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LP eccentricity, spindle hole center,The fix??????

Hi all,

I'm one of those audiophiles, 67 years of age, that wonders about the effect of the accuracy of the center hole. Some of the LPs I put on the TT have play due to a center hole that's punched out of round, too large or what ever.

I'm playing a record on a Denon 308 direct drive table using a system devised by a LJT Mfg in Canada to reduce eccentricity and help flatten warped records using a peripheral ring clamp in conjunction with a 1420 gram spindle clamp. The trio comes along with a cnc machined polycarbonate centering disc that straddles the record after the clamp ring is set registering on the outside diameter of the record. I can feel play regarding the center hole as I implement the OD centering device. I'll measure it tomorrow, just a few thousandths. The music sounds fine to my ears but I wonder what the relationship is to the record grooves, the outside diameter, and the center hole.

A while back a TT was made that had an extra arm that MEASURED THE ECCENTRICITY of the record and re centered the disc for play, it sells for big bucks if you can find one.

FINALLY, Your thoughts on the question?

regards, Ken Fritz
kftool
t_bone
1,182 posts
 
Dertonarm,
For simplicity's sake, I agree that a 'minimum spindle' plus off-center adapter should work fine. For the sake of the search for perfection (such as in the thread about drive systems), you'd need a lot of them and a way to measure. The one 'problem' with this is that not all of our TTs have removable/interchangeable spindles.
dertonarm
1,042 posts
 
Dear T_bone, you know I like to look at TT and tonearm questions from the physical and geometrical point of view first.
Well - even if you use say 30 adapters with a step of 0.1mm each in compensated eccentricity, it will still be a fairly easy, cost-effective and very precise solve to the problem. We have 2 fixed points here - the spindle hole in the LP and the spindle of the TT.
To compensate the given eccentricity we have 3 options:
a) compensate at the platter itself and leave spindle and center hole alone = Nakamichi's approach (the whole platter compensates the eccentricity of the LP...... I see it working and I do not have a sense of "good solution" - the sound isn't anything to write home about either...)
b) widen the center hole to compensate eccentricity at the problems core itself - the LP (= modification of teh LP's spindle hole making it hard if not impossible to play the LP on any other turntable.. and results in a huge decrease in value. Certainly not the way to go for a collector of highly priced vintage vinyl..).
c) decrease spindle diameter to compensate eccentricity at the spindle. Solving the problem again at the very core of the problem. Modification can be done to almost any TT.

What I can say is that the method I described works very good in everyday handling.
You make a note for any specific eccentric LP and have an adapter with the specific compensation at hand in a few seconds.

There is no free lunch here.
Honestly - I can not see any other option aside from the 3 mentioned above.Do you have any idea?
Anyone else?
t_bone
1,182 posts
 
Dertonarm,
I am not positive I understand the way kftool's existing clamp system works, but if I do understand correctly, it effectively does away with the spindle completely (after all, as long as the record is centered with a peripheral guide and a heavy weight in the center, and there is enough friction between the record and the material beneath, one does not actually need a spindle... and that would be a 4th way.

Though I agree that a mechanical way is possible, and the small center spindle method is probably the easiest to implement if starting from ground zero...
dertonarm
1,042 posts
 
Dear T_bone, the system Kftool describes does provide pressure with the outer ring plus the center weight and further - by straddling the LP in its center - does provide something like a "material tension inherent pressure" by creating something like a "small convex bubble" at the center. This works great in providing high surface contact pressure over a very high percentage of the records surface. As the center weight is fairly heavy (approx. 3 lbs) there is enough down force provide without clamping to a spindle. Can't really tell from the description either whether the spindle was omitted.
Kftool - can you please clarify this point?
tbg
5,263 posts
 
Has2be, years ago (over 30), I bought a system, which included a rasp for making the spindle hole larger and adhesive rings much like those for sheets in a loose ring notebook. There was also a wooden base with a pointer. You used it to center the record and to widen the hole. Once centered, you slid the adhesive ring down the spindle to "permanently" center the record. You then flipped the record and put another ring on that side. It was a tedious process which I only did perhaps five times. Somewhere I have those records.
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