Turntables—A Short History and Explanation
Turntables are getting very popular again. People are rediscovering the romance and appeal of vinyl, plus there is the now-solidly-entrenched faction that simply believes that analog-produced music sounds better than digitally-produced music. So, this is probably a good time to take a step back and look at the history and development of the modern turntable and what the major design considerations were. There are two main types of turntables in use today—belt-drive and direct-drive—so we’ll explore how they work, what the thought is behind each one, and what the pluses and minuses are of the two types.
First, a little turntable history. When stereo was first introduced in 1958—when single-channel music systems (“mono”) became 2-channel stereo systems—the most popular turntables were automatic “record changers.” These were turntables that could play several records in a row. Users would stack multiple records onto the tall central spindle and the turntable would automatically drop the next record down to the platter when the previous record was finished playing. Since a typical record contained about 20-25 minutes of music on a side, stacking four or five records was a convenient way to enjoy well over an hour of uninterrupted music.
Garrard RC-88 changer about to “drop” a record
Idler Wheel (“Rim Drive”)
Record changers needed a drive system with lot of torque in order to spin at the correct speed even when the platter was loaded down with several records. They used a high-torque drive system called an “idler wheel,” sometimes called “rim drive.”
The idler wheel was a small wheel about 1.5” in diameter inside the rim on the underside of the platter. It was driven off the main turntable motor and “geared down” to the proper record speed of 16 2/3, 33 1/3, 45 or 78 RPM.
Idler wheel was a dependable, simple, gutsy drive system. All the popular turntables used them, like the Dual 1009 and 1218, the Miracord 50H Mk II and 40A, and most of the Garrards, like the extremely popular RC-88 of 1960.
Dual 1218 idler wheel changer
They had two main downsides:
- Over time with heavy use, the idler wheel could
develop a “flat spot,” imparting a thump-thump-thump sound to the
Replacing the wheel was inexpensive and fast, however.
- Ported speakers were especially prone to the interference and distortion caused by these “subsonic” frequencies, which is why amplifiers and receivers in the turntable era had front panel “rumble” filters that cut the low frequencies, usually below around 60Hz. It cost you some bass, but it cleaned up the sound. Sealed speakers (“acoustic suspension”) were pretty much immune to “rumble” because their woofers were better damped, which is just one of many reasons that sealed speakers like AR, KLH and Advent were the market leaders in the 1950’s through the 1970’s.
Serious audio/equipment aficionados (“audiophiles”) distained the notion of stacking and dropping records on top of each other and grinding their fragile grooves against one another. No, instead, serious audio enthusiasts were “one record at a time” users. That being the case, there was no need for the high-torque idler wheel drive system, since single-play turntables didn’t need the torque to power through the weight of all those records sitting on the platter. A single-play turntable only needed enough torque to spin one record. There must be a quieter way to do this than with a noisy idler wheel, with its mechanically-coupled rumble.
There was a better, quieter way. It was called the belt-drive turntable. In the early 1960’s AR (Acoustic Research, the people who invented the small high-performance “sealed” speakers that revolutionized the entire stereo industry) came out with a simple, inexpensive, belt-drive single-play turntable. It was simply called “The AR Turntable” and it sold in the millions. Millions. Its basic audio performance in terms of speed accuracy and absence of rumble was far superior to the standard record changers of the day.
The AR belt-drive single play turntable
The AR Turntable (and other belt-drive turntables) used a rubber belt that stretched from the turntable’s motor around a lip on the underside of the platter to spin the platter. The inherent vibration-damping trait of the rubber belt meant that these turntables had much quieter operation than most idler wheel units because the motor’s natural vibrations would simply be damped out and absorbed by the rubber belt before they reached the record. It was (and remains) a system of beautiful and inherent simplicity and efficiency.
There were two main downsides to belt-drive:
- The belts would stretch over time and slip,
resulting in inconsistent platter speed (known as “wow” and “flutter”) and
would require replacement. Replacing the belt was fast and inexpensive, however.
- The overall torque of a belt-drive system was much lower than idler wheel, which is why stacked record changers were always idler wheels—you needed that gutsy torque to spin a heavy platter laden with the weight of 4 or 5 LPs. A belt-drive system just couldn’t do it. But as we said, that didn’t matter to the serious audio enthusiast. They didn’t want to stack records.
Then around 1972, Panasonic introduced a new drive system, under its Technics brand name: Direct Drive and the now-classic Technics 1200 turntable.
Technics 1200 direct-drive turntable
In a direct-drive turntable, the platter sits directly on the drive motor (often speed-controlled by a quartz-control system, like a fine Swiss watch), which spins at exactly 33 1/3 or 45 RPM—far slower (and therefore more quietly, with less vibration) than the motor in either a belt-drive or idler wheel system. And they were torquey too—although by the 70’s, stacking records on top of each other 1960’s-style had fallen out of favor, so there weren’t really any “direct drive” record changers.
Direct-drive didn’t require that the user replace an idler wheel or a drive belt. They were essentially maintenance free. (Maybe a drop of lubricating oil once every 6 months or year. That was it.) Their speed accuracy was great. They were quiet—although truth be told, they did still impart a little noise to the rest of the system. A minor downside was that since the platter sat directly on the motor (that’s why they call it “direct drive”) whatever small amount of noise and vibration the motor did produce went right to the platter.
Audio enthusiasts still debate the relative merits—plus and minus— of direct drive vs. belt drive. Belt-drive aficionados insist that the insulating properties of the rubber belt imbue it with superior acoustic characteristics compared to a direct drive turntable. Belt-drive supporters also say that the character of the noise that a direct-drive motor transmits to the platter is more objectionable than the noise transmitted by a belt system (having to do with the spectral content and harmonic structure of the noise signal, etc.). Direct-drive proponents argue all day long that any differences in noise are minimal and theoretical and are totally swamped by direct-drive’s real-life advantages in speed accuracy and reliability.
In reality, the overall superiority of one turntable over another has as much—if not more—to do with its tonearm characteristics as it does with its drive system. Straight vs. S-shaped tonearms, tracking angle distortion, tonearm mass (and compatibility with cartridges of differing compliances), pivot friction, dynamic vs. static balance systems—there are lots of things to consider.
Let’s look at these issues and give them a brief overview:
Straight vs. S-shaped
With a tonearm, one of the most important characteristics is the weight or mass of the tonearm. It stands to reason that the lower the tonearm’s mass, the better it will glide over the record’s grooves and track the slight ups and downs of the record surface (after all, no record is perfectly flat). Another design consideration is lateral balance, the notion of having equal mass distributed on either side of the tonearm’s pivot. As with most things in audio engineering, there always seems to be a tradeoff.
A straight tonearm can have the lowest mass since there is literally less material from the pivot point to the headshell. But with the offset-angle of the headshell, there is very slightly more mass to one side of the pivot point than on the other side. Theoretically, this imbalance can lead to a small amount of audible tracking distortion.
“S”-shaped tonearms, by virtue of their curved shape and their headshell being right in line with the tonearm, have equal mass to either side of the pivot point. That’s good. However, if you “straightened out” an S-shaped tonearm, it would be longer than a straight tonearm, and thus have greater mass. The classic tradeoff. Good for bad. Bad for good.
The pivot point of the tonearm should have as little friction as possible, obviously, since that friction is a major determinant of how easy and unrestricted the tonearm’s action will be as it moves across the record. Manufacturers used all manner of bearings, knife edges, pointed terminations and the like to ensure the lowest friction possible. The combination of tonearm mass and pivot friction make up a very significant portion of tonearm performance.
Balance and Tracking Force
Another important consideration for tonearm performance is the manner in which the tonearm is balanced and how the tracking force is applied. Most tonearms are balanced (to a horizontal “level,” floating in air) by turning the counterweight behind the pivot closer or farther away until the arm is free-floating perfectly level with the weight of the cartridge installed in the headshell at the other end. Once the arm is balanced, the tracking force is applied, in accordance with that particular cartridge’s tracking capability.
Ahhhh….but the way in which that tracking force is applied can actually make a surprising difference in the performance of the arm/cartridge combination. Dual had a great system: they used a coiled spring located right at the tonearm pivot point to “squeeze” the arm down with the exact amount of tracking force you wanted:
¾ gram, 1 gram, 1 ¼ gram, etc. The beauty of this method was that it was accurate in any plane, meaning even if the turntable was not sitting on a perfectly level surface, the tracking force was still accurate.
Dual 701 Belt-Drive Turntable with Coil-Spring Tracking Force System
In contrast, a gravity-type tracking force adjustment (such as using the counterweight to apply the tracking force) required that the turntable be perfectly level, since the weight was, in effect, being “pulled down by gravity” in order to be accurate. If the turntable wasn’t on a level surface the actual tracking force would vary slightly from the indicated force. Enough to be audible? Maybe, maybe not. But definitely enough to annoy an OCD audiophile.
The worst method of all for applying tracking force was the so-called “sliding weight” method. Here, after the arm was balanced, an actual small sliding weight would be moved along the tonearm towards the headshell to apply the tracking force. The farther from the pivot (closer to the headshell), the greater the tracking force. Here was the problem: As the weight was slid along the tonearm, the effective mass of the tonearm increased as the tracking force was increased. It’s akin to holding a 5-lb brick in one hand close to your body—easy. But extend your arm all the way out while holding that same brick, and it becomes impossible. That’s a perfect example of the “effective mass” being increased. The actual mass is the same—it’s the same 5-lb brick and the same person holding it. But the relative positioning makes all the difference.
Philips had a really nice manual belt-drive turntable in the early ‘70’s—the model 202—that used the sliding weight tracking force method. A serious drawback to an otherwise nice turntable.
Philips 202 Turntable: Sliding weight clearly visible mid-arm
The record master (the metal “parent” that presses all the “offspring” vinyl copies) is cut with the cutter positioned at 90˚ to the centerline radius of the disc. 90˚. But you can see that with a pivoting tonearm, the playback stylus of the cartridge is never positioned at 90˚ to the grooves all across the record. The amount by which this playback tracking angle deviates from the 90˚ cutting angle is called the tracking error, and it is audible to some degree. Traditional pivoting tonearms—both straight and S-shaped—angle the headshell such that the stylus’ position relative to the record’s grooves is a “good compromise” across the entire record surface, fairly consistent from lead-in to lead-out grooves. There are two points on the record where the angle is at the desired 90˚, and over the rest of the record, it’s off. However, the tracking-angle error in a correctly-angled headshell is pretty small between those two ‘good’ spots.
Fortunately (or unfortunately, depending on how you look at it) most listeners aren’t really aware or bothered by the tracking angle distortion, because it’s relatively low in level, and even more importantly, the listener almost never actually hears a record played back without this tracking distortion for comparison. You hear an amplifier playing clean and clipped, and you can compare them. You hear a speaker bottoming out and not bottoming out, and you can compare them. But most listeners only hear records played with tracking angle distortion. They have nothing to compare it to.
In point of fact, tracking angle distortion is not that horrible a problem. As these two charts illustrate, a tracking error of as much as 5˚ only corresponds to a 2nd-harmonic distortion of less than .2%, which is very low. Still, purists will argue, it’s additional distortion, on top of amplifier and speaker distortion, so any distortion that can be eliminated is a good thing.
In consumer electronics, when there is a technical problem, engineers rush in. If the engineers are successful, the sales/marketing people rush in right after. Such was the case with tracking distortion.
What’s needed to eliminate tracking distortion is a turntable with a tonearm that positions the cartridge such that it plays back the record at the same 90˚ angle at which they were cut. Sounds simple and logical, but the execution is quite difficult. With a conventional pivoting tonearm, the arm moves freely, literally being “pulled” across the record by the stylus as it plays the continually diminishing spiral diameter of the record. (Now you can really see how important tonearm mass and pivot friction is, since the entire motion of the tonearm depends on how easily that tiny, fragile stylus can “pull” that comparatively huge, massive tonearm along with it).
Tangential-arm turntables have their tonearm (and thus the cartridge’s playback stylus) positioned at 90˚ to the record grooves, just like the cutting stylus was, so their tracking error is zero. Great.
But in order for the tonearm to move across the record, it’s necessary for the arm to be controlled by very precise electric motors that push the arm across the record, rather than a conventional pivoting arm which is pulled across the record by the stylus. The electric motor arrangement of the tangential-arm turntable is a very particular, complicated arrangement, fraught with oft-realized opportunities for failure. In practical terms, the degree of objectionable audibility of tracking distortion that was “solved” by a radial-arm turntable ended up being the living embodiment of that old phrase, “Too complicated by half.” In practical market terms, it just ended up not mattering one whit to the majority of users.
Nonetheless, there were some clever tangential-arm turntables that hit the market. In spite of their mechanical complexity, high cost and often-questionable reliability, when they worked, they accomplished exactly what they claimed to do: eliminate tracking error distortion. Were they a huge audible improvement over the conventional pivoting arm turntable? No. Were they expensive and finicky? Yes. But their existence deserves to be noted.
The Rabco units were pretty much the original linear-trackers on the market. Technics also had a series of models that worked quite nicely, using what was called a “P-mount” cartridge. P-mount was the industry’s attempt in the late-1970’s at simplifying cartridge mounting with a simple plug-in system that used a standardized configuration across all brands. It only enjoyed modest acceptance since audiophiles disdained the limited cartridge choices and restricted adjustments of the one-size-fits-all approach.
Rabco ST-7 Linear Tracking Turntable
The Garrard Zero-100
This turntable deserves its own in-depth write-up, considering what a singularly unique and innovative product it was. What if tracking error distortion could be eliminated inexpensively and simply with a conventional pivoting tonearm? Wouldn’t that be great? All the mechanical simplicity of a normal pivoting tonearm, no complicated electric motors, plus the audible superiority of zero tracking distortion. Now, that’s something customers would eat up.
That was the thought behind Garrard’s Zero-100 automatic turntable. Using an ingenious—but mechanically-simple—“auxiliary” arm alongside the main arm that caused the moveable headshell to continuously pivot to the correct position such that the stylus was always at the 90˚ playback angle, the Zero-100 was one of the most clever and cost-effective solutions to an existing audio problem ever devised. It worked perfectly. Aficionados swear that records played on the Zero-100 have a clarity and openness to their sound simply unavailable from ordinary pivot-arm turntables, regardless of their tonearm sophistication. The design was so well done and precisely-executed that the “auxiliary pivot arm” added virtually no effective mass or pivot friction compared to an excellent traditional tonearm.
Garrard was a first-line turntable company and, expectedly, the rest of the Zero-100’s performance was quite good. Interestingly enough, the Zero-100 was an idler-wheel-driven stacking record changer, not a higher-end belt-drive single-play design. One might think that an audiophile-oriented feature like zero tracking-angle distortion would not be of that much interest to the record-stacking crowd, but this is yet another good example of how product planning/marketing people are just regular ol’ folks like you and me. Little inexplicable errors in judgment happen in all walks of life. Apparently, turntables from 1971 are no exception.
Garrard Zero-100 Turntable
Idler-wheel-changer or not, the Zero-100 was an excellent turntable. Its basic performance—rumble, wow and flutter, speed accuracy, tonearm friction, etc.—was quite excellent and it never suffered any excessive reliability problems despite the complexity of the articulating arm. It sold well as a singular model during its roughly 4-year run, but Garrard never introduced any additional follow-up pivoting-arm models in the ensuing years, nor did any other manufacturers emulate the design in their own products. In the end, the Garrard Zero-100 turntable was the quintessential example of the dictum, “A solution in desperate search of a problem.” But it was a fascinating product, a great example of clever, cost-effective engineering that redounded convincingly to the customer’s benefit, even if that benefit was mostly theoretical.
Zero-100 perpendicular at lead-in grooves, halfway through record
Paradoxically, this entire tonearm/cartridge discussion is not as relevant as it once was, because most turntables today come with a pre-matched and -mounted cartridge, whose compliance, tip mass and tracking capabilities have been chosen to compliment the host turntable’s tonearm’s characteristics for optimum compatibility and performance. (At least, we hope so!) You can read more about the tonearm-cartridge interface in our Turntable Buying Guideline Article.
Direct Drive and the Rise of the DJ
One advantage of direct-drive is indisputable, however: The rugged, high-torque, low-maintenance qualities of direct-drive turntables made them perfect for DJ’ing and scratching effects. Without direct-drive turntables, DJ’ing would never have happened. You can’t DJ with a belt-drive Thorens TD 125 or an idler wheel Dual 1229.
Today’s direct-drive DJ turntables—like the Denon DJ Prime VL12—put a premium on user/DJ interaction in the live performance realm, rather than on ultra-refined music reproduction in a quiet living room like the audiophile turntables from 40 years ago. Where yesterday’s music listener didn’t want the turntable to exhibit any speed variance whatsoever, today’s professional DJ uses their turntable as a live performance instrument. Intentional speed variations, adjustable torque for fast musical start-up and precise “scratching” effects, a rugged cartridge/tonearm system that can stand up to the rigors of heavy-duty use under party conditions, these are all requirements of the professional DJ turntable.
Denon DJ Prime VL12 professional DJ turntable
Therefore, these days, turntables fall into three broad usage categories: The casual music listener, the “serious” audiophile music listener and the DJ. Turntables intended for each of these user groups are markedly different, with specific emphasis on the performance, convenience, adjustability and durability characteristics that are most important to their intended market. Club DJ turntables are all direct-drive with extensive speed-adjustment capabilities that enable the DJ to create a wide range of special effects, whereas music-listening/audiophile turntables are either direct- or belt-drive. The idler wheel is long gone, but at least now you have a full understanding of how and why we got to where we are today.