Hi Jim. I haven't done much research on changing motors on the WTC. I think in general that a DC non-cogging motor is better than an AC motor. But it has to have a good speed control system.
I tried the Origin Live DC motor system the other day on a TT that I was evaluating for someone, and it worked quite well. The only thing was that I didn't care for the way you have to set the speed adjustment. They don't have a dial on the front, you have to turn the controller box over and use a small screwdriver to adjust speed, while you have a strobe disc on the platter. Other than that, it did quite well.
The Teres DC motor system is superior, I think, but it requires a strobe pattern to be permanently applied on the underside of your platter, and an optical sensor to be installed in the plinth to read the strobe pattern.
Redpoint has a good DC motor system, and I have heard of people who have replaced very high end TT motors with it to good effect, and it needs no strobe pattern or sensor installed. It uses the same Maxon Swiss-made motor as the Teres, but a different kind of controller.
For AC motors, I have heard excellent reports about the Walker Motor Controller being used on a number of different turntables.
