Poul Ladegaard's Air Bearing Tangential Tonearm

Poul Ladegaard's Air Bearing Tangential Tonearm!

Hello all DIY friends!

Now I have finished adapting the article on Poul Ladegaard's excellent DIY air arm into English. I have not converted metric into inches. You who still use inches better get used to metric, the sooner the better!

The main file is a complete translation of the original article as it appeared in the June issue of the Danish magazine 'high fidelity'. Lest you think this is a violation of copyright, I can assure you that the policy of the source magazine is that all material can be used without permission if it isn't to be used for commercial purposes.

The picture files are grayscale jpegs scanned from the article and are very valuable if you are going to build this arm. Each picture file has an explanatory description.

It is my profound hope that you will find the needed answers to all questions concerning the project in the translated files. I have commented to some paragraphs where I found it useful. I have built this arm myself, so I am aware of the problems. Please read the files thoroughly before asking me any questions. I had only the article to lean on and it was enough for me.

I don't have a lot to add, but I do have a few points:

AIR PUMP:

Pumps intended for use with fish tanks are great for an air arm. Bear in mind that some pumps are noisier than others, so think about where you can place the pump. A good idea is to keep it sufficiently far away from the listening room to avoid the noise they make. You should add a 10-15 liter (abt.3 gallons) tank to smooth the air flow. And it's crucial to have some way to adjust the air flow from the pump. Most pumps use solenoids that are powered directly from the wall voltage. These can be made quieter by inserting a step down transformer. Here you Americans and others with 120 V wall voltage have an advantage.

If the temperature difference between the room where the pump is and the room where the record player is is sufficiently great, condensation may be a problem. In that case you need a gas drier. This I know nothing about.

I use a RENA 301 pump which works great and is cheap. But it's noisy. Check out pumps like Whisper 2000 if you need a quieter pump. Quiet pumps are generally more expensive.

GROUNDING:

ALL the metal parts of the arm assembly should be grounded to the preamp ground. Experiment with different arrangements for best results. If the carriage and arm base are not connected electrically (with a flexible wire) a static buildup tends to develop due to the friction of the air flow onto the carriage, finally discharging to cause loud pops in your speakers. This I found out myself.

LEVEL:

Make sure you are able to adjust the level of the turntable with great accuracy. I added a separate level adjustment to the arm assembly, because it's pretty hysterical about perfect level. This means that the arm in the present form can not be used if the plinth of your turntable is mounted on springs or other elastic principles. The large moving mass would upset the mass balance enough to make the arm mistrack. Keep this in mind before you start building.

VTA:

The vertical Tracking angle is clumsy to adjust on this arm. Ingenious souls may wish to add some sort of adjustment feature for this. I'll scan a picture of a different DIY arm with a simple VTA adjustment that should be easy to copy. This will be made available here some time this month (may '94).

ALIGNMENT:

The very idea of tangential arms is to have the needle tracking the record with a perfect tangent at all times. So you need to carefully align the arm base, arm and cartridge to get all the angles right. An easy way to do this is to find an awful old record that you hate so much you never want to listen to it again. Now draw a narrow line across the exact middle of the record with a tiny, sharp object. Put it on the platter and make sure the stylus tip falls into the tiny groove you cut at both the beginning and the end of the record side. If it does, you have perfect tangential tracking, provided that your cartridge and arm are at perfectly right angles. How to do that you'll have to figure out yourselves.

THE ARM ITSELF:

Can be made from any familiar material you have handy. Don't despair if you can't find a broken Badminton racket or other source for carbon tubing. Arms have been made from all sorts of materials in the past, so feel free to experiment.

TRACKING FORCE:

Is measured with a suitable device intended for the purpose. If you can find that cheap Ortofon plastic thing it'll be enough to do the job. (Comes with most Ortofon cartridges when you buy them. Ask a dealer.)

Now I can't think of anything else to add, except that you owe it to yourself to build this arm. Read the article and find out why this may be the superior alternative to any arm, and at a ridiculously low cost. DIY projects of such brilliance aren't seen very often. Why Poul Ladegaard didn't patent it I don't know.

GOOD LUCK!

Thomas Dunker