plinth for tts8000

Anthony, If you really want to do this right and I think that turntable is worth it, you mount it on a 1" thick aluminum plate which also mounts the tonearm and suspend/hang the plate with four springs, one at each corner. The trick is to rate the springs so that the plate bounces below 3 Hz. Look at the big SME turntables and the Sota Millenium table to get a basic idea. You can have the plate anodized any color you like. The springs can hang from hooks and each corner hidden by a tube which as an example could be PVC pipe veneered with wood or whatever. These could also serve as the feet of the table which could be leveled by raising and lowering the hooks. This would be a really fun project and you would come out of it with the worlds first properly isolated direct drive turntable!

Mass does nothing to isolate a turntable from environmental rumble. Not concrete floors or granite tops or heavy plinths. The only way to isolate a turntable from the environment is a stable suspension tuned to less than 3 Hz. Such a suspension isolates the turntable from everything above 3 Hz. Anyone can make a solid plinth look good. The trick is to make a suspended one look good. Avid does a good job as does Basis. The SME's are sort of industrial but very impressive in person. The Dohmann is an acquired taste. The Sota more or less classic. 
Lewm has done a lot of work with slate and drilling holes in slate is not easy. It chips very easily. One could make a suspended slate turntable.
You can suspend anything.
Put a seismometer app on your phone. Light up the app and place your phone on a table. Tap the table lightly with a finger and you will see the needle twitch. Right now I have my phone on the desk. I see every key stroke on the phone. The desk is on a concrete floor. I bang the floor with a foot and it registers on the phone. I just opened and closed the door to the office and that registered on the phone. The lightest tap of a finger registers on the phone. You think your rack is solid? Check it out with this phone app. You are in for a big surprise. Put the phone on your platter and start tapping around. Can you jump up and down in front of the turntable without it registering? What happens when your refrigerator compressor starts up or the washing machine.

@lewm , The torque would be a problem only at start up but you can suspend a high mass (SME) just use stiffer springs. 
The MinusK isolates beautifully, probably better than any other design but it is not user friendly. You have to locate the mass on it just so or it will bounce to one side or another. You have to treat the turntable gingerly or you get it bouncing. 
A hanging suspension ala SME and Sota is the most stable. The Sota is handily the most user friendly because the sub chassis is internalized and you can rest your hand on the plinth to "Q" the record without upsetting anything. The motor is isolated from the sub chassis. During play the sub chassis does not visibly bounce causing any noticeable flexing of the belt unless you intentionally disturb it. Wow and flutter are less than 0.05%. Better yet the turntable is now locked into speed regardless of any change in friction. The hanging suspension is so stable it just does not matter. SME uses a counter belt. Some people use them without it. A solid heavy plinth is simple and very easy to make unless you torture yourself by doing it in slate:-) Get that seismometer app put it on your platter and bang around. Let us know what you discover!  
No, I do not like direct drives and one reason is you can not get a suspended one. I also do not slip "Q" records and do not need the torque. This Sony however is a classic and built like a tank. I can understand the attraction.