Spin Doctor #4: Platter Mats, Clamps, Weights & the Timerette
The next time you're preparing to play a record, try doing a little experiment. Once you have the record mounted and spinning but before you lower the stylus into the groove, lower your gaze to just below record level and look for a gap between the platter and the record. It helps if there's a light source or a brightly colored wall behind the platter. You may discover a gapthat very little of the record's playing area is making true contact with the platter mat or (if there is no mat) the platter.