Air Bearing

DIY TANGENTIAL AIR-BEARING TONEARM – THE GLIDER

Before to write any word on how to build and use this kind of  tonearm, I want to pay respect to the man whom invented it, and who is now listening the ”celestial music” all day long : Mr. Poul Ladegaard. Also, I want to mention Vic’s  beautiful and inspired implemented idea: to invert the Ladegaard tonearm and split the two movements of the tonearm – vertical and horizontal – having as result a more compact and easy to use tonearm, with separate bearings for each kind of movement.

DIY wise, this project was the most exciting one I ever build, except maybe my first tube amplifier :)   As some guys are saying on diy audio forum, this tangential tonearm project could be completed in just one afternoon! It’s true to some extent, depending how far you want to go with this project.

DIY Terminator style prototype

The theory behind this tonearm could be found here, thanks to Roscoe’s good will. If you are interested in the inverted design, all data could be find on Vic’s pages on Terminator style air-bearing  here.

I have experimented three versions of this ”Terminator” style air-bearing, the differences between the versions being at the vertical bearing solutions, tonearm-wand materials and construction and different internal wiring solutions. The first drawings are presented bellow, and helped me to check the optimal dimensions on my particular record player machine and tonearm length, as well as slide length and height comparing to the platter. The first issue, revisited once, could be seen in the image bellow:

And these here are some details regarding the arm-wand construction for this first implementation:

As could be observed from the upper images, the bearing for the vertical movement of the tonearm is made by a special cutter blade and two resting aluminum squares. The two aluminum pieces are sticked to the upper glider that floats over the rail. The arm-wand is made by a carbon tube made for aeromodelling. The carbon tube was treated as follows: a tiny aluminum tube was spotted, which external diameter to fit with a small play inside the carbon tube. By using an elastic glue, the inner aluminum tube was glued inside the carbon tube. By doing this, we have a screen for the internal wire by putting the inner tube to ground, and also we killed the internal resonances inside the arm. Tonearm tube and counterweight tube are not in the same line in order to make a shorter wire path from tonearm to the phono preamplifier interface . The interface consists in U shaped aluminum block fixed to the arm system body; one the lest side of the u block there is a 5 contacts mini-DIN mother jack, and on the other side two RCA mother connectors – to connect the arm wires with the phono preamlifier input. The mass of all moving parts  – tonearm+counterweight+ slider+ vertical bearing aluminum squares+wire = the lateral effective mass of the tonearm. In our case, for this particular experiment, the total lateral effective mass is 98 grams.

For the cartridge holder, as well as the central sustaining element that links all the arm-wand elements (front tube, couter weight tube support, the bearing blade) I was using 20 years old dried wenge wood (down left image).

The wire used in this kind of tonearm is very important for the good behavior of the tonearm across its trajectory over the LP. In the upper right image could be seen the silk wrapped litz wires (bought from Vic of transfi) as well as the connectors used to link the tonearm wires with the outside world.

Here there are some pictures of the first and second versions of the air-bearing tonearm:

Fist prototype with VDH DDTII cartridge mounted is seen in the upper image. At this prototype, the glider rail was not matching perfect the shape of the support (air injecting) rail. That mean a higher air-pump pressure was required to function, my SERA 550L aquarium air pump was set at maximum to allowed the arm to float free. Also, after few weeks of resting, the aluminum L profile rails have been suffered enough oxidation to prevent the upper gliding rail-profile to freely float/move !!! So, be careful: either you will fabricate your rails from rust free materials, or you must to take good care on how to prevent oxidation after matching the upper/lower aluminum profiles if using aluminum.

I ended up b using some treated aluminum profiles, but matching two L rails was a real pain and time consuming. Once the rails are matched to perfection, I was been able to drop the SERA 550 Liter/h air pump (that is noisiest than a WWI tank machine:) and move to a more silent, small and modern air pump made by New Air NW33 (2x 190 Liters/h). This pump is two times smaller than SERA or RENA. The upper slide + tonearm assembly is now easily floating with a less thicker air cushion. The lower rails system (consisting in a two L profiles sandwiched) is supported by a hard wood piece, and is fixed by a single brass screw+ plastic washer to the tonearm support (upper left image).

This way, the supporting rails could be angled compared to the LP surface, or could be adjusted in position ap and down, in order to achieve the proper VTA setting . Two fine tuning/blocking screws are used to preserve the horizontal leveling of the tonearm. All the adjustment are performed with the main brass screw freed, which will be tighten when proper set was achieved. For the Tonearm L shaped support I was using a 3mm thick composite carbon front plate and a bakelite lower 9mm plate.

Another unwanted phenomenon is that the upper/lower L profiles are not a perfect match, the lifting pressure drops across the tonearm trajectory, especially at the end of the LP reading.

Something about the internal wires now. There is no way to use grounded wires to this project, most common ones being too heavy or elastic. This is not an issue if you use an input MC transformer, which will make things somehow easier on hum rejection side, especially if you are configuring your toneram internal wiring in a balanced mode, as Morgan James recommended. The wires must to be arranged in a way it will not obstruct the free tangential movement of the tonearm. This is possible if you arrange the wires in a vertical loop supported by a hard wire at the middle of the tonearm trajectory. This is a very god and cheap solution, which is easy to implement with care. When wiring the tonearm, I was using also a 0.08mm hard wire as the ground wire.

The Glider – DIY air bearing tonearm with sapphire bearings  for vertical movement

Well, after making all tests with the Terminator style tonearm versions, I just wanted a change for the vertical bearing. Having the experience of the RUBY unipivot tonearm in hand, I was having the idea to improve the mechanics and sound of  the Terminator design. The problem was how to set and align the two jewel bearing points.

First, let’s describe what jewel bearing is: A jewel bearing is a plain bearing in which a metal spindle turns in a jewel-lined pivot hole. The hole is typically shaped like a torus and is slightly larger than the shaft diameter. The jewel material is usually synthetic sapphire. Jewel bearings are used in precision instruments, but their largest use is in mechanical watches. ( Jewel bearing definition, application and drawings link)

Now, being the small dimensions of these fine pieces of watch crafting, the problem of their alignment rises more forceful :)  I was using the inverted solution: the two shafts of the bearings sits in the upper position, being  jointed to the arm-wand assembly. Their vertical position could be adjusted/fixed by a simple screw system.

The lower part of the bearing, consisting in a brass screws supporting the V sapphire jewels are linked to the supporting arms of the upper slide. Due to their threaded shape, the V jewels could be also adjusted. Actually, the final adjustment is done from here, as the upper partd of the bearing are already set at the same height by using a very precise template. For the horizontal alignment, I was using a simple technique :

- I fixed first the upper shafts of the jewel bearings, pairing the height of each at the same level on a precise template on the tonearm assembly

- I linked then the first upper rail hanger, containing the right lower jewel sapphire to the slider, in a fixed position

- by building a small aid device, I was glue in the second rail hanger, while keeping the right and left bearing assemblies into place. That was hard to get, but the third time it worked ! This was not an elegant way of doing it, but it was the cheapest and most effective to do it on the kitchen table :D  This is the DIY way for those who forget it ;]

With proper tools and CNC machines, this problem could be solved in a more elegant way, an I know how to tackle it if needed. In the upper image, the Glider could be sen from the front, with the marvelous Lyra Delos cartridge on position caressing  a happy LP. The device above the Lyra is not a Shamanic stone that cures all the diseases of your system or soul, but just a copper computer RAM sink, used as a weight to compensate for the very small effective mass of the Glider tonearm !

About the tonearm wand system.

The tonearm wand was made by  a sandwich consisting in:

- a composite carbon plate 2.0 mm thick

- a n intermediate soft plastic layer 0.15 mm

- a 3 mm wenge wood plate

The tonearm is inert acoustically speaking.

The cross piece that supports the hard steel bearing shafts was crafted

by an square aluminum solid bar. The counterweight was crafted by

brass, and is linked to the carbon side of the tonearm. The wires for this

latest  version are almost the best Clearaudio  litz wires, received as gift  from a good friend. Very thin and

extraordinary flexible while the sound quality is amazing.

Glider air bearing tonearm sound.

The sound of Glider is almost perfect, at least for my system. The sound of this tonearm was a kind of reward  for all those years I was spending back in the days.

I don’t want to full somebody with this, but don’t loose time on trying to build some other type of tonearms. They all sounds good and could be very nice to build, but this one was designed ” To terminate the Terminator”! . Maybe there are lots of tonearm design out there, but there is no way to find one to be build on the table kitchen and still to compete with multi-K industrial ones.

Thank you so much Vic!

This page is dedicated to the memory of Poul Ladegaard.

© attitube 2011

for those interested in this design for non-commercial purposes, don’t hesitate to contact me  grid@attitube.com

 

 

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grid (at ) attitube (dot com)
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