Direct Drive

@pedroeb

Three phase is easily obtained by driving a 3 phase motor with a 1 phase, and tapping the 3 phase power inputs. Viola, 3 phase power. But 3 phase is more complicated than it looks, and so is better left alone.

But it’s pretty much academic if you have a two phase motor with a quadrature motor controller, that is, producing sine and cosine. Then run the motor with sine and whatever mixture of sine and cosine gives the smoothest results. Pretty much the same performance as 3 phase with less grief.

And must agree with Lew on this. Turntable is most important, tonearm next, cartridge last. IMO. Anyway, you can’t get close to top performance from, say, a 10K cartridge with anything less than a first class TT and tonearm, say 50K or preferably more. My own tonearm adjusts azimuth to less than 1 minute of arc, and just this evening I found myself changing over a +/- 2 minute range with clearly audible results. Not many arms can do this, and unless they can, cartridge performance suffers.

@terry9

Thanks for your thoughts.

I've been thinking about tone arms with azimuth adjustment as I believe the stylus' axis needs to be perpendicular to the record even if it means the head shell is not at all parallel to the record.

My own tonearm adjusts azimuth to less than 1 minute of arc, and just this evening I found myself changing over a +/- 2 minute range with clearly audible results.  Not many arms can do this, and unless they can, cartridge performance suffers.

@terry9 - How do you measure these small angles and what tonearm are you using?  Isn't any tonearm capable of infinite azimuth settings if it has a rotating headshell (or rotating arm wand for linear trackers) that locks into position?

Thanks for agreeing with me, T9, but my point was not that the TT is most important; it was that flippant generalizations, like “differences between turntables…” are not helpful and may be misleading. And of course you can’t leave out the tonearm.

@pedroeb 

"Where do I get 3 phase when my house is only single phase? Surely AC motors are asking for trouble."

Two entirely different things.  Phase does not necessarily mean AC, and AC does not necessarily mean sinusoidal.  In these instances we're primarily talking about BLDC motors.