Does any Audiogon member have a Holbo air-bearing turntable?

To respond to a few questions: I am aware that the Holbo air bearing arm is likely not traveling in tiny arcs across the LP, depending upon the stiffness of the air bearing to prevent that, and I assume it is stiff enough.  LT tonearms that are much more prone to do that jig across the LP surface are the servo controlled ones, like the original Rabco SL8 and copies thereof, including the Goldmund T3F and I think the Revox LT tonearm on the Revox TT.  There may be others. These rely upon a motor to pull the pivot, which is riding on a solid rail, across the LP. To activate the motor, a tiny switch is situated so as to sense when the stylus tip gets minutely ahead of the pivot. The switch makes contact and then activates the motor which pulls the pivot a minute bit ahead of the stylus and then switches off, etc. The Clearaudio LT which once had another name that escapes me, and which has virtually no arm wand, as I recall relies upon gravity to help the cartridge traverse the LP.  The platter is dished toward the center.

@lewm 

I am aware that the Holbo air bearing arm is likely not traveling in tiny arcs across the LP, depending upon the stiffness of the air bearing to prevent that, and I assume it is stiff enough

Hi Lew

I can confirm that the Holbo tone arm feels incredibly stiff.  The bearing tube, which is bolted at right angles to the tone arm tube, is quite long.  I have gently held the head-shell and the bearing tube and tried to twist and rotate the arm to no avail - could feel no movement.  All it will let me do is raise and lower the head-shell vertically and slide the whole arm assembly sideways - something that should only be done with the air on!

Mind you, I can feel no platter movement at all when I switch the air supply on and the platter lifts 10 microns.  If the drive belt is fitted, there is no perceptible delay between switch on and the platter starting to rotate.  No air, she no rotate.  That is how it is shipped!

I can also confirm that I cannot hear any sound at all from the combined electrical and air supply unit, unless I make bone contact with my skull, in a pretty quiet environment.

Any servo-controlled tangential tracking arm will move in small arcs as you describe, because there has to be an error signal to get the servo motor to kick in, and another to switch it off.  I think B & O made one.

From my understanding, at least some Clearaudio tangential arms are carried on gantries above the record, which have to swivel out of the way.  The arm is mechanically supported on a glass tube. 

The Holbo tone arm is long enough to completely clear the record when in its home position and there is no mechanical connection once it is lowered except a tiny, soft air tube, less that 2-mm diameter, and four silver Litz wires.

@richardbrand Well after my posts getting wiped out twice now, I’ll try a third time and be brief. I am glad your Holbo made it safely to you, and have fun trying your slab and hemispheres under it. I find these tweeks interesting, and sometimes difficult to know initially if improvements are brought about or not. The overall noise floor of Holbo is already quite low. Interested in your findings! More later! Tim

Just to add a bit, my Holbo sits on the relatively simple BASE platform, and I believe it does help overall, the music seems to flow a bit better with it than without. My lowboy rack that the Holbo sits on, is situated on a carpeted floor on concrete slab floor. Everyone’s mileage I am sure differs with various tweeks etc., and in the end it is your own ears that matter! Enjoy and have fun! 

@frazeur1 

I find these tweeks interesting, and sometimes difficult to know initially if improvements are brought about or not

I have not even fitted a cartridge in it yet, so not really tweaks!

I decided it would be good to keep my Garrard 301 operational for comparison, so I had to find somewhere to put the Holbo, either a cabinet or a rack. The Solidsteel S3-3 is among the cheaper audio racks sold in Australia, but has nothing special to absorb vibrations.  I like your BASE platform but it is quite expensive so for under A$200 I thought sandstone blocks with constrained layer damping would not do much harm.  The Sorbothane concept came from Bostjan and then it was a matter of getting the right shape and quantity.  There's lots of tuning I could do, but probably laziness will win!