How to properly isolate a turntable?

do you have a suspended table? a lid for the the table?

Only way I got rid of my feedback years ago was to put the table in the next room. this was with a Ariston Rd 110 similar to linn.

I am guessing that you don't want to spend big bucks. You might try and find a used Bright Star Audio Air Mass. If you do use an air blader system, it is imperative to keep it level. There are othe types of isolation devices descussed here on Agon or other sites as well. Good Luck.

There are many approcahes depeding upon your intended cost.

Place a good quality shelf under the turntable, such as a Neuance, Mapleshade, or a Black Diamond. You can even go homebrew with a slab of MDF. Then use a sheet of heavy-duty (the pink antistatic) bubble-wrap between your rack & the isolation shelf. This is a proven approach used by some highly knowledgable members here.

Instead of the bubblewrap you can set the shelf atop a set of Vibrapods, superballs, sorbathane pucks, etc. Be prepared to experiment for your prefered sonic signature.

Tried everything except a wall mount and 300-500 lb granite platform (couldn't make the wall mount work in my room & didn't want to gamble on the platform). Moved the table in the end. If you have suspended wood floors, low frequency feedback can be a bugger.