I think a linear output cannot be output directly from the DAC, so this is the correct linear output.
As for the mod, I tried to change the cheap resistor and capacitor in the I/U of the DAC, tried different combinations, it sounded best with the Japanese Shinkoh resistor, the sound is more wider, more natural, high frequencies are perfect, not as sharp as in the stock, also a good resistor Takman karbon (need try to burn more), compared to them, the stock version is a bit dirty and boring, sounds wrong in some moments, but mod is no finished, I tried it on my DD iem, but will also soon try this diff on my new Raptgo planar hybrid.