My house is built on a three foot thick concrete slab about 30ft by 50ft - the turntable (as well as the house) sit on that.
So? Why should this make it immune from vibration?

I have been over 40 years doing this, what do you think I haven't tried.
I don't know. You tell me.

It is only suspended suspension turntables or rigid no suspension turntables that suffer from this to any great extent - the PL-71 is neither.
Is that a statement of fact and you dictating like you accuse me of doing? Or is it just your opinion?

Read it again and see how it comes across. I could say equally to you, based on your statement above: "Once again the only experience that has any validation is yours!" Where have I heard that before, I wonder?

What you describe is not what I hear, or many others for that matter.

Marco.