Isolated Ground causes ground hum.

When i touched that wire to the ground post on the preamp, hum occurred. Thanks 

@dangcaonguyen

By law, you MUST bond them to the house ground.  You can't just create a new ground field, and run a copper wire to your outlets and call it ground.

Best,
E

@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.