Lionel said:

Unfortunatly I don't know anything about turntable technology. I am
dreaming of what means "air bearing". I love nice mechanics.

Umm......what's a bearing?
The point where the platter revolves around and rests on.
For example a Thorens has a ball bearing.
Air bearing means the platter is hold in position by force of air.
Too bad one can't use a 60 kg platter, one would need a huge and noisy
compressor in the garden shed.

Same goes for the arm.
Normally, there would be friction btw. arm and suspension.
The air bearing would remove most of it, in theory it should be
possible to move the arm by means of the groove position.
In practice, this would lead to extensive groove distortion.
Some kind of servo mechanism must be used, but the idea of a nearly
frictionless arm is still attracting me.
Kind of like chasing the perpetuum mobile :-)

Recently on a Sunday I have been to a vinyl market (used and new).
I have been a little bit desappointed because of relative high prices.
French are snobs.
Note that I haven't watched like you for "batch-sales".

You said it.......a dedicated vinyl market.
One has to scrounge places where aficionados don't think about.

Just like radio hamfests: about the worst place to buy tubes, because
everyone knows their value too well.

--
Sander deWaal
Vacuum Audio Consultancy