Manufacturer's Specifications:
Stabilizer Plate Diameter: 11.81 in. (300 mm).
Thickness: 0.374 in. (9.5 mm).
Weight: 3.087 lbs. (1.4 kg).
Basic Material: Duraluminum.
Suction Unit (AT661)
Power Source: Two C batteries, 3 volts d.c.
Current Drain: 500 mA, loaded.
Low-Voltage Operational Limit: 1.64 volts.
Time Required to Obtain Suction: 7 seconds or less (110-cc capacity load).
Obtainable Vacuum: 400 mm Hg or better.
Limiter Operation Vacuum: Over 350 mm Hg (3 volts d.c.).
General Specifications:
Dimensions: 2.79 in. (71 mm) W x 1.61 in. (41 mm) H x 5.16 in. (131 mm) D.
Weight: 6 oz. (168 grams) without batteries.
Supplied Accessories: Spindle adaptor, turntable platter spacer, record compressor, cleaning leather, suction nozzle, two C batteries.
Price: $295.00. Company Address: 1221 Commerce Dr., Stow, Ohio 44224.
During the Consumer Electronics Show held in Las Vegas in January 1982, Jon Kelly, President of Audio-Technica U.S., demonstrated a prototype of a vacuum record-clamping device that replaces the turntable mat and converts the turntable to a vacuum-platter turntable, clamping the record in place for over an hour. This item was, indeed, unique! A vacuum-suction system is used to flatten out all record warps, usually of the "dish" or "pinch" type, on a 12-inch (30 cm) record. At the same time, it firmly bonds the vinyl record to the vacuum platter, thus eliminating the ever-present problem of vinyl resonance. In the prototype shown at the CES, the vacuum was created with a hand-operated vacuum pump. I was of the opinion that this type of vacuum pump would, after a while, become a nuisance such that the Disc Stabilizer would not be used except by the most avid audiophile. Apparently, many people were in agreement because it wasn't long before I was informed that the vacuum pump would be battery operated.
During the summer CES, held in Chicago last June, Audio-Technica introduced the modified version with the battery-operated vacuum pump. With this innovation, the AT666EX Disc Stabilizer can be used to modernize most direct-drive turntables and possibly any belt-driven turntable currently available. Some older spring-suspension turntables may require a heavier type of suspension spring capable of handling the additional three-pound weight. Further, the turntable manufacturer should be asked if the bearings can withstand the device's three pounds; I am quite certain, for example, that the Linn Sondek's can't.
Vacuum-platter turntables are not a new idea, inasmuch as they have been around for a few decades. Their primary use is to hold (bond) the acetate record blank (lacquer) firmly to the cutting lathe turntable when a master disc is being cut. About three or four years ago Luxman introduced their PD-555 turntable with a vacuum-suction system that is excellent, but the price is almost $3,000. Subsequently, Luxman produced at least three additional turntable models utilizing the vacuum-suction system, but still employing a manual vacuum pump and still fairly expensive. I understand that the Michell Gyrodec is a vacuum-suction turntable utilizing a bellows-type vacuum pump (looking somewhat like a concertina bellows) that is placed over the center pin when drawing the vacuum. Thorens recently announced that they were introducing a new turntable (TD226) with their VCM vacuum system, but here again the price is beyond the reach of most audiophiles. Undoubtedly, there will be a number of others soon.
The Audio-Technica AT666EX Disc Stabilizer is a precision-machined, duraluminum vacuum-platter turntable accessory. It has thin, rather flat, rubber seals located around the outer edge, just inside the bead on the record surface, and at the inner area just before the raised label area. The pliable, thin rubber gaskets are 7.5 mm wide. The outer diameter of the outer gasket is 297 mm, and the outer diameter of the inner gasket is 120 mm. When a record is placed on this vacuum platter and held down evenly across the entire record surface with a record compressor or heavy turntable mat, an air-filled chamber is formed. The vacuum platter has channels going from the formed air-filled chamber to a suction (vacuum) outlet tube on the vacuum platter rim. The vacuum pump attaches here when drawing a vacuum. On the opposite side of the vacuum platter rim is a small, hand-turnable relief valve. It breaks the vacuum, allowing the record to be removed from the vacuum platter.
After the battery-operated pump creates a sufficient vacuum by removal of air from the chamber formed by the record and vacuum platter, the pump automatically stops.
The gaskets, which have a tacky feel, firmly attach themselves to the record rim and label, permitting no air to enter the formed chamber. In turn, the record is immediately pulled (sucked) flat against the vacuum platter surface, effectively eliminating the warps. When the vacuum is drawn, atmospheric pressure exerts a force of about 551 lbs. (250 kg) on the record surface, forming a solid bond between the vinyl and the metal vacuum platter and making the record effectively a part of the vacuum platter.
After using the AT666EX over a long period of time, it may well be advisable to replace the rubber gaskets in order to keep the device in a mint-like condition. Those who have more than one turntable can purchase, separately, additional stabilizer plates.
A word of caution--the rubber sealing gaskets and the record surface contacting these gaskets must be scrupulously clean if the vacuum is to be maintained for at least 30 minutes. The average length of an LP record is about 27 minutes, with a rare record lasting 33 minutes.
The advantage of a vacuum clamp system is that it eliminates record warp, distortion, and resonance problems associated with the usual manner of playing records. Feedback, both acoustic and stylus, is usually the cause of disc resonance that results in an increase in distortion and sound-smearing. The same sort of distortion and sound-smearing can also occur in the absence of acoustic feedback but in the presence of stylus feedback.
Test Procedures and Results
All tests were performed under the following conditions: Constant ambient temperature and humidity at 75° F, 67% humidity; constant ambient temperature at 84° F, 70% humidity, and constant ambient temperature at 66° F, 70% humidity. Each temperature change required that all elements remain at that temperature and humidity for a period of three to four hours.
Records used in the tests were cleaned with the Discwasher record-cleaning system. The rubber gaskets of the Disc Stabilizer were cleaned in various ways, e.g., with a dampened and wrung-out cleaning leather (chamois), Scotch tape, 25% to 50% ethyl alcohol, pure white cake soap, and a plastic kitchen sponge. Again, a word of caution: The only 25% to 50% alcohol permissible for use in cleaning the rubber gaskets is ethyl alcohol (also known as ethanol, grain alcohol or grain spirits). Neither methyl alcohol (also known as methanol, carbinol or wood alcohol) nor isopropyl alcohol (rubbing alcohol) should be used as they frequently contain other ingredients (e.g., lanolin) which are harmful to rubber. A trade secret--if ethyl alcohol is not available, 100-proof (not 80 proof) vodka (e.g., Smirnoff or Wolfschmidt) may be used inasmuch as it is 50% ethyl alcohol and has no additives, such as flavoring agents.
Stolichnaya vodka is not acceptable because it contains a flavoring agent. If you wish to use a 25% alcohol solution, dilute the acceptable vodka 1:1, one ounce of distilled or mineral-free water and one ounce of vodka.
The Technics SP-10 Mk II direct-drive turntable was used in these tests in combination with the Audio-Technica AT666EX Disc Stabilizer. Where necessary, the Luxman PD-555 vacuum turntable was used as the control.
The records used in testing had an average mild warp, and one record was very warped.
To get the platter and rubber gaskets clean enough for my lab tests I experimented with a number of procedures.
In the first of these, I dampened the cleaning leather in water, thoroughly wrung it out, and then applied the chamois to both the platter and rubber gaskets. A second technique involved using a 50% alcohol-dampened, lint-free cloth to wipe both platter and rubber gaskets. A third and more thorough method was to take a plastic kitchen sponge dampened with plain tap water, lightly rubbed on a cake of white soap, and then applied to the metal platter and rubber gaskets. The soap was then removed with a tap-water dampened plastic sponge, and the entire platter and the rubber gaskets wiped with a 50% alcohol-dampened, lint-free cloth.
After any cleaning procedure, if some lint and dust remain on the tacky rubber gasket, the adhesive side of Scotch tape (or Audio-Technica's AT6104 Dust Cleaner) should be dabbed, not rubbed, over the entire area of the rubber gasket to remove the foreign matter. The record areas that will be in contact with the rubber gaskets should be dabbed with Scotch tape to remove any foreign matter.
The absence (zero warp) or presence of warp was visually checked with the aid of a tonearm and cartridge combination. The check points were about 1/2 inch beyond the record edge, in the middle of the record, and about 1/2, inch from the run-out groove.
The record compressor was used at all times to press the record evenly against the Disc Stabilizer when establishing the vacuum seal. Using the electric pump, the vacuum seal was established within five to six seconds.
Due to the nature of this study, I requested two additional Disc Stabilizers so that initially each device would undergo only one cleaning test.
When using the first cleaning procedure (the damp chamois) under any of the temperature and humidity conditions, the vacuum seal did not hold well and warp was visible for 12 to 15 minutes after establishing the vacuum seal and zero visual warp. However, the record could be played reasonably satisfactorily under these conditions since only the outer edge showed the presence of warp, and the stylus was already playing the middle of the record.
Therefore, the sound was not affected too much by the visible presence of some edge warp. Because the rubber gaskets are tacky, they continue to adhere to the record, and about 25% of the vacuum remains. An increase of the ambient temperature to 84° F only prolonged the time required to establish the vacuum but did not appear to have any effect on the length of time the vacuum held. A decrease in ambient temperature to 66° F did not appear to have any visible effect on the test or the length of time the vacuum held. From the temperature studies, I concluded that the AT666EX is not temperature sensitive.
When using the badly warped record in these tests, there was some difficulty in establishing a vacuum seal. When the vacuum was established, the normally raised edge of the warp area was flattened, but the usual condition of the record called for a part of the record to be raised (i.e. warped). Accordingly, this created a strongly positive upward force that continuously worked against the vacuum seal and in about 9 or 10 minutes broke the vacuum seal.
All the test results following the second cleaning procedure were, in general, quite similar to those of the first cleaning procedure. However, when the third and more extensive cleaning procedure was used, the vacuum seal held for 27 minutes. Apparently, records that are badly warped cannot be flattened for the entire playing time. This record was checked on the control device, the Luxman PD-555, where the problem was not encountered.
Because of the problems associated with the first two cleaning procedures, I concluded that the Disc Stabilizer and the rubber gaskets were contaminated during the manufacturing and/or assembly period and needed a more thorough cleaning. Consequently, I cleaned the entire Disc Stabilizer using the third cleaning technique.
The test results were dramatic. A vacuum seal was established at zero warp that held for a period of two hours and 20 minutes, although a moderate amount of warp was visible across the entire record at the end of the time period.
The badly warped record stayed reasonably flat for over one hour, starting with zero warp. The average warped record was held flat for proper playing with just a barely perceptible warp seen at the outer edge on some records at 25 to 30 minutes. Most of the mildly warped records remained flattened for more than 30 minutes, long enough to eliminate the problems caused by warp during play.
After using either of the first two cleaning procedures on the Disc Stabilizer, I conducted a number of experiments at an ambient temperature of 75° F, 67% humidity. Using an average, mildly warped record, I established a vacuum seal and zero warp, then reattached the vacuum hose to the Disc Stabilizer and turned the vacuum pump to the "On" position. On the average of about once every 5.9 seconds, the vacuum pump started to draw a vacuum for less than a half second, reestablishing the original vacuum. This action was observed for 30 minutes at a time for a total of four hours. Under these conditions it became evident that a small leak developed 4 1/2 minutes after the original vacuum was drawn and verified for zero warp. When the 30-minute time period had elapsed, the constant action of the vacuum pump maintained the vacuum despite the leak. When the vacuum was permitted to leak, the experiment ended within 15 minutes.
When the third cleaning procedure was used this phenomenon did not occur. With the pump attached as above, the vacuum seal held from 25 to 30 minutes before the vacuum pump was activated to reestablish the original vacuum. This test was repeated four times with reasonably similar results.
It should be mentioned that the more extensive third cleaning procedure was needed only once-when the Disc Stabilizer was first used. Thereafter, use of the dampened cleaning leather appeared sufficient. The Scotch tape process was used at all times to remove any possible lint or dirt that was not picked up by the cleaning leather. Of course, at some time in the future when the Disc Stabilizer has become soiled, it may again be necessary to clean the entire Disc Stabilizer, using the third technique.
Use and Listening Tests
Having spent quite a number of hours listening to records played on the Luxman PD-555 vacuum turntable during the past couple of years, I had a reasonably good aural reference point when listening to records played with the aid of the Audio-Technica AT666EX Disc Stabilizer. In my opinion, it is incontrovertible that a vacuum-turntable system, in combination with a good tonearm and cartridge, dramatically improves the sound output from any record. For proof, it is necessary only to play a record on the Luxman PD-555 vacuum turntable with and without the vacuum-clamping device and then repeat the process using the Audio-Technica AT666EX Disc Stabilizer. The results are truly amazing.
Aurally, the AT666EX was practically identical to the Luxman control system, with clean sound, particularly in the treble and upper midrange. It was a bit difficult to identify the turntable when playing a record under "blind" conditions, the Technics SP-10 Mk II turntable fitted with an Audio-Technica AT666EX or the Luxman PD-555 with its own built-in vacuum-clamping device.
In conclusion, I find the Audio-Technica AT666EX Disc Stabilizer to be a superb and effective vacuum record-clamping device. I recommend it without reservation, particularly to the audiophile who has almost everything.
-B. V. Pisha
(Source: Audio magazine, Jan. 1983)
Also see:
Audio-Technica AT 6006a Safety Raiser (for tonearms) (Aug. 1982)
Audio-Technica AT160ML Cartridge (Sept. 1984)
audio-talk from audio-technica -- Number 7 in a Series (ad, Sept. 1984)
ADC Model LMF-2 Tonearm & ZLM Phono Cartridge (Jan. 1979)
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