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DIY linear tonearm
DIY linear tonearm
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Old 2nd June 2019, 06:45 AM   #2981
nocdplz is offline nocdplz
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Thanks for infos, Ralf. I didn't know the origin of the name and the beautiful story of that brave man, but I've always loved that little locomotive and its daily hard work; Dumbo is one of the first films seen in my childhood.
Believing that even elephants can fly - by dreaming and wanting - is perhaps essential to "think out of the box", to survive the boredom of what we are convinced to know too well.

ciao - carlo
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Old 4th June 2019, 02:35 PM   #2982
nocdplz is offline nocdplz
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It seems that there is no need for air bearings, and pumps and so on, to make a good linear tracker. Just first build your own mini lathe like this one, with acceptable tolerances.
YouTube
(on air bearings, of course).
Now look at that spindle running (1 '10 "- 1' 30"): no lubrication, no air bearing ...

with great envy - carlo
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Old 13th June 2019, 07:27 PM   #2983
walterwalter is offline walterwalter  Ukraine
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Default Lil Casey Carbon

Hi again, Carlo. Eduard has finished carbon version of the arm. This time it was listened to on the same advanced audio system, as before. This time with Koetsu cartridge. Audiophiles are completely blown away with the sound, no one feels it is possible to return to another arm and still tolerate the sound. System owner is already addicted to Lil Casey.

Actually, in my country, audiophiles are addicted to the well known foreign brands, and nobody likes domestic products, as well, as DIY components, no matter how good they are. This time they feel opposite, and it speaks for itself.
Actually, people want to know full name of Lil Casey developer, in order to be grateful to you.
Best wishes and congrats,
Walter
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Old 13th June 2019, 08:12 PM   #2984
Marik is offline Marik  United States
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Question:

Did anybody try to make a linear tracker with magnetic levitation?

Best, M
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Old 14th June 2019, 07:41 AM   #2985
nocdplz is offline nocdplz
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dear Walter, thank you all for those compliments, also on behalf of the little Lil Casey.

Since retirement i like diying to waste time: not to make the best arm in the world (I hate too crowded clubs) but to experiment with the different types, looking for solutions to the problems they pose.
Ergo I have no desire to fool anyone, starting from myself. As says an old (retired of course) friend salesman: two very different, very exclusive, $$uper expen$$ive equipments should sound exactly the same: there are no scales claimed to weigh "better".

So for us diyers there are only two questions we have still to ask:
- does an arm with 0 offset (radial - linear - or pivoted) work better than a normal pivoted one? and if so, When, Where, and Why?
- does a radial rail arm work better than a normal linear passive (air bearing included) arm? and if so, When, Where, and Why?

I have explored almost all the types of arms (suspended arms excluded, forgive me) checking their limits: now if I were to build my last arm I would think of a simple (?) non-ideological one, which would get the right amount of side force just from the stylus drag. Easier said than done, isn't true?

carlo
full name: Carlo Ballestrero - living in Prato (near Florence), born in Rome too long ago.

Last edited by nocdplz; 14th June 2019 at 07:53 AM.
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Old 14th June 2019, 09:20 AM   #2986
walterwalter is offline walterwalter  Ukraine
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Default The arm

Well, now we know exact name, to whom to be grateful, thank you very much, Carlo. Good things should have correct names. As to the question of which component sounds better, it isn't simple. There are lots of speculations concerning, and lots of opinions. As for me, I trust my own perception, as well, as of some experienced audiophile friends. Some of them are so sensitive and well trained, as to the extent of almost being phychics. Human hearing perception is not democratic, and polit-correctness doesn't apply to it. Even ability to hear high frequencies vary a lot for different individuals, not considering more complicated aspects of sound. I would apply what I said to Lil Casey. It sounds much better, than other arms, and difference becomes even more evident, as you gradually use better and more sophisticated cartridge. And difference is really huge. It reminds me my first experience in 1982 with tube amp (made by Vladimir Lamm, who resided in my city back then, and whom I knew), after decade of listening of average hi-fi solid state amps. It was kind of revelation, and now, with Lil Casey it is revelation again.
In both cases sonical difference may be explaned by different physics.
Walter

Last edited by walterwalter; 14th June 2019 at 09:44 AM.
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Old 14th June 2019, 10:09 PM   #2987
niffy is offline niffy  England
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Quote:
Originally Posted by Marik View Post
Question:

Did anybody try to make a linear tracker with magnetic levitation?

Best, M
Sorry Marik,

It's not possible passively using permanent magnets. Check out Earnshaw's theorem for the reason why. If you are thinking of something like those globe toys that suspend a sphere in mid air there are many Many problems to overcome. The globe toy works by rapidly modulating the magnetic field, basically dropping and catching the globe repeatedly. This will cause the levitated object to vibrate, not a good thing for a tonearm. Also a levitated carriage will not be held stably and would have a lot of freedom of movement in directions you don't want. You may have seen the recently introduced magnetically levitated deck. Check out the horrendous level of wobble the platter has. This is a purely gimmick product. Another problem is the strong magnetic field required. Do you want a very strong modulated magnetic field anywhere near your cartridge. And finally the arm would be completely physically disconnected from the deck leaving no possibility of mechanically grounding the arm. Good mechanical grounding is one of the most important design considerations.

Hi Walter, Carlo,

I think the most likely reason that the lil Casey sounds as it does is the elimination of the bending modes. These are present in all long tonearm designs and are the single greatest cause of colouration in most. By getting rid of the arm tube you also get rid of the colouration it introduces. Until you hear an arm without bending mode colouration you don't realise just how much most arms have.

Niffy
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Old 16th June 2019, 01:44 AM   #2988
super10018 is online now super10018  United States
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magnetic levitation linear arm may work if it can be constructed as in the drawing. Its concept is very similar to air bearing.
Attached Images
File Type: jpg magarm.jpg (20.1 KB, 160 views)
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Old 16th June 2019, 06:15 AM   #2989
nocdplz is offline nocdplz
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Right.... so all that remains is to build magnets that way, or recover some from the NX01 Enterprise wreckage.
On - Angling for 90 - thread someone had already talked about the Halbach Array, but the results are still top secret ....

just for fun - carlo
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Old 16th June 2019, 07:45 AM   #2990
niffy is offline niffy  England
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Modern manufacturing techniques would easily allow the construction of a magnetic array as Jim described, it could just as easily have a halbach array built into it. Regardless of how fancy you make your magnet array it will be unstable and collapse. If using permanent magnets the system HAS to have at least one axis constrained in order to achieve stability. The only magnetic levitation that works using permanent magnets is something like the levitron toy.

Levitron - Wikipedia

This system is still constrained by the gyroscopic action of the spinning top. Having your tonearm spinning around is unlikely to result in good sound quality.

The only practical way to make a tonearm magnetically levitate is to use an active system.
The magnetic gap does not need to be large. All the toys and gadgets (like the levitating turntable) have large visible gaps so that they look impressive. By making the gap smaller you will make the carriage more dimensionality stable and less wobbly and you will not require such a strong magnetic field. In order to maintain stable levitation the magnetic field has to modulated, basically picking up and dropping the arm repeatedly. This will cause the arm to vibrate at the frequency of the modulation. The modulation frequency will have to be well into the ultrasonic region, say 100khz. Class-D amplifiers work at this sort of frequency and some of them (Hypex) sound very good so introducing a high frequency modulation doesn't need to be a problem. You may run into a problem of the coils acting like antenna and strongly transmitting at 100khz.
Maglev trains seem to work fine and are smooth in operation so it should be possible to do the same with a tonearm. The engineering challenges of building such an arm are not trivial. I can see no benefits of using Maglev over an air bearing and several disadvantages. And don't forget about the good old mechanical linear tracker with its superior mechanical grounding.

Purely passive magnetic levitation lives next door to the perpetual motion machine.

Niffy
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