Grand Prix Audio Monaco direct-drive turntable Page 2

The platter-spindle-and-bearing assembly is immersed in an oil bath. The stainless-steel spindle shaft rides in a solid, single-piece bearing/mount structure of phosphor bronze. The vertical load is supported by a high-precision silicon-nitride ceramic ball riding on a bearing pad of a proprietary alloy chosen after careful listening to many different materials.

The Monaco's DSP-based motor controller is housed in a separate enclosure and connects via umbilical to a multi-pin Lemo jack fitted neatly inside a carbon-fiber cylinder that juts from the rear of the Monaco's plinth, below and to the left of the armboard. The module's front panel includes pushbuttons that control power (On/Off), select speed (33, 45), and vary the speed up to ±1%, in 0.2% increments, monitored by 10 LEDs. The controller works with an encoder disc on the platter's underside, on which are printed more than 4700 lines, and an optical reader mounted in the vicinity of the armboard. This servo system allows speed corrections over 4000 times per second. Such an extraordinary degree of speed control, and the direct-drive motor technology itself, requires a relatively lightweight, fast-reacting platter.

The Monaco's platter is "highly proprietary," according to the white paper, but of close tolerance (to 0.0005" in some areas) and machined from a solid billet of high-silicon magnesium alloy. While the alloy provides intrinsic damping, "other materials" applied to the platter surface provide additional damping, and give it a mysterious velvety-rubber feel that is almost addictive. The platter assembly incorporates a flywheel of phosphor bronze designed to properly locate the platter's center of gravity relative to the thrust bearing while providing additional damping and inertial control.

The critical drive system, built in the US to Grand Prix's specs, is based on a 12-pole DC motor with a hand-wound coil system and a high-tech ceramic magnet rotor whose position is tracked by a series of Hall sensors, which in such designs are usually arrayed around the system's periphery like the numbers on the face of an analog clock. (A Hall sensor is a transducer whose electrical output varies in response to variations in a magnetic field.) The sensors continuously inform the DSP controller of the relative positions of the rotor and stator; the controller then commutates the motor, according to the white paper, "in a manner that eliminates any torque variation as the magnets pass from pole to pole. The result is a running motor that is said to be dead smooth; all 'notching' has been eliminated."

In the white paper, Lloyd holds a magnifying glass to the many well-known problems of belt drive, dismissing it as "a hopelessly flawed method of turning a platter." He takes a whole page to explain the "fundamental flaws" and "trade-offs" of belt-drive designs, and claims that "today the belt drive design architecture has been fully developed and maximum levels of performance were found years ago." Yet the white paper, I feel, glosses over the tradeoffs inherent in low-speed direct-drive motors. The most important of these, torque ripple, is a jitter-like physical phenomenon, as the rotor's permanent magnet tends to grab from "jumping" electromagnetic field to "jumping" electromagnetic field. The Monaco's servo system will, of course, detect and attempt to correct these minute, ripple-induced speed variations more than 4000 times per second, but can such a system achieve perfection? "Speed" perfection (wow and flutter), yes, but "jitter" perfection?

Despite all of this—and despite whatever torque ripple the Monaco does or doesn't produce, and however how much a belt or O-ring slips and oscillates—the bottom line is: How does a turntable sound? How does it make you feel when you listen to a record?

Setup and Use
All high-performance audio products should come as well packaged and documented as the Grand Prix Monaco. It arrived meticulously packed in a wooden crate, accompanied by one of the better instruction manuals I've seen, as well as a complete set of the tools needed to set up and maintain it.

Alvin Lloyd himself set up the Monaco in my room, initially placing it on my Finite Elemente Pagode stand. After he'd (naturally) suggested that it would perform better on Grand Prix's own carbon-fiber stand, I requested one (total cost as supplied: $4981.78). The handsome Monaco would look good anywhere, but it definitely appeared more at home on a carbon-fiber stand than on one finished in light maple.

After the 'table is leveled, oil must be injected into the bearing; if the Monaco is run dry, it will be damaged. Removing a circular pad on each side of the spindle insert and rotating the platter grants access to two small holes in the bearing structure, into which go 5ml of oil, administered via syringe (oil and syringe supplied). After waiting 30 minutes to let the oil settle and the trapped air escape, you add another 2ml of oil. After another 30 minutes, you carefully measure the oil level with a supplied dipstick—what else, given Lloyd's automotive background?

Company Info
Grand Prix Audio
P.O. Box 1948
Durango, CO 81302
(970) 247-3872
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