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What happened to linear tracking?

SA-708 said:
So what moves a pivoted arm across a record? Would it not be that same stylus pressure?
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Sure, but in the case of a traditional arm, it's the mass of the arm and stylus that are responding to the tracking of the groove. In the case of the LT arm, there is some feedback mechanism and the arm is motor driven.

Which also begs the question as to what noise is introduced to the arm and stylus by the motor and mechanism that moves the arm back and forth? It has to be > 0.

It's all a tradeoff. In the case of the traditional arm, the angle of the stylus in the groove, skating pressure, etc. In the case of the LT approach, the feedback mechanism, the motor and the gearing of the arm..

Out of curiousity, what is the stylus pressure for either approach? It's been a while since I set up my LT table, but I seem to remember 1.25 - 1.5 grams. For my traditional table, I think it's on the order of .75 grams.

bs
 
You can also pick up this bad boy: http://www.audioadvisor.com/prodinfo.asp?number=CLTT2

At $10K, it's easily twice my system's entire price.

But if you can afford the $10K tone arm, you can afford the $170K turntable it's designed to go with.

And, no, I'm not trying to start up one of THOSE kinds of rows. After all, if I had the cash and space, I'd probably have me one.
 
bshorey said:
Sure, but in the case of a traditional arm, it's the mass of the arm and stylus that are responding to the tracking of the groove. In the case of the LT arm, there is some feedback mechanism and the arm is motor driven.
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And friction (which is hopefully extremely low).

bshorey said:
It's all a tradeoff....
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As is everything.

bshorey said:
Out of curiousity, what is the stylus pressure for either approach? It's been a while since I set up my LT table, but I seem to remember 1.25 - 1.5 grams. For my traditional table, I think it's on the order of .75 grams.

bs
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My Soundsmith SMMC-2 tracks at 0.75g on my B&O TX-2 linear tracker.

Another advantage to linear trackers is their ability to deal with records that might be challenging for pivoting arms...

TX-2 tracking a warped record.
 
Not accepted by the audiophiles except for the exotic air bearing expensive arms. Not usable by DJ or archivist types for their needs. P-Mount on many of the affordable models not suited for either needs. The better ones were nice even if they didn't catch on.
 
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For me the major issue is no skating/antiskating that introduces imbalanced tracking force between channels amongst other ills. IGD is also a non-issue.
 
Hi,

Simple fact is IMO LT turntables were introduced because manufacturers were
developing CD linear tracking solutions in r&d and no other major real reason.

Top end is one thing, but the bottom end stuff control circuitry ended up in
CD players. Having said that, if you know your Technics models, you can
pick up a very decent LT fully automatic models for not a lot, just make
sure its been little used and looks like it, servicing can be tricky.

The good sound quality of the short arms set them apart somewhat.

I got a good full width Technics for a friend who needed a "childproof" deck.

rgds, sreten.
 
flavio81 said:
5. And it's a complex solution to a problem that isn't really a problem.

A very interesting paper on VE, "digital simulation of tracking distortion" shows convincingly that the distortion introduced by the tracking error on your typical 9" arm should be below audibility and way below the other distortions introduced by the pickup/stylus/cantilever, not to mention the distortions introduced by the speakers!!
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JonL said:
This may or may not be true in practice, but I've got a problem with it from a theoretical point of view. I think distortion compounds itself. The statement that "the distortion introduced by the tracking error...should be below audibility and way below the other distortions introduced by the pickup/stylus/cantilever, not to mention the distortions introduced by the speakers..." implies that only the worst distortion offender in the chain is significant, and lesser contributors don't matter. Taken to an extreme, let's say the speakers have 2% THD. Then it supposedly wouldn't matter if the amplifier had 1.9% THD, the preamp another 1.9%, the turntable yet another 1.9%... get my point? I think that not only do the distortion components add, anything distorted early in the chain gets distorted yet again by every signal processing stage that follows. From that point of view it makes sense to try to absolutely minimize the distortion at the source first, with every succeeding stage being of *slightly* lesser importance.

All that said, I have both linear and pivoting tonearms in my system. I prefer the linear tracker for a number of reasons, but I don't detect any difference in distortion between the two. My system is decent, but there are certainly far more resolving systems that might make differences more audible.
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As an engineer I'd like to chime in on this discussion. I have seen this type of argument used in discussions of noise, distortion and other impairments and imperfections many times in any number of fields. It is always based upon the typical impairments of properly functioning devices used in the system. In the typical sound reproduction chain speakers have distortions in the realm of 5%~10%. Amps are typically less then 0.1%. Even if you have incredibly low distortion speakers, they will not fall below 2%~3%. Likely, the amp used with such speakers will also be of high quality and distortion would likely be lower then the 0.1% I sited. But even at 2% for the speakers and 0.1% for the amp (low for the speaker and high for the amp) the distortion product contributed by the amp is only 5% of the distortion contributed by the speaker. This is by the way, a worst case scenario where the amp is merely mediocre with extremely good speakers. This is, in my opinion, an unlikely pairing. With the amp's distortion being less then 10% of the speaker's, it is unlikely to be heard when listening as it is being overshadowed by the speaker's. Since the speaker is more likely going to be closer to 5% or more and the amp is more likely to be perhaps one to three orders of magnitude less then what I used in the example (more likely about 0.01% or 0.0001% instead of 0.1%) the amp's distortion is insignificant.

I used the speakers and the amp in this case because that is what I am familiar with. I cannot and therefore do not site tracking error vs cartridge distortion as I do not know the typical levels there, but I an reasonably confident that most cartridges do significantly better then the 5% typical of many speakers out there.


Just my thoughts on the matter.

Shelly_D
 
I'm also an engineer (ME, not EE), and while I used extreme numbers in my example, I still think that small amounts of distortion can be compounded by subsequent stages to the detriment of sonics. Evidence? None, just opinion. Considering all the hoo-ha one hears about the difference in higher order harmonic distortion components between tube and solid state gear, where those differences are on the order of a fraction of a percent, I think there's a lot about the audible effects of distortion that isn't well understood, at least by the casual enthusiast -- myself included.
 
bshorey said:
I've got both styles of turntables as well. My impression is that whatever distortion is introduced by arm angles with a traditional tonearm is more than offset by the mechanisms used to move the LT arm, and the fact that it requires some level of stylus pressure to move the arm? If the vinyl isn't perfectly centered, the problems get worse.

bs
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The problems of a vinyl not being perfectly center how would that only effect a Linear Tracking arm and not a pivoting arm. If fact since the linear arm is already almost tangent to the groove the difficulties would be less than an arm that is not tangent in the groove and a pivoting arm is not excluded from having to deal with the groove not being centered.

As far as the air bearing not having any friction it will still require some force would it not to move the weight of the arm and cartridge. In a servo driven arm the needle tracking in the groove does not require it to move the arms weight accross the disc, just the slight deviation of the angle of the arm then uses a motor to driver the carriage so I don't see how friction has anything to do with it. No matter how low the friction is on a bearing of any type, it still takes some energy to move weight in a direction. I don't know what moves an arm across the disc on an Air Bearing table, but unless their is a drive system to move the arm, the needle will have the load of moving a mass, where as in a LT table with a motor to move the arm the load won't be required of the needle. On a pivoting arm does not the bearing on the arm have fiction? But since a seperate force moves the carraige on a LT it is not depended on friction since the needle doesn't need to direct the arm across a disc, a motor does all that work for it. The only force the needle needs to do, is move the arm at a slight angle to the track,

I do know one thing, LT's are much more of a pain to maintain, even more so as they get older, probably some more than others. But Pivoting tables can also have problems as well, I have both and both of them have given me problems, of varying degrees.

I have had some less then quality LT's in the past Technics cheap ones and Sansui junk one, that you could hear the arms motors on very quite passages or on the run out at the end, it sounded like a low rumble, but I can not hear any sounds from the transports on my better ones.
 
HI Ken,
With an air bearing, there are two elements that must be driven. And they must be driven by the stylus as it tracks the groove.

First, there is the inertia of the arm assembly. The groove is pulling the arm to the center of the record. This inertial force is zero if the groove pitch does not change. But, the pitch of the groove is not constant. Modern records are cut with variable pitch grooves to maximize the number of grooves (yes, I do realize there is really only one groove) and, thus, the recording time. So, each change of groove pitch acts on the arm as an acceleration, both positive and negative. If the pitch change is fast, the resulting arm acceleration could be large and be significant. But the pitch actually changes very slowly so the acceleration is very slow and, thus, very small. It is not significant but it is there. Remember, a pivoted arm must also react to pitch changes.

Next, the tone arm leads must follow the arm as it tracks across the record. Again, this is a very small force but it is there.

Neither of these forces can be called friction. Rather, the first is an inertial force and and the second is a spring type torsional force. They are tiny to the point of being insignificant.

A good demonstration of the lack of friction is when the tone arm is leveled. To do this, the VTF is negated such that the arm just floats over the platter. If you then give the arm a gentle shove it will travel to the inner stop, bounce off of it and rebound to the outer stop. Then it will rebound to the inner stop again. This oscillation will continue for a while, maybe a minute, until the arm finally comes to a stop. One of the first "Ah Ha" moments a new owner has is when they first perform this test. It is amazing how little friction there is in the system. By comparison, a pivoted arm has so much friction that they seem to be mired in axle grease. An air bearing is truly amazing.

Sparky
 
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shelly_d said:
I used the speakers and the amp in this case because that is what I am familiar with. I cannot and therefore do not site tracking error vs cartridge distortion as I do not know the typical levels there, but I an reasonably confident that most cartridges do significantly better then the 5% typical of many speakers out there.

Just my thoughts on the matter.

Shelly_D
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Yes, more or less my point exactly. When one component introduces less distortion than the threshold of audibility, then said component isn't really needed to be improved. Your example with the cheap amplifier and great speakers is good, although it's purely theoretical since two amplifiers can produce 0.1% THD at a certain rated power, but one could go real astray once that power is exceeded, while the other can stay clean and pure.

Back to the topic, the paper, "Digital simulation of tracking distortion" by R. Tollerton, does exactly that: simulates the distortion of the waveform caused by the contact points of the stylus tip in the groove being 'slanted' (non tangential). The amount of 'slant' (time error directly related to tracking angle error) can be varied and the resultant waveform heard for judging how audible is the introduced distortion. A great idea. This threshold is found out using synthetized tones, but the same listening test done with normal music masks said distortion enough to allow a threshold 10x higher...

The threshold is also related to modulation velocity and record speed, which is very interesting.

Anyways, he finds a 'threshold of audibility' and finds that the angle error for going over that threshold is >2.11°. Any correctly set-up 9" arm has an error smaller than 2.11° over the whole range. Also modulation level should be below 25cm/sec to stay below the threshold. Normal program levels are below that value.

The interesting thing is that this is not only in the horizontal direction but in the VERTICAL direction too... Now, in this case, with cartridges coming out of the factory with vertical tracking angles as mistaken as 30° (instead of the 15° or 22.5° standards), we can infer that this is the real devil, and that a normal 9" arm should suffice.
 
JonL said:
I'm also an engineer (ME, not EE), and while I used extreme numbers in my example, I still think that small amounts of distortion can be compounded by subsequent stages to the detriment of sonics. Evidence? None, just opinion. Considering all the hoo-ha one hears about the difference in higher order harmonic distortion components between tube and solid state gear, where those differences are on the order of a fraction of a percent, I think there's a lot about the audible effects of distortion that isn't well understood, at least by the casual enthusiast -- myself included.
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I absolutely agree with you. With the other argument, taken to its extreme, it sounds like you could have 5% distortion in every element of the chain and the distortion would be the same as just the speakers themselves with 5% distortion, and everything else being distortion free. That's not going to happen. It would sound terrible. We're dealing with one signal. If distortion is applied at different points in its path, the distortion will compound. It will not mask, as it is not all happening at once. The signal is passing through in a sequence. The distorted signal from the turntable, will then reach the preamp, which will distort that signal, then the amp will distort that distorted signal in some other manner, and the speaker distort that thrice distorted signal even further. I don't think you need an engineering degree to understand that, and you certainly don't need one to hear it in an audio system. Or just use a different audio system to illustrate it (though the distortion is not exactly the same, it gets the point across): an electric guitar. Run two distortion pedals in sequence. Turn the one closest to the speaker farther into distortion, the one closer to the guitar end less. Hit the higher-distortion pedal first. The signal will distort, and it will sound a certain way. Hit the one closer to the guitar-and still, the distorted signal will change. The distortion will compound. The greater distortion does not cover up the lower distortion, they add together to create a different distortion. The speaker distortion/mask fallacy would pretty much even negate the need to set up a cartridge. There is no way you'd hear changes in VTA or even slight tracking errors if nothing below the speaker's distortion level mattered.
 
sreten said:
Simple fact is IMO LT turntables were introduced because manufacturers were developing CD linear tracking solutions in r&d and no other major real reason.
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I'm 95% certain that Bang & Olufsen and Harman/Kardon (Rabco) were both selling linear tracking turntables well before they started developing CD players.
 
You are correct about B&O and Rabco being around many years pre-CD. But with the linear trackers, better ones then and now cost lots of money to buy and on upkeep. A Rabco arm was $169.50 back in the late 1960's. Or just over the cost of an entire Thorens TD 150 new. Which in the day was a lot of money for most people. My AR XA cost over $100 less in 1973 for perspective.
 
I used to wade into the technical end of this discussion, but having used a Mitsubishi LT 30 for a while, I came to the conclusion that the technical arguments for or against linear arms were less important to me than the ergonomic issue -- I want to be able to place the stylus in the groove of the track I want to hear, without having to wait.
This is also an argument against automatic tables (and to some extent against cuing devices), and its a matter of personal taste.
But I suspect a fairly large portion of the audiophile market is similarly impatient, and give that most non audiophile listeners moved quickly to CDs when they came out, a market that consists only of patient audiophiles probably wasn't big enough to support more than the tiny cost no object manufacturers.
 
Nat said:
I used to wade into the technical end of this discussion, but having used a Mitsubishi LT 30 for a while, I came to the conclusion that the technical arguments for or against linear arms were less important to me than the ergonomic issue -- I want to be able to place the stylus in the groove of the track I want to hear, without having to wait.
This is also an argument against automatic tables (and to some extent against cuing devices), and its a matter of personal taste.
But I suspect a fairly large portion of the audiophile market is similarly impatient, and give that most non audiophile listeners moved quickly to CDs when they came out, a market that consists only of patient audiophiles probably wasn't big enough to support more than the tiny cost no object manufacturers.
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This is probably the biggest factor for me as well in looking at LT versus pivoted tonearms.

I owned and used a Beogram TX-2 linear tracker for many years. It was a great performer and I definitely recognize the appeal and advantage of LT tonearms. However, the TX-2, a full automatic design, was very slow and tedious to cue up, select particular tracks, etc... with all movement dictated by the motor driven tonearm.

In more recent years, I've been doing audio transfer and restoration work as a business. I typically need to select and sample loud passages on a record in order to set recording levels. Cueing quickly by hand and fast cartridge swapping are absolutely essential features. So linear tracking tonearms, as nice as they are, don't really fit my needs.
 
I actually like the cueing of the TX-2. The built in light is perfectly positioned to highlight the spaces between tracks, and it's easy to use the left and right buttons to position the stylus very accurately. It takes a bit longer than cuing with a manual pivoting arm, but on my Thorens, when I bend down to see where the stylus is I cannot see the space between the tracks clearly. I seem to always miss, and therefore rarely try to cue up a record anywhere but from the beginning. I can certainly see where a table like the TX-2 would be unsuitable for professional use where the tonearm has to be moved around a lot.
 
The slow cueing on my LT-30 is not something I view as a drawback, though I see how some would be annoyed by it. I'm an impatient person and it helps me just relax and take it easy. It's also nice having an automatic around. My other tables in use are manual and sometimes I'm doing something and leave the stylus in the run out groove a bit too long- and have even forgotten about it once or twice when really into something else. Oops.
 
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