If the digital cable makes a big difference, you might consider changing your DAC. I used to hear things like that when digital was new, but it’s been decades since I could detect meaningful differences among digital cables, whether AES3 (the new name for AES/EBU), S-PDIF, or even USB cables.
I thought I must be mistaken, until I read that Steve Hoffman (well-known mastering engineer) flat-out stated he couldn't hear any differences among digital cables.