Mijostyn, you say, "... since when are air bearings not mechanical? There is a shaft in bushings just like any table except this one. "
Not so. Not at all. In my first post I specifically mentioned an air cushion in three dimensions. That is achieved by the New Way air bushings. Look it up.
Although the thrust bearing accounts for most of the friction, hence the noise, the shaft bearing generates enough noise to be easily noticeable. Please re-read my post regarding conclusions - noise is not in the 20Hz region, it's in the 5KHz region.
Further, @ct0517 notes how those attuned to such things can hear the difference between different engine oils. I expect that you can too - just before and after an oil change. It's not some deep psychological thing with your pride of ownership - the sound changes.
Last, I suggest that you conduct your own experiment. Get your platter up to speed by hand, and listen to the purity. Get that sound firmly in mind. Then disconnect the belt and do it again. It will sound different - and better - at least, it does with all 3 motors I have tried. What has changed is noise from the sleeve bearing on the motor - it's gone.
Not so. Not at all. In my first post I specifically mentioned an air cushion in three dimensions. That is achieved by the New Way air bushings. Look it up.
Although the thrust bearing accounts for most of the friction, hence the noise, the shaft bearing generates enough noise to be easily noticeable. Please re-read my post regarding conclusions - noise is not in the 20Hz region, it's in the 5KHz region.
Further, @ct0517 notes how those attuned to such things can hear the difference between different engine oils. I expect that you can too - just before and after an oil change. It's not some deep psychological thing with your pride of ownership - the sound changes.
Last, I suggest that you conduct your own experiment. Get your platter up to speed by hand, and listen to the purity. Get that sound firmly in mind. Then disconnect the belt and do it again. It will sound different - and better - at least, it does with all 3 motors I have tried. What has changed is noise from the sleeve bearing on the motor - it's gone.