Direct Drive vs. Idler Drive vs. Belt drive

@atmasphere 
Once the motor is prepped for operation it might not do that. I pulled the motor out of my Technics as I am taking it to a machinist so I can run a longer spindle. Its really quiet!

That had not occurred to me. Thank you! Good to hear, so to speak.

But I can't hear the sleeve bearings on my little Premotec either - not until it is connected to the platter by a belt, and then only through the playback amplification. So I think that sleeve bearings are a problem anywhere in the chain, and the closer to the platter the worse it is. What do you think?

@mijostyn , comparing my big Nottingham Analogue Mentor with improved plinth, motor, and motor controller (all to Dais standard), to my DIY air bearing, is indeed no contest. The air bearing is dramatically better. Same model tonearm (TransFi Terminator), same identical cartridge (Koetsu).

But I can't hear the sleeve bearings on my little Premotec either - not until it is connected to the platter by a belt, and then only through the playback amplification. So I think that sleeve bearings are a problem anywhere in the chain, and the closer to the platter the worse it is. What do you think?

When the belt is tensioning/loading the bearings from the side (as happens with a belt), they're going to make more noise. When the bearing and the motor are synonymous, then its the thrust bearing that is likely more important.

Thanks, Ralph.  That's a very key point about direct drive (the absence of a force in the horizontal plane that pulls the spindle shaft up against the bearing wall) that the belt-ers choose to ignore.

Good point, both.