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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
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.
old_6eyes
46 posts
 
You could use an extra mat or mats to raise the record so that the spindle isn't in the way and center the record visually. This requires no modification of spindle or record. VTA will be off, of course, that's the part that makes it a less-than-perfect solution.

Removable spindles would be handy for this too, like the older Duals, etc.

I like the smaller spindle w/adapters idea.
kftool OP
104 posts
 
Dertonarm,

The center spindle was not omitted. The spindle dia. on the
Denon is .284 inches; the smallest diameter generally found on LPs. If i find a record with a larger hole I notice the back and forth motion of the arm. I then put the polycarbonate centering device back on the clamp ring and diddle it back and forth which re locates the LP on the smaller spindle. Putting the arm back on tells me if it's centered properly, or at least as best as my eye can tell. I believe most, if not all tables have a spindle dia of .284 inches, at least my two Sota tables have that same dia.

Ken
dertonarm
1,042 posts
 
Dear Kftool, those 0.284 inch do equal the 7 mm in metric world. That is indeed the standard.
Thank you for setting this straight.
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