What cause tweeters hiss ?

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.

Consider the obvious.  The tweeter is a transducer, it has no intrinsic energy of its own (other than the kinematic energy imparted to it by gravity which will not produce a sound unless you drop it on the ground).  If you take the tweeter out of the speaker and hold it to your ear you may hear noise.  Obviously the tweeter alone has no power going to it so it can't be 'transducing" so what you hear is similar to what you hear when put a seashell to you your ear at the beach (go look that up, the education will be good for you).

Tendinitis is another possibility for a un-powered tweeter appearing to be hissing.  If you have a mild case of it there is there is a chance that by concentrating on the tweeter, you are perceiving the results of this medical issue.

Otherwise this question is wrong.  One must as 'Where the signal coming from?"  The answer would have to be the electronics driving the driver.  Something is producing energy, this is a great trouble shooting exercise to sharpen you inductive (not deductive, no matter what you think of you readings of Sherlock Holmes, he was a master of inductive rather than the deductive reasoning processes.  Again, do some homework, it will be good for you.

@itsjustme @perazzi28 @oldrooney @gs5556 @jb1 @clearthinker @erik_squires Dear all, thanks for your advise and sharing thoughts.

Finally I have discovered the culprit, it’s my 15 years old Cardas XLR interconnect. (even I have had tried phase invert at both Ares II and E280) .

After I replaced with a normal decent Ugreen XLR interconnect. No more hiss on both tweeters.

Should I get a better XLR interconnect?

@perazzi28 all high-end audio equipment here are 3-pin UK with ground connected and with IEC 60320 C13 power cable.

Interesting.

So premium interconnect can worsen SQ as well as improve it!