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Old 29th April 2014, 08:42 AM   #1
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Default New principle linear tonearm and phono cartridge (DIY)

Personally I am interested in the quality of the sound of the reproduced music. I am not interested in “grand designs”. Nevertheless, I am born with 2 right hands so after a while I mostly replace the last prototype for a more sophisticated one. And that’s why - at the moment - I cannot show photographs of the linear tonearm that’s gleaming in the shop-window (I have to make a new turntable too).


Click the image to open in full size.

I am not the only one that has build this tonearm, someone else has build a prototype too (see photo above). His opinion about the quality of the sound: “Black silence between tracks; voice and instruments separate from each other; wonderful tight base (non-booming); sweet musicality from top to bottom, front to back and side to side”.

Moreover, the tonearm is impervious for the quality of the cartridge. It facilitates every cartridge optimal: from the Audio Technica MM AT-91 (25 euro) to the Ortofon Anna (5000 euro). I have tested all those different VTF’s in combination to the cartridge weights. The image below shows one of my own prototypes.


Click the image to open in full size.


This tonearm functions not like all the other fixed pivot and linear tonearms. It is a total new principle to facilitate the cartridge (physics). Only the friction – pull – between the rotating record and the tip of the stylus of the cartridge is responsible for the movement of the tonearm from the outer side to the inner side of the record. Without servo mechanism or air bearing. The stability of this principle of “moving the pivot” is tested with 12 inch records of different duration: between 4 and 26 minutes. But besides of that, this tonearm is really simple to build and all the materials cost about 40 euro (inclusive 900 ml ice cream). The image below shows the composition of the tonearm.


Click the image to open in full size.


The phono cartridge is not build yet. I have ordered some materials to make the first prototype (new principle). Because this cartridge is planned to function with this new type of tonearm I have incorporated the cartridge to this topic.
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Old 29th April 2014, 09:42 AM   #2
soyuz is offline soyuz  Chile
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Quote:
Originally Posted by Tom Bloem View Post
The phono cartridge is not build yet. I have ordered some materials to make the first prototype (new principle).

interesting ! , do you mean a new principle different from moving magnet, moving coil, strain gauge... could you elaborate a little more.
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Old 29th April 2014, 02:21 PM   #3
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It looks like the subject of this thread :
Late model Well-Tempered owners here? - Page 8 - Turntables and Tonearms Forum - Vinyl Engine
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Old 29th April 2014, 03:40 PM   #4
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@Soyuz,

“New principle” is not restricted to the type of the transformer (mechanical vibrations into electric frequencies and amplitudes). I don’t think that one of those generators – electromagnetic, piezoelectric or by photodiode/-transistor – will outperform the others. It is more the way how we practice the whole process of transforming the mechanical recording into the electric signal.

Click the image to open in full size.

And from that point of view the DIY cartridge is – like the linear tonearm – not a known principle. The image above shows the semi-realistic appliance. It is clear that one of the targets is to get 100% channel separation.

@Arch Stanton,

You are quite right. Unfortunately the forum of vinylengine has not much visitors that DIY by themselves. Repairing audio equipment is more their profession.
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Old 1st May 2014, 02:31 PM   #5
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Today I got the ordered neodymium magnets. The image below shows the ordered types (the background is P280 emary paper). Just the 3 smallest types available because I was afraid that the smallest – 1 x 1 mm – probably wouldn’t work well, despite of the specifications. And… replacing the topmost magnet – see the image of the cartridge in the post before – by a stronger one, will increase the push off between both magnets.

I have to say that I didn’t realize myself that small neodymium magnets are like insects: they jump up in the air if other neodymium magnets come nearby. So you have to use brass tweezers…

Click the image to open in full size.

The weight of the smallest magnets – 1 x 1 mm – is 0,006 gram, just the weight of a stylus and cantilever together. Therefore, I liked to start the first experiment with these magnets. To buy a transparent tube with an inner diameter of 1,1 mm somewhere, isn’t easy (I couldn’t find one). So I made one myself.

The experiment is quite simple: 2 magnets with opposite pole into the tube and a weight of ˝ the VTF of 1,5 gram on top of the uppermost magnet. To secure low friction I put some silicon oil into the tube. The image below shows the experiment.

Click the image to open in full size.

The distance between the 2 small magnets appeared to be about 1,75 mm. A bit more than the distance between both magnets at the image of the cartridge. Doubling the magnetic power of the uppermost magnet – just by adding another magnet – increased the distance into 2 mm. Nevertheless, I prefer a symmetric structure.

Conclusion: when the vibrating bottommost magnet has enough “power” to create a suitable voltage in a DIY coil that surrounds the tube, it is time to think in a serious way about the fabrication of a simple prototype.
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Old 1st May 2014, 04:22 PM   #6
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Hello Tom
I see you have 'picked up' (no pun intended) on Henk's design for a tonearm recently featured in the Vinyl Engine forum. I've been asking questions and gaining a good understanding as to how it works- and am just about ready to make a prototype-looks very interesting indeed.......
Chris
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Old 1st May 2014, 05:13 PM   #7
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Well Chris, I am "Henk". I always choose different short name's so I don't get confused whwn I get a mail about something that I hardly can remember. My real name is at my own site.
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Old 1st May 2014, 05:28 PM   #8
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Well
You live and learn-my real name's Chris by the way. I'll let you know how I get on, Henkytom!
Regards
Chris
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Old 1st May 2014, 08:28 PM   #9
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Is it possible to DIY a “microscopic” cartridge?

Well, that isn’t so difficult. You only have to choose those solutions that are DIY’able. For example, I have silver wire of 0,008 mm thick. But I will not use this wire to make a coil with a lot of windings. That’s far too difficult without a stereo microscope. Nevertheless, when I use a neodymium magnet to “drive” the coil, I can reduce the windings and use silver wire of about 0,08 mm thick.

Moreover, with a bit puzzling it is possible to find simple solutions. See the image below; I have made pictures of the first experiment. The tube is made of transparent heat shrink tubing. I only had to look for a needle of about 1,05 – 1,1 mm thick. I rubbed the needle with silicon oil, stuck it into the heat shrink tubing and heated it. At the end in cold water and glued upon a piece of transparent plastic. When the glue was dry I removed the needle and got a straight tube with an inner diameter of 1,1 mm… Simple.


Click the image to open in full size.

The image at the right hand shows the two 1 x 1 mm magnets without any weight upon, so their mutual distance is 5,42 mm. The image at the left hand includes a weight of 1 gram upon the uppermost magnet (it is a carbon tube). When I increase the weight to 1,25 gram, the mutual distance altered to nearly 1,63 mm
(some high end cartridges have a VTF of 2 x 1,25 gram = 2,5 gram). With other words, those two small neodymium magnets can “operate” within the VTF bandwidth of common MM and MC cartridges.

When you think it over, you probably see a problem because the magnetic ricocheting force surely will damp the amplitude of the stylus. Will it?

The amplitudes arise from the rigid modulated groove. Therefore, the bottommost magnet will move according to the modulations of the groove. Just because the connection between the stylus and the bottommost magnet is a rigid one (again the image).

Click the image to open in full size.

Thus, when there is no uppermost magnet the stylus will lose the rigid contact with the bottommost magnet. Therefore the uppermost magnet constantly pushes the bottommost magnet to the stylus (via the small carbon rod).


Now you can understand why this hypothetical cartridge is meant for the linear tonearm of this topic. The constant magnetic push from both cylinders will manage the tonearm far better along the horizontal bar than the suspension of a traditional MM and MC cartridge.


The first experiment was successful, so I ordered a long brass tube with a wall of 0,2 mm thick. To get the coil as close as possible around the magnet. Thus I have to wait a week.

Last edited by Tom Bloem; 1st May 2014 at 08:35 PM.
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Old 1st May 2014, 08:58 PM   #10
sreten is offline sreten  United Kingdom
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Hi,

Sadly the the cartridge and turntable performance is not
impervious to the quality of the the arm, and as ever
the turntable, then the arm, then the cartridge matters.

The cartridge, though ingenious has no merit over
a mechanical suspension versus a magnetic one.

rgds, sreten.
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