What cause tweeters hiss ?

Tahquitz, you are saying that you had a 4,000+ Hz ground loop?

Elaborate please.

Possibly he needs to shield his chassis, but that's very different.

I have owned many expensive and moderately priced amps over the years and none are dead silent. If you can't hear from your listening chair don't worry about it. If you have to know, then you have to isolate what is the source. So the only way to do that is to disconnect the entire system. Then you connect the amp and speakers and listen. Then keep adding 1 piece of equipment at a time until you isolate the offending device or cable. Once isolated, then you can work on a solution. You may even discover that your system is fine & there is something on your homes electrical grid that is causing the hiss.

It seems to me that if the noise goes away when you unplug the DAC, then the problem is in the DAC or its source.
 

Try floating the ground with a cheater plug and see if it dissappear. Generally, the only component that you have to ground is the preamplifier. 

I should have stated to try a cheater plug on the Denafrips Ares II power cord. Many cheater plugs sold today are polarized and have a green tab on them. You should leave the tab in place.  If the cheater plug eliminates the hiss than you are good to go.

Sometimes, due to the polarized (for the common side of the outlet) plug you may have to carefully remove the wide areas of the polarized side of the plug to make both prongs equal.  That way you can rotate the plug in either direction.  It can make a difference.

Second, if your interconnects are single ended then make sure to wrap them around each other in a helix configuration.

From your description, you do not have a preamplifier.

Hope this helps and the cost is inconsequential.