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

Showing 3 responses by mijostyn

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.  
Just another reason to get a Sota. Better motor, better suspension, better bearing (magnetic thrust control), Better tonearm mount and you can throw the wall shelf away (which does not work in all cases.) 
The LP 12 has more "upgrades" than any other audio device on the planet. What a racket and LP12 people drink the Kool Aid. The LP 12's two basic problems are it's suspension design and cheap construction.