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B-J Tangential Tonearm

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B-J Tangential Tonearm

Postby edgarryan » 29 Aug 2017 19:16

Giving up on finding a cartridge slide for my GE A-501 tonearm, I remembered I still have an unmounted B-J tangential tonearm. Tried to attach it to my turntable using the supplied instructions and mounting template, but I could not understand it. What baffles me is the arc. So, obviously I have to move the template once I have mounted the base of the arm, but how far from the base should I move it? Will a small or great distance affect the geometry?

http://i853.photobucket.com/albums/ab94/ersfaustino/20170830_015733_zpsp3h0ldnh.jpg

http://i853.photobucket.com/albums/ab94/ersfaustino/20170830_015855_zpswf8hhcqb.jpg
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Re: B-J Tangential Tonearm

Postby nat » 29 Aug 2017 22:47

I looked for the manual in the library, but there doesn't seem to be a BJ listing. Since you have the literature, how about sending a scan to the library?
I can't open you photos, and so I don't understand your question -what is the arc you refer to? - but it is clear to me that you do need to mount the arm at the right location. It hardly makes sense to use a tangential arm if its alignment is wrong -- you will almost certainly have greater tracking error at all points on the record than if you were using a standard pivoted arm.
The only benefit of a tangential arm is that it can have close to zero distortion across the record, but that will only be true is the stylus is, in fact, on a radius to the center of the spindle. All other aspects of the arm are less desirable than those of a conventional arm - less rigidity, more friction, more resonance (simply because there are more things to resonate.
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Re: B-J Tangential Tonearm

Postby Copperhead » 30 Aug 2017 01:42

nat wrote:I can't open you photos, and so I don't understand your question -what is the arc you refer to? - but it is clear to me that you do need to mount the arm at the right location. It hardly makes sense to use a tangential arm if its alignment is wrong -- All other aspects of the arm are less desirable than those of a conventional arm - less rigidity, more friction, more resonance (simply because there are more things to resonate.


Nat, just to confuse things a bit. The BJ is not a conventional tangential arm, it works on more or less the same principle as the Garrard Zero 100.
Your point about vibrating parts is bang on, even more so with this design. I owned one and never managed to set it up satisfactorily.

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Heavily modified Crosley, Armstrad amplifier and two large terrapins.
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Re: B-J Tangential Tonearm

Postby edgarryan » 30 Aug 2017 06:26

20170830_015733_zpsp3h0ldnh.JPG
20170830_015733_zpsp3h0ldnh.JPG
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Re: B-J Tangential Tonearm

Postby nat » 31 Aug 2017 23:39

Okay: Here is my guess as to how to set the arm up.
The base is like that of the SME, where the whole arm is moved back and forth in the base to align the stylus. Bend up the side of the template and place it on the spindle with the arm pivot where you want it. Mark the screw holes etc and mount the arm. Mount the cartridge (if there isn't a cartridge sled, it might make sense to mount it first and install the stylus after the arm is mounted).
Once the arm and cartridge are in place, put the template back in some convenient position and move the arm toward the spindle until the stylus can sit on the curved line (this is way in from the run out groove, and I suspect that it is meant to be the limit of arm motion, so you may need to loosen the arm in its sleeve to go that far). If needed, move the arm in the base back and forth until the stylus is on the curve and the headshell is perpendicular to a radius line from the spindle.
The reason you align on an arc is that BJ doesn't know where you will place the arm on the plinth, or the template, either. And, of course, that arc is the line that the stylus needs to be exactly perpendicular to, regardless of where on the curve it is.
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Re: B-J Tangential Tonearm

Postby edgarryan » 02 Sep 2017 19:24

Should the stylus trace the whole arc, or just any point in the arc?
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Re: B-J Tangential Tonearm

Postby nat » 03 Sep 2017 17:17

Just a single point. When the arm is at the limit of its inward motion, fix it in its pivot. Then move the base back and forth until the stylus is on the line.
The arc is to allow for different locations of the arm base on the plinth and/or different locations of the template. Since the arc is a section of a circle with the spindle at the center, any point on the arc is perpendicular to a radius, which is what you want for the stylus to be.
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