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LP Thickness/Taper

If anyone has ever wondered how LP thickness varies from lead in to runout, I just measured it.  It's well known that there's a taper to LPs, but I have never seen any actual data.

This is a 120 gram record.  The thinnest part near the beginning of the first track is 0.0415", and the thickest part at the very end of the last track is 0.0470" (+/-0.0005"). 

I know there are many ways to set azimuth, but most most people tend to do it optically with a mirror on the platter.  So, if you set your azimuth like this and are confident that you have it perfect, it will automatically be 0.12 degrees off due to the taper of the record.  I'm sure all records will have a slightly different taper, but I can't see it varying too much.

ketchup
fredapplegate
103 posts
 

Theo has it. LPs were thicker at the edge and at the label so the lps didn't scratch each other when they dropped from a changer onto the spinning disc below.
I had a Garrard SL95, Dual 1219 and a trusty Benjamin Miracord 50H. Amazing machines.

And then there was DynaFlex...

ketchup OP
699 posts
 

@lewm 

Since the angle of incline appears to be constant from outer to inner grooves, seems to me if you set azimuth correctly at any point on the LP surface, there would be no problem related to a changing azimuth angle.

You are exactly right.

ketchup OP
699 posts
 

Just measured another one for fun This was a 158 gram Hickory. The thickness of the grooved portion ranged from 0.053" at the beginning of the first track to 0.063" at the end of the last track. This means that the top surface of the LP will be at a 0.18 degree angle if it’s laying on a flat/level platter, or your azimuth will be off by 0.18 degrees if you set azimuth with a mirror on your platter.

That’s a lot. I just had two precision shims next to each other that measured 0.0 degrees and 0.12 degrees, and it was very easy to see the difference.

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