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Record clamp/weight and turntable speed

Hey all. So today I thought for the first time if having a substantial weight or clamp on the spindle affects the platter rotation speed. It doesn't for me, as far as I can tell, but if not, why would that be so?
128x128simao
xaak
43 posts
 
Don't know where you've been for the past 400 years, dover, but "proper" never has meant "reflex" not in any dictionary I have ever seen. But I tell you what, since you want to argue so much, find me the clamp you think is "proper" as described above. One that clamps the record down so flat and secure it has to be lifted by the edges after playing. You find that one for me, post a link like I did for mine. That way I can explain in detail what you missed and why it is, compared to mine, not a proper record clamp.
VPI.  Screw down with threaded spindle.  Washer between the platter and the record.  Mine was a TNT 3, (25+ YO design). I had to lift the edges to release the record.

I still miss that table, sorry I sold it.
larryincmh
74 posts
 
@lewm thank you for your response.  As for the VTA, the current cartridge (Grado Prestige Gold) was set up by a shop with the factory mat plus a felt (I think it is) 70's anti-static mat and the two of them together is about the same as the replacement cork mat I just bought.  So, I believe it is very close if not the same height off the platter as it was before.  I just introduced this weight though and had no clue prior that there would not be enough spindle still sticking up to catch the hole in the weight. I think I will not worry about it for now and continue to listen to a number of my very favorite go-to albums that I have heard so many times that if the SQ is off, I will certainly know it.
simao's avatar
simao OP
1,831 posts
 
@xaak - My Herbie's Mat has a rubber washer between the platter and record. What does that do for the physics of clamping?
xaak
43 posts
 
It depends. I’m not familiar with the Herbie’s Mat. How thick is the washer? Does it rise above the level of the mat?

By far the most effective way to clamp with a washer is with a threaded spindle and a tapped concave bottom clamp. This allows sufficient force to flatten a record against the platter and effectively create a vacuum between the platter and record. However, if you don’t have a threaded spindle, you can try something like the Record Doctor clamp and see if that works It has the right kind of bottom, but has a tightening mechanism that uses friction in order to hold the spindle. You would have to exert some degree of downward force while tightening it to get the same effect, if you can even do that.

VPI clamp: https://cdn.shopify.com/s/files/1/0105/4542/products/vpi-deluxeclamp-3_1800x.jpg?v=1571265214

Record Doctor Clamp: https://www.audioadvisor.com/images/RDRC_BLK_BTTM.jpg

Edit:  I believe also the Sota Reflex clamp does something similar with friction, but as you snap the lever down, it grabs the spindle and moves the weight downward to clamp the record tight.  I can't find a picture of the bottom, but you can add a rubber ring around the periphery if it doesn't have a concave base.
simao's avatar
simao OP
1,831 posts
 
@xaak. I run a VPI HW-19 Mk4 with a screw on clamp. The Herbie's mat washer rises about 2-3 mm above the mat. The VPI platter has a concavity which matches up nicely with the Herbie's. Thank you for explaining the reasons behind that! 
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