THE TONE ARM In principle the job of a turntable is simple: to suspend the pickup cartridge in mid-air while spinning the record under it. But since the record may contain groove modulations as small as a wavelength of light, this job must be executed with extreme accuracy. The tone arm must be stable, rigid, vibration-free, friction-free, and very low in inertia so as not to alter or impede the tracking of the groove by the stylus. Both NAD turntables employ the same high-quality tone arm. It i