How to proceed?

@stuartk hit me with the few tracks where you hear this sibilance. If available on qobuz and tidal, I’ll check what they sound like here. Can do it tomorrow I’ll be foggy today with the New Year celebration LOL

@audphile1 

I don't stream but Patty Griffin's "Useless Desires" is a particularly good example, if you don't mind looking it up. 

The thing is, I'm hearing it (with Aqua) on many tracks that never used to bother me.  This is why it's  a big deal. When I can't enjoy music I've loved for decades, it's a problem. Again, I never had this issue before I got the Hegel and the Jay's.

I had my hearing checked this year and was told there's nothing physiological that would cause this.

@stuartk 

Crystal clear. Qobuz stream…but… I can hear the potential for it. It is partially a recording but your components just let it fly. I can 100% guarantee you that if I had those Analysis Plus Silver Apex XLR it would cut thru my eardrums. 

This is something that interconnects like the AZ would most likely tame to a level where it would be listenable. I know exactly what you’re hearing now. This was good!

I’ll add….to further tame this after the interconnects, I would put the AQ Hurricane high power cord on the hegel. Smooth out that bandwidth and add texture and body to the mids.
Don’t sell the DAC it will be a mistake

@stuartk "When I run my Jay’s transport direct into the Hegel’s DAC, fatigue goes away and while there is still some sibilance, it is not nearly so exaggerated."

If this is the case, as you may be wondering, perhaps there is some form of impedance or voltage synergy mismatch going on between your Aqua DAC and the Jays transport that exaggerates the issue somehow [when paired together].

You might be on the right path borrowing/trying different dacs and transport combos paired with your Hegel 390 amp. You already proved the Jays transport does ok with your Hegel amp’s AKM internal dac, directly. A few more steps to narrow it down perhaps.