Linear Tracking Turntables - Best??

The problem with air-bearing arms is that the lateral mass is often a multiple of the vertical mass. So you can be tracking at the right weight for the cartridge, but the lateral mass can cause visible left-right motion in the cantilever. When this happens, the tracking error is significantly higher than that of a radial tracking arm!!

The solution is a cartridge with a lower compliance. This might not work out all the well when it comes to simple tracking, as the vertical component (mechanical resonance) might not be satisfied. 

I used to run a heavily modified Rabco arm many years ago that got around these problems- but then had other problems, most notably mechanical resonance in the track in which the arm ran. I do think linear tracking is the way to go, but have yet to see an embodiment that solves all the engineering problems.

@larryi, there is a problem with this statement:

 Bass is typically mastered monophonically, which means only lateral movement of the stylus tracing the groove.  The higher effective mass in the horizontal plane would keep the arm from moving so easily so that all of that bass information is imparted to moving the cantilever which means that all of the bass information is actually recovered by the cartridge.

The problem is that bass is not mastered monophonically! Its mastered in stereo like everything else. Dealing with out-of phase bass is a problem in modern recordings, which is why a lot of mastering houses employ a passive device that makes the bass mono for a few milliseconds until the out of phase bass problem has passed. We have such a device in our mastering suite, but prefer not to use it; so far anyway I've found that if you just spend a little more time with a mastering project and do some test cuts, you can sort out a way around the out of phase bass without resorting to processing, which I like to avoid.

Further, the higher lateral mass simply means that the arm can be moving one way while the cantilever is going the other way. I've seen this in air-bearing arms with cartridges that are too compliant, and in one case at a local dealer's shop (House of High Fidelity of St. Paul, no longer in business) the excess motion resulted in the cartridge body shedding the cantilever entirely! So this issue should not be ignored or overlooked!

FWIW, I'm a huge fan of the idea of linear tracking. I think there is a way to make it work too; it will have to be a solution that has the vertical and lateral tracking masses being the same, while at the same time having the arm bearings in the same plane as the LP (to avoid change in tracking pressure on bass notes or warp).

Some of the alternative solutions like the Schroeder arm might do the trick. I'm still looking for the bearings to be in the same plane as the LP; not seen that yet.

Donc55 that's why the only ones I would use are the air bearing ones.
Atmasphere the ET2 can be set with the bearing at the level of the LP.
The ET is also stupidly well priced for what it is.  SOTA for under 1K used.  I think it's because a lot of people are afraid of it. And no it does not require constant adjustment. Once set it stays that way.

The ET does indeed have the bearing at the right plane. The problem is the lateral tracking mass. Lightening up the arm would likely help but the real place to lighten things up is in the bearing itself. Have there been any carbon fiber air bearings? I'm not aware of one, but if such were produced, it would be a simple method of reducing this issue considerably!

The fact that additional air pressure and a larger tank makes an air bearing sound better should tell you something. The engineering principle involved here is that the cartridge has to be held in perfect locus relative to the LP surface while still being able to move freely. To that end, there can be no slop in the platter bearings and the plinth must be absolutely rigid and dead such that the base of the arm moves in the same plane as the LP surface should there be vibration. The bearings of the arm must have no slop such that the arm is rigidly coupled to its base. Any difference between the locus of the cartridge and the surface of the LP will be interpreted as a coloration.

It is that latter part where the issue lies. Because there is slop is why increasing the pressure and adding a tank improves the sound. Essentially it reduces the effect of the slop. But the slop can't be eliminated entirely else the bearing would not work. Now we are talking about microscopic tolerances, but grooves on an LP are microscopic too.  The only way around this is not not have slop which is impossible with an air-bearing arm.

Now I'm not saying an air bearing arm does not work- Bruce could not have stayed in business over 25 years if the arm didn't work! What I **am** describing though is the envelope that needs to be pushed.

@ct0517 , Thanks for your explanation- I bet there are a lot of owners that don't check that!

I can't really imagine any slop affecting the performance.

The engineering issue is similar to the steering and suspension in a car. If there is any slop, the result is scary and dangerous handling. In a tone arm/cartridge situation, it plays out as a coloration. That is why there can't be any slop, if indeed a neutral presentation is your goal.