I cannot respond from experience with the OL DC motor system on an LP12. However, I have used the OL DC motor system on an OL turntable, and I have a Teres turntable with a DC motor system, AND I owned a Linn LP12 Valhalla for about 11 years.
In my opinion, the DC motor system has alot to recommend it over the typical AC synchronous motor that is used in the LP12. OL puports to use a Maxon motor that is Swiss made, and from the same company that provides the DC motors to the Teres company. Their controller is not feedback regulated for speed, and is user-adjusted by a separate strobe system that is not provided in the kit. At least it wasn't in the kit that I received. You adjust the speed with some small trim-pots on the circuit board and then you depend on it being right from there on. Not as sophisticated as the Teres system, but it is similar to several of the other DC motor systems on other TTs out there.
Basically, there is no doubt that improving the motor controller of the LP12 is a worthwhile undertaking. Of all the ways to do it, changing the motor to a DC type has the most theoretical advantage. Whether this theoretical advantage actually manifests itself in the outcome is based upon the execution of the design by the mfr. I can say that the OL DC motor system that I used worked well enough, but I was not too enamored with the way the speed was checked and adjusted. After I got it adjusted, it seemed to work fine.
Of the other types that keep the AC motor, I have heard from users that the Lingo puts noise on the AC line that can interfere with other components. I have also heard that the Naim Armageddon was an excellent improvement that didn't put noise on the AC line.
In my opinion, the DC motor system has alot to recommend it over the typical AC synchronous motor that is used in the LP12. OL puports to use a Maxon motor that is Swiss made, and from the same company that provides the DC motors to the Teres company. Their controller is not feedback regulated for speed, and is user-adjusted by a separate strobe system that is not provided in the kit. At least it wasn't in the kit that I received. You adjust the speed with some small trim-pots on the circuit board and then you depend on it being right from there on. Not as sophisticated as the Teres system, but it is similar to several of the other DC motor systems on other TTs out there.
Basically, there is no doubt that improving the motor controller of the LP12 is a worthwhile undertaking. Of all the ways to do it, changing the motor to a DC type has the most theoretical advantage. Whether this theoretical advantage actually manifests itself in the outcome is based upon the execution of the design by the mfr. I can say that the OL DC motor system that I used worked well enough, but I was not too enamored with the way the speed was checked and adjusted. After I got it adjusted, it seemed to work fine.
Of the other types that keep the AC motor, I have heard from users that the Lingo puts noise on the AC line that can interfere with other components. I have also heard that the Naim Armageddon was an excellent improvement that didn't put noise on the AC line.