Disk drive apparatus

A disk drive apparatus comprising:

• a turntable having four or more projections each of which has predetermined height, which are arranged at positions wherein a circumference is divided at equal intervals, and the tips of which are substantially on the same plane, for supporting a mounted disk by using said four or more projections;
• a clamper having four or more projections each of which has predetermined height, which are arranged at positions wherein a circumference is divided at equal intervals, and holding said disk between these projections and the projections on said turntable;
• positioning means for holding said disk between the projections on said turntable and the projections on said clamper disposed opposite to each other;
• a sub-base to which a spindle motor for rotating said disk is secured;
• a main base over which said sub-base is installed via elastic bodies;
• and
• a balancer having arc-shaped tracks with a plurality of arcs having a central angle of less than 360 degrees and balance members provided so as to be movable on said arc-shaped tracks, and provided so as to be rotatable integrally with said disk.