Manufacturer's Specifications:
Turntable:
Drive System: Belt.
Motor Type: 16-pole synchronous.
Speeds: 33 1/3 and 45 rpm.
Speed Accuracy: 0.2%.
Wow & Flutter: 0.06% DIN wtd. peak.
Rumble: -77 dB, DIN B weighted.
Dimensions: 18.8 in. (47.8 cm) W x 14.5 in. (36.8 cm) D x 5.9 in. (15 cm) H.
Price: $289.00 without arm, $459.00 with MAS-282 tonearm.
Tonearm:
Type: Low-mass, straight, statically balanced.
Effective Mass: 6.5 grams without cartridge; 7.3 grams with accessory counterweight.
Headshell Offset Angle: 25.5°.
Tracking Force Range: 0 to 2.5 grams; to 3.6 grams with accessory counterweight.
Allowable Cartridge Weight: 3 to 10.5 grams; to 14 grams with accessory counterweight.
Price: $195.00; accessory counterweight, $18.00.
Company Address: Music & Sound Imports, 30 Snowflake Rd., Huntingdon Valley, Pa. 19006, USA.
In a world full of turntables made of aluminum and plastic, it is a pleasure to encounter one made of good old-fashioned wood. I'm not just talking about the wooden top plate, with its attractive oiled finish; the MAS Mk. I turntable is manufactured almost entirely of wood and wood derivatives.
The only metal parts in the system are the motor, bearing assembly, springs, and a few odd screws. This is one turntable, you can be sure, in which the sound will not be colored by metallic ringing.
The base is made of thick, high-density particleboard, as is the spring-suspended subchassis on which the platter and tonearm are mounted. The heavy, inert 4.4-pound platter is machined from a disc of Tufnol, a dense resin-bonded paper matrix similar to Bakelite. In the words of the turntable's designer, Colin Walker, "Tapping this platter in an attempt to induce ringing will result in (a) failure and (b) a sore knuckle." The MAS Mk. I turntable is manufactured for Music & Sound Imports by the firm of C & J Walker in England, using essentially the same drive and platter system as the highly regarded Walker CJ55. Its design is traditional: The platter and tonearm are suspended together on a floating subchassis, which is suspended from the top plate via three compliant coil springs that isolate the record-playing system from external vibrations. The low-speed synchronous motor is fastened to the base, its rotation transmitted to the platter via a pulley and a thin rubber belt. Compared to many of today's more exotic designs, the interior of the Mk. I looks simple, even crude; but what matters is its performance, which in most respects is very good indeed.
The Mk. I is available in two versions; one has a blank tonearm board, while the version reviewed here is pre-cut to accept the MAS-282 tonearm. The MAS arm requires only a single mounting hole; a drilling template and fastening wrench are included in the package. It is a straight arm with desirably low mass and an ADC-type detachable headshell.
Mounting and aligning a cartridge in this headshell is relatively easy, and an alignment protractor is included to assist in optimizing the lateral tracking. Anti-skating bias is provided by a small weight hanging from a thread which passes over a pulley to five fastening points, to match bias and vertical tracking force in 0.5-gram increments. The captive signal cable, emerging from the bottom of the tonearm pillar, is 1 meter (39 inches) in length, and terminates in gold-plated RCA plugs plus a ground wire.
A chart provided with the arm shows how the frequency of the infrasonic arm/cartridge resonance is related to the cartridge compliance and the total effective mass (cartridge plus arm). The instructions recommend that the resonance should fall between 8 and 13 Hz. If it's above 13 Hz, brass weights (weighing 2.2 and 4.4 grams) are available to be mounted between the cartridge and headshell; this will raise the effective mass and lower the resonant frequency.
The instructions supplied for setting up the turntable, and installing and adjusting the tonearm, are skimpy to the point of inadequacy. Audiophiles with experience in setting up other manual turntables will manage without difficulty, but if your experience is limited to turntables that come out of the box ready to run, you may need to depend on the skills of your dealer. The procedures are straightforward: Remove the fiberboard bottom panel, locate and drill the mounting hole for the tonearm, mount the arm, remove the transit screw to free up the spring suspension, put oil into the main bearing, install the drive belt, and put on the platter and mat.
The final step involves adjusting the compression of the three coil springs until the platter is level and floating at the correct height.
Since the Tufnol platter is acoustically "dead," there is no need for a thick rubber platter mat to suppress metallic ringing; a thin felt mat is supplied with the turntable to cushion an LP disc and damp its microphonic vibration.
The MAS Mk. I is a "manual" turntable, pure and simple; it doesn't automatically cue the beginning of a record or switch off at the end. It has exactly one operating control-a pushbutton to start and stop the platter rotation. To change from 33 1/3 to 45 rpm, you must lift off the platter and move the drive belt to the larger of the two pulleys.
Measurements
The following measurements were made by my colleagues Alvin Foster and J. K. Pollard of the Boston Audio Society.
The turntable speed, which is not user-adjustable, was 0.47% fast at 33 1/3 rpm, and was unaffected by variations in a.c. line voltage from 75 to 130 volts. The wow and flutter was 0.065% unweighted and 0.04% DIN-weighted, well below the threshold of audibility. The platter torque was rather low, evidently because of belt slippage; the drag of a Discwasher brush slowed it to a crawl, and it even slowed noticeably under a 10-gram load. So if you plan to use a Dust Bug brush, you probably should reduce drag by taping a quarter on its rear end to serve as a counterweight.
The indicated vertical tracking force was accurate to within 0.1 gram. Although the anti-skating is adjustable only in 0.5-gram steps, it proved satisfactory, since skating compensation can only be approximate anyway. The arm cueing was well damped, providing a gentle descent of the stylus into the groove with no sideward drift. The arm exhibited very low pivot friction and no detectable play, a result which is consistent with the claimed bearing tolerance of only 10 microns. The capacitance of the tonearm wiring and signal cables was measured as 100 pF in each channel.
While the overall rumble was very low, the motor's fundamental vibration frequency of 120 Hz is transmitted to the record and was audible via headphones, especially when playing records whose own surface noise was very low.
However, this hum-like sound was not noticed at any time via loudspeakers, even at quite high playback levels.
The tonearm's infrasonic resonance behavior was assessed with a Shure V15 Type IV phono cartridge. Since the MAS-282 tonearm has very low pivot friction and no provision for damping, the arm/cartridge resonance was very pronounced, rising to a 30-dB peak at 11 Hz with the Shure's damping brush disengaged. Engaging the damping brush brought the resonance down to a 10-dB peak from 15 to 19 Hz.
One of the major byproducts of an undamped resonance is exaggerated cantilever deflection in response to surface irregularities and disc warps, and a consequently large variation in the effective vertical tracking force that acts to hold the stylus in contact with the groove. A strain-gauge cartridge was installed in order to observe these effects directly; on a visibly flat record, peak-to-peak variations of 0.8 gram in effective tracking force were detected, and on a severely warped disc the effective VTF went negative as the stylus departed the groove and went into free flight. Therefore, it is recommended that the MAS tonearm be used with an external damping device or with phono cartridges having internal stylus damping. (This advice, of course, applies to all tonearms that have low pivot friction and no provision for their own damping.) In an informal test of a turntable's acoustical and mechanical isolation, we normally turn the preamp volume control to maximum and then stimulate the turntable with acoustic and mechanical excitations to measure the resulting hangover and feedback. But the MAS system immediately went into feedback when the volume control was advanced, even without excitation. This shouldn't happen, of course, especially in view of this turntable's theoretically "correct" suspension system, but evidently the severity of the arm/cartridge resonance was enough to overcome the suspension filtering.
The basic "bounce" frequency of the suspension is about 5 Hz, and it is moderately well damped by foam cores in the coil springs, making it less sensitive to footfalls than some turntables of similar design. The 5-Hz frequency is low enough to provide a valuable degree of vibration filtering at the usual tonearm/cartridge resonance frequencies (8 to 14 Hz). As usual with spring-suspended turntables, tapping on the top plate produces only a slight thump in the loudspeakers, while tapping on the side or front edge produces a severe thump or even groove-skipping. Regardless of a designer's good intentions with respect to mechanical and acoustic isolation, it is still important to place the turntable on a stable support that is as vibration-free as possible.
The tonearm signal cable emerges straight down out of the tonearm pillar, forms a short loop, and is fastened to the turntable base. Since the cable is not particularly limp, it may provide a significant path for conducting vibrations from the base into the tonearm, bypassing the spring suspension. (It was even possible to produce an audible thump in the loudspeakers by tapping the cable.) The old AR turntable had a better arrangement 20 years ago, with very limp, flexible wires running from the tonearm to connectors on the base, where the main signal cables were attached.
Since both the MAS Mk. I turntable and MAS-282 tonearm are of British origin, it seemed appropriate to install a British phono cartridge for a final extended listening test-in this case a Goldring 920-IGC, which has a modified van den Hul stylus and a significant amount of internal stylus damping.
The Ortofon and NAD test records confirmed that the arm/ cartridge vertical resonance was now centered at 13 Hz and, while quite pronounced, was not extreme. Because of the concerns noted earlier about motor vibration and acoustic feedback, the turntable was installed in a wide-range playback system containing the excellent ADS PB-1500 powered subwoofer system. Several low-bass "torture" records, featuring subterranean pipe organ pedals and the well-known Telarc bass drum, were played at high volume levels. Flutter and groove-skipping could be induced by pounding on the floor or rapping on the side of the turntable, but no feedback problems arose from the musical sound, even with the volume control at maximum.
Most important of all, the reproduced sound was excellent. Even at thunderous bass levels the instrumental textures were clearly defined, the background noise was very low, small details were heard with exceptional transparency, and the stereo imaging was both deep and stable.
---Peter W. Mitchell
Peter W. Mitchell is a writer specializing in the areas of audio, video and microcomputers as well as a consultant who provides design advice and technical writing services to NAD and other manufacturers.
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(Source: Audio magazine; Dec. 1983)
Also see:
Heybrook TT2 Turntable and Tonearm (Nov. 1984)
Marovskis Audio Systems MIT-1 Phono Cartridge (Nov. 1981)
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