Turntable speed accuracy

In my experience, belt drive TT's with AC moters with ample torque and low friction fair better than DC motor driven TT's all else being equal.

Perhaps you should listen to a good DD turntable with a coreless DC servo-controlled motor alongside you Raven AC-2 as I have?
No real comparison actually........
Our dear friend Lew wanted a moratorium on discussions of the merits of turntable drive types but I think that's difficult when it comes to the subject of speed consistency and accuracy?
We have heard of the supposedly superb accuracy of some belt-drive turntables according to the Timeline but as yet we have seen no real evidence?
Is someone able to upload a clip of one of these belt-drives with the Timeline....onto YouTube?
Perhaps you Andrew?

Dev,
The Lenco is pretty near infinitely adjustable, as the idler wheel is driven by a tapered shaft that is an extension of the rotor of the motor. So, if the Lenco was off, it simply needed to be adjusted by moving the idler wheel with respect to the variable circumference of the drive shaft. This is how Lenco attains the 3 speeds (33, 45, and 78 rpm). Rather than fiddle with the idler wheel, I made fine adjustments to the speed of my Lenco via my Walker Motor Controller. As to the SP10 MkII, Hiho got it right. Although there is no user accessible speed adjustment, the proper set-up of the outboard power supply WILL result in exact correct platter speed. If the one you tested was not spot-on, then the tt needed some TLC, is all.
Sarcher,
You make a valid point about the fact that if you move the motor pulley close to the platter, the belt will have a smaller area of contact with the drive pulley than when the platter is distant from the pulley. I was merely commenting that both SME and Nottingham recommend proximity of the two. It is not as good a solution as using a capstan, a la the Artemis tt.

As to the question of hum, I am very surprised to read that you have a problem with hum when the motor is close to the platter on whatever turntable. In most cases the motor and its pulley can be placed or is permanently installed at the left rear corner of the plinth such that the cartridge never gets closer than 7 or 8 inches from the motor (half the diameter of an LP plus half the diameter of the label). I don't know of any cartridge that should be THAT sensitive to the EMI or RFI put out by a typical BD motor. The Lenco motor is right under its platter, and I have never ever heard an issue with induced hum. It is said that Grado cartridges are or were unusually hum-sensitive; perhaps you use a Grado. (I have a Grado TLZ and never had a hum problem with it, however.)

And finally, all this chat is still overlooking what I thought was the real issue: speed variation due to stylus drag. None of the above mentioned observations really tell us anything about that. Unless sensitivity to stylus drag is gross, the Timeline may not reveal it. I guess if the speed is "off" with no load, it is unlikely to be stable with a load, but maybe not. One possible benefit of intentional viscous drag or the "eddy current brake" used on the Garrard 301/401 I think would be increased speed stability in the face of stylus drag, a very good way to deal with it.

Lewm,
Have been reading this for awhile and want to ask a question while throwing in another variable.
The SME, I have the SME 10, is set for Sumiko Celebration, which I have, other turntables use other stylus makers or Sumiko for their voicing.
Has any one tried to see if the degree or speed that the turntable is off is neutralized when the stylus is lowered and its drag can be added to the equation? IOW is the difference from perfect speed via the timeline cancelled once the arm/stylus is lowered and music is playing?

Dear Uru, I am not the font of all knowledge on this subject, hardly. But what you suggest does seem logical; the speed of a tt may deliberately be set to slightly fast with no load, so that it then achieves perfect speed with the load of stylus drag. But in principle, I would prefer a motor or drive system that is robust enough to maintain proper speed under all conditions, because the load of stylus drag is varying all the time due to the groove modulations and also in relation to the distance of the stylus tip from the spindle. It would therefore be impossible to know in advance and for all LPs "how fast" is fast enough to result in correct speed in the presence of stylus drag. So, IMO, this is where torque, the compliance of the drive system, the speed corrective capacity of the drive electronics, etc, come into play.

Thanks, Dev. I was just joking, but your post does move me closer to getting a timeline just to satisfy my curiosity.

And when I'm unhappy with the results (I pessimistically predict), I'll wish I had Lewm's skills or at least easy access to someone with similar skills.