Turntable speed accuracy

Don, I think you underestimate the situation.

"Speed variation "is" noticeable on classical piano "IF" you have played a piano, but typically the audience could care less. "

I cannot play piano, or any other instrument, or read music. I'm certain I do not possess perfect pitch. But when I listen to piano recordings I am quickly aware if the sound becomes either sour or cartoonish. That tells me something slowed down or sped up. It could be my turntable, it could be the power line, it could be someplace in the recording chain. But it is not difficult to hear when a recording does not sound like a live instrument. (And yes I understand there are multiple other factors in the "sounds live" experience.)

A friend of mine has progressed through a series of decent tts over the past few years. He started by adding a Teres rim drive to his VPI Scout (big difference, even greater than the VPI rim drive), then through a series of DD tables from Technics, Kenwood, and Luxman. More recently he got a Micro Seiki belt drive (not sure of the model but it was not the low end). Speed was not accurate and the MS motor could not be adjusted/repaired to run the proper speed.

On an inspiration he adapted the Teres more with a proper sized pulley (and reversed the rotation direction) to drive the heavy MS platter via a string drive. This is a person who has decades of experience in this hobby and he believes he now has the best tt set up he ever owned. I have not heard every iteration he experimented with but will say with everything from a full symphony crescendo to a sustained piano chord it provides beautiful and believable playback.

Ct, "Can someone technical explain to me what "5kg - cm" really means in laymans terms."

From the SP-10 Mk2A Operating Instructions:

"If 500 tonearms of 2 g. tracking force were placed on a record at the same time the turntable would still maintain each rated speed."

If this is correct, it does seem to offer a reasonable margin. ;-)

Halcro, as I posted on 11/16 the SP-10 Mk2 manual states that table will maintain correct speed if up to 500 arms could be lowered simultaneously while tracking at 2 g. Even with an error range of 10%, it should be correct with up to 450 arms! From that, your three arm test was not much of a challenge. ;-)

However I suppose the problem with the Technics statement is the table could "maintain correct speed" with up to 1K gram weight applied. That could be different from not maintaining speed at the moment the weight was applied. In other words, should one allow say one revolution to correct the speed with this weight? That would be a big difference in sonic terms.

So if I'm understanding this, your laser mark should be measured precisely at the moment each stylus is lowered onto the record with no time interval to allow your table to correct for the added drag.

Tonywinsc, you have used the term "runout" several times. I believe this is intended to relate to the accurate centering of the record. But in all my years in this hobby I've only heard the term runout applied to the area at the end of the recorded material where the stylus rides a continuous circle. Am I the only one not understanding this term?

Now back to the basic subject of this post. It seems to me the motor/bearing/platter have four tasks:
- providing a stable platform for the record,
- not introducing any noise which may be picked up by the stylus,
- rotating the record accurately at the desired speed (this might be considered the overall average speed), and
- maintaining that speed through the mili-seconds when interference might occur from imperfect motor rotation, power line fluctuation, stylus drag, etc.

If I am correct, it is the last of these tasks which may be the most difficult to achieve. I've never seen a Timeline, only a demo video. But I have two comments. First I agree with Lew that the distance to the sensor mark would be important. But secondly if the mili-second interference does not occur at the point when the sensor mark is reached the error may not be noticed. In other words the speed might have recovered by the time the sensor hits the mark. Does this make sense or am I misunderstanding something basic here?

My friend Raul. Thanks, got it!

Or as was once suggested, "it's as clear as mud but it covers the ground."*

* Observation by a non-engineer.

The argument between measured performance and audible performance must be as old as our hobby. Both sides of that coin are being described here regarding speed.

I don't have any musical training and I expect my perception of timing (tempo) is better than my sense of pitch, which is certainly not absolute. A few years ago when I bought my SP-10 Mk 2A I had a tech friend go through all the calibrations described in the Service Manual. The strobe showed steady speed but when I listened to any recording with a sustained piano cord I could clearly hear a wavering. My friend could not find a correction for that so I took it to a professional tech. With the aid of one of my observed recordings he was able to find another adjustment that eliminated the wavering. After that there was not observable difference in the strobe but there certainly was an audible difference.

Thus I don't feel any need to investigate this Timeline device.

Lew and others with "the big spindle" issue. Could you stack enough metal washers on the spindle to leave only the top exposed, then use that to center the Timeline? If the top of your respective spindle is slightly rounded this might work. If your spindle is machined flat across the top then I suppose you could only "approximate" centering.