sjtm
I have never experienced any issues with vibration, i.e when walking around while playing an lp. I had assumed the concrete floor and thick carpet, along with the heft of the cabinet and contents, provided excellent isolation.
from my past experiences, the key imo is you want to turn your cartridge/system into a type of stethoscope for your room. Also poured concrete slabs are far from perfect containing air pockets. Your rig could be on one of them. How to find out ?
sjtm
Is there a good inexpensive solution to solve this isolation issue?
There is an inexpensive way and it can be kind of fun too.
With system on mute and set to the lowest volume.
Place record on the platter - not spinning - and lower your stylus onto it.
Unmute and slowly start raising volume to what represents a loud level for you.
Your cartridge/system has now become a stethoscope to your room.
So ....standing near the stand, start jumping up and down .......like you have won the lottery. (waving arms optional)
Dance in front of, beside, and behind it if possible. Is anything heard through the speakers when you do this ?
If yes your turntable stand is not on good ground. Move to another spot.
Good luck.