PLATTER DRIVE SYSTEM
In the NAD 5020A the diecast aluminum platter is driven by a vibration-absorbing soft-rubber belt. The motor is synchronous in its operation (which means that it locks onto the AC power-line frequency and maintains precise rotational speed unaffected by variations in line voltage), but it also contains an induction rotor to provide the high starting torque needed to get the platter up to speed.
The NAD 5080A is a direct-drive unit: the turntable’s central spindle is the shaft of the motor. In many early direct-drive designs this approach caused high levels of infrasonic rumble, because conventional electric motors deliver their power in a series of torque pulsations (“cogging”) instead of a smooth rotary flow. (E.g. with a “12-pole” motor there are 12 pulsations per revolution.) In the NAD 5080A this problem is completely eliminated with the aid of a new coreless, slotless, brushless motor which exerts a constant magnetic force throughout the entire 360-degree rotation of the platter. Thus the advantages of direct-drive operation are fully realised with no off-setting disadvantages.
As an added convenience a Pitch control is provided for adjusting the speed over a 6 percent range, and an included strobe allows you to set the speed to exactly 33.3 or 45 rpm.
EXTRA FEATURES
The decorative soft-rubber mat is actually an integral part of the engineering design, efficiently suppressing any resonant vibrations in the metal platter. The fiberglass-composite base resists abrasion or wear and is supported on spring-loaded large-diameter rubber feet for improved resistance to vibration and acoustic feedback.
