A while back I was connecting a hard disk to do backups on my PC and I eventually realized this was affecting the sound even though I was using optical. One would think this would not be possible because optical isolates the dac from the PC. Any noise or RF on the source side may affect many things, for example, the optical transmitter that is converting the electrical signal to light, this can create a lot of jitter or even changed bits. A DPLL can correct for jitter in Chord dacs on optical more so than in other dacs. Roon, Foobar, Jriver all sound different even though they all are bit perfect but that is what my ears hear, servers similarly generally sound better, a lot of funny business going on that sometimes doesn't even make sense. They have cleaner power supplies, lower noise/RF overall so don't affect other stuff as much, better clocks etc. A good dedicated audio server can certainly help, problem is they aint cheap. I remember Rob saying it was to allow for some headroom (3dB) to prevent clipping.