concrete (cinder) block tower with wood chopping block for turntable stand

Your blocks may need careful attention to sit flat wtihout rocking.  You can use shims or swap blocks around to eliminate motion.  If you want to go first class buy a $5 bag of morter and use a very thin layer of morter between each set.

You ca also set the butecher block in mortar.

Jerry

If you ever want to move it maybe thin sheets of rubber in between the blocks would be a wiser choice than mortor.

Interesting... I couldn't see these rocking due to the sheer weight of each block. These are 16 " front to back (DEEP), 8" wide, and 8" tall. Each block must have weighed near 40 Lbs. Not so much out of necessity, but more about not being very impressed with sub $1000 3 shelf single wide racks. It's a second system with a budget, and I don't want to spend over $2K on a rack. But if I was to do that it would be a Box Furniture modular rack. 

I think the idea of cinder blocks is bad, mortar or not. They will never be flat or fit perfectly. A purpose- built stand for turntables is a better idea. Look at Adona racks. It will look and perform better than blocks and you'll be happier in the long run. Cinder blocks are for college kids.