X16 is a digital volume, which is a lossy control method. It is best to add a preamplifier to control the volume, which is lossless.
The X16 has no preamplifier, and the sound is faint. The preamplifier is very important and cannot be missing. It is wrong to think that the volume can be adjusted without a preamplifier.
Roon adjusting the volume will make the sound quality worse, because adjusting the digital volume is harmful. The best way is to adjust the volume on the equipment behind the decoder, such as preamplifiers and combo amplifiers. If there is no preamplifier or combo amplifier, please control the volume in the decoder. This method is also better than controlling the volume in Roon.