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

The centering turntable was the Nakamichi Dragon CT. Link is below.

http://www.vinylengine.com/library/nakamichi/dragon-ct.shtml

There was also the Nakamichi TX1000 (the CT's bigger brother I thought).

I believe it is more easily solved using a method like you describe, though that requires a 'virtual spindle' rather than a real one, and some kind of ranging apparatus. As you hint in your post, if physical and working off the outer edge of the disc as a reference, this only works if the stamping is done so that the outermost groove is equidistant (or actually, the 'appropriate distance' (because the appropriate distance should decrease linearly by the groove spacing over one revolution)) from the edge of the disc. If done based on the grooves (the ideal), that requires another ranging device measuring groove placement on the surface rather than either spindle or outer edge in order to set the records place on the mat. That sounds difficult.

On the face of it, the Nakamichi solution is actually somewhat elegant, because the timing and distance of the "swing" is perfectly regular and therefore easily programmable, and it is not very fast, so there is no 'hysteresis' involved in 'violent' direction changes (assuming overhang of zero - if overhang is not zero, it becomes a bit more complicated I think). If there were slits in the TT platter/mat which allowed laser ranging to the underside of the record with enough frequency, this could be set by the TT before the stylus touched the vinyl, otherwise it would have to be done based on the arm being mechanically sensitive to the swing.

I, for one, would be interested to see Dertonarm wade in...

Hi Ken.I know a Fello who back in the seventies started doing what many would think is crazy but since he never had plans on reselling any albums and like alot of us back then he bought two copies of favorite lps. He was quite the tweaker long before it was so popular. He actually made a jig that laid the album perfectly centered and protected from surface scatches. He then using a drill press with a very sharp forstner bit carfully cut out a perfect centered clean hole exactly the size of a 45 adapter he machined himself.When the album was placed on the platter with the adapter he sat the weighted clamp that he machined which had the center machined out to fit over the adapter. Yes it did cut out some of the label obviously but every record he played the arm tracked straight and steady with no eccentricity at all. Definately NOT recommending this just thought I would share this. Some thought he was crazy but I admired the fact he fixed the problem. Also he always reminded me that others think he was ruining the lps but he said "I just ruined everybody elses ability to borrow them".Cheers

Has2be,

Whenever you think you're the craziest person on the planet, someone trumps you.

Thanks for the reply, Ken

Dear Kftool, dear T_bone, the best possible way to solve the problem with the notorious LP eccentricity should be a pure mechanical one and - most important - should go without any alternation on the given LP itself (widen the spindle hole etc. etc.). I think the way to go is to decrease the spindle diameter and provide a kind of adapter (or a small 3-4 unit set with different ex-center adapters) which balances the LP-eccentricity. I have done so in my fist TT design back in the early 1990ies. It works fabulous and without any alternation or harm to the LP physics (sometimes you want to sell a LP....... a wide center hole does not really add to the value...) . The procedure itself is a matter of 30 - 50 seconds. Even LPs with eccentricity up to 3 mm (which is a lot...) when played with this adapter were dead quiet center in play. The modification should be done at the TT's spindle - not at the LP. The Naka's TX-1000 does cure one problem with an extreme amount of work and technical (electronic) periphery - and opens up a few boxes of other problems by doing so. A friend of mine just had a Nakamichi TX-1000 restored past week and put to work. More electronic than in any of our preamplifiers (which phono board....). But - it works. But so does the mechanical approach described here.