how do you level a turntable?


...if neither the TT nor the table same sits on have feet which are adjustable?
lindisfarne
You need a bubble level and some shims to insert under your TT feet. I've used layers of electrical tape with good results, but anything will work. It just needs to be thin so you can gradually increase the height.
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If you have a turntable with soft feet, the above methods would be fine. If you have a turntable with hard feet or cones, using soft shims may affect the sound of the table. I use a 3 1/2" thick maple platform under my turntable. To level the platform, I installed brass 1/4"x 20 threaded inserts. Then, I used a short length of threaded brass rod to install Black Diamond Racing footer cones. Each corner can be adjusted very precisely.
Depending on your stand's legs, but many can have a threaded foot retrofitted. If hollow steel square tubing is used most Ace hdwe stores have adjustable feet that will fit. If there are wood legs they can be drilled and have a metal threaded endcab/footer installed.