When CD first came out the state of the art was about 14 bits for ADC and DACs. If the source preemphsized and the player deemphasized you could get less sensitivity to quantization noise with those CDs. This hasn’t been a problem for decades.

If you have a source that is preemphasized and you don’t use a deemphasis filter on it you will accentuate the higher frequencies.

If you have a source that isn’t preemphasized and you use a deemphasis filter on it you will attenuate the higher frequencies.

These days the CD pre/de emphasis flag is often lost somewhere in the ripping, storing, playing chain and pre/de emphasis causes more headaches than it solves. With a PS Audio transport and a PS Audio DAC and any of I2S, TOSLink, S/PDIF and/or AES/EBU connecting them you get a system that handles pre/de emphasis as it was originally designed.