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Old 17th December 2016, 06:44 AM   #2251
niffy is offline niffy  England
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Hi Tom,

Designing a cartridge is not something I have personally contemplated though I have studied them in some detail. Mainly looking at how they interact with and transmit energy to the tonearm. Your brief description sounds like you are not using a cantilever. I think that Decca made several cartridges like this. As your cartridge is mechanical (it uses a physical stylus) it will still have to have a suspension of a certain compliance. Coupled with the damping you mention and the mass of the cartridge body/arm effective mass this will create a spring-mass-damper system the same as any other cartridge. This will still result in a transfer of energy to the tonearm. This is unavoidable in a mechanical system unless the cartridge is decoupled from the tonearm. Decoupling the cartridge creates another spring-mass-damper system between the cartridge and arm with its own resonant frequency. This would have to be below the audio bandwidth in order not to place a resonance in the audio bandwidth. Decoupling a cartridge in this way is difficult to implement and counterproductive.
Oops run out of time to write more right now.

Niffy
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Old 17th December 2016, 09:07 AM   #2252
Tom Bloem is offline Tom Bloem  Netherlands
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@Hiten,

You are right, a bearing is much better. So I have made a bearing from a low voltage connector and a stainless spoke. See this picture. The short peace of the spoke is glued into the outer tonearm tube.

@Niffy,
It is difficult indeed. But I will give it a try. Maybe in January.
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Old 17th December 2016, 11:37 AM   #2253
niffy is offline niffy  England
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Hi again,

Got cut short in my last post.
Virtually all commercially available cartridges have bodies that are made of a rigid material that usually also have good self damping properties. The aim of these bodies is to couple the generator as solidly as possible to the tonearm without allowing any unwanted resonances between the two. There are several aftermarket cartridge decoupling devices available. In certain circumstances where there is a mismatch between arm and cartridge or a particularly lively arm they may be beneficial. They will definitely make the sound different but not normally better. Cartridge manufacturers put a lot of work into developing their products. If decoupling of the cartridge was beneficial it would be built into the cartridge.

Re your post that arrived between the two parts of mine. Definitely have a go at making a cartridge you might have a game changer. It's something that is way beyond my capabilities.

Niffy

Last edited by niffy; 17th December 2016 at 11:50 AM.
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Old 17th December 2016, 04:39 PM   #2254
Tom Bloem is offline Tom Bloem  Netherlands
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@Niffy,

It is way beyond my capacities too if the cartridge is identical to a traditional MC cartridge. Fortunately it is quite different. The most difficult job is the alignment of the stylus with the coils (100% symmetric). When this is perfect done, the channel separation of a phono cartridge can reach about 50 dB. Thus I have to find a trick to do this job in a controlled way (maybe with the help of a laser beam and magnifying mirrors).

This schematic drawing shows both dampers (red and blue). Vibrations from both dampers that are equal to each other will vanish, the other persist. However, this is not 100% reality. Moreover, the remaining vibrations of the left channel will influence the right damper and visa verse. So there is a lot to think about. In January ;-))

Sorry to all, this was off-topic...
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Old 18th December 2016, 07:33 AM   #2255
niffy is offline niffy  England
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Binocular microscope under polarized light?

Off topic but interesting.
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Old 18th December 2016, 02:06 PM   #2256
Tom Bloem is offline Tom Bloem  Netherlands
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@niffy,
Yes, I have thought about it. But buying a binocular microscope for 1 or 2 cartridges is a bit overdone because I have a monocular microscope. Anyway, first Christmas and "happy new year"! ;-))
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Old 18th December 2016, 03:56 PM   #2257
niffy is offline niffy  England
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Hi Tom,

A good binocular scope is expensive.
Adapting the light source of your existing scope with the addition of a polarized filter shouldn't be very costly. By rotating the filter you should be able to find a setting that allows you to see the facets of the stylus more clearly than under non-polarized illumination.

Niffy
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Old 18th December 2016, 05:00 PM   #2258
Tom Bloem is offline Tom Bloem  Netherlands
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@niffy,
Thanks! A good idea, I give it a try!
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Old 18th December 2016, 05:43 PM   #2259
directdriver is offline directdriver  United States
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Quote:
Originally Posted by niffy View Post
I think that Decca made several cartridges like this. As your cartridge is mechanical (it uses a physical stylus) it will still have to have a suspension of a certain compliance. Coupled with the damping you mention and the mass of the cartridge body/arm effective mass this will create a spring-mass-damper system the same as any other cartridge.
In recent production, the newly introduced Audio Technical ART-1000 is similar. As you can see the coils are right above the stylus but it has a rather long cantilever from stylus to the suspension. I'm curious what material is the cantilever. Reportedly it's very hard to make and only one person knows how to make the coils and install them properly.

Fascinating stuff!


Click the image to open in full size.

Click the image to open in full size.
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Old 19th December 2016, 01:31 PM   #2260
niffy is offline niffy  England
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Hi DD,

The amount of cool stuff you find never ceases to amaze me. My initial reaction was the same as the guy in the video, high tip mass and long cantilever, surly not. But as the coils are attached right at the stylus and not at the other end of the cantilever the negative effects should be alleviated. Nice find.

Niffy
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