UPS on DC controlled tables?

Why do you want to put a UPS which generates dirty electricity, to feed your
turntable? What do you expect to gain from it?

Yup it's dirty - but it's voltage stable. Certainly wouldn't want to do this on anything I was listening thru - but on a DC controlled TT - all I want is stable speed -if I feed it a solid stable voltage on it's input - it should output a stable solid DC output - this isn't the end of potential speed instability - but would? eliminate one variable?
Or not?

TT using DC motor already has DC voltage regulator built-in, that is how you
adjust the speed of DC motor. There is absolutely no benefit to put a UPS in
front of it. In fact, the dirty electricity generated by UPS will pollute the rest of
your system. If your TT doesn't have a regulated power supply for the DC motor,
you will be better off to use the UPS money to upgrade the TT. UPS, in my
opinion, is the wrong solution to a most likely non-existing problem.

How about plugging in the DC TT power supply/motor controller into a device like the old PS Audio Power plants. in other words power conditioning and AC voltage regulation devices? Would that make a difference?

I doubt it, Avliviero. DC regulator for motor control is very easy to do and
inexpensive. The technology has been perfected for quite some time. There is
no reason for manufacturer to put in subpar regulator. Unless you have a cheap
TT and your AC line is extremely unstable, I don't think it will make any audible
difference. Besides, if your AC line is so unstable that it will affect TT, I think it
will have a more profound impact to the rest of your system. In order words, if
you have AC line problem, I would address it for the rest of the system before
putting a power plant just for TT.

Sidssp,

Thats a good point.although I suspect the impact of ac on speed control would be more audible than on pre and power amps

Not the same as a UPS but in the same vein, I have been using an upgraded external power supply.

I am using an HP 6200B lab power supply with my DC motor Sota turntable. I bought this because I noticed minor speed variations that my non-audiophile family could not hear. This is a highly regulated DC supply that allows fine adjustment of voltage up to 40 volts. The turntable motor assembly already has a voltage regulator. As others point out, a voltage regulator in a turntable is not necessarily complicated: mine has a standard chip and a few other parts.

There are at least two advantages to the HP power supply: 1. I like the way it looks, and 2. More seriously, it unexpectedly allowed me to diagnose a bearing issue with the turntable. I set the power supply to monitor current draw and noticed a periodic fluctuation. When I turned everything off and rotated the platter I heard a faint rubbing sound that I hadn't noticed before. I disassembled the platter, thrust plate, and bearing, cleaned everything, and relubed. Then I carefully leveled the turntable and gave the platter a good spin. Total silence.

Reconnecting everything again, the speed issue is gone and the meter now shows a much smoother current draw. In summary, I'm not sure that the lab power supply improves the overall sound when everything is normal but it did prove useful, looks very serious, and at the least, allows me to monitor voltage and current closely.