TT speed

Sorry, you will need to restate your question as I don"t have a clue what you are asking.  Also, state the type of protractor, single point, arc etc.

Ditto to what testpilot said.  I think you are saying that the two alignment points afforded by some types of protractors are typically separated by 20 degrees, using the arm wand and the pivot as the definers of the angle. But tone is about the constancy of turntable speed, not a factor much affected by alignment. The custom of checking alignment at two points is to improve the accuracy of the process vs just aligning to one point, which typically used to be the inner null point of a particular alignment algorithm.  The classic Dennesen protractor used one alignment point, for example.  Anyway, tone is speed.  A 1000Hz tone recorded at the location of the inner null point will look different, if you could see it, from the same tone recorded at the outer one.  So ideally the record cutting process accounts for the accuracy of the frequency, and then we need an ideal turntable with constant speed.  Then you would hear 1000Hz at both locations on the surface of the LP.

Sorry, you will need to restate your question as I don"t have a clue what you are asking.  Also, state the type of protractor, single point, arc etc.

@testpilot It is a paper protector for a 9” arm which has 13mm of overhang. Maybe Baerwald? I don’t know for sure.

@lewm I am saying that when aI go from the outside to the inside, I need to rotate the platter somewhat… maybe 20 degrees, but probably less. 

So I am saying that the arm moves in a way that makes it advance or retard with respect to the platter spreed. I need to remove some rotation the platter more going from the inside to the outside. (Add rotation if going form outside to inside) 

The stylus is not moving linearly along a fixed line radially inwards. It is moving in an arc that is not perpendicular to the track’s direction.

 I am still thinking tracking error, but the aspect of speed throws me off that idea. 

At least it is not a large number, but maybe it accounts for a tiny perception of tonality in people with pitch perfect hearing?
(Not me)

Any alignment of a radial arm is a compromise. The alignment procedure is supposed to achieve the least amount of distortion across the entire record surface, not eliminate distortion. So, to fuss over it excessively is futile.

Use an arc protractor.

Align stylus tip to arc for full sweep. Make parallel to only 1 grid, inside or outside, your choice. DONE. No guessing. No trial and error, no back and forth. The 2-point protractor is archaic and very inaccurate. 
 

I have 123 cartridges, so doing alignments is common. Takes about 5 minutes. I use Lofgren B DIN mostly. Sometimes Stevenson DIN. The Arc protractor is deadly accurate and quick. I use it for conical, elliptical, HE, LC, MR tips. I get no IGD. Haven’t heard that in years. 
 

For printing your free arc protractor, you need your pivot to spindle distance; it’s a spec for your turntable or you can measure it. Choose your alignment (Lofgren A/Baerwald, Stevenson, Lofgren B) EIC/DIN/RIAA null points, and print. Easy peasy!

You are connecting two parameters that are not related. The stylus tip does not need to know where it is on the surface of the LP in order to reproduce the frequency accurately. It’s essentially a point in space.

For any pivoted tonearm, the stylus will describe an arc starting at the outermost grooves and swerving inward to the right of the spindle as it heads toward the lead-out grooves.  When you use a typical 2-point protractor, like the Feickert, you can see this effect, because the protractor is helping you to locate the stylus and cantilever at each of the two null points defined by any of the 3 standard alignment algorithms.  By definition, the stylus tip and cantilever should be parallel to the groove or perpendicular to the center of the spindle, at a null point.  You have to rotate the protractor to set each of the two null points because the tonearm pivot defines one and only one arc upon which the null points have to be set.  Please try to visualize that if my words are insufficient.  Alignment can affect distortion characteristics, but it does NOT affect fundamental frequency.  Because no matter where you are on the arc, the cartridge is reproducing what is encoded in the grooves at that point.  When a test LP with a 1000Hz tone is created, it is done with a lathe that ideally automatically compensates for the changes in groove length (a spiral with an ever diminishing radius, heading toward the lead-out grooves).  Your rotating the protractor is just to locate each of the two null points, has nothing at all to do with speed accuracy.  So long as the platter maintains constant speed, 1000Hz is 1000Hz everywhere on the LP surface.

I think that what he is saying is that the stylus tracks an arc across the record, which means it is at some point slowly moving forward (retarding, in terms of time), then at the top of the arc, it starts to retreat (speeding up).  Both the slowing of time and the speeding up covers the entire side of the record and covers such a small number of degrees of arc (hence small fraction of one cycle of the record) that it has nothing to do with what can be perceived in terms of pitch change or timing.

Larry, You wrote, ...."at some point slowly moving forward (retarding, in terms of time), then at the top of the arc, it starts to retreat (speeding up)"  I think you would agree that although the velocity of the stylus tip does decrease as it moves from the outer grooves toward the inner grooves, just because path length is getting progressively shorter per revolution of the platter, this has zero effect on pitch, assuming a perfectly created test LP and a turntable with perfectly constant speed.

lewn,

Yes, of course this has nothing to do with pitch. 

I suppose that since the speed variation from the stylus movement angle is lower than most W&F specs it is not really a concern.

I think that what he is saying is that the stylus tracks an arc across the record, which means it is at some point slowly moving forward (retarding, in terms of time), then at the top of the arc, it starts to retreat (speeding up).  Both the slowing of time and the speeding up covers the entire side of the record and covers such a small number of degrees of arc (hence small fraction of one cycle of the record) that it has nothing to do with what can be perceived in terms of pitch change or timing.

^Well put^ sir, that is exactly what I was trying to say.

  I think you would agree that although the velocity of the stylus tip does decrease as it moves from the outer grooves toward the inner grooves, just because path length is getting progressively shorter per revolution of the platter, this has zero effect on pitch, assuming a perfectly created test LP and a turntable with perfectly constant speed.

The fact that the cartridge moves some number of degrees of platter rotation, effectively would be the same as running the platter bit faster or slower… assume that the patter was, say, perfect in its speed,

The fact that the platter speed variation is greater than this Mathematical tracing delta makes it somewhat a moot point.

OP, Though I couldn't get what you were describing, it finally came clear when larryi posted. Whether it matters or not, it still is something that I had never considered before. A new thought for me. I very much appreciate discussing or learning about these sorts of topics. 

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. 

@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.  

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.

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.

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."

That statement is not correct.

Holmz is correct - on a pivoted arm the stylus is advancing and retarding relative to tangent, therefore there must be a timing error, but it will be minuscule on rotation re adjacent grooves.

I had pitch problems with my VPI Hw-19, with a linear tracker (Clearaudio Triquarz) as well as a pivot arm (SME V). Now, with a Hanss T30, with a superior dual motor / 6 string system, I don't have them.

@cleeds the error would need to be less than the W&F “noise”, and my stab at the error would be about 0.11 Hz at 1 lHz.

So it is likely to be more of an intellectual oddity than a severe problem.

Mathematically though. I believe that a linear tracker and pivoting arm would produce very slightly differing pitches.

It still twists my mind, but I enjoy the talk. Thanks. It is almost like an original thought for me that now will be a challenge to analyze.

 I see different perspectives here that don't jive. One aspect can be true from a certain perspective, but to change the perspective may be not to disprove the first, as it may seem. The second perspective may not be in line with the subject as was first supposed.

 Then there are of course those who chime in with what seems to be relevant but is not.

  Just thinking out loud here. Appreciate the thread.

You're arguing that tangency affects pitch? If so, that violates the Fourier Transform. That's not possible and, as I mentioned, also easily disproved with a test record.

I would rather use the term orthogonal or radial over “tangency”.

The stylus in the linear tracker runs straight along the radial spoke towards the spindle.

But let’s suppose that we set up the linear tracker to be at, say, a 45 degree angle and adjusted the alignment so that cartridge was derotated by the 45 degrees to be  exactly tangent to the track (which is an absurdity with a curved sound track - unless it was maybe a curved “linear” tracker…).

It should be easy to see in that case, that as the linear tracker moves inwards that with each rotation and the stylus moving towards the spindle, that it gains or looses a a bit of angular platter motion because it is displaces off of the radial spoke.
In the end it has gained or lost 45 degrees of platter rotation between the beginning and and of the LP.

Then there are of course those who chime in with what seems to be relevant but is not.

Me perhaps? 😀
it is a small number, so its is not likely relevant…

It just got me doing an Ah-ha with a chin-scratch, beard-stroking and the pate-rubbing.

 I know, it is a small number, but just the thought made my brain explode. I doubt that I will understand it. This course of logic doesn't come easily to me, and so that may be the reason it fascinates me. 

 The things that we may never understand (speaking for myself really) don't defy observation of occurrence, just maybe the ability to understand.

In plain English the issue is expressed in less than two lines.

I think OP refers to the old potato that with a pivoted arm the stylus follow an arc across the disc whereas a parallel tracker follows a radius.

As did the cutter across the master.

If this concerns him he should buy a parallel tracker like I have.

@cleeds , nice to have you back again cleeds. Theoretically pitch is affected but the effect is so slight that it may well be unmeasurable. 

@lewm , the turntable spins at a constant speed. As the arm travels in to the center of the record the radius that the stylus is on shifts clockwise, this is what I an calling translocation (I think I borrowed a medical term). This slows the speed of the groove by the stylus ever so slightly lowering pitch. This would probably never be measurable never mind noticeable but, it is real. It is not as professor cleeds says, "zero." 

The .11Hz change in pitch is WAY off the mark--that was calculated by looking at the angular difference at its extreme, which are many minutes apart, then calculating what this angular change means in terms of pitch.  But, say the recording is of a 1,000 hz signal, at any point along the record, it is playing a 1,000 hz signal, which is what you would hear no matter where on the record, you are playing.  To the extent the very tiny movement forward or backwards from the movement of the tonearm along an arced path changes pitch, it is extraordinarily small, and the amount of movement is dependent on the time frame one uses to measure the change.  If one measures say a two second interval, there will be an extremely small change in position relative to the starting position, which, I suppose, could represent a theoretical pitch change; a one second interval would then be about half as much of a change, and .5 sec, half again (kind of a Zeno's paradox).  The instantaneous pitch (if there can ever be such) would respresent a point with no change at all.

The fallacy of comparing the two extreme points on the record and calculating the difference as a change in pitch, is somewhat like the following analogy:  Suppose I have a fifteen foot long car.  If I move it ten feet forward, what I have after the move is a fifteen foot car whose location is 10 feet different from where it originally was located.  It is not a stretched out 25 foot car covering the interval of its movement (again a problem Zeno grappled with).  

Personally I would not use an FFT for fine measurements.

A better method would be shift the 1kHz down to DC and then plot the phase as a function of time.

The width of the FFT bins will mate it appear like it is one frequency, but it will be a chirp in frequency,. And with any spindle hole offset, it will be a chirp with with a sine wave riding on top of it.

There will no now way to get the sample rate high enough to have the FFT size be high enough to get any sub Hz resolution.
And with the chirp and sinewave it will be smeared within the bin to all buggery.

Holmz, if you are thinking of how to prove or disprove your frequency hypothesis, I fear we cannot do the experiment in the real world, because we require a perfectly created, perfectly centered, and perfectly flat LP on a TT with perfect speed accuracy, in order to examine the phenomenon you claim exists (and others do too, in fairness). Imperfections in any of the foregoing elements would likely cause a frequency distortion that would drown out the effect you want to detect. Fourier or no Fourier. But we can argue until the cows come home.

By the way, I was thinking that your observation, that you have to rotate the platter by about 20 degrees in order to set the two null points using your protractor, is really a product of how your particular protractor was made. It is possible to imagine another protractor where the cartridge can be aligned at the inner and outer null points without having to rotate the platter at all.

@lewm I agree it is somewhat meaningless in term of the platter speed and W&F levels…

But ignore the protractor and just draw a radial spoke on the paper. And there too… as the stylus moves inwards walk in “platter rotation space”… (well all except a linear tracker)

We do not need to do an experiment, as we can do it all solely with trigonometry.
(I might write a program to show it.)

However for an experiment we could do it with a two arm table if one of the arms was a LT. Then we would time align at the start… or we would just do a cross correlation every so often to show the offset as a function of time, which is the time delay as a function of platter position.

This method (being a relative measurement) would remove all the W&F and platter speed, but still probably includes some effect from the offset holes.

@cleeds 

Your belief is easily disproved with a test record - it’s easy to measure the frequency of a test tone on an LP.

We've already shown that measurements reveal it doesn't exist. It's easy to measure a 1 kHz tone on a test record.

Unfortunately you can't see the wood for the trees.

If you draw a line across the 2 null points of a pivoted arm, and are using Baerwald for example, then at the beginning of the record the stylus is behind the line, as it crosses the first null point it will move ahead of the line, and then as you cross the second null point it will fall behind the line.

Assuming the record is travelling at constant speed, then the motion of the stylus forward and back relative to the line must alter the apparent speed, as seen from the record groove, albeit minuscule.

Your fervour for FFT analysis appears to be an impediment to understanding basic maths and physics.

Your fervour for FFT analysis appears to be an impediment to understanding basic maths and physics.

• The FFT is pretty much sub-optimal for anything but gross frequency related analysis.
• There is the cross correlation (time domain) - which requires some known signal to compare the measurement to.
• Or there is direct phase, which is superior to FFT analysis.
  • Phase is the derivative/integral of the frequency 
  • So the rate of change of the phase give us the frequency much more accurately than super long FFTs to achieve small FFT bin width.

dover

Assuming the record is travelling at constant speed, then the motion of the stylus forward and back relative to the line must alter the apparent speed, as seen from the record groove, albeit minuscule.

You are really confused.

Your fervour for FFT analysis appears to be an impediment to understanding basic maths and physics.

You are really confused. I’ve never, ever mention FFT analysis. You’re apparently confusing FFT analysis with the Fourier Transform, an indicator that you’re having issues with your "basic maths."

The Fourier Transform is the theorem which explains how digital and analog audio work. It also disproves your fantasy that phono cartridge tangency affects frequency. As I’ve mentioned, I can also disprove your fantasy by measuring the frequency of a test tone as it’s played from a test record. It’s not difficult to do.

Of course, you’re free to imagine and fantasize that you’ve found some flaw in the Fourier Transform. A Nobel Prize awaits you if you can show you calculations. Good luck with that!

It’s interesting how some people think math is intuitive, and that they’d rather pursue a fantasy than understand what is really basic math. What’s odd is that they’ll resort to such personal attacks and invective in defense of a fantasy, while attacking those who understand the underlying science. But this is a hobbyist’s group, not a scientific forum, so I guess that’s to be expected from time to time.

The only thing unusual in this instance is the ease with which the claim that tangency affects frequency can be disproved.

We all get a bit snippy at times.  I'd rather ignore that and get on with this somewhat interesting discussion. (At least it beats talking about what phono stage a stranger should buy.)

Dover, I respect your knowledge, and I certainly agree with your thesis about what the stylus tip is doing with respect to the two null points. But the movement you describe is not happening on a stationary LP; it's happening on an LP moving past the stylus tip at 33.33 rpm (ideally).  Everywhere at any point on this LP, the 1000Hz test tone has been encoded by a perfect cutter lathe.  In practice, the stylus tip is just a point on the surface of the LP; it doesn't "know" where it was a fraction of a second before or after any particular event.  How can this phenomenon change the fundamental frequency?  The analogy about moving a 15-foot auto 10 feet and then thinking about how that affects its length is not a bad one for making the argument that there is no effect.  This is definitely not the same as a DJ doing "scratching", which I think holmz said is what inspired him. 

If you and the others are thinking that tangency to the groove per se and lack of tangency in between or before or after either null point is altering frequency, that I can understand, but I don't think that would alter the fundamental tone of 1000Hz; what it probably does do, where there is lack of tangency, is to produce distortions.  Harmonic distortion would produce some frequencies that are multiples of 1000Hz, and other forms of distortion would produce odd frequencies, but the 1000Hz signal is still there.  I am guessing you know this.

I just thought of a way one might test this idea.  You would need the shortest pivoted tonearm possible with the greatest tracking angle error, since, I am thinking, TAE correlates with this movement forward and rearward with respect to the straight line radius of an LP.  The more TAE, the more relative movement, the greater would be the frequency modulation.  Among present day tonearms, I am thinking of the Viv Float 7-inch underhung tonearm.  Underhung tonearms, which have zero headshell offset angle, inherently have much greater TAE than do conventional overhung tonearms with headshell offset.  And for an underhung tonearm, the shorter the arm the more will be the TAE.  So, if one could compare a linear tracker to a 7-inch Viv Float, on the same TT with the same test LP, one might be able to detect a difference in frequency stability.

@lewm I mentioned the scratching more as humour, but that is also the motion needed in the wrist if we put a spoke onto the record and help the stylus tip on it as the move from outside to inside.

I already gave the method for a relative test using a linear tracker and pivoted arm earlier. And an estimate of 0.11 Hz offset at 1kHz.

A relative measurement removes the platter speed and W&F from the equation.

But where does one get an LP with a tone on one side? If there a link?

@cleeds if we change the speed of the patter we would alter the tone’s frequency.
The tracking of a pivoting arm would look equivalent to linear motion of the overhang, moving slowly, in a linear tracker arm.

albeit, it is close to zero.

holmz

if we change the speed of the patter we would alter the tone’s frequency.

Yes.

The tracking of a pivoting arm would look equivalent to linear motion of the overhang, moving slowly, in a linear tracker arm.

What you’re saying isn’t clear, but a properly installed pivoted pickup arm has a fixed overhang. Overhang isn’t affected by tangency - that’s fairly easy to measure. As @lewm explains above, the stylus tip is always exactly where it needs to be.

I am sure it doesn’t matter, but unless the track is running in a circle, the pivoting arm will produce a very slight chirp in the tone.

The example of a linear tracker with a moving overhang is obviously not something that one buys… but it was yet another example to convey the effect of what is happening with the arm, that makes the platter look like it is advancing or retarding as the arm moves inwards.

What was an “ah ha” moment for me, was obviously not shared well or described too clearly.

Everywhere at any point on this LP, the 1000Hz test tone has been encoded by a perfect cutter lathe.  In practice, the stylus tip is just a point on the surface of the LP; it doesn't "know" where it was a fraction of a second before or after any particular event.  How can this phenomenon change the fundamental frequency?  

The cutter lathe is moving in a straight line.

A pivoted arm is moving in an arc.

They are not congruent.

Does your direct drive turntable speed up and down to bridge the gap on each rotation ?

@dover

“Bridge the gap” or…

😎

 It also disproves your fantasy that phono cartridge tangency affects frequency. 

I have never claimed that.

What I have said is that the stylus on a pivoted arm, for each 1.8 seconds, deviates from the position of the cutter head at the same time interval.

Frequency is a red herring because the deviation would be so small it would probably be less than that generated by normal tt issues around stability.

I am the OP, so it was my fantasy not @dover .

It is not “tangency”, but the walking of the point across the platter dues the arc of the tone arm.

But as was pointed out in the very opening post it amounts to “a bee’s phallus” amount of shift… I used the term, “it is not much”.

(Where “Bee’s _ick” is the Australian slang term for “a small and almost immeasurable amount”. I believe that the UK uses the acronym of “SFA”.)

My main claim was that I found it “somewhat interesting”.

What is more interesting now, is that we do not agree whether it is truely happening, or just a fantasy.
And also that my communication likely uses a lot of body language and hand motion to describe physical things.

holmz 

I am the OP, so it was my fantasy not @dover .

It bears repeating. This was very cool discussion to me. It begs the observation of even daily life. We see what we see, but do we?

  Thanks so much for keeping civil a topic that was entertaining and informative.

   Cheers, Greg >>>>>>>> P.S. Don't forget to think.