Thanks Caelin promptly reply.
I am also using Shunyata Hydra AV, should plug the new Sigma Digital to Hydra power distribution, or directly plug to wall socket ?
P.S. I am also using Alpha Digital PC to plug into LPS for NAS and hub switch. I find Alpha digital kill the noise very effectively by plug it to wall and then my whole hydra AV also be benefit because I use zitron cobra (20A) to connected to the same wall socket.
This is what I usually recommend:
Wall outlet => Alpha-HC => Hydra
or
Wall outlet => Sigma-HC => Hydra
Wall outlet => Alpha-digital => LPS