Some (JVC and others) Plinths are simply composite wood chips and glue with veneer, some are simply a tall frame with a thinner top layer, like that joke of a multi-layered thingy Linn is passing off, see the 3rd photo from below
and some are thick with cutouts which is what I think of as a Plinth.
The 7 layer plinths, CL-P1; CL-P2 (mine with two removable arm boards); CL-P3 (my friend’s with three removable arm boards) are solid 59mm thick plinths with cutouts, 4 layers of composite wood chips/glue and 3 layers of some compound, with real wood veneer with a finish coating (Linn should be ashamed)
I wonder how it would measure/compare to Panzerholz and Permali in the link you posted elsewhere
https://www.tapatalk.com/groups/audioqualia/damping-factor-values-t29.html#google_vignette



