I have owned several linear tracking arms.
Air bearings don't work. I am sure all of you have noticed that the more pressure you put in the arm, the better it sounds. The problem is that there is a violation of a fundamental turntable design rule, which is this: for proper LP playback, there can be no bearing slop between the surface of the platter and the cantilever of the cartridge.
Air bearings by definition have bearing slop, and this is why they sound better as you add more pressure.
The other problem, already mentioned, is that due to the excessive lateral tracking mass, it is the cantilever of the cartridge that defines the tracking error **not the arm**! This is because the cantilever has to flex to move all that mass.
The result is that a good quality arm like a Triplanar or Phantom has lower tracking error than any air-bearing arm!
In order for a straight-tracker to actually do its job right, it cannot have any slop in any of its bearings. Linear tracks do exist that have no slop, so it would not be that hard to devise an arm that also has no slop, using a servo not unlike what the old Rabcos used (updated of course). Arms like that don't exist right now so for the time being, radial tracking arms rule the State of the Art roost. |
The idea that a pivoted arm of correct effective mass is going to induce greater side-to-side excursion than an air-bearing straight-tracking arm strains credulity. |
Lewm, I built a servo for the Rabco (which uses contacts, not relays) so the contact had only to get below 1 Megohm and the motor would run. Then I put a large capacitor across the motor so it would ramp up slowly and turn off slowly. The result was that the motor was always on, and would set its speed according to the rate that the LP grooves dictated. This eliminated 95% of the hassle of that arm- it was reliable and quite precise as far as linear tracking was concerned.
Later I had an ET but after eating a few cantilevers, I ditched it. Obviously I had the wrong cartridges in it; you could sit can watch the cantilever move back and forth as the arm tried to negotiate the LP. If you have ever seen the arm 'wobble' you know what I am talking about.
There are cantilevers that are stiff enough so this effect is reduced. What is not known (IOW I have seen no measurements to this effect anywhere) is how much the cantilever actually moves to make the arm move. IOW if the cantilever flexes by only a few degrees (which will not be visible to the naked eye) than any advantage of straight tracking is lost to radial tracking where this does not occur (of course this phenomena could occur with a radial tracker too, but most cartridge designers are expecting a certain effective mass in the arm and so this should not be a problem).
Short arm tubes such as seen in the Souther have two issues. The first is that the arm bearings cannot be in the plane of the LP so tracking pressure will change as warps and bass frequencies are negotiated. The second is that warps will cause wow.
BTW to be clear about something: its impossible to have an air bearing that has no slop. If there was no slop, there would be no place for the air to be in the bearing. With precision machining and tight tolerances, the arm can be poised on its cushion of air, and not move too much- until it is disturbed by the motion of the cartridge. The fact is that the arm has to move back and forth and yet stay exactly on its locus. If it moves even slightly out of locus that will be interpreted by the cartridge as a coloration. Its a bit of a trick.
I'm pretty sure that everyone agrees that air pressure and holding tanks to promote stable pressure are important to the sound of the arm. If that is **not** the case, then I would agree that air bearings work... Right now I have a Triplanar, and I've had several pivoted arms before that, not because I think anyone of them are the state of the art, but because what I think is required in a straight tracker does not exist. I regard radial tracking arms as a temporary solution. |
Sometimes an LP is rare enough that you put up with what you are able to find. All LPs have some warp. When speed variations are introduced, its likely that when they are subtle you are more likely to hear them as a wavering in the soundstage.
I had a Cosmos for a long time- it is nice to have the records be really flat. |
Lewm, Exactly!
About ten years ago I did initial sketches on a tone arm that used a mechanical track that had zero bearing slop. The are was otherwise conventional in that it used a pivot like a radial tracking arm, and a servo that was light-beam activated. Of course I never built it, instead I handed it off to a tone arm manufacturer, but it seems like its not likely to see the light of day anytime soon if it ever does. But it is a design that solves this problem.
I own an LP cutting lathe, and every time I look at the lead screws and do the setup on the cutterhead itself, I think about doing a linear tracking arm. Right now its more important to run the lathe than make a tone arm... |
Mepearson, not to muddy the waters too much but I spotted a comment from Dertonarm that needs correction: the bearings in the Triplanar as good as you can find. They are custom-built by an aerospace bearing supplier, and are 3 or 4 grades higher in hardness and polish than the bearings found in the SME 5. There is only one manufacturer in the US than can make the bearing and they are the most expensive part of the arm as I understand it. |
Pgtaylor, its the arm tube. It has a mid-frequency resonance and is poorly controlled by the materials within. That's where the Graham and the Triplanar take it to task.
The Sayles arm looks brilliant. Now can we have a version that puts the bearings in the plane of the LP? |
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Samujohn, in a word, no. Fred's point about using vacuum is well-taken; record warp will contribute to the issues of air-bearing linear trackers. This quote The problem is that most tangential arms have historically not been well designed or executed. is the most telling. Mikelavigne, about 20-25 years ago someone figured out that the Reynolds number for a bumble bee's wing was not being calculated correctly. Once the right Reynold's number got into the math, it turned out that bumble bees fly just fine. That example does persist though, just like most people still think that Marconi was the inventor of the radio. |
One thing about the tape experience is how locked-in the soundstage is, and the complete lack of strain experienced with the most complex musical passages. This is something I have only seen a few times with LP systems. If you have not experienced what I am talking about, its hard to understand only in the context of vinyl playback. Those who have tape systems know what I mean.
IMO this is an area that all LP systems must strive to perfect. |
Darkmoebius, he's right. Tubes make lower-ordered distortions, much more preferable to the human ear than the higher, odd-ordered distortions of solid state.
Tube distortions can be dramatically reduced by careful design. There's more about that over on the amps/preamps forum :) |
The second order thing about tubes in general is only with SETs- when operating push-pull even-ordered harmonics are cancelled. The nice thing is that you don't get the 5th, 7th and 9th which are unpleasant and used by the ear as loudness cues. |
I get the impression that Samujohn speaks for many of us in his last sentence :"...It's about the enjoyment of music -and friends."
I've always wondered how far can we take our technology and for me straight tracking arms were always an expression of that. I've always been a fan of the idea of them, and often more disappointed by them as a result. It is why I run a pivot arm (BTW the Triplanar has such hard bearings in it that they got investigated by the Department of Homeland Security because they use more of them than Boeing...), but regard it as a temporary measure until I see what I want in a straight tracker.
OTOH I've also wondered if there might be a way to solve the problem the other way 'round- by building a cutter head system that cuts radially rather than straight, although in looking at my cutting lathe, seems like it might be quite an undertaking... |
Their list of amps is incomplete :)
It does seem as if a lot of 'advances' in technology are a sort of race to the bottom: mp3, and CDs to name a couple we are all familiar with. Many of the changes I saw in 'hifi' receivers over the years (I used to run a service shop) were changes made simply to reduce shipping and assembly costs.
Other technologies are moves forward, like when overhead valves supplanted side valve (flathead) technology in internal combustion engines. |
Syntax, I could not disagree more. I've spent the last 20 years working out what the human hearing/perceptual rules are, and then making sure that our gear obeys those rules. This work is on-going- I am also exploring what Chaos Theory has to say about audio electronics, and have further research showing how important it is for the playback system to reflect human perceptual rules, backed up by some well-known neuro-scientists.
Now maybe I have got my own findings and the like, but I know I am not the only one who is engaged in such research. Its true that there is less research than there was 40 years ago, but it is not true to say that current equipment is made simply to sound pleasing. There is a difference between that and being made to be as good as it possibly can be with the known science. |
Over the years I have been involved with a fair number of recordings, some of which have made it to LP, others CD only and still others that only exist as R2R.
What I have found is that having a master tape to help me with evaluation is extremely valuable. Further, working with the musicians and developing the recording techniques for a particular project helps a lot too.
The primary thing is that you know what it sounded like live. If you go to LP from there, you know what the LP should sound like and it gives you a really valuable leg up on assessing other parts of the playback chain, for example the tonearm.
On the last recording I did, I installed Western Electric tube mic preamps that I had rebuilt into the studio, and we ran them directly into the recorder, bypassing everything else. This is what I mean by developing the recording technique. Of course the technologies always falls short of the live musicians, but its all worthwhile as long as we keep two things in mind: strive for the best, and enjoy the music. |
Cjfrbw, I agree with a lot of what you posted, I just don't think that should stop us as audiophiles/manufacturers or whatever from trying. I think intention plays a huge role- the guy that gets into a high end audio business to make money is there for the wrong reasons, just like any other field of endeavor except maybe banking...
Frogman, I also agree with nearly everything you said but I don't understand how you came to the opposite conclusion, or is it that the matter is that ephemeral?? |
