It can be bright for some but I call it 'detail'. The 'detail' on the top end can seem to some as detracting from the low end on some tracks. That said, with the THX/Elex pairing, sub bass is still there. On track 27 - CANTO AT GABELMEISTER'S PEAK from The Grand Budapest Hotel (OST), the sub bass clips my headphone drivers. If the 'detail' isn't wanted, fortunately, the D1 has sound coloring built in to the DAC. The 'Tube 1' setting on the D1 can take the highs down just a tad while keeping the mids and lows. If that's still not enough, there's settings 'Tube 2' and 'Tube 3'.
Hope that helped.