Linear tracking - a myth debunked?

[merrylander]

Pardon my skepticism but who keeps badly warped records? Frankly I won't even play them on my Planar 2 or PX-2 as they sound bloody awful. If they cannot be flattened they go in the trash bin. Even with the low filter on the woofer still reacts.

 

[lini]

(...) What cartridge are you running on your SL-5? I have one sitting on a shelf in the basement.

Scott: Revive it! It's a neat little DD - wish I never sold mine... Anyway, mine originally came with a Technics EPC-P24S - not a bad sounding cart, but still an entry-level model (foremost due to its entry-level needle - the body as such isn't bad at all...), which becomes obvious as soon as one tries something better. I've put an Audio Technica AT132EP on mine a bit later and was pretty happy with that combo, which let me hear a lot more details than before and to my ears also easily beat my father's Braun PS550 (very nice looking table, btw) with Shure M95ED...

Greetings from Munich!

Manfred / lini

 

[SaSi]

I was under the impression we were trying to debunk the LTs by virtue that they can't play unplayable LPs.

Just kidding here - so that I'm not misunderstood. My main TT is a Revox B791 and my secondary one a Technics SL-1200MkII

 

[nashvillebill]

Finally, the patented Garrard Zero100 tonearm design emerges, with all it's "nasties" as described by Sparky. Perhaps a few moments of discussion and analysis could be revealing.

How "nastie" is "nastie"? Air bearings are "almost" frictionless, how much is "almost" compared to "purpose" designed non air bearing friction?

Just wondering. :scratch2:

Peace. Regards.

Since I don't actually have a Zero100 sitting here to measure and analyze, I can only speak from my personal experience designing and building other mechanisms using 4-bar linkages.

All bearings must have some amount of clearance, and all bearings (even air bearings) have some amount of friction. Having 4 pivot points really accentuates these problems. Also, now there's a lot more mass to move around, and more deflection to contend with. There could be resonance issues too. And, if the geometry wasn't perfect, and the machining slightly out of tolerance, all of these issues get compounded. As a general rule, the more degrees of freedom you have, the less precision you get.

So the Zero100 on paper--well, maybe I should say looking at a photograph-- looks like a very elegant solution to a tough design problem, but having extra pivot points and arms gives us lots of opportunities for additional problems.

 

[Karma16]

To reiterate: my original question was whether the wear on stylii in linear arms was actually 'perfectly' symmetrical -- I didn't see how it could be since even though both sides of the groove wear on the stylus, the overall arm does move in one direction, and the outer groove side must be giving that force. It may be small indeed, but it is an unbalanced force.
I am hesitant to agree with the idea that once the motion is established it moves essentially without further force being needed -- groove modulation varies all the time, so groove to groove distance changes constantly, and the arm needs to be moving first faster than slower and then faster again and so on. So there will be forces in both directions, but the overall tendency is toward the center, so there ought to be more wear on outer edge of the stylus.
Just to make clear -- the question I was asking is not how linear arms work -- I've fixed enough of them to have a clear understanding, though I've not worked on air bearing arms - but to ask about the absolutness of Karma16's claim that the wear is perfectly symmetrical. I'm not doubting its better, but to claim its perfect seems to me to go hand in hand with the claim that linear arms have no tracking error -- again, better may be true in the best cases, but its impossible that they have no tracking error.

HI Nat,
I can do no better than judge symetry by what I see under the stylus microscope. The wear facets appear perfectly symetrical. Beyond that I can't say. This statement gains credibility when the facets exhibited by pivoted arms which are decidedly aysymetrical.

Sparky

 

[markd51]

Very interesting topic, I have read through some of it, but not all.

I think one point that basically all can agree on, is that the Anti-Skate mechanisms on virtually all Pivotal Tonearms, are basically nothing more than a Band Aid. As has probably been explained here by Karma, and perhaps others as well. that the needed AS Forces differ at different points of an LP.

For years, I've been told, that playing Blank Tracks on a Test LP is not the correct way to dial in Anti-Skate.

With that being said, I seem to note many vinylphiles of late bypassing the use of Antiskate altogether, and I'm wondering actually what advantage this has, if any at all? Wouldn't this actually be more of a detriment, that will cause more LP inner groove wear, as well as acellerated wear on inner side of a Stylus?

Wouldn't playback then be more prone to inner groove distortion? Wasn't that one of the ideas of using torture test tracks, to insure Antiskate was set to a acceptable setting, to lessen distortion to the least amount? Wouldn't no Anti-Skating exasperate this malady?
Mark

 

[Jody Thornton]

Technics SL-J Series

You know - I realize that they were cheap pieces of caca, but those Technics LTs from the mid-80s have a place in my heart. I can enjoy LPs but with the ease of a CD Player (makes me feel like I'm the "gramps" I suppose...lol! - no insult to the group intended)
.

 

[nashvillebill]

Very interesting topic, I have read through some of it, but not all.

I think one point that basically all can agree on, is that the Anti-Skate mechanisms on virtually all Pivotal Tonearms, are basically nothing more than a Band Aid. As has probably been explained here by Karma, and perhaps others as well. that the needed AS Forces differ at different points of an LP.

For years, I've been told, that playing Blank Tracks on a Test LP is not the correct way to dial in Anti-Skate.

With that being said, I seem to note many vinylphiles of late bypassing the use of Antiskate altogether, and I'm wondering actually what advantage this has, if any at all? Wouldn't this actually be more of a detriment, that will cause more LP inner groove wear, as well as acellerated wear on inner side of a Stylus?

Wouldn't playback then be more prone to inner groove distortion? Wasn't that one of the ideas of using torture test tracks, to insure Antiskate was set to a acceptable setting, to lessen distortion to the least amount? Wouldn't no Anti-Skating exasperate this malady?
Mark

Let's look at the numbers I spouted earlier, from my Dual 1225. Running 1.5 grams VTF. The tonearm is angled so the offset is about 3 inches; the coefficient of friction of diamond-on-vinyl is maybe around 0.1, which means the drag is .15 grams "force" (remember, technically a gram isn't a unit of force, but we tend to use it that way anyways).. Now how much does this equate to, as far as the extra force that the stylus is being torqued against the inner groove? Well, the tonearm is about 9 inches long, so this is easy: the extra "force" skating inward equals 0.05 grams.

So the stylus is being pushed down with a VTF of 1.5 grams. The skating is trying to push the stylus towards the inner groove with a force of 0.05 grams. Now this would be for a perfectly smooth groove, and ignores the peaks/valleys of the music that's on the groove. The actual inward skating force can vary quite a bit.

However...we've ignored the friction in the tonearm bearings, and the force it takes to twist the tonearm wires. The outer groove is pushing against the stylus to move it inwards--it has to push to overcome the friction of the tonearm bearings. (If these bearings were truly frictionless, as Sparky mentioned a long time ago, the stylus wouldn't need any force from the outer groove; once it got started on its movement inwards, it would continue.)

So this force opposes the skating force--in effect, it's a built-in anti-skating force! Does it realistically cancel out the skating force inward entirely? I dunno, I haven't tried to measure the friction in my tonearm bearings.

 

[teac4010]

Since I don't actually have a Zero100 sitting here to measure and analyze, I can only speak from my personal experience designing and building other mechanisms using 4-bar linkages.

All bearings must have some amount of clearance, and all bearings (even air bearings) have some amount of friction. Having 4 pivot points really accentuates these problems. Also, now there's a lot more mass to move around, and more deflection to contend with. There could be resonance issues too. And, if the geometry wasn't perfect, and the machining slightly out of tolerance, all of these issues get compounded. As a general rule, the more degrees of freedom you have, the less precision you get.

So the Zero100 on paper--well, maybe I should say looking at a photograph-- looks like a very elegant solution to a tough design problem, but having extra pivot points and arms gives us lots of opportunities for additional problems.

As you pointed out, the Zero100 design is compromised in several areas but it does demonstrate the concept of zero tangential tracking error with a pivoted tonearm in a mass produced 1970's product. The Thales tonearm, mentioned earlier in this thread, is the epitome of design excellence. A bit higher priced.

Oh well, we all agree zero tracking is the goal. FYI I included some dwg's of the Zero100 arm. Peace. Regards.

 

[niklasthedol]

Skating force is a dynamic force depending on where on the LP the stylus is.
The further in on the LP, the more skating force.
Anti skating mechanisms are dynamic as well, getting more powerful the further in on the LP the stylus is, equating the force of skating.

As I mentioned earlier, I have no asymetrical wear on several styluses here, all used in pivoted arms.

They were examined thoroughly in different microscopes; a watchmakers powerful eyemagnifier 2x/6x/10x, a digital microscope 10 - 200x 1280x1024, an optical 50-1500 x microscope and even a stereo microscope meant for surface inspection.

If there is skating force on pivoted arms, why would there be wear on the side of the stylus in touch with the outerwall/side of the groove. Very unlogical.

I believe that asymetrical wear on styluses from use in pivoted arms comes from misalligned set-up.

We all know that beyond 90% of all TT's are set up far from ideal.

No TT, not even with tangential arms, are set up perfect.

Most parameters in use when setting up arm/cartridge with VTF, zenith, azimuth, overhang, matching of dynamic compliance and effective arm mass etc. etc are so many factors at stake at the same time that perfection is not possible.

I don't think that comparing the best pivoted arms with the best tangential arms unambiguous will show us what's best.
Both construction principles have pros & cons.

My motive for posting pics of the Thales arm was to show that here's an attempt to combine most of the advantages from both worlds.

I just still don't quite get this:
Is there or is there not any skating force on the thales arm. It claims to have 0° tracking error.
What exactly is triggering the skating force?

"dolph"

 

[Old_Tech]

Linear sounds better to me...

I noticed the difference right away with my ST-7 having owned Garrard and Dual TT's that were so beautiful. As far as wear goes, it is mainly at the tip of the stylus as their is minimal wear on its side due to the constant correction for off axis during tracking. Running at .75 grams it takes years to wear the stylus.

 

[ke4jhj]

I just still don't quite get this:
Is there or is there not any skating force on the thales arm. It claims to have 0° tracking error.
What exactly is triggering the skating force?

"dolph"

Skating forces are created not from tracking error, but from the offset angle of the stylus.

Most pivoting tonearms are designed so that the cartridge is mounted at an angle, usually 18 to 22 degrees with respect to a line drawn from the arm pivot to the stylus. This offset angle minimizes the tracking error as the tonearm pivots from the edge to the center of the record. Although the Thales arm and the Zero 100 arm both have, in theory, near zero degree tracking error, both arms use an offset angle. Therefore, both arms will have skating forces that should be dealt with.

Most linear tracking tonearms have no offset error to deal with. Although most LT designs allow a pivoting action of the tonearm, the slide and servo systems keep the error close to zero. Because of this design, there is no offset angle for the cartridge. The cartridge, or more importantly the stylus, is in a straight line with the tonearm. Because of this, there is no skating force that the turntable has to correct.

Another situation to consider is with the DJ style straight arm underhung tonearm designs. Although to most of us, these designs are a disaster to performance and to the life of the record. The appeal is to those who "scratch". On these tables, there is no offset angle for the cartridge. This allows "improved" tracking during scratching. This is because there is no skating forces therefore no anti-skating adjustments. However, the tracking error is extremely large, approaching twenty degrees. That's why conical styli are a must with these designs.

So, at least in my opinion, zero tracking errors improve playback quality with less distortion and wear on records and styli. The offset angle is where skating forces are created and must be dealt with by anti-skating to minimize wear and distortion. The offset angle design was created to allow a pivoting tonearm to have minimum tracking error.

I hope I didn't confuse everyone, including myself.

 

[Mopic5]

Skating force is a dynamic force depending on where on the LP the stylus is.
The further in on the LP, the more skating force.
Anti skating mechanisms are dynamic as well, getting more powerful the further in on the LP the stylus is, equating the force of skating.

"dolph"

Hi Dolph,
Actually, I believe the inverse dynamics are at work. Stylus friction/drag is the main causal influence on centripetal force. While it seems intuitive that a sharper groove curve and congested modulation on the inner tracks would be causal influences, it is the record speed under the stylus that is the prime influence. Greater speed = greater drag = greater skate.
All best,
Mario

 

[lini]

(...) I hope I didn't confuse everyone, including myself.

I'm not quite sure... Imo, you get skating forces on a straight dj style arm, too. I'd expect the skating force curve to look much wobblier on these, though...

Greetings from Munich!

Manfred / lini

 

[nashvillebill]

Skating forces are created not from tracking error, but from the offset angle of the stylus.

Most pivoting tonearms are designed so that the cartridge is mounted at an angle, usually 18 to 22 degrees with respect to a line drawn from the arm pivot to the stylus. This offset angle minimizes the tracking error as the tonearm pivots from the edge to the center of the record. Although the Thales arm and the Zero 100 arm both have, in theory, near zero degree tracking error, both arms use an offset angle. Therefore, both arms will have skating forces that should be dealt with.

Most linear tracking tonearms have no offset error to deal with. Although most LT designs allow a pivoting action of the tonearm, the slide and servo systems keep the error close to zero. Because of this design, there is no offset angle for the cartridge. The cartridge, or more importantly the stylus, is in a straight line with the tonearm. Because of this, there is no skating force that the turntable has to correct.

Another situation to consider is with the DJ style straight arm underhung tonearm designs. Although to most of us, these designs are a disaster to performance and to the life of the record. The appeal is to those who "scratch". On these tables, there is no offset angle for the cartridge. This allows "improved" tracking during scratching. This is because there is no skating forces therefore no anti-skating adjustments. However, the tracking error is extremely large, approaching twenty degrees. That's why conical styli are a must with these designs.

So, at least in my opinion, zero tracking errors improve playback quality with less distortion and wear on records and styli. The offset angle is where skating forces are created and must be dealt with by anti-skating to minimize wear and distortion. The offset angle design was created to allow a pivoting tonearm to have minimum tracking error.

I hope I didn't confuse everyone, including myself.

Dave is correct in that if it's a truly straight tonearm, if you draw a line from the tonearm pivot point to the stylus, the cartridge body would be centered on, and square with respect to that line, not at an angle. In this case there is no skating when the stylus is at a point where the tracking angle is zero. Get away from that null point, however, and I believe the cartridge would skate. Could skate either inward or outward, depending on the direction of the tracking angle error. This is because the drag from the stylus no longer acts in a direction that goes through the pivot point, the tangent of the groove is at an angle (tracking error).

I'd have to draw this with a free-body diagram to confirm this, I'm visualizing the force resultants in my head right now and that's dangerous.

And on Mario's point: if the groove were smooth, friction (and therefore skating force) would be independant of speed. We wouldn't have any music to listen to then, however...

Bottom line, anti-skating is NOT a trivial exercise. Linear tracking seemed like an ideal solution because it eliminates tracking angle and eliminates skating forces. It's just the implementation of linear tracking (or a 4 bar linkage concept) that has difficulties.

IMHO Technics did a pretty fair job of producing a line of linear trackers that still fit most everybody's budget.

 

[Alaric]

Try a Yamaha PX-2.

 

[Karma16]

Three Cheers For This Thread

Hi All,
Forums can be wonderful things. Who would have thought this thread subject would have received this much attention? I personally am very gratified. I thought linear tracking was one of the well kept secrets of hi fi.

I was wrong. A lot of people "get it". Pretty neat. This thread has it all. Knowledge, joy, questions, skepticism, answers, and wonderful pictures. It's what forums are best at doing. Maybe this thread will take others hi fi experience to another level. I sure hope so. :thmbsp:

Thanks everyone. It's been fun.

Sparky

 

[markd51]

Hi All,
Forums can be wonderful things. Who would have thought this thread subject would have received this much attention? I personally am very gratified. I thought linear tracking was one of the well kept secrets of hi fi.

I was wrong. A lot of people "get it". Pretty neat. This thread has it all. Knowledge, joy, questions, skepticism, answers, and wonderful pictures. It's what forums are best at doing. Maybe this thread will take others hi fi experience to another level. I sure hope so. :thmbsp:

Thanks everyone. It's been fun.

Sparky

Sparky, I think the whole thing can boil down to implementation, quality of build,whether Pivotal Arms, Linear, Direct Drive, Belt Drive, Tape Drive, Idlers, etc.

I certainly wouldn't ever condemn a top of the line Galibier Turntable, with Triplanar Arm, nor would I ever turn away a Table such as the Walker Proscenium either, a Table that no doubt needs three grown men to lift.
These two are just many that have achieved the state of the art, and if the money was there, I sure wouldn't shun either, I would probably live happily ever after! Mark

 

[Pio1980]

I've owned and used a Souther SLA-3 tangental linear tracking servo-less arm set-up for ca 25 years with complete satisfaction. Aside from the anti-resonance mods done by me it only demands that the rails and rollers be spotlessly clean. It tracks offset and warped records better than anything else I've tried. Simple and effective, but not perfect. There are theoretical and practical issues with it's very low effective mass and lack of absolute rigidity in the mechanical "grounding" of the cart, unlike the best pivoted arms. Still, it is a good and viable mix of design compromises favoring effectiveness and stark self-contained simplicity.
S.B.

 

[Pio1980]

The Marantz SLT-12

A pantographic linear tracker from the '60s using a relabeled Shure cart. How any compliant cart ever dragged that Rube Goldberg's nightmare thru a cycle is beyond reasonable expectation.
http://www.thevintageknob.org/MARANTZ/SLT12/SLT12.html
http://www.audiokarma.org/forums/showthread.php?t=53080

I think this thing was roughly contemporary to the vastly superior but still heavily flawed RABCO SL-series servo-tangental arm.
http://www.thevintageknob.org/THEVAULT1/RABCO/RABCO.html
More linear arm lore;
http://www.soundfountain.com/amb/ttrabco.html
The Rabinow & Codier arm was the original accessory tangental linear arm and proof-of-principle of their joint study of tracking error/tracing distortion in pivoted arms.
The RABCO is still one of the most interesting things I saw in the '60s audiowise, along with the gorgeous Mac chrome chassis tube amps. MMMM!
S.B.