How to proceed?

@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.

@stuartk 

perplexing- yet interesting as to why this would suddenly become so apparent to you. I do have a question though. When you set up your new transport did you set it up to run in “over sampling” mode?

@designsfx 

No. The display clearly indicates when oversampling is engaged. Out of curiosity I tried it when I was listening through headphones, tonight. Thin and harsh! Listening through phones with the Hegel dac is much clearer than with Aqua, which sounds very dark by comparison. My headphone setup is very modest- old Grado SR225 through Schiit Jotenheim but the difference is quite apparent

@audphile1 

Can you think of a less costly alternative to the Hurricane?

@decooney 

 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].

Yes, perhaps. Rather above my pay-grade, although I have experienced certain anomalies in the past that might be explained by this theory. My Empirical Audio re-clocker did not play nice with my Simaudio 260DT transport and more recently, a similar issue arose when I attempted to mate a Snake River Audio Boomslang coax cable with the Jay's. 

@stuartk less costly would be AQ Tornado. But I would start with the interconnects first.  That would be your biggest improvement. One change at a time.