Turntable power supply/motor’s role in SQ for belt drive TT


I’m trying to understand the ways that an upgraded motor/power supply can improve the sound quality of a belt driven turntable. 

OK - speed control that is more precise, I get that. But is there some inherent electrical noise from the motor that makes it way into the analog signal thus producing an audible distortion through the cartridge/phono stage?

I’m also curious about why an AC motor would be less desirable than a DC motor (for a belt driven turntable. 

Some back story: I am preparing to send my 35 year old Linn Sondek LP12 turntable out for servicing and upgrades. Linn has the promotion going on where you get the new Karousel bearing for “free” when you spend at least $4,000 USD. Kind of a gimmick, I know. But I would like to get at least the Lingo 4 power supply and am considering “Akurate” level “Radikal” power supply for more $$. I am looking forward to spinning my old vinyl again soon and hopefully with upgraded SQ as well. 

Thanks for any replies.
masi61
My table has gone through a whole bunch of iterations as it has evolved to where it is now. https://systems.audiogon.com/systems/8367 This was not a case of simple upgrades from one table to another. This was modifying or upgrading one tiny little thing at a time. Motor power cord. Motor. Controller. Controller power supply. On and on. Dozens of things. Over more than 20 years.  

You can debate "why" certain things work all the rest of your life. If it turns you on go for it. If you need a story take your pick. In the end, "why" does not matter. What matters is does it sound better. If the motor, controller, and power supply are better, it will sound better. Whether it is worth it or not only you can decide, and you will know only after the fact. And that's the end of the story.
masi61
... is there some inherent electrical noise from the motor that makes it way into the analog signal thus producing an audible distortion through the cartridge/phono stage?
There shouldn't be if it's a decent turntable and is properly setup. That doesn't mean that motor vibrations couldn't find their way into the audio signal, but electrical noise from the motor shouldn't be an issue.
I’m also curious about why an AC motor would be less desirable than a DC motor (for a belt driven turntable. 
I don't think that a DC turntable motor has any inherent advantage over an AC motor at all and in fact, the opposite may be true.
I owned three Linns. The SOTA is far superior. Is is not funny and I am dead serious. The Linn has so many weaknesses it can not be repaired. What do you think all these upgrades are about. It is just that back in the day it was the best table you could buy but look what it was up against. I kept going for supposedly better tables only to swear and return to the Linn and tip toeing around my apartment. By today's standards it is worse than a cheap Technics direct drive and everybody her knows how I dislike direct drive tables. I do find the Grand Prix Monaco very intriguing. I  love the aesthetic.  
@mijostyn - I’m happy for you that you like your SOTA and respect that you moved on from the 3 Linns that you previously owned. If you had done a proper wall mount you would not have had to tiptoe around your apartment. Can we get back to the task at hand though? I mean this thread is not about whether or not a Linn turntable is bettered by some other design - that’s why this hobby is so cool, there are lots of legit designs. 

I’m probably going to go with the Lingo 4 for cost reasons which is an AC design. I’m going to have to inquire or audition to determine bass sound quality/articulation between the Lingo 4 AC motor and the standard chassis Radikal with its more exotic DC motor.