Manufacturer's Specifications:
Turntable:
Drive System: Belt.
Motor Type: Synchronous.
Speeds: 33 1/3 and 45 rpm.
Speed Drift: Less than 0.1%.
Wow 8 Flutter: Less than ±0.1%, DIN peak weighted.
Rumble: Better than-73 dB, DIN B weighted.
Tonearm:
Type: Pivoted straight tube with non detachable headshell.
Effective Mass: 12 grams without cartridge.
Nominal Length: 9 1/8 in. (231.8 mm).
Effective Length: 8.3 in. (210.8 mm).
Stylus Overhang: 18 mm.
Cable Capacitance: 100 pF, max.
General Specifications:
Dimensions: 17 1/2 in. (44.5 cm) W x 14 1/4 in. (36.2 cm) D x 6 1/4 in. (15.9 cm) H with dust cover closed.
Weight: 26 lbs. (11.8 kg).
Price: $679.00 with Heybrook tone arm; $498.00 without tonearm.
Company Address: c/o D'Ascanio Audio, 11450 Overseas Highway, Marathon, Fla. 33050.
One rarely mentioned advantage of this type of floating suspension is that it blocks the acoustic feedback caused by the dust cover. In many turntables the large, thin dust cover acts like a sail, efficiently intercepting sound waves in the air and coupling their vibrations into the turntable system. (I have reduced the acoustic sensitivity of some turntables by as much as 20 dB by simply closing their dust covers and placing pillows on them.) But in a floating-subchassis design, like the Heybrook, the dust cover's microphonic vibration is coupled only into the base, where it remains isolated from the platter and stylus.
The TT2 can be purchased with a blank tonearm mounting board or with Heybrook's own arm installed (the version I tested). The instruction booklet describes how to readjust the suspension to accommodate tonearms of differing weights, in order that the drive belt will be correctly centered on the crown of the pulley. The instructions also devote considerable (and well-deserved) attention to a subject some turntable designers neglect: Routing and fastening the tonearm cable in a semicircular loop to minimize its tendency to conduct external vibration and defeat the floating suspension.
The signal cables of Heybrook's own tonearm are relatively thin and flexible for this reason.
The thoughtful design of the TT2 extends even to its rubber feet, of which there are three rather than the usual four. Three feet provide an unconditionally stable platform, while objects mounted on four feet often can be made to rock.
Aside from the extra effort that installing your own tonearm may require, the amount of time and labor involved in setting up the TT2 is about average for turntables of this type. The important first step, one that must be done by either the dealer or customer, is to remove the inner platter, inject oil into the main bearing, and reinstall the platter and shaft. The only awkward part of the process is installing a cartridge in the arm, since the headshell is not detachable. (An optimum combination of rigidity and low mass is obtained by omitting the usual headshell plug-and socket fitting, with its potential for loss of low-level information.) As in many turntables, the counterweight assembly turns on a threaded shaft to balance the arm and set the vertical tracking force. But the assembly is unusual in two respects: First, there is no calibrated dial, so you must use an external gauge when setting the tracking force. Second, the counterweight is in two sections--after finding the correct setting, you rotate the two halves against each other to lock them on the threads so that their position (and the tracking force) cannot be changed accidentally.
Similarly, the threaded anti-skating weight has no calibration scale. The instruction booklet advises using a test record to find the best anti-skating adjustment. This is good advice with any turntable, since the amount of skating sidethrust is not a fixed percentage of the tracking force, but can depend on the shape of the stylus tip.
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 unaffected by variations in power-line voltage from 75 to 130 V and was 0.3% fast. The speed change from 33 to 45 rpm is accomplished by lifting off the outer platter and moving the drive belt to the larger of two pulleys on the motor shaft. The measured wow and flutter was 0.03% unweighted and 0.018% DIN peak weighted (superb performance). Because of the inertia of the heavy platter, the low-power synchronous motor takes nearly 10 S to bring the turntable up to speed. However, once it is running, the drive system is more successful than many other belt-drive units at the task of maintaining a precisely constant platter speed despite small variations in drag. There was no change in speed under a 10-gram load, which means that the TT2 is completely safe for use with Dust Bug-type disc-cleaning devices. This also implies that the TT2 is unlikely to exhibit "dynamic wow" due to the varying drag of the stylus in heavily modulated grooves.
The thin, felt platter mat does little to suppress metallic platter ringing, but happily there is relatively little ringing in the heavy, two-part aluminum platter anyway. Users who wish to suppress LP-disc microphonics and the last vestige of platter resonance should experiment with soft-rubber mats and spindle clamps to press the record down into uniform contact with the mat.
In our informal test of a turntable's isolation from acoustic and structure borne feedback, we turn up the preamp volume control while tapping the table to observe the resulting boomy hangover. The TT2's performance was exemplary: The tapping produced only a slight thump with no audible feedback hangover, even with the volume control at maximum.
While the floating suspension provides outstanding immunity to vertical impulses, the closely spaced springs tend to encourage rocking motions of the suspended arm/platter system.
Therefore, for best results the TT2 should not be located where any lateral or rocking motion can be transmitted to it. The manufacturer recommends placing the TT2 on a relatively lightweight shelf or table, presumably on the theory that a low-mass shelf will not transmit vibration efficiently to the relatively high mass of the TT2.
Spectrum analysis of the lateral and vertical rumble, using an unmodulated test disc, yielded excellent results, with levels below -60 dB at most audible frequencies. There were no peaks traceable to motor vibration; below 30 Hz, the rumble spectrum appeared to consist solely of groove noise amplified by the infrasonic tonearm/cartridge resonance, indicating that the turntable has little or no rumble of its own. With the brush of a Shure V15 Type IV cartridge engaged to damp the arm resonance, the rumble spectrum remained below -50 dB at infrasonic frequencies; with the brush raised, the rumble spectrum peaked at -35 dB around 5.5 Hz.
The measured capacitance of the tonearm's 1-meter signal cable was 143 pF in each channel. The arm's hydraulically damped cueing had a smooth and gentle action, with no sideways drift of the arm as it rose or descended. But as often happens when the cueing lever is on the floating sub chassis rather than being mounted on the base, the entire platter/arm assembly tended to bounce slightly when the lever was moved; and this may change the location of the stylus on the record.
Since the Heybrook tonearm has little pivot friction and no provision for damping, arm/cartridge resonance can produce exaggerated cantilever deflection (with a consequently large variation in the effective vertical tracking force) in response to warps and record surface irregularities. We use a strain-gauge cartridge to observe these effects. The variation in tracking force was 0.7 gram peak-to-peak on a visibly flat record, increasing to 0.9 gram on a mildly warped disc.
Therefore, with the Heybrook arm (as with other undamped arms), some form of damping should be added when high-compliance cartridges are used, unless the stylus assembly has significant internal damping of its own.
An alternative approach, without damping, would be to use a medium compliance cartridge so that the resonance frequency falls well above 10 Hz; the resonance won't then be stimulated either by disc warp signals (which generally fall below 5 Hz) or by external vibrations passing through the suspension's 5-Hz mechanical filter.
Use and Listening Tests
In listening tests (employing a Goldring cartridge with moderate compliance and some internal damping to help control infrasonic resonance), the Heybrook TT2 was a pleasure to use and a joy to hear. Like a great ocean liner, it imparts a sense of total stability and reliability, serenely, undisturbed by what is going on around it. Stable and transparent are the words that come to mind to describe its sonic performance. Stereo images are precisely focused without wander, and the wealth of low-level detail appears to be limited only by the groove noise and rumble of the record itself. With the TT2's virtually total freedom from rumble and acoustic feedback, the sonic benefits of techniques like low-noise pressing and Direct Metal Mastering are especially clear.
--Peter W. Mitchell
Peter W. Mitchell is a freelance writer (specializing in the fields of audio, video and microcomputers) and a consultant providing design advice and technical writing to NAD and other manufacturers.
(Source: Audio magazine, Nov. 1984)
Also see: Monster Cable Alpha 2 Cartridge (Apr. 1987)
Linn Sondek LP12 Turntable (Nov. 1983)
= = = =