What cause tweeters hiss ?

something is not quite clear here.  If the amplifier has the volume all the way down, no sound ought to come from the inputs. It MUST be in the amplifier stage(s) following the volume control. Typically a circuit is switches --> volume --> preamp line stage --> power amp/current amp.

So i suspect this is not electronics hiss at all, but some kind of high frequency interference that comes from whatever device (Denefrips????) is connected.  Note i have  Denefrips and it is very, very quiet.  It is also isolated at its USB input.  That said i also isolate my bridge and power them independently.

@westcoastaudiophile

have you tried another DAC?

I don’t have extra DAC, only D90 and Ares II.

@gs5556

Does the Sony CD player have a two prong plug or three?

Two prong without ground.

The problem could be in the XLR connections of the digital sources.

Isn’t XLR connection a balanced analog type ? I have tried RCA connection Ares II to E280 after removed XLR, I can hear hiss too.

So i suspect this is not electronics hiss at all, but some kind of high frequency interference that comes from whatever device (Denefrips????) is connected.

@itsjustme Valid point and noted.  Ares II is connected via USB from music streamer Auralic Aries Mini, Auralic Aries Mini is powered by Topping P50 Linear PSU recently bought. 

I will test with another USB cable or original Auralic power adapter to observe the hiss issue.

If the volume is turned a long way up a low level hiss will usually be audible if you put your ear close to the tweeter.  The hiss is a noise product of the amplifier but will be at a very low level relative to that of any signal that is connected (don't connect a signal at that volume level).  The level of the hiss can be defined as its level relative to that of the signal - signal to noise, S/N, ratio.  In a well-designed amplifier the noise level will be less than 1/1000th of the signal level.

All amplifiers generate noise, but if the amp is functioning correctly it will always be inaudible from the listening chair at any sensible volume level.

@clearthinker Thanks for your reply.  I have read several topic about hiss at Audiogon forum on faint hiss issue is not uncommon.  However, when my CD player is connected to amplifier (without playing music) , there is no hiss from tweeters .  Only when I connect my both DACs , I hear the hiss.  As @itsjustme pointed out , could be USB cable ground loop issue from my music streamer  ?! 

I will check it up later by isolating USB cable , turn on DAC, turn on integrated amplifier (zero volume) with interconnect connected.