how do you level a turntable?


...if neither the TT nor the table same sits on have feet which are adjustable?
lindisfarne
If you can remove the TT feet, you can replace them with adjustable ones. If you can't remove them, maybe you can use some other form of adjustable isolation. There's also TT wall shelves.
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.