Turnable database with TimeLine

I would argue with Tony on different grounds. I think you CAN know if drift is due to "speed being something other than 33.33 exactly or if it is changing during play." At least you can know it to the accuracy of the frequency of the laser flashes on the Timeline. (Since I don't have one in my possession, I cannot describe it exactly.) I think it has more than one laser, at least two and maybe four. (Again, "I think" the early version had fewer lasers.) Let's say that the worst case scenario is it has one laser, which means that there will be a flash of light every ~1.8 seconds. Assuming the astuteness of the observer is not a limitation, that means one could detect whether speed has varied during the 1.8 second interval between flashes. If speed is just inaccurate but is not subject to stylus drag, then the drift of the laser spot will be a constant amount in one direction or the other. (Halcro just gave an example of that with the Raven.) If speed is being now and then momentarily retarded due to stylus drag (or other cause), then the laser spot movement will be irregular or regularly irregular or irregularly regular, within the limits of detection determined by the frequency of the laser flashes, which would be every 1.8 seconds divided by the number of lasers flashing per revolution.

There are two subjects here: 1) How well do the differing turntables hold speed to exactly 33 1/3 rpm? 2) What is the effect on platter speed during heavy groove modulation?
Subject 1 is being answered with the Timeline device testing. And the Timeline device is being used appropriately for these measurements. This is a perfectly valid and interesting exercise.
Subject 2 is also a valid and interesting point. The Timeline device, however is not the appropriate tool in this case. A fine tachometer is required. I find this subject interesting and especially if it were possible to compare the results of speed control with a heavily modulated record on all three basic drive types- belt, direct and idler.

Halcro,

I just watched your video of the Raven, and I must say I am puzzled by the speed changes. What's causing it? Assuming the VTF is stable, as it should be, why would the turntable speed up as the tonearm tracks toward the spindle?

Lewm, I also thought that there is a new version of the TimeLine with more lasers around the perimeter of the device. However, I just spoke to a dealer today who confirmed with Roy Sutherland himself, that there is only one TimeLine version and that the device has not be changed since its introduction. There is only one laser on the device. It flashes at some interval to create six equally spaced dashes around the room. This description is consistent with the unit that I borrowed to make my videos. Apparently, I had the original and only version.

I have tried a digital tachometer and found that I could not get repeatable readings even while I held the device against the edge of a table and pointed the beam toward the reflective tape. It varied by an amount much greater than my KAB and the Timeline indicated, so it must be defective or I was not using it correctly. I will try it again.

Actusreus.
Assuming
1)the stylus drag is constant throughout the LP
2) the TT slows due to stylus drag,
3) speed control is open loop ( maybe)
Then it will naturally increase in speed as it tracks towards the centre grooves.
This is a torque moment effect. On the outer grooves, the drag is acting on a larger radius so it requires more torque from the motor to counteract this.