By Alan Lofft
above: Tangential-tracking turntables have been made by Bang & Olufsen for more than a decade. Shown here is a view of the Beogram 8000
APPEARENCES can be deceptive. What looks like a simple enough task-rotating a disc platter at a constant speed with a support system that allows a phono cartridge unrestricted movement in tracking the inwardly spiraling record groove-on close examination turns out to be fraught with considerable technical problems, many of them inherent in the analog system of sound storage devised by Edison and Berliner. And with the shadow of the digital Philips/Son), Compact Disc looming on the horizon, discussion of the traditional turntable concerns-flutter, rumble, tone-arm geometry, and so forth-might seem oddly out of touch. After all, what relevance does talk of drive-system accuracy, lateral tracking error, or mechanical isolation have when the Compact Disc may relegate these subjects to the back shelf of audio history? Inelegant or not, the grooved analog disc is still the world standard, and it will remain so for at least the next few years. Industry pundits now envisage the transition from all-analog to all-digital record production as taking as long as the move from mono to stereo: perhaps ten years. Even if you decide to purchase a CD player in the near or distant future, you're still going to need an analog turntable to play all those treasured discs in your collection that-for economic, musical, or technical reasons-are unlikely ever to be reissued in the digital CD format.
So the old concerns of turntable buyers are still valid. And this year, technical innovation and competition for the audio dollar have combined to offer better performance and more re fined (and useful) convenience features for less money than before. Two years ago, who would have believed that an automatic direct-drive turntable with tangential-tracking tone arm and microprocessor control would be available for only $200? But as good engineering reduces some of the old analog-disc vexations (rumble, for example) to (mostly) inaudible levels, other turntable parameters-effective mass of the tone arm, mechanical isolation, flutter, tone-arm geometry-take on greater practical significance. In addition to performance aspects, today's turntable buyer must also consider pivoted vs. tangential-tracking tone arms, direct vs. belt drive, "servo controlled" tone arms, and at least four levels of automation.
Turntable Drive Systems
Any turntable drive system must rotate the platter on which the disc sits at a specific, constant speed, free of any rapid speed irregularities (flutter), slower speed variations (wow), or long term instabilities (drift). Vibrations and noise from the turntable's motor must not reach the platter, where they will be detected by the cartridge and re produced as a low-frequency rumbling noise along with the music. Any of these problems, if sufficiently severe, will have unpleasant audible consequences on music reproduction.
Perhaps the simplest means of achieving all these goals is the belt-drive system. A motor attached to the turntable base, spinning at about 300 rpm, drives a relatively heavy platter by means of a flexible rubber belt or band.
The rubber belt prevents most of the motor vibration from reaching the platter, and the momentum of the platter overcomes any small speed fluctuations caused by motor-speed irregularities or belt slippage. In the simplest models, the motor is an a.c. type whose speed is regulated by the a.c. line frequency (which is held very steady); hence the term "a.c. synchronous" is used to de scribe this type of turntable motor.
An outstanding virtue of synchronous belt-drive design is its simplicity. It can be found in inexpensive turntables from JVC, NAD, Marantz, Fisher, and others, as well as in moderate-to-expensive models from Europe (Thorens, Dual) and the United Kingdom (Linn, Mission, STD, Ariston, Systemdek, Michell). The difference between less costly and more expensive models is mainly a function of platter weight as we] as sophistication of the suspension/vibration-isolation system and the tone arm.
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THIS MONTH'S COVER:
The Pioneer PL-7 featured on the front cover of this issue is a fully automatic, direct-drive turntable with quartz-PLL speed control. It has a straight, statically balanced Polymer Graphite tonearm. Price: $200.
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Rather than relying on just the flywheel effect of a heavy platter to smooth out momentary speed fluctuations, many belt-drive models (Pioneer, Harman Kardon, Dual, Thorens, and Technics, for example) incorporate a method of speed regulation called servo control. This system compares the speed of the motor (or revolving platter) to an internally generated, fixed reference frequency (or voltage) and supplies instantaneous correction when any speed discrepancies are detected.
Servo-controlled systems usually produce less flutter than a.c. synchronous drives, and they also allow for electronic, rather than mechanical, speed change as well as vernier adjustment of the playback speed (pitch control).
A further refinement of servo control is possible through the addition of a phase-locked loop (PLL), perhaps in conjunction with a quartz-crystal oscillator. These features do appear on belt-drive models, but very rarely; they are mostly associated with direct drive, the drive system that virtually dominates the turntable market for models priced between $150 and $500. With direct drive, the platter rests directly on the shaft of a low-speed (331/3- or 45-rpm) motor. This would seem to encourage the transfer of vibration directly to the platter, but the very slow rotation of the motor places most, but not necessarily all, of the rumble frequencies in the infrasonic region, below audibility. Since the platter and motor can be considered an integral unit, the servo control of a direct-drive turntable reacts very quickly to minute speed fluctuations, enabling direct-drive models, as a class, to achieve somewhat lower flutter figures than belt-drive systems.
Although many direct-drive and belt-drive turntables produce essentially inaudible amounts of rumble, the exact distribution of rumble frequencies differs from one model to another, and sometimes the rumble can reach audible levels at audible frequencies. Rather than trust the somewhat confusing state of rumble specifications and measurements, do an in-store test: while playing music, set the volume control to a level that is as loud as you're ever likely to want for listening, make sure the system's tone controls are set "flat," and then play the "silent grooves" between cuts on an LP through speakers with good bass response. (Do not play the lead-in groove for this evaluation since it is usually filled with built-in rumble.) All you should hear is the groove "swish"; if you hear any low-frequency rumbling, try another turntable. Use the same record for all the tests, since the built-in rumble from the pressing and record-cutting lathe can vary from one disc to another. (Variations in perceived rumble can also be caused by tone-arm/ cartridge problems; see below.)
The Tone Arm
An ideal tone arm would suspend and maintain the phono cartridge in perfect alignment to the record groove, allowing the cartridge and stylus to follow the groove inward with no lateral resistance to its movement across the record.
This utopian tone arm would also permit the cartridge to negotiate large record warps or other disc-surface ripples without causing violent oscillations of the cartridge/tone-arm combination and without disturbing the orientation of the stylus to the groove. In practice, these ideals are somewhat compromised, regardless of whether the arm moves in a straight line (called a linear-tracking or tangential-tracking arm) or describes an arc across the surface of the disc (a pivoted arm), as shown in Figure 1. But with careful tonearm design--and exacting accuracy in cartridge installation--either type of arm is capable of extremely accurate recovery of musical information from the record groove.
When a master disc is "cut," the cut ting head and stylus move on a straight, radial rail from the outside edge to the inner portion of the disc.
Tangential-tracking tone arms essentially attempt to duplicate this movement with the playback cartridge and stylus. The approach, in theory at least, is supposed to create the least difference between the cutting- and playback-stylus alignments and hence the least amount of distortion in playback. Therein lies the appeal of the linear-tracking arm. But, with few exceptions, radial arms do deviate from perfect tangential alignment to the record groove. A record groove is not an equally spaced spiral; if it were, then it would be a simple matter to propel a tangential arm smoothly across the disc at a constant speed. Since the groove spacing varies, the arm's horizontal speed must also vary. This is accomplished by letting the spiraling groove itself pull a linear-tracking arm slightly away from perfect tangency; the servo system controlling horizontal arm movements senses such deviations and uses them to vary at which the arm moves across the disc.
The deviation from tangency required to get the arm in a linear-tracking turntable moving either inward or outward can typically be 0.5 degree.
The traditional pivoted tone arm, anchored at one end to a corner of the turntable, swings in an arc across the disc, producing a varying inherent degree of error in the angle of the cartridge to the groove. By offsetting the angle of the cartridge/headshell assembly relative to the arm shaft (or by using an S- or J-shaped arm) and by care fully choosing the angle of offset in relation to the arm's length and position, the tracking-angle error (and any distortion due to that error) can be reduced to zero at two points on the disc.
At all other points, the errors of a pivoted arm can be reduced to levels (typically 2 to 3 degrees) that are audibly insignificant and measure only slightly greater than those of a tangential-tracking tone arm.
All of this, however, assumes correct tonearm design and perfect cartridge alignment in the tone arm, two things not always achieved in either type of tone arm. There are numerous examples of pivoted arms with incorrect con figurations, and even the most meticulous audiophile is unlikely to mount a cartridge in a pivoted or tangential arm with an accuracy greater than ± 0.5 degree in angle or less than 1 millimeter in position. As Peter Mitchell, president of the Boston Audio Society, has convincingly pointed out, these practical factors combine to cancel any theoretical superiority due to tangency accuracy of a linear-tracking tone arm over a pivoted one. An alignment-protractor accessory can help the buyer of a pivoted-arm turntable to achieve correct tone-arm geometry and to reduce tracking-angle error.
Technics' introduction of "P-mount" plug-in cartridges for both its linear-tracking and pivoted-arm turntables effectively removes the possibility of alignment or positioning errors in cartridge installation. The P-mount system replaces the headshell and cartridge-mounting hardware with a simple receptacle that the cartridge plugs into, thus forming a positive, mechanical interlock between cartridge and tone arm. The system is being adopted by other manufacturers, and P-mount cartridges are now available from several of then-, freeing the less nimble-fingered turntable buyer from the tedious and exacting task of cartridge installation as well as ensuring a high degree of alignment accuracy (assuming, of course, that the manufacturer has calculated the arm geometry correctly be forehand). Manufacturers are also be ginning to pay attention to the problems of installation and alignment for conventional cartridges. Shure's V15 Type V cartridge comes with its own special alignment tools, for example, and other cartridges come premounted in headshells.
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A linear-tracking arm allows the stylus to be in nearly perfect tangency to the record grooves at all points in its path.
A pivoted arm with an offset headshell will have zero tracking error at two points (indicated by arrows) and a maximum of 2 to 3 degrees of error at other points on the record.
Figure 1. The theoretical advantage of a linear-tracking turntable (left), also called tangential-tracking or straight-line-tracking, over one with a conventional pivoted tone arm (right). A straight pivoted tone arm with an offset headshell (or an S- or J-shaped arm with no headshell offset) will hold the cartridge exactly tan gent to the record groove at only two points. (The positions of these points vary according to the degree of offset; a straight arm whose headshell has no offset will be tangent at only one point.) At other points on the record, the cartridge may have a tracking-angle error of up to 2 or 3 degrees. A linear-tracking arm's headshell is theoretically tangent to the record groove at all points; in practice, the amount of tracking-angle error is de pendent on the electromechanical accuracy of the servo-control system. It is usually 0.5 degree or less. A linear-tracking arm also requires no antiskating correction. However, a possible disadvantage is that linear-tracking machines are inherently more complicated mechanically than pivoted-arm turntables. Most use photo-optical arm-displacement sensors to control the servomotors.
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One definite advantage that linear-tracking tone arms do have relates to skating force. Since the frictional drag of the record groove is always along the longitudinal axis of a tangential-tracking arm, the downward pressure of the stylus on both groove walls is identical, as it should be. In a pivoted arm, how ever, the geometry of the tone arm and the groove friction combine to create a force that tends to pull the stylus to ward the center of the record (it "skates" inward), so that there is more pressure on the inner groove wall than on the outer one. If not compensated for, this pressure differential can produce uneven record wear and distortion due to mistracking (since the outer groove wall may be traced with too little tracking force). Most pivoted-arm turntables therefore have antiskating mechanisms that apply a compensating outward push to oppose the skating force. (The mechanism may be a spring, a hanging weight, or a magnetic-repulsion system.) No antiskating system can ever be set perfectly, however, since the amount of antiskating force required at each moment varies with the level of groove modulation, the modulation frequencies, the distance of the cartridge from the center of the disc, the stylus shape, and the composition of the disc material. In contrast, a linear-tracking tone arm generates no skating force, so it re quires no antiskating force. In this respect it is ideal, though superiority due to a banishment of skating force, by any means, is difficult to hear at best and is usually inaudible.
The friction of a tone arm's bearings (rather than their type-ball-race, knife-edge, etc.) should be considered in choosing a tone arm (or turntable), especially if a high-compliance premium cartridge is to be mounted in an integrated turntable's pivoted arm. The delicate stylus assembly must carry the combined mass of the cartridge and tone arm across the record; if there is excessive horizontal friction in the arm bearings, the outer groove wall will have to provide the necessary force to overcome it. As a result, tracking of complex, highly modulated passages may be degraded. The lower the vertical tracking force (VTF) the cartridge requires, the more important arm friction becomes. For medium-compliance, middle-line cartridges, a bearing friction (in milligrams) amounting to 5 percent of the tracking force is acceptable, but for high-compliance, low-tracking-force cartridges, a bearing friction of 1 percent of the recommended VTF is ideal. The lateral bearing friction of the best separate tone arms is typically in the range of 10 milligrams. Recently, a number of manufacturers have started providing arm-bearing friction specifications for their integrated turntables.
Finally, in making a choice between the pivoted or linear-tracking arm, buyers should be aware that linear-tracking models are inherently complex: a combination of servomotors, pulleys, worm gears, and/or rollers is employed to move the arm carrier along its guide rail. Pivoted arms, in contrast, are usually quite simple, and simplicity in a mechanical design generally implies high reliability.
Arm Mass and Resonance
When a weight suspended by a spring is disturbed, it "prefers" to bob up and down at a certain rate. Similarly, when stimulated by a record warp, the combined mass of a cartridge and tone arm likes to bounce up and down on the springy stylus suspension at a certain rate. The rate of this bouncing-the tone-arm/cartridge resonance frequency-is determined by the springiness or compliance of the stylus suspension, the effective mass of the tone arm, and the weight of the cartridge body. (Effective mass is the relative massiveness at the headshell end of the arm, which matters more than the arm's total weight.) Most record warps occur in the range of one to seven times per second-in other words, at 7 Hz or less. If the tone-arm/cartridge resonance frequency also falls in this range, a record warp will trigger a violent bobbing of the tone arm, resulting in cartridge mis-tracking, powerful infrasonic signals that can cause woofer distortion, and possibly even skipped grooves (see Figure 2). The vertical cartridge motion also moves the stylus forward and back ward in a "scrubbing" motion. This produces a particularly annoying flutter modulation of the musical program, heard as a waver in the sound as the warp passes beneath the stylus. The bobbing action rapidly alters the vertical tracking force as well, producing too much force on the uphill side of the warp and far too little on the downhill side, a problem that is exacerbated by a massive tone arm. Changes in tracking force can result in mistracking and distortion over the warped portions of the record. The trick, then, is to keep the tone-arm/cartridge resonance frequency above the region of record warps (7 Hz and below), yet below the audible frequency range (starting at around 20 Hz); the range from 10 to 12 Hz is considered ideal.
The tone-arm/cartridge resonance frequency can be raised into the ideal range by reducing the compliance (springiness) of the stylus assembly, by reducing the weight of the cartridge body, or by reducing the effective mass of the tone arm (through more skeletal construction or lighter-weight materials). Since a significant reduction of stylus compliance results in poor bass tracking ability, the other two routes are generally chosen. For example, several leading cartridge manufacturers have introduced models with greatly reduced overall weight. With its P-mount system, Technics has eliminated the headshell and mounting hardware on its cartridges, thus lowering their mass; moreover, since the mass and compliance of the cartridges that can be used with a P-mount turntable are known in advance (the characteristics of P-mount cartridges are standardized whatever the manufacturer), Technics claims to have optimized the resonance on all their P-mount turntables at 10 Hz. Combining the cartridge and headshell into a single plug-in unit (an approach taken by Audio-Technica, Ortofon, and ADC) will also lower the over all effective mass and raise tone-arm resonance.
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Figure 2. Tracking a warped record. If the vertical motion of the cartridge, headshell, and tone arm that is caused by a warp is not properly damped, an oscillation at the resonant frequency of the combined system will set in. This oscillation causes variations in tracking force and cantilever angle. The resulting motion causes the stylus to change speed relative to the disc.
Record moving in this direction.
Tracking force increases here as the warp forces the stylus and arm up.
On the downhill side of the warp, cantilever tension keeps the stylus in the groove while the cartridge lags behind.
Up-and-down cartridge motion
Back-and-forth stylus motion ("scrubbing")
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Figure 3. The four basic types of turntable drive and suspension systems (front views). While there may be other systems and combinations of systems used in some units, these are the most common. Often execution is more important than design.
(a) Simple Belt-Drive Design Dust cover Light wood or synthetic base Rubber-shock-mounted motor Rubber drive belt (b) Simple Direct-Drive Design Decoupled feet Compliant feet (c) Elaborate Belt-Drive Design Dust cover, motor, and base are insulated from the platter and tone arm.
Simple pads Direct-drive motor Floating subchassis Rubber drive belt (d) Elaborate Direct-Drive Design Dust cove
'Tunable" isolating feet Special nonresonant compound base or, with increasing price, a more massive wood or synthetic base Loose,-floppy" springs Simple wood or compound base - Special nonresonant compound base
Direct-drive motor
Floating subchassis
Stiffer isolators instead of loose springs
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By now it should be clear that per haps the biggest advantage of most, but not all, tangential-tracking turntables is a much shorter, lighter, and therefore less massive tone arm. The arm tube on many linear-tracking models is typically half the length of a typical 8 1/2- to 9-inch pivoted tone arm. Such short tone arms can easily keep the tone arm/cartridge resonance in the ideal range. In pivoted-arm turntables, there is an increasing emphasis on reducing arm mass through spare, bare-bones construction and the use of new, light-but-rigid materials (carbon fiber, titanium, and the like), a trend evident in the integrated turntables from Onkyo, Pioneer, Harman Kardon, and others.
Ultra-low arm mass and lightweight construction may not be quite the panacea it is thought to be, however. Experiments conducted at Canada's National Research Council demonstrated that several ultra-low-mass arms displayed a high sensitivity to structural resonances excited by stylus vibrations in the groove. These resonances extended well into midrange frequencies; worse, loud music exacerbated the resonance peaks by as much as 30 dB! A more traditional arm of medium mass was largely insensitive to these effects. It would seem that specially rigid and light materials (such as the aforementioned carbon fiber) are more resistant to these structural resonances.
Not only should the arm/cartridge resonance fall at the proper frequency, but its strength should be reduced or damped, because an undamped arm/ cartridge resonance can exaggerate turntable rumble, floor-conducted vibration, or low-frequency mechanical feedback from the speakers. A viscous-damped hinged brush attached to the cartridge absorbs much of the shock of record warps and lowers the amplitude of the arm/cartridge resonance.
Turntable manufacturers have also taken steps to reduce arm/cartridge resonances. Dual decouples part of the counterweight from its tone arm with a flexible material; this antiresonance filter vibrates in the region of the resonance, but out of phase, thereby canceling much of the resonance peak. A technically ingenious approach to lowering effective mass and controlling arm resonances can be seen in the "Ser vo-Tracer" or "Bio-Tracer" pivoted arms on some Denon, JVC, and Sony turntables. Servomotors within the arm correct any unusual, rapid arm motions (such as those from record warps).
These techniques can theoretically re duce a tone arm's effective mass to zero while suppressing resonances entirely.
Some manufacturers attempt to make an issue out of the shape of a pivoted tone arm. Though most pivoted arms nowadays use a straight arm shaft, an S- or J-shaped tone arm can work just as well and needn't be more massive. For example, by using titanium tubing and moving the headshell sockets close to the arm pivots, SME has achieved very low effective arm mass in its highly regarded Series III tone arms.
Suspensions and Vibration
A phono cartridge is an acutely sensitive but terribly undiscriminating vibration detector: it can't separate the musical vibrations from the record groove from other vibrations trans mitted from the external environment, whether they are from footfalls on the floor, speaker cabinets shaking the turntable shelf, or high-volume sound energizing the plastic dust cover. A good turntable suspension will reduce these external vibrations (along with the turntable's motor noise) to audibly insignificant levels. If a suspension is inadequate, enough of these disturbances may reach the platter and tone arm to cause muddied or boomy bass, coloration of midrange sound, howling feedback, or groove jumping (with heavy footsteps). The wise turntable shopper should know beforehand where the turntable will be located as well as any eccentric physical characteristics of the listening room (old springy wood en floors, for example), because different types of suspensions (see Figure 3, page 49) react somewhat differently to particular installations.
The suspension in Figure 3(a) is typical of many belt-drive turntables. Rubber motor mounts and drive belts insulate the platter from motor vibration, and compliant "feet" on the base help damp out external shocks. The base may be made of light wood or a nonresonant synthetic compound. This type of suspension will yield adequate isolation when the turntable is located well away from the speakers. Note that there is no acoustic insulation between the dust cover and the turntable base (or the tone arm), so acoustic pickup at high playback volumes might be expected.
(Incidentally, you can improve the isolation of any simple turntable by placing it on a 1-inch-thick slab of particle board laid on top of a sheet of urethane foam of similar-or greater thickness. Make sure that the turntable is level and steady, however. Special accessory isolating feet are also available for placing either directly under the turntable or under the board; experiment for best results.) Quite similar is the suspension in Figure 3(b), which is typical of inexpensive direct-drive turntables whether they have pivoted or tangential-tracking arms. Flexible feet are the principal means of isolation, but at higher price levels you will find a more massive wooden or synthetic slab as the base (Yamaha, Denon, Sansui, JVC, and other manufacturers take this approach in their top direct-drive models). Such bases often weigh about 25 pounds, double that of inexpensive models.
Thanks to a basic law of physics-it takes a great deal more energy to set a large mass in motion than a small one-a turntable with a massive base along with decoupling feet can be placed fairly close to speakers played at high volume. The heavy base also resists excitation by dust-cover vibration.
The more elaborate belt-drive suspension in Figure 3(c) anchors the mc tor and dust cover to the base but suspends the platter and tone arm on a subchassis with loose, floppy springs.
As long as this type of turntable is placed on a secure shelf or table, the suspension system provides excellent isolation from floor-conducted or acoustic vibrations. However, springy wooden floors or a shaky shelf can ex cite the floppy suspension, causing groove jumping. This type of jiggly suspension also takes some getting used to when cueing a record and can be quite unnerving to inexperienced users-a consideration if babysitters, family, or friends will be operating the turntable.
Typical of Technics, Pioneer, and Dual direct-drive models, the suspension in Figure 3(d) also has a floating subchassis but utilizes much stiffer isolating springs, a nonresonant-com pound base, and compliant feet, which in some cases can be "tuned" to sup press a specific low-frequency vibration. This suspension may offer slightly less isolation than the previous type, Figure 3(c), but it is much less sensitive to instability from springy floors or a shaky shelf.
Where the machine's design permits, you can check the isolation characteristics of a turntable by placing the stylus in the record groove with the platter stationary and giving the shelf on which the turntable rests a sharp rap with your finger. The weaker the "chunk" you hear through the speakers (or the headphones), the better the turntable's rejection of external vibration.
A good record mat (see Figure 4) should, by supporting the grooved area of the disc, suppress "microphonic" pickup by the disc of acoustic energy in the listening area. Record support by raised rubber ridges or pods is to be avoided, although record clamps may help as long as they aren't too heavy.
"Sticky" rubber accessory mats have been found to be very effective in sup pressing disc resonances, but they're a bit inconvenient: the adherence between the mat and disc usually necessitates peeling the mat off the record. A technically elegant, though costly, solution to the problem of disc/mat resonance is available in the accessory Audio-Technica Disc Stabilizer and either of two Luxman turntable models.
These use an air pump to form a vacuum bond, lasting for the duration of play, that sucks the disc down tight against the platter.
Automation and Niceties
Perhaps a decade ago, buying a record changer (a turntable that automatically plays a stack of LP's) meant a serious compromise in performance.
Well, that time is past; direct-drive and belt-drive changers from many manufacturers have virtually the same wow, flutter, and rumble specs as their less automated brethren. For the record collector who wishes to avoid the inconvenience of having to get up and change records at the end of a side (and it is inconvenient sometimes) but is not overly fastidious about record handling, the major consideration is whether the convenience outweighs the added complexity intrinsic to the operation of an automatic changer.
For most turntable buyers, however, the major decision will be choosing among single-play automatic, semi-automatic, and manual turntable models.
A manual turntable requires the user to do everything: remove the arm from its rest, place the stylus on the record, and return the arm to its rest at the end of the side. Mechanical simplicity is a manual turntable's main virtue. With a little more mechanical and electrical complexity, a semi-automatic model offers automatic shut-off and arm-return at the end of play, a pleasant convenience. (There are also in-between types that only lift the arm at the end of a disc; you have to return the arm to its rest manually.) For those who find greater peace of mind in not having to manipulate the delicate cartridge and arm at all, an automatic clearly is the right choice. Buying an automatic often brings other niceties: some models have sensors built into the platter to detect the disc size or to prevent the turntable from operating unless a record is on the platter (a fine childproofing feature). Other automatics will repeat the same side over and over (handy at parties). Some of the least expensive tangential-tracking models have, built-in muting to silence the initial impact of the stylus on the disc, a nice touch. In fact, buyers who choose a tangential-tracking model usually get pushbutton, servo-con trolled cueing; you never need to touch the arm even when cueing manually.
Once automatic arm-control functions have been incorporated into a turntable, microprocessor selection of individual cuts can be added relatively easily. Some linear-tracking models can be programmed to play cuts in any or der, repeating some and skipping others (haven't you always wanted to play Janis Joplin's Pearl without having to listen to Mercedes Benz one more time?). Programmability is even avail able on some pivoted-arm turntables.
Human engineering with respect to controls and features shouldn't be over looked. Turntables with their controls mounted outside the dust cover are more convenient and offer fewer opportunities for dust to settle on your records. Check whether the dust-cover hinge operates smoothly and whether the cover will stay open when it should (it should, of course, be closed when you're playing a record). Try the cueing controls: does the stylus return to the same spot when it comes back down? Is the stylus-force gauge easy to read? Does the counterweight on the tone arm have a good friction clutch to retain the correct balance setting? Do all the controls work smoothly, or does operating them set the suspension into a jiggly oscillation? If you like to play DJ and back-cue selected cuts, check the platter's start-up time. Some direct-drive models have plenty of torque and reach full speed in less than a revolution.
Some belt-drive units with heavy platters often take from 4 to 7 seconds to stabilize at speed. A strobe-assisted, vernier adjustment of platter speed is useful to compensate for drag from a too-heavy record-cleaning brush or to tune the pitch of a disc to match that of a musical instrument for playing along.
For installations where space is at a premium, there are a number of alter native designs of considerable appeal.
Sony, Aiwa, and Pioneer all have front-loading turntables with retracting drawers that extend at the touch of a button; some even have tangential-tracking tone arms. The front-loading format allows the turntable to be stacked with other components, but make sure that you can still see the disc to cue up a selection manually when the unit is stacked (programmable cueing mitigates the latter problem). The foot-wide turntables with tangential tone arms built into their covers are very compact, but they need to be placed in good light so that individual cuts can be seen through the covers for cueing.
Mitsubishi's vertical-loading format seems ideally suited to shallow shelving but requires lots of vertical space. Both Kenwood and Sharp also have vertical-format models; the Sharp unit is even able to play both sides of a disc without turning it over (around?).
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Raised label area; Raised edge bead of disc protrudes beyond edge of mat.
Indentation in mat accommodates label area.
Mat supports grooved area of disc.
Platter
Figure 4. An ideal record mat. The model was derived from laboratory and listening tests performed by the Canadian National Research Council. Note how the groove area of the record is evenly supported by the mat at all points.
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Clearly, the current crop of turntables offers an extraordinary range of features coupled with, by and large, impressive performance. But this makes choosing a particular model all the more difficult. Still, buyers should feel assured that in selecting a unit from any of the major manufacturers, they will be getting a turntable whose performance and specs (particularly with respect to rumble, wow and flutter, and tone-arm mass) are considerably better than those of most models of only a few years past. Five or six years ago it was almost impossible to find an integrated turntable with a low-mass tone arm; to day there are many. Some audiophiles may not be able to find one model with all the features and the performance they want. For them, the answer may be two turntables: a modest automatic model for family and friends to use and an uncompromising manual turntable with separate tone arm for purist pursuits. This solution--at least for this writer--keeps everybody happy!
Turntables: How to Evaluate the Specs
How to Judge a Vinyl LP Record Without Playing It