vacuum requirements for LP record (vinyl)

[banpuku]

In designing a state of the art audio turntable, one of the critical elements is to have a flat LP secured to the platter surface. We are considering using a vacuum chuck with porous metal technology.

An LP weighs 180 grams and is 0.070" thick, on average. Most LPs have < 0.01" warpage, but some moderately warped LPs have variance of > 0.05". The diameter of an LP is 12".

The vacuum chuck would have a porous surface area from the center of the LP out 5.75" toward the edge of the LP. The final 1/4" of the LP will rest on a rubber seal that is slightly elevated / proud from the vacuum chuck surface.

My question is this: what vacuum pressure should we use, know that a vinyl LP can be scratched and thus we do not want to "over" vacuum. Also, we need to ensure that the vacuum does not introduce any micro-vibration into the LP surface.

Thanks in advance for any help.

 

[TenPenny]

I seem to recall reading somewhere that a typical vacuum on a turntable will be 0.5psi, but I'm sure every manufacturer has their own black magic.

As they should, when you're asking people to pay $10,000 for a turntable.