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I have just modified my Shroeder clone...again. I was having trouble with azimuth rocking. The magnets either wanted to be this way or that way. This is controlled by two things as I see it. 1. The counterweight being way down low, and 2. The bending point of the string being some distance above the upper magnet.So, what I did was make a piece from plastic that the string goes through, and it's location is adjustable, so now I can adjust it to the point where the "azimuth rocking" starts, then back it off.
Oh, stiff arm- almost forgot. When the bend point of the string is too high, then the top magnet has to "swing" when the arm moves up and down, which it doesn't want to do, due to the lower magnet trying to keep it centered. I haven't a clue as to when this stiffness is too much. Is there something related to tracking or sonics that is affected by arm stiffness?
Follow Ups:
I only saw pictures of Schroeder’s products.
To separate myself from morons, who litter the Asylum, I’m presenting a picture of a clone I’m working on.The main symptom of a stiff arm is unstable VTF. VTF on a stiff arm will be extremely sensitive to changes of vertical angle.
I may be wrong but my approach is different than yours. Rather than stiffening the arm suspension like you described, I tried to make it less wobbly by shaping the magnets and centering them better. As you can see I have also reversed the whole thing to move the pivot point up.
When I finish the arm I’ll give you more details.
Marek
(since I may be one of those morons), but in M.'s defense, Frank Schroeder not only doesn't mind if one-off diy'ers copy his arms, he'll offer helpful advice.
You have your table set up outside! ;)Beautiful job. And thanks for the answer. Unstable VTF would most definately be the primary symptom. Our "pivot tubes" look very similar- mine is shown above, and I have pics of my project in my gallery.
Notice that my arm goes downhill 1.5 degrees, but everything concerned with the magnet and string is sraight up in the vertical.
I’ve been admiring your TT since you’d presented it. You can see my humble attempts in my gallery.
I made a couple of things differently than what’s on your drawing.
I drilled the magnet 1/16” on both sides and 1/32” through. My 1/32” string has even more freedom of movement = more wiggly arm. My magnets are shaped on end: the stationary is conical, the other semispherical that stabilizes my wiggly arms. I also used a pole pieces made from soft steel. My experiments with different pole pieces are too few to be conclusive. I understand the pole piece should strengthen the magnetic field on axis of magnet making the design less wiggly. I also left more AL around magnet.
The biggest change in my second clone (the one in the picture) is the arm hanging from a magnet not from a string; that changes the geometry of design and the forces in it.
As I said I may be totally wrong, I am still working on both of them.
Marek
This morning, and got a quick, helpful reply. Why didn't I think to do that in the first place? I guess that is why we keep you around here :)
Thanks, Garth
I am leary about offering any suggestions.I have been researching this arm for some time now. I hear many more complaints about the string being too loose. Perhaps this creates the azimuth rocking you have described.
Come to think of it, I have never heard anyone complain that their string is too tight.
As long as it does not bind the vertical movement of the arm then you should be good as long as you center the magnetic fields so the arm balances properly. I find it fascinating to consider that as you overtighten the string you could be producing a mechanical dampening to the arm just as silicone dampening would provide......perhaps this could assist you to finalize and optimize your stylus interface.
Where to finalize your string setting seems to be user preference and cartridge optimization.
Let us know how it sounds when you have it all completely set up to your satisfaction.
.
nt
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