Where do you connect the ground cable from turntable when bi-amping?

I came across your article (http://av2day.com/2014/05/bi-amping-vertical-vs-horizontal/) when learning how to do bi-amping, the article presented a very detailed and comprehensive discussion on the topic which can’t be found anywhere else, it really helped me a lot, really appreciated.
As a newbie, I have one more question regarding the ground cable, how do you connect the ground cable from the turntable to your two amplifiers?
 
It will be highly appreciated if you could provide some guidance.