I don't remember if the X3 gain control does the output. The good news is if you use Walnut as a DAP then you can use the digital volume controls to make the volume knob less sensitive. There is no way to get it any quieter when using as an amp, though. I don't know if your X3 is rockboxed. If it is, you could load a flat EQ preset and lower only the gain (not any of the frequency bands) will do the same effect.