What cause tweeters hiss ?

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I’m not sure how you get any sound at all with the power cord unplugged. 😁

😆  My bad, just illustrate how to remove the hiss/hum by discharge to the ground.

They are a real thing that can occur with USB or coaxial digital connectors.  I have never heard of this causing more than excess jitter though.

Right, it could be USB cable , will test it later. Thanks

@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.

@clearthinker When I tested with the CD player, I isolated the DAC power supply, CD player using RCA out to Integrated Amplifier , no hiss.  

I just tested my Ares II , removing both toslink and USB input, hiss is still there , it is very minimal though.  I will leave it now.

Thanks guys for your input and sharing. 

@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.

@itsjustme

My bad. English is not my native speaking language. Let me rephrase my sentence.

1. Accuphase E- 280, as I mentioned in my first post , integrated pre/power amp. I further check E280 spec, their preamp to balanced output gain is 18dB, looks like quite high.

2. Hiss disappear when I disconnect power cord of Ares II

3. Power off my Denafrips Ares II

@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.

@oldrooney hi, thanks for your detail explanation on the XLR pin terminals construction,  i am not electronic savvy, and furthermore this XLR interconnect may have reached its life span after 15 years ? I will leave it, lucky that I have a spare XLR that connect to my headphone amp. Temporary this will replace my old Cardas. Thanks again.

I do check and isolate one by one interconnect  as well audio equipment connected to my integrated amplifier .  As for Ares II, it was not recommended to have both RCA and XLR to be connected due to the R2R design with high output impedance.  Thus I have dropped and removed the RCA cable , left XLR cable. 

The hiss remains until I removed my Cardas XLR cable from  Ares II to Accuphase E280 while both DAC and integrated amp power on.  Then I used another pair of cheap Ugreen XLR cable to test.  The hiss went dead silent. 

I just read through this article and it explains the hiss, buzzing could be due to broken cable. 

One thing to note ... my old Cardas XLR cables are longer 2m each,  new one is 1m.  A longer XLR cable may subject to noise interference than shorter one.  Also the 15 years old XLR may not have a good shielding against WIFi ... perhaps.

Some of the answers are funny though.  You guys make my day more joyful.