Turntable speed accuracy

Lewm, I meant DC motors. As far as I know the following DD's use DC motors - EMT948, Technics SP10mk2&3, Sony PSX9, Kenwood Lo7D, Exclusive P3. The Denon DP100 uses an AC motor.
DC motors react to variable loads quite differently to AC motors. Seems to me there is potentially as big a difference generated by DC/AC motor choice and implementation as there is by drive type.
Actually, I believe I'm right with regard to DC motors - DC motors do not self correct when speed fluctuates, hence the need for servos or speed sensors at the very least. Question is as Brinkmann suggests there is a trade off on sound "quality" between fast recovery and soft recovery type servos. Too fast and you get overshoot and more correction.
Platter mass also factors into the equation as well in that it can dampen the servo action in a DD TT.
There was no argument or generality suggested, but a question posed if you reread the post.

Dover, I think my response to you was too harsh. I apologize. Denon DP80 uses a 3-phase AC synchronous motor and also uses a quartz-referenced servo. Speed is monitored via a tapehead that "reads" the inner rim of the platter as it rotates. Knowing this, I was a bit confused when I read about The Beat turntable, which also uses a 3-phase AC synchronous motor that is claimed to self-correct by virtue of being so. (I think with The Beat there is a small amount of constant drag on the bearing, and the motor works against that.) Suffice to say that we need a motor expert here to straighten this out. I do think that the motor technology has not changed at all since the late 70s and that the designers of the tables you list used motors that they felt were best suited to the task. There are many high-dollar belt-drive turntables that use DC motors and no servo, as you know.

Lewm, no worries. I think there is a lack of real info as DD manufacturers and vendors placed more focus in their advertising on the fact that it is DD. I know the SP10mk3 and Lo7D well and agree with your descriptions of the difference in sonic signature. The Denon DP100 looks very interesting.

Travis has a DP100. But where is Travis (aka T_bone)?

Lewm: "Lets keep in mind that what you quote from the Brinkmann website is a commercial"

Yeah, I know. It's full of their own propaganda but I was too lazy to edit the pertinent parts so I just posted the entire section on drive system.... didn't mean to impose their bias on anyone. But it's still a good read for me and for the most part I agree with them about having a gentler servo system instead of a iron-fisted one and it resembles my own experience, granted there's always exception out there. I think this is a great thread as it allows people to focus on one of the most important and underrated aspect of a turntable: speed accuracy. It's been fun.

P.S. Yeah, where is Travis or T_bone? I miss him.

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