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TT speed

When I use a protractor to align the stylus I do the alignment at the inside, and then rotate the platter maybe 20 degree when I move the arm to the outside of the LP, or protractor.

On a linear tracking “arm” it would not need to rotate at all.

At 33-1/3, then 15 minutes would be about 500 rotations. And that 20 degrees would be a delay of 18th of a rotation.

So a 1 kHz tone would be about 0.11 Hz below 1000.
It is not much, but seems kind of interesting... maybe?

holmz
holmz's avatar
holmz OP
2,328 posts
 

Thanks @4krowme it was great that Larry could describe it better.

I felt like a scratch DJ moving the platter back-n-forth over the protractor when it occurred to me.

So it is more of interesting… but not entirely relevant.

If we had a short recording where the tracks were widely spaced, then the error gets bigger than say a super long “LP” record with more tracks being closely spaced. 

mijostyn's avatar
mijostyn
8,570 posts
 

@holmz , I understand what you are saying. The translocation of the stylus is so slow that it's effect on pitch is insignificant. Warps in the record surface and eccentricity of the spindle hole are far more significant in terms of pitch irregularity.  

lewm
13,519 posts
 

What? To be clear, I am questioning what seems to underlie Holmz’ thesis. Maybe I could understand if you (Holmz) were to define the "top"of the arc, just for starters. But I still cannot agree that pitch errors are caused by or related to the position of the stylus tip on the LP surface, again given a perfect recording on a turntable with perfect speed control. I would also ask Mijostyn to say what is meant by "translocation" of the stylus. I seem to be missing something.

cleeds
6,093 posts
 
mijostyn
The translocation of the stylus is so slow that it’s effect on pitch is insignificant.

Assuming a perfect record (absolutely flat, hole exactly in the center), the "translocation of the stylus" will have zero affect on pitch. Zero.

Assuming a perfect test record, you could playback a pure 1kHz tone from the beginning of the LP to the end. Any deviation would be the result of the turntable’s w&f, not any "translocation of the stylus."

holmz's avatar
holmz OP
2,328 posts
 

What? To be clear, I am questioning what seems to underlie Holmz’ thesis. Maybe I could understand if you (Holmz) were to define the "top"of the arc, just for starters. But I still cannot agree that pitch errors are caused by or related to the position of the stylus tip on the LP surface, again given a perfect recording on a turntable with perfect speed control. I would also ask Mijostyn to say what is meant by "translocation" of the stylus. I seem to be missing something.

Let’s say that the top of the arc is the outside edge of the LP, and the bottom is the spindle side.

  • Assume that the platter would spin at exactly 33-1/3.
  • When I put a protractor on it and start at the outside, and then move to the inside, I need to rotate the platter to get the stylus on the arc.
    • so the stylus goes backward and would end up behind the spindle
  • However with a linear tracking air bearing arm, I do not have to rotate the platter at all, and it’s protractor is a straight line.
    • It runs straight towards the spindle
    • zero angular platter change.

If I play the LP with both the regular arm, and also with the air bearing linear tracker arm, where does that required rotation of the platter end up? The rotation needed to get stylus onto the protractor?

Those two arm styles are not the same in terms of angular platter change.

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