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SME record clamp causing convex playing surface

I have an SME Model 10 turntable. I recently noticed that by following the manual's recomended procedure for playing records, ie. placing the included washer under the record label, placing the LP on the platter and then screwing down the record clamp, the LP's surface becomes convex. The center of the LP is raised higher than its perimeter forcing the stylus to run uphill as the record plays. I confirmed this conditon with a bubble-level. I also presume this causes there to be a space between the underside of the LP and the platter surface, greatest in the center and decreasing until the vinyl meets the platter near the perimeter, which can't be good. Does this condition, presumably on all SME tables, cause problems with channel balance, pitch, record/stylus wear? It seems to me that the ideal playing surface would be completely flat. Has anyone else made this observation?
peterayer
pcosta
241 posts
 
You are clamping it to tight
peterayer OP
1,382 posts
 
Thanks Pcosta, I thought of that. If I don't tighten the clamp at all, the LP is flat but raised entirely off the platter by the thickness of the washer. If I tighten the clamp just enough so that the outer edge of the LP touches the platter, the LP is indeed pressed into a convex shape. My suspicion is that the supplied washer is simply too thick to allow the LP to both lie flat on the platter and maintain complete and good contact with the micro-grooved platter surface.
pcosta
241 posts
 
Does this happen to all your records?

How thick is the washer. Is it black. What is the diameter.

When I had mine. you tighten it enough so the record does not raise on any part or the record edge. Tap the edge all the way around to see if you got it all, and adjust accordingly.

Paul
chadnliz
3,736 posts
 
Is it the factory original washer? Maybe if its a used unit it was replaced and a bit thicker.
peterayer OP
1,382 posts
 
This occurs with all of my records, any thickness. It is the original black SME washer that came with the table which I bought new from a dealer. I don't know the exact thickness or diameter of the washer, but I think it is just over an inch in diameter. I will measure it later. I do tap the edge, or check it visually, to make sure there is contact all around the perimeter of the LP and tighten it only enough to achieve this contact and no more.

Having thought more about this phenomenon, I think VTA is constantly changing because the tonearm angle is going up as the stylus is riding up hill slightly with each revolution as it travels toward the center of the LP. Perhaps I should contact SME or Sumiko.
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