Turntable Rack Mounted to Foundation

If you are in a real basement, the "walls" are probably either concrete or concrete block up at least 5 feet or more. In which case you might want to consider mounting a couple of 6 foot long butcher block (maple) shelves on welded steel brackets that are lag-bolted every 2 feet into the wall.

It's not that there's anything wrong with a rack unit sitting on a solid concrete slab floor, except that very few of them are truly rigid, and always require some kind of isolation shelf.

Properly designed and detailed concrete or block Wall-mounted surfaces can't move -- period.

.

Let me clarify: when I said "very few of them are truly rigid" I was referring to audio racks, not concrete slabs.

Concrete slabs don't vibrate in the audible spectrum, and almost not at all in the mechanical spectrum (below 12 Hz. or so) therefore it's unlikely, unless you live next to a railroad line or an interstate, that you'll have anything to contend with except airborne vibration from the music itself -- and that's really negligible, even for turntables, unless they're positioned right in front of a woofer (also unlikely I imagine?)

.