Isolated Ground causes ground hum.

@erik_squires 
Thank you,
and that was what I did. My outlet is still keeping as normal, 1 ot, 1 neutral, and 1 ground. I only added the extra isolated ground bond the the chassis of the preamp. Is it the same as I bond it to the common ground of the Edison?
Please let me know if what I an thinking is right?

I figured out where the problem is. It is on the Conrad Johnson amplifier. When I plugged it into the outlet out of my dedicated line network, or when I used the cheat plug, the hum was gone.
Now, anyone has any idea of how to fix it will be much appreciated.
 Thanks 

I'm not an electrician, but I have two ground rods installed to my house.
  There is an earth ground attached to your service panel (circuit box) which is the ground for all circuits in your house. 
  If you have a dedicated AC line, it is also grounded to your house. You may attach a ground rod to this line which has an isolated hot and neutral to your system. 

There can only be one ground for the entire house and your components must share this ground.

I stand under correction but i Have found that if all are common ground with good rca cables that should sort it unless one of your devices has a switch mode power supply, that can cause chaos!

colin, assuming there is a common ground, in theory there should be no grounding issues using RCA cables. But not all components use the same grounding scheme, so there may be a difference in ground potential which cause ground faults. Also some RCA cables use a ground connection, some don’t. In these situations there may be hum or noise introduced.

With a SMPS the issue is noise. These power supplies can bleed noise or interference back down their power cord into the mains thus contaminating the entire system.
Some modern components are using high quality internal SMPS’s. It’s the wall-warts that add noise and are not as effective as a linear power supply.