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Old 19th July 2013, 02:40 AM   #131
kevinkr is offline kevinkr  United States
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I'd probably be interested in a GB down the road a ways.
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Old 19th July 2013, 12:58 PM   #132
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I'm going to build something like this.
Have an air-bearing tangential tone arm,
but after so many years I want something without an air pump.
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Old 20th July 2013, 04:43 AM   #133
Calvin is offline Calvin  Germany
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Hi,

in #108 I put down some thoughts about the carriage/arm design.
Is a trangular shaped framework! Similar to the one shown in #93 a superior solution to a single straight arm wand?
I think so, but I' like that discussed.

jauuu
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Last edited by Calvin; 20th July 2013 at 04:46 AM.
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Old 20th July 2013, 05:40 AM   #134
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Quote:
Originally Posted by Calvin View Post
in #108 I put down some thoughts about the carriage/arm design. Is a trangular shaped framework! Similar to the one shown in #93 a superior solution to a single straight arm wand? I think so, but I' like that discussed.


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Old 20th July 2013, 05:43 AM   #135
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Default Hey Calvin I agree and so did Bo

Quote:
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Hi,

in #108 I put down some thoughts about the carriage/arm design.
Is a trangular shaped framework! Similar to the one shown in #93 a superior solution to a single straight arm wand?
I think so, but I' like that discussed.

jauuu
Calvin
I discussed this with Bo asking if a single larger diametre thin wall tube would be and improvement ant he said no it would not be an improvement rather it would sound worse and that he had tested exactly this and that a pair of small diametre thin wall tubes were a much better option. Bo had devised a very simple yet effective test method to show easily the difference between different tone arm tubes.
The method is very clever in its simplicity as were many of Bo's ideas. The test involved playing a blank record or flat plastic disk with each arm design. When the arm is playing the blank disk you gradually turn up the volume control on your preamp until you reach the point where resonant feedback, the onset of which will be quite abrupt. Make note of the volume setting where breakaway takes place. Switch arm assemblies a repeat the test. The arm which permits the highest volume setting before feedback sets in is the the more rigid of the two designs and will be the arm which sounds better when listening to music. So like Bo to see the obvious. All has design improvements showed that increasing stiffness and rigidity and elimination resonance and motion improved the quality and quantity of the retrieval of detail from the disk. Best regards Moray James.
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Old 20th July 2013, 07:19 AM   #136
Calvin is offline Calvin  Germany
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Hi,

thanks for sharing this thought. I think, it covers an important, but different issue to my Question. How does the force applied to the needle lead to a movement of the who arm and are there differences between different shapes of arm and carriage? Is the triangular framework more efficient in translating the force effecting upon point A (the needle) to a movement at points C and D (the bearings), or doesn't it matter at all (assuming infinite stiffness of the arm construction)?

jauu
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Old 20th July 2013, 08:56 PM   #137
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This thread is getting interesting now . I might have gone with a triangular arrangement, but in the end that meant more mass and the solely the reason I didn't do it. I eventually opted for a carbon fiber 1/8" tube which proved the lightest yet while still maintaining rigidity, as for the bo Hansen test I can't get feedback on a blank disk but don't wish to test the limits of my electrostatics again . I can however attest to the benefits of having the carriage arranged so that the counterweight falls in the same plane as the bearing pivot rathe than a straight through arm tube because of the design. By having the counterweight in the same plane as the tonearm the line of pivot is more like a pendulum and wildly changes tracking force, moving it to the horizontal/vertical pivot really improved tracking and being a low slung weight puts the center of gravity to around the middle of the glass tube. It was however a compromise between ease of use ( bar not too low), and accuracy tracking warps in which only extreme cases will lose that perfect 90 degree tangency.



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Old 20th July 2013, 09:22 PM   #138
AuroraB is offline AuroraB  Norway
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Colin - your carriage weighs in around 20g's, right?
What may be concidered a max, or possibly an ideal weight? as little as possible...?
Some years ago, a carriage made from balsa truss work was pictured, but I cannot find the pic....
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Old 20th July 2013, 10:14 PM   #139
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Aurora b,


Ideal weight would be a tough one to pinpoint as it coincides with the cartridges compliance. Even at 18g lateral mass that might be hefty for a high compliance cartridge, but for a mid compliance cartridge 18 grams puts system resonance in the safe zone and warps won't give scary woofer pumping. Unfortunately none of this stuff is a one size fits all , but at best we can design for the most common scenario of mid to mid lower compliance. Ideally you want a weight that keeps the cantilever straight and centered on pressing eccentricities.


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Old 20th July 2013, 10:52 PM   #140
batsong is offline batsong  United States
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Colin, it is interesting what you say about the counterweight being on the same plane as the pivot. What do you think about having the wand on that same plane as well?
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