LP12- Power Supply- Need education

No problemo.
if the new SOTA Eclipse motor is DC, and unless Carlin has totally changed his original design, I would bet the control is done on the incoming AC before it’s converted to DC to drive the motor.

Dear Bdp, I’d like to hear from Bill Carlin himself, if he really said what you say he said. If Bill did say that, of course I would yield to his far superior level of knowledge, compared to mine. But to take your point, first of all, DC is Direct Current, meaning it has no frequency; therefore it has no phase differential. So there can be no such thing as "3-phase DC". In a DC motor that operates off the wall socket, there is a conversion of AC to DC. (Teres had a DC motor that incorporated a battery option, I think.) I am guessing that AC to DC conversion may be happening in the new SOTA Eclipse motor AFTER the power supply works on the AC side to regulate speed. I really don’t know what’s going on there, but I also saw what maybe you saw on the SOTA website. It does mention the term "3-phase DC", which is an oxymoron. They’ve probably dumbed it down for us audiophiles. But most of all, if you read my earlier post, I too recommended the Eclipse upgrade, so we have no argument there. I don’t think a DC motor has inherently more torque than an AC motor. One DC motor may have more torque than another AC motor, etc. But there is no general rule. And anyway, where did I say that AC motors were superior to DC motors? (Your comment suggests that I did say that.)

I do know that the original AR X turntable was built as you say, with the motor on firm support and the platter suspended. Probably that was also the case for the Thorens TD125. (At one time or another, I owned both.) In my opinion, that’s a problem of design for suspended belt-drive turntables that has to be dealt with in one way or another in order for platter speed to remain stable when the suspension is disturbed. My AR X and my TD125 were no great shakes for speed stability. Finally, I have not been bashing the Linn LP12 or even the SOTA; I am just pointing out some issues. Nothing is perfect.

Mijo, With due respect, I think the old problem with the SOTA Sapphire was that the motor was mounted on a stationary platform while the platter, of course, was suspended.  When the suspension was activated, that caused the belt to stretch and contract in time with the bounce.  This resulted inevitably in speed instability that was quite noticeable.  In fairness to SOTA, I heard or read they solved that problem a while back.  DC motor would not be as good as their latest Eclipse option, the one that incorporates the PE technology, which works on AC synchronous.

Mijo, perhaps the modern or updated versions of the Star Sapphire are speed stable, but my late 90s Series III was anything but.  At the time, it was all I had to judge by, and it had me thinking that it is the nature of vinyl not to be able to deal with sustained piano notes. Then I found out, after owning a succession  of other turntables, that the star sapphire was the absolute worst in that regard. Every belt drive, idler drive, and direct drive turntable that I have owned since about 2000 is superior to the Star Sapphire in speed stability, and its shortcomings are quite easily heard. I do respect SOTA as a company, and rumor has it they fixed their problem, whatever it is or was. Surely they’ve now fixed it with the adoption of the Phoenix Eng control system. But please don’t suggest that speed instability can’t be heard.

Saburo, thank you for the correction. I admit I was not familiar with the very latest Linn add-ons. Perhaps they’ve been inspired by Phoenix. My general point about the capacity for speed correction is still my recommendation, while I also recognize it can be a negative if not done well.

None of the power supplies mentioned here, including any of the Linn options or the VPI PSs, incorporate a feedback mechanism whereby instantaneous changes in platter speed can be sensed and corrected. What you do is to set the PS such that your platter is turning at 33.333 rpm using one or another technology (recommend KAB strobe device)  to monitor the speed while you set the power supply. After that, the platter is on its own; the PS cannot account for belt slip, belt creep, stylus drag, etc. Phoenix Engineering made an aftermarket power supply with a separate tachometer that connects to the PS and feeds back speed errors that could be due to any of the above, which are then corrected.  PE no longer markets these devices, but SOTA has worked out a deal with the PE engineer, Bill Carlin, and essentially PE equipment can now be purchased through SOTA. Some think this sort of mechanism introduces new problems due to the act of correcting the aberrant speed, which, such persons think, has the potential to be as audible as is any momentary degradation of speed control.  I don't agree based on my personal experiences.
The mentioned method of running the turntable motor on reduced voltage to reduce noise does not always work well with all types of motor, and carries with it the penalty of a loss of torque. In fact, I think at least one of the VPI devices works by lowering voltage and/or current. I don't know whether Linn uses an AC or DC motor, but if you can adapt an AC synchronous motor to your Linn, then in my opinion the very best option is to buy such a motor and the SOTA/Phoenix Engineering products to run your Linn.  In my experience, ANY competent motor power supply makes a huge upgrade for a belt-drive motor, but the PE stuff is the absolute best.
I am not a big fan of suspended turntables with lightweight platters, but if I had to optimize one, I'd go that route.  I do use the original PE gear to run my Lenco, and I am very happy with the results.