Are linear tracking arms better than pivoted arms?

Livemusic, Good point about lateral mass. I have lately started using a Dynavector tonearm, which is deliberately designed to present a high mass in the horizontal plane. I can only say it is a great sounding tonearm with lovely bass response. However, I think the possible negative effect of high mass in the horizontal plane is ameliorated (at least) by the pivoted design of the Dyna tonearms.

"Make sure you use a surge tank with it and an air filter on the output of the tank that feeds the arm tube. You can build your own surge tank for dirt cheap by going to home depot or Lowes and buying a chunk of PVC pipe and two end caps and two air fittings."

This in a nutshell is why I have never owned an airbearing linear tracking tonearm. I just don't want to be bothered with tubing, tanks, gauges, and pumps, not to mention the noise from said pump. But if I did seek out one, it would not be the ET2. Since I don't have the scratch for a Rockport Sirius or Walker, I would go for the Trans-fi. But in the end I agree with Mike. The whole argument is specious, because "it depends". Or as Syntax said in simplest response to the OP, "no".

Ralph, servo arms have inherent problems too. The Rabco depended upon the arm swinging in a "micro"-arc so as to activate a relay that then switched in a tiny motor that drove the pivot along a rail. Thus in fact the Rabco (and the copycat Goldmund T3) transcribed a series of tiny arcs across the surface of the LP, which may place even more stress on the cantilever than does a well designed air bearing tonearm.

Hey 213 Cobra (Phil), I too was a friend and customer of Julius' in his end stage as a manufacturer. Over a period of 5-7 years I bought two amps from him, a stereo unit and then an H3aa. I have a vivid memory of standing in his shop space while he helped me box up the H3aa's, so I could carry them to my car. There were home-made power transformers that had been recently wound and "dipped", hanging on a wire to dry. The place smelled like a freshly tarred road on a hot summer day. He was a very sweet guy, a real "class act". Just a month ago I was visiting a record store that is virtually across 72nd St from his Broadway and 72nd St walk-up "factory". I looked for the door that used to lead up to his 2nd floor space, but could not identify it, because the building has been modified since.

I think the difference in the stress on a cantilever caused by a straight line arm vs a pivoted arm has to do with inertia, primarily. Lets assume there is zero friction. The cantilever is therefore bearing only the inertia (in the horizontal plane) of either a pivoted arm or a straight line arm. Inertia is related to mass and is the property of a static object to stay static and of a moving object to continue to move in the same direction and at the same speed (in the absence of friction). In the case of a pivoted arm, because it is rotating with respect to the pivot, which does not move at all, the net inertial mass is lower than for an air-bearing straight line arm, where all parts of the arm from front to rear have to be moved equally by the force on the cantilever alone. Many air-bearing arms have very low mass arm wands to compensate for this issue. Then in the real world there also IS a force on the cantilever necessary to overcome friction, to add to the problem. The cantilever has a huge mechanical advantage in overcoming friction at the pivot, but no such mechanical advantage in overcoming friction at the air bearing. Obviously, all these forces are tiny, else the cantilever would not last more than a few mm of travel. I am not about to argue that these things nullify the potential goodness of linear tracking.

DT and Atma-sphere, The Triplanar bearings are needle-type bearings, are they not? Hence I don't know how they would be comparable to ball-type bearings and whether the same quality ratings apply. Of course, they are not from Schweinfurt so obviously could not be so great. Did you ever see the movie "Twelve O'clock High"? Clark Gable and Gregory Peck play two US airforce officers based in England, and the whole issue is bombing those bearing factories at Schweinfurt, every night. Anyway, the stress on bearings in any tonearm is infinitesimal compared to, for example, a wheel bearing in an automobile or a crankshaft bearing. So I think bearings rated 7 and lower would probably not make an audible difference compared to bearings rated 11.

What is the effective mass of the Thales? Seems as if it would be very high.

Mepearson, Grounding is a black art, to say the least, but I suggest that a separate wire from tonearm body to the ground plane in your preamp might very well eliminate at least some of the residual hum you talk about. The ground achieved via the cables only accounts for the signal, not necessarily for the tonearm body. For example, my own RS-!A tonearm is unuseable without such a separate ground wire (hum is dominant), whereas I have never had to ground the Triplanar in this manner, and it is totally hum-free.