10 or 15 degrees. The message of the wiggles is distorted, and the record wears unevenly and more quickly, as does the stylus itself. This is known as "tracking error."
In the old days, before the deep thinkers got at this business, the solution to tracking error was simply to make the arm longer. A short arm tracks a small circle, presenting a more steeply curved arc as it crosses the record; a long arm makes a shallow arc with a closer resemblance to the desired straight line. Then it was discovered that curving the bead of a fairly short arm, by correct degree, would substantially reduce the average tracking error over the course of a whole record (Angling the pickup in a straight arm gives the same geometric effect).
Although many hi-fi authorities will still insist on the long arm (which requires a very large installation space), a recent tracking-error test came up with the tiny Ferranti arm as the most accurate tracker in the business. The new Garrard arm may be adjusted to any desired length from 10 to 16 inches, which allows complete flexibility of installation. New ideas include arms which simply hang over the disc; a pickup bug (similar to the bug which holds the cutting stylus) running over the record; and the B-J, a British import, which is really two arms attached to a single pickup and swinging separately so that the pickup is always aligned with the groove.
The vertical pressure of the playback stylus on the record will be a key factor in both stylus and record wear, and the various tone arms employ various ways to get the right "tracking weight." Some use springs at the rear end of the arm. In others the nonbusiness end will extend some distance beyond the pivot, counterbalancing the weight of the rest of the arm and the pickup. This means bigger installation space. The GE Baton arm features a head,attached to the arm itself by a swivel. Most pickups are made to respond best at a tracking weight of four to eight grams, but the pickups themselves are not all the same weight. The viscous-damped Gray 108-C adjusts any pickup to four or six grams of vertical pressure. The GE balancing bar is calibrated and has a moving screw, giving a choice of tracking weights. Both the spring and the counterbalanced arms often have some mechanism by which the tracking weight of the stylus can be increased or decreased. But none of these measurements will do you much good unless you know the actual weight of the pickup you are using and the weight of the pickup for which this particular arm was designed. You can measure the final vertical pressure of any arm and pickup on any one of a dozen gauges---preferably the Audak ($4), which is most accurate because it is a balance, with replaceable weights, and has no springs. But even an accurate measurement (which should be made, with all arms) does not tell you what will happen on warped records.
Tonearms and Warped Records
If many of your records are warped, certain precautions are indicated. In general, the lower the mass of the arm-and-cartridge assembly which has to take the jouncing from a warped disc, the better the results. The GE Baton arm, the Pickering, the Garrard, the Shure and the Weathers arms are engineered to operate well on a warped disc.
Matching Arm to Pickup
The functioning of the pickup, however, is more important than the perfection of the arm. Most pickups operate best in arms made by the same manufacturer. In some cases no other arm will do. The Ferranti, Leak, Shure and Weathers pickups will hardly work at all in another maker's arm. With the GE and Fairchild pickups you have a choice of arms, because these are the most popular in the business and every arm is more or less prepared to bold them. The Rek-O-Kut arm is designed to hold almost any pickup.
The cheapest recommended turntable and the cheapest separate arm will cost you, between them, about $80. For half this money you can buy the German-made Miraphon record player, with an excellent four-pole motor, a solid turntable and a very decent arm. It will not track quite so well as the separate arms, and the turntable is not so well weighted for the avoidance of wow and flutter. But you'll have to be pretty good to catch the difference, and the price is definitely right.
If you have a large quantity of 78-rpm or 45-rpm records, you will probably want a record changer. Getting up to change records every four to six minutes is unquestionably a nuisance, and it diminishes the pleasure of a phonograph. Since the argument for high fidelity is an increase in pleasure, there is no practical sense to the purist argument which rules out the record changer from all high-fidelity installations.
There may be no practical sense to it, but there are sound theoretical reasons behind it, which can be summarized. The motor of a turntable has one job, turning the table. The motor of a changer must also work, through intricate gears, to lift and move a tone arm out of harm's way and to push records one on top of the other. It does its basic job less efficiently because it has too many other things to do. The tone arm of a separate installation merely holds the stylus on the groove, and swings in as the record plays. The tone arm of a record changer must also trip a mechanism which starts the changing cycle. As it leans against this switch, toward the end of the record, it drags the stylus against the outside edge of the grooves, distorting the eventual sound and (more serious) wearing out the shorter grooves.
Since record changers do not have heavily weighted turntables, they lack the flywheel effect which makes for constant speed on precision instruments. The turntables are rarely a full 12 inches in diameter. This means that the vinylite record sags slightly as the stylus plays its outer area-and the stylus wears more heavily against the outside of the groove. Pickups are made to perform most accurately when the stylus is directly perpendicular to the flat record. A tone arm can be adjusted to hold the stylus in this position if there is to be exactly one record on the turntable. A changer, however, plays stacks of records, and the tone arm will bold the stylus perpendicular to only one of the records. The stack problem has other aspects, too. It increases the weight of the turntable which the motor is turning, and the turntable is likely to run slow as the stack builds up. Moreover, it never did a record any good to be dropped, and then to be gripped in the grooves of another record.
Nevertheless, except in the very best systems (which will pick up the changer's characteristic low-frequency rumble) the record changer is an adequate way of playing records. Those with an all-LP collection will not want it (the man who is too lazy to change records every 25 minutes is too lazy to live), but others are likely to find that its convenience outweighs its defects. Many hi-fi families own both a changer and a precision turntable the former to accompany Madame's housework; the latter for more serious listening.
Record changers come in all varieties. The ultra-fancy kind, which turns records over, has not been made for hi-fi use-it takes a special and pretty poor cartridge. But the Thorens, Garrard, Miracord, Glaser-Steers, Collaro and Webcor (in descending order of price) are eminently hi-fi goods.
(Excerpts from the book Hi-Fi All-New 1958 Edition)
History of Phono Cartridges
Fitment. Aside from cartridges made long ago (before the 60's) and Bang&Olufsen, which used a proprietary cartridge fitment, there are only two fitment styles in the whole world of stereo cartridges. These styles are called half-inch and p-mount. All magnetic cartridges have similar outputs and load requirements, and are functionally interchangeable.
The great majority of cartridges are "moving-magnet" type and have (nearly) identical values for impedance and capacitive load. Within the same fitment, all cartridges are basically interchangeable. However they can vary a great deal in sound quality. The only exception would be moving-coil cartridges, which look the same but cost a ton more. They have much lower output and require either an additional gain stage in the phono preamp or a step-up transformer.
Vintage Styli. Most cartridge manufacturers do not support their old cartridges. Finding an original stylus for your cartridge is likely to be fruitless, expensive, or just not the best option. The original cartridges shipped with new turntables were usually not the best type available. Instead of replacing the stylus in your original cartridge, replacing the whole cartridge is a much better option.
First, the cartridge body does suffer from exposure to the room air. Any ferrous particles will be attracted to the coil/core assembly inside the cartridge body. Over time, these particles do build up and inhibit the cartridge's performance.
Second, a replacement stylus assembly usually costs as much as the whole new cartridge. Stylus assemblies are the most expensive part of the cartridge.
Third, and most important, you can get much better sound from a well-selected new cartridge. The biggest difference between cartridges is the quality of its stylus. The most common stylus types are shown here:
A higher-quality stylus will meet the record groove wall along a wider surface area, allowing more accurate tracking and reducing stress forces at the stylus/groove interface. The groove wall has to push the stylus tip back and forth at very high speeds. If the force required to do this is spread out along a wider surface area, then the pressure and stress are reduced. High stress on the groove wall damages records by occasionally popping out small amounts of vinyl material. At the micro level, the vinyl material behaves under high stress as a concrete roadway would under intense heat. In short, better styli make better sound and reduce record wear.
This stress analysis photo shows the effect of a 2-gram tracking force.The elliptical stylus (Left) contacts the groove in a concentrated area with high pressure. The MicroLine stylus (Right) contacts the groove over a larger area, resulting in reduced pressure, improved tracking and signal clarity, and less record wear.
Turntable Basics has chosen these cartridges because of their high-quality styli and excellent sound.
Stylus: Biradial, elliptical nude diamond .4 mil x .7 mil
Tracking Weight: 1.0-2.0 grams (1.5 recommended)
Response: 20 Hz- 22 kHz
Output: 3.5mV RMS
Channel Separation: 22 dB @ 1 kHz; 17 dB @ 10 kHz
Channel Balance: 1.5 dB
Cantilever: Tapered alloy tube
Load Impedance: 47,000 Ohms
Load Capacitance: 100-200 pF
You will need a phono cartridge alignment tool to install this, or any half-inch mount cartridge correctly. Running any cartridge that is not aligned correctly will damage the needle and your records, and sound poorly. Cartridge performance is also determined by the quality of the turntable, tonearm, foundation, wiring and amplifiers. If a turntable is having problems with excessive rumble, improperly mounted tonearm etc, then any cartridge mounted on it would sound poor as a result. Because cartridge performance rests on so many variables and is essentially subjective, returns will only be accepted if the cartridge is defective.
p-mount w/half-inch adapter
Stylus: Biradial, elliptical nude diamond .4 mil x .7 mil
Tracking Weight: 1.0-1.5 grams
Response: 15 Hz- 25 kHz
Output: 5.0 mV RMS
Channel Separation: 26 dB @ 1 kHz; 17 dB @ 10 kHz
Channel Balance: 1.5 dB
Cantilever: Tapered alloy tube
Load Impedance: 47,000 Ohms
Load Capacitance: 100-200 pF
Stylus: 0.12 mil Nude square Micro-Linear
Tracking Weight: 1.0-1.8 grams (1.4 recommended)
Response: 20 Hz- 20 kHz
Output: 4.0 mV RMS
Channel Separation: 27 dB @ 1 kHz
Channel Balance: 0.8 dB at 1 kHz
Cantilever: Tapered alloy tube
Load Impedance: 47,000 Ohms
Load Capacitance: 100-200 pF
Coil impedance : 3,200 ohms at 1 kHz
Coil inductance (mH, 1 kHz) : 490
Dynamic compliance (x10-6 cm/dyne) : 10
Static compliance (x10-6 cm/dyne) : 40
Dimensions (mm) : L17.3 x W 16.0 x H 28.0
Mass: 6.5 grams
History of Phono Cartridges
Technically, the word for it is "transducer." A phonograph record is a physical fact: a thing. A turntable produces physical motion, the spinning of a disc. But the pickup lives partly in the physical world of its wigwagging stylus, and partly in the electrical world where all the rules are subtly different. It is the job of the pickup to transform the physical motions produced by the record, the turntable, the tone arm and the stylus into electrical signals containing the message from the frozen sound.
Many of the new pickups are smaller than the nail on your little finger, and most of them weigh less than five cents' worth of pennies. They are a triumph of miniaturization, a striking exception to the usual mechanical rule that the more delicate the work you have to do, the bigger the machine you need for it. For pickups deal with motions that can be measured only in hundreds of thousandths of an inch, and with electrical signals as small as a few one-thousandths of a volt-and many of them at once.
The most difficult part of the job is mechanical. The pickup must hold the stylus tightly enough to keep it in the groove even when it is jolted hard by a strong low-frequency signal. At the same time, it must let the stylus swing freely within the groove. When there's a pause in the groove's modulations, the stylus must spring back firmly to dead center, without any extraneous vibrations. At the same time, it must comply effortlessly with the correct vibrations when the music begins again.
Pickups: The Four Basic Types
Pickups embody various mechanical designs, and use different means of translating stylus motion into electrical energy. The four basic methods are called "magnetic", "dynamic", "piezo-electric" and "capacitance." The first two work by a "constant velocity" response, which means that the power of the signal created depends on the speed with which the needle whips around the wiggles. This is the exact reverse of the process by which the cutting head and stylus cut the record. Piezo-electric (crystal and ceramic) pickups and capacitance pickups have a "constant amplitude" response. This means that the power of the signal depends on the width of the wiggle from its crest to its trough, the degree to which the stylus is displaced from its center or rest position. Neither method is necessarily superior to the other, but the fact is that a majority of the satisfactory high-fidelity pickups are constant velocity-magnetic or dynamic.
The most popular magnetic pickup made---also one of the best and one of the cheapest---is the General Electric "variable reluctance" cartridge, in which the stylus is set in the end of a cantilever spring connected at its other end to a small permanent magnet. The stylus and vibrates between two iron pole pieces which extend up into the pickup chassis and form the cores of two small copper-wire coils. The pole pieces are yoked together at the top, close to the permanent magnet. This creates a complete circuit-magnet through stylus bar to pole pieces and back to magnet. As the stylus vibrates it feeds this magnetic-flux circuit alternately through the two pole pieces, inducing an electric voltage in the copper-wire coils. This voltage is led off to your preamplifier and emerges from the loudspeaker as musical sound.
Early GE cantilever stylus assemblies were too massive to transmit very high-frequency vibrations. New GE stylus assemblies, which fit the old cartridges, solve the problem. Extraneous vibrations of the stylus and the lever are damped pretty effectively by tiny elastic binding blocks.The GE comes equipped with one stylus (for 78 or microgroove) or two styli (one for each type of record) in a single cartridge. Anyone can take out the old stylus and put in a new one on the GE pickup, and the new two-stylus assembly is made in such a way that either stylus can be replaced separately. Maintenance is simple-just clean away the dust that gathers in the gap around the stylus. GE's -new, 1958-model VR-11 is made to track at a vertical pressure of only four grams. All the other variable-reluctance pickups cost considerably more than the GE, and there is some question about whether they are worth the extra money---except in a very expensive rig. The German-made Miratwin has extra values, however, for cheaper installations, too, because its output is five or six times as great as the GE's, since it needs less "gain" from the preamp. Among inexpensive preamps, where hum can be a problem, the Miratwin may be a safer buy-especially since the price difference between Miratwin and GE is now considerably less than the price difference between an elaborate and a simple preamplifier. The Pickering, which operates on somewhat different principles, and offers reliable viscous-damping of resonances, gives better high-frequency response than either the GE or the Miratwin, which may or may not be worth the extra cost.
A new "moving magnet" pickup---the Shure---is just coming onto the market now, and making a well-deserved splash. Engineered to the smallest tolerances of any pickup, the Shure is the most delicate and probably the most accurate of variable-reluctance designs; the output is very low, usually requiring a special transformer. Made to track at a vertical force of less than two grams, the Shure competes on at least equal terms with the fancier dynamic pickups, It costs as much, too.
In magnetic pickups the voltage which corresponds to the motion of the stylus is induced in a stationary coil by a "moving iron" element. In dynamic pickups the coil itself moves. Generally speaking, this design produces an even smaller voltage than the variable-reluctance magnetic design. Thus dynamic pickups give extremely low output and require either a top-quality preamplifier or a separate booster transformer. The most popular of them is the Fairchild, in which the wire coil is wound directly onto the duralumin bar that holds the stylus. It is an extremely accurate pickup, and the least fragile of the low-output dynamics. Fairchild makes only single-play cartridges, which means that you must buy two (each of which costs as much as a double-play GE) if you have both microgroove and 78-rpm records. The cartridge must be returned to the factory for stylus replacements minor drawback.
About the only disadvantage of the Fairchild (except for its price) is that the magnetic field extends some distance beyond the cartridge itself. If your record player has an iron turntable, the magnetic pull will increase the effective tracking weight of the stylus, speeding up both record wear and stylus wear. Most people who want to spend $75 for their pickups will also want to spend the necessary money for a machined-aluminum custom turntable. For those who use this pickup with a record changer, however, Fairchild makes a pad which sits on the turntable and keeps the cartridge safely away from the pull of the steel turntable.
Many experts f eel that the new Electro-Sonic Laboratories cartridge, especially in its imported Danish version (the American model is built to a Danish pattern), is or ought to be inherently the cleanest dynamic pickup, perhaps because of the appealing logic of its design. It is, however, extremely expensive (up to $100 for a single-play cartridge and balanced arm; no dual-stylus model is made) and terribly temperamental about working conditions. Like all pickups using magnets, it gathers dust, and cleaning it requires elementary knowledge of mechanics. In short, the ESL (as it is affectionately known in the catalogues) is for hobbyists and specialists rather than the average listener. Even here, it is seriously challenged by the Shure and the splendid British Leak ($70 with arm), which knowledgeable people say measures "flatter" than any other pickup. But it has almost no vertical compliance---which means it won't play warped records. The new Grado, just coming on the market at the end of 1957, gains vertical compliance by an ingenious plastic stylus bar and viscous-damped conical assembly. This is the one, you may recall, that has the radium dot to ionize record surfaces.
Crystal and ceramic pickups operate on an entirely different principle, chemical rather than electrical. It has been known f or some time that a crystal made of Rochelle salts will bend without breaking, and will give off an electric signal when made to bend. In piezoelectric pickups the head of the stylus (or, more commonly, a lever attached to the head of the stylus) is inserted into the crystal or ceramic (a synthetic crystal). Its side-to-side swing bends the crystal, and the result is a fairly sizable electric signal. The piezoelectric pickup has certain advantages over the magnetic. It gives off a much larger voltage, which means that it can be used without a preamplifier. Moreover, any extraneous noises that enter the system through the pickup will be far less important, because the intrinsic musical sounds are coming through with 60 to 70 times the strength they would receive from a magnetic cartridge.
The induction coil that makes the electrical signal in the magnetic pickup may in its wanderings come within the field of the turntable motor and transmit a dose of 60-cycle hum, while the piezo-electric pickup is impervious to stray magnetism. Finally, the magnetic is unsatisfactory in moist climates, because condensation forms between the poles of the magnet, eventually corroding the guts of the pickup; the ceramic (not the crystal) is impervious.
Nevertheless, a satisfactory magnetic pickup is easier to design than a satisfactory crystal or ceramic. The stylus in a magnetic pickup need push only a light coil of wire or an equally light metal tube, while the stylus in the piezoelectric pickup must bend a crystal. A baseball which hits a heavy wire screen at 60 miles an hour may dent the screen; a locomotive which hits the screen at that speed will go right through it. In every pickup, the stylus moves at the same speed. If it is to do more work, it must have greater mass.
The greater the effective mass of the stylus, the less responsive it will be to the back-and-forth push given by the moving wiggle on the phonograph record. It will have greater inertia, greater tendency to keep traveling in whatever direction it has been pushed. The strong low-frequency pushes, therefore, will tend to drive the stylus right out of the groove. Keeping the stylus in the groove will demand more stiffness inside the pickup, more resistance to the free motion of the stylus. Most piezoelectric pickups are therefore inaccurate at the lower f frequencies. And the piezo-electric pickup is a constant-amplitude device. The electric signal is caused by the bending of a crystal: the greater the degree of bending, the greater the signal. Records are cut, however, by a constant-velocity cutter, which makes the strength of the recorded signal proportionate to the speed with which the stylus whips around the wiggles. Low-frequency signals become wiggles of considerable amplitude, and high-frequency signals wiggles of infinitesimal amplitude.
Thus the piezo-electric pickup distorts the recorded signal by giving a loud voltage to the low-frequency notes and a soft voltage to the high-frequency notes. Moreover, there may come a time, at very high frequencies, when the amplitude of the wiggle is not sufficient to make the crystal bend, and the piezo-electric pickup will not respond at all.
None of this is quite as bad as it looks. As explained previously, high-frequency signals are boosted when records are made, to mask surface noise; low-frequency signals are attenuated, so that grooves can be kept narrow and lots of grooves cut into a single disc. The piezo-electric pickup, in boosting the bass signals and diminishing the treble signals, acts to equalize the distortion built into the phonograph record. While it will not boost or diminish on a curve that exactly matches the "recording characteristic" of the record, it will do a fair-enough job. And by eliminating the equalizer as well as the preamplifier, it enables a big cost corner to be snipped off. No piezo-electric pickup yet produced commercially will respond throughout the audible range, but a few of the new designs fit the stylus so closely into the ceramic that an electric signal will be produced by wiggles as narrow as 14,000 cycles. From 14,000 cps to 17,000 cps, which is the utter limit of normal hearing, represents a range of less than two whole tones in the musical scale, so a pickup which responds to 14,000 cps is quite adequate even for very high fidelity. Two piezo-electric pickups are made for installation in a full high-fidelity rig: the Electro-Voice Ultra-Linear and the Sonotone. Both companies make special preamps to handle their pickups.
Among all the other piezoelectric pickups, the experts have good words only for some Astatic crystals, the Sonotone, the British-made Collaro and the Dutch-designed Ronette ceramics. These would be adequate for low-cost hi-fi machines, except that even the minimum hi-fi amplifiers now include preamplifiers and are built for use with magnetic pickups. Most of the straight amplifiers presently on the market do not even have an on-off switch, let alone such refinements as a volume control. They are meant to be used only with a separate preamplifier control unit. So the crystal or ceramic cartridge fades away as a possible buy for anyone building a set from individual components. Where it is still important is in the packaged machine, usually portable or table-top, which uses the stronger voltages from the piezo-electric pickup to sidestep the expense of a preamplifier, and thus gives value for money in the $125-$175 price range. People who are looking to improve a well-loved package unit with a crystal pickup, though, might try substituting a Ronette for the old crystal. They'll hear the difference.
Capacitance or FM Cartridges
The less work the stylus must do, the more accurate the pickup can be. In magnetic, dynamic and piezo-electric pickups the electric signal is generated by the motion of the stylus itself, which requires a certain minimal bulk. Even with the most careful engineering a vertical pressure of four to eight grams is necessary to make such pickups work properly, and the moving mass of the stylus must remain a measurable quantity. If you could design a pickup, though, in which the signal voltage was already there, and the motion of the stylus would merely modify it, then...
Then you would approach the perfect pickup. Literally hundreds of patent applications have been filed on such designs, and a few such pickups have actually been manufactured. The most successful of them is the Weathers, which is called a "capacitance" pickup because engineers enjoy using such words, or an "FM" pickup because it works similarly to FM broadcasting. Briefly, the works of the Weathers pickup consist of a fixed metal plate onto which is fed a very rapidly oscillating charge, and a free-floating plate which in rest position stands parallel to its neighbor, a tiny air gap away. The floating plate is attached to the stylus. As the stylus traces the wiggles in the groove of a spinning record, it causes the floating plate to flutter toward and away from the charged plate. As the air gap expands and contracts, the oscillating current is modulated by the frequency of the vibration of the stylus.
The Weathers pickup cannot be bought alone. You also need the Weathers box with the oscillator which feeds the unmodulated and detects the modulated current, the way a radio tuner detects an FM broadcast. The combination costs $40 with a sapphire or $55 with a diamond stylus. Since the Weathers will not operate properly in any tone arm but its own, you had better add $15 for the arm and buy the package. The advantages of the Weathers are numerous. Since it tracks at a pressure of only one gram, it wears both records and styli much more slowly than any other pickup---except, perhaps, the Shure. A stylus will last about 20 times its normal life in a Weathers pickup. The moving mass of the stylus has been reduced to the point where it is scarcely measurable, which means that the frequency response is practically unlimited: the Weathers has tested out to 30,000 cycles. Because the vertical pressure is so low, the record can safely be
played while resting on a center cushion no wider than the label. The grooves never touch the turntable, and thus they pick up much less surface dust than those of the average record.
But all this is balanced, in most households, by the Weathers' one overwhelming disability: it is disgustingly fragile. A cross look can give it a case of intermodulation distortion. It must be fixed in place and left alone, and it is not recommended for any household in which more than one person has access to the phonograph. For bachelors, or people with unnaturally good control over the spouse and children, the Weathers is excellent. For others, it is just too delicate.
The Weathers pickup can be purchased with any of five styli: a 78 diamond or sapphire, a microgroove diamond or sapphire, or a "truncated" sapphire which will play all kinds of records. Because of its exceedingly low tracking weight, the Weathers can use an all-purpose needle without ruining records. No other pickup today can make this claim. Some of the cheap crystal pickups come with a single all-purpose stylus, but they invariably chew up both vinylite and shellac records in a very few playings.
A new and correctly shaped stylus will ride in the grooves of a record with its weight on two points at the sides of the groove. As the stylus wears, it will develop "flats" at these two points. Now a 10,000-cycle wiggle, halfway through a long-playing record, has a length of about .001 inch. If the flat on the stylus has a length of .001 inch, the stylus will simply ignore the 10,000-cycle wiggle. A worn stylus will therefore cut the frequency response of the phonograph, regardless of the newness of all the other elements. Worse, it will cut the record. A sharp edge forms at the point where the hemisphere tip of the stylus begins to flatten, and the edge gouges away the wiggles in the record groove. At four grams of vertical pressure the stylus presses on its two resting points with a weight of nearly 20 tons per square inch, and a sharp edge with such weight behind it will soon ruin a record.
An osmium stylus, which is standard equipment on crystals and ceramics of the second grade, will develop slight flats after playing only two or three LP's and may begin to damage vinylite records after as few as 10 playings (the wider groove of the old 78 does less damage to the stylus and, generally speaking, a 78 stylus will be safe enough for three times as many hours as a microgroove stylus). Few people are willing to change needles that often, and even if they were, the expense would be enormous. No need for it: the the sapphire is much cheaper.
An average sapphire stylus will give about 35 or 40 long plays before it begins to scratch records. With luck, it may go to 75 plays in safe condition. Since an LP plays almost an hour, this is not an insignificant amount of music, and in the average home would mean that the stylus would need to be replaced every two months or so. For most pickups the replacement cost is about $2. Pickups that must be sent to the f factory for stylus replacement should not, however, be bought with sapphire styli. The replacement charge on them is usually higher.
For LP's the recommendation is always the diamond. The purchase cost of the stylus will run somewhere between $8 and $16, but the diamond will last from eight to 30 times as long as a sapphire, which means that it costs much less over the long run. It also gives you fewer worries about what is happening to your records. A worn stylus will ruin records long before it begins to sound bad, and the man with a sapphire usually loses part of the fun of his phonograph because he is listening for that first sign of wear. A diamond should be good for at least 300 hours, and it may give 1,000 hours of listening before it goes sour. There is a considerable difference between 300 and 1,000, and the man who lives far from the madding crowd may find it difficult to decide when his stylus wants replacement. In most larger cities, however, a record store or hi-fi shop will have a 150-power microscope set up for the purpose of examining styli-and you can see for yourself whether or not the tip is dangerously worn.
It is dangerous to try cutting corners on the cost of a new stylus. When you buy a stylus you do not buy just a tip, but a complete assembly which is a vital part of your pickup. A "retip" soldered onto the old assembly is likely to change the very delicate balance within the pickup and produce distortion in the final sound. For the more common pickups-notably the GE-stylus manufacturers such as Walco and Tetrad produce perfectly good stylus assemblies which will work as well as the manufacturer's own. For other pickups, however, it is advisable to buy the stylus made by the company that makes the cartridge. You have put a lot of money into a phonograph, and the sound of that phonograph depends initially on the accuracy of its pickup. It doesn't pay to save two bucks on a stylus and distort the performance of the machine as a whole.
(Excerpts from the book Hi-Fi All-New 1958 Edition)
Phono Cartridge Alignment Tool.
An essential tool for installing any phono cartridge. Obtaining correct overhang length and alignment is essential to obtaining proper audio reproduction, and avoiding unnecessary record and stylus damage. This is a precision job and cannot be done by eye alone.
Based on long-accepted alignment geometry, but superbly executed, this alignment tool has a combination of features not available anywhere else. It is also the easiest to use.
The mirrored surface makes all measurements easier and more accurate. The mirror's parallax effect allows the elimination of sighting errors, and provides better lighting, critical in making fine adjustments on small parts. The two null points on the alignment tool are surrounded by concentric squares instead of a grid, so that the user will be measuring the cartridge body's lineup against parallel lines at each edge.
Finally, the horizontal sight-line, which is to be pointed at the pivot point of the tonearm when measuring alignment in the outer grid, ensures correct overhang length on any tonearm, irrespective of its effective length. There is an inverse relationship between the effective length of the tonearm and the optimal offset angle of the headshell.
Regardless of effective length, the two "null points," at which the stylus should be perfectly tangent to the groove, are the same. A properly designed and mounted tonearm will allow the cartridge to line up properly in both grids.
Complete instructions are included. They cover:
leveling the turntable
adjusting vertical tracking angle
calibrating and adjusting the tracking weight
setting overhang length
adjusting the tracking angle
checking and adjusting azimuth
Because some turntable models (i. e. Empire, Thorens, Luxman, VPI, Systemdek, Well Tempered) have larger spindles, this alignment tool is available with either a standard or oversized spindle hole. Please specify which model you need, or, which turntable model you own.
Stylus Force Gauge
Correct tracking force is not optional. Incorrect stylus force will damage your records as well as your stylus. Running the tracking force too low can be as damaging as running it too high. Always follow your cartridge manufacturer's specifications when adjusting tracking force. This simple balance-beam stylus force gauge is easy to use. Simply place the stylus on the mark indicating desired weight and adjust the tonearm counterweight until gauge balances straight and level. Ideally, this adjustment is best made with the stylus sitting at the same level as it would during playback. Either place the force gauge directly on the platter pad, or remove the platter pad and rest the force gauge on the mirrored alignment tool. The mirror will help determine when the gauge is perfectly level.
Ensuring that your turntable platter is perfectly level is critical to obtaining correct tracking performance. This simple, accurate bubble level is perfect for the job. Remove the platter pad and place the level on the bare metal platter with the motor off. Place shims under the foundation as necessary to make the bubble appear in the center of the printed circles. Observe the motion of the bubble to test for wobble in the foundation. Do whatever you can to make the foundation heavy and stable, to prevent the transmission of feedback to the turntable. Quiet foundations allow enhanced detail and dynamic range in the audio signal.
Reference: Turntable Basics
Home | Audio | DIY | Guitar | iPods | Music | Links | Site Map | Contact