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Stylus-Drag..Fact or Fiction?

Most audiophiles can't seem to believe that a tiny stylus tracking the record groove on a heavy platter could possibly 'slow-down' the rotating speed of a turntable.
I must admit that proving this 'visually' or scientifically has been somewhat difficult until Sutherland brought out the Timeline.
The Timeline sits over the spindle of the rotating disc and flashes a laser signal at precisely the correct timing for either 33.33rpm or 45rpm.
By projecting these 'flashes' onto a nearby wall (with a marker attached)....one can visualise in real-time, whether the platter is 'speed-perfect' (hitting the mark at every revolution), losing speed (moving to the left of the mark) or gaining speed (moving to the right of the mark).

RAVEN BELT-DRIVE TT vs TIMELINE 
Watch here how the laser hits the mark each revolution until the stylus hits the groove and it instantly starts losing speed (moving to the left).
You can track its movement once it leaves the wall by seeing it on the Copperhead Tonearm.
Watch how it then speeds up when the tonearms are removed one by one....and then again, loses speed as the arms are dropped.

RAVEN BELT-DRIVE TT vs TIMELINE
Watch here how the laser is 'spot-on' each revolution with a single stylus in the groove and then loses speed as each additional stylus is added.
Then observe how....with NO styli in the groove.....the speed increases with each revolution (laser moves to the right) until it 'hits' the mark and then continues moving to the right until it has passed the mark.

Here is the 35 year-old Direct Drive Victor TT-81 turntable (with Bi-Directional Servo Control) undergoing the same examination:-
VICTOR TT-81 DD TT vs TIMELINE 
128x128halcro
phoenixengr's avatar
phoenixengr
94 posts
 
"But I was a bit puzzled by your statement: "A 24 pole motor turns at half the speed of 12 pole motor so the frequency of the cogs is identical in both (120Hz)." In a direct-drive turntable, doesn't the motor have to turn at 33.3333 rpm, regardless of the number of poles? And therefore might there not be a theoretical advantage to having double the number of poles?"



My statement was in response to the assertion that adding more poles reduces cogging (it doesn't).  Doubling the number of poles does not change the vibration signature because it will also cause the motor to turn at half the speed (assuming the same 60Hz drive signal).  Both a 12 pole and a 24 pole motor will produce vibration from cogging at 120Hz (10 revs/sec x 12 poles at 600 RPM  and 5 revs/sec x 24 poles at 300 RPM).  The amplitude of the vibrations is directly proportional to the power consumption of the motor, not the number of poles.  If you go to the link I provided, you will see that the measurements bore this out.

The motor on a direct drive table does turn at 33.333 RPM so the number of poles will determine the drive frequency needed in that case (RPM=Freq x 60/pole pairs or Freq=RPM x pole pairs/60).  If the motor uses steel pole pieces, it is subject to cogging and the frequency of vibration will be 0.555Hz x number of poles;  in most cases, this would be below 20 Hz so it will show up as rumble.  To run a DD motor from 60Hz would require 216 poles.


From what I've seen, most of the DD tables use a DC motor with servo control (feedback) to maintain proper speed.  This of course, comes with its own set of problems.

chakster's avatar
chakster
6,144 posts
 
Audiophiles are strange.

It is obvious that adults can’t develop perfect pitch (see why), so most likely none of you can detect such a tiny difference in pitch/tone by ear in a blind test playing records on your turntable. Even professional and very well educated musicians does not have a perfect pitch. How to develop perfect pitch? Watch this. I found it very interesting.

If you could detect a difference in tone between 33.333 and 33.334 then you’re not a human, or you must be 1 of 10 000 people trained for a perfect pitch since you’re baby.

In other words: If your turntable spinning slightly faster or slower you can’t detect it anyway when it comes to such a tiny difference people describing here above.

C’mon: 33.333 or 33.334? Are you serious?

Only 1 out of 10 000 people might have a perfect pitch and the only reason for this is because they’re born in a family of musicians and they were trained in the first 4 years of their life. Just watch this video.


P.S. I am using top japanese DD turntables with two tonearms on each and all those DDs are stable as hell.

Stylus-Drag ? Even if the tracking force is 1-3g, how about 900g record weight we’re putting on top or the record each time we play it? "Stylus-Drag problem" does not exist for me. Happy listening.




richardkrebs
422 posts
 
chakster.

I said... "I don't claim to be able to hear this difference"

You seem to be agreeing with me?.
phoenixengr's avatar
phoenixengr
94 posts
 
"Dear friends: I would like to know if each single LP was recorded/cutted at exactly/accurated 33.333..rpm and if for any reasons exist tiny deviations from 33.333..rpm accuracy why or how can we or not detected through an accurate TT that spins at exactly 33.333...rpm during play time of LPs?"



The most popular motor for the cutting lathes is a Technics SP02 direct drive motor which is quartz locked for speed accuracy and weighs ~110lbs with plenty of torque.  W&F are rated at 0.0084% RMS.  In terms of absolute speed accuracy, it should be more accurate (and more stable) than most of the DD tables playing the LP it cuts.

http://pspatialaudio.com/lathes.htm

mikelavigne
2,200 posts
 
of course, this is a natural selection problem. far beyond numbers or instruments. my son-in-law is a physicist working for the Allen Institute. they do brain research. he assembles big data for the neuroscientists.

he said in maybe 10 years they will be able to replicate a cubic cm of mouse brain tissue. but right now it’s too much data to replicate. he does not think he will live long enough for them to be able to do that for a cm of human brain tissue. just too much data.

so when we think that we can measure what our senses have evolved to sense, we are kidding ourselves. and not just the hearing part. the whole body is involved in whether we think something is fake or real.

which is why getting as close to absolutely steady as possible means more to our musical sensibilities than what we view as corrected speed. there are no naturally occurring servos.

In general, accurate rotation is obtained by servo-control by negative feedback, but at the micro level, if it rotates or becomes faster, it detects it and slows it, and repeats the operation to make it faster if it gets slower. If you try to measure a period with a small level, you cannot measure the instantaneous state, so you should measure the average value. Therefore, fine vibration generated by servo-control cannot be measured by the measuring instrument, it depends on the human ear.

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