In windows I use the SMSL SU9-Pro USB driver 5.5.0 and foobar uses that proper output.
It means that if I change the volume in Windows, the volume doesn't change.
(However if I change it in foobar, it does change)
In the DAC I'm in fixed mode, it show -0.0dB. In variable mode I gain a little something, but not much by being able to raise it to +2.0dB.
Output with RCA cables gives low volume + early distorsion.
Output with XLR produces the described result around 60dB at 99 volume (max).
My Stealth is plugged with an XLR cable.