Old iMac using iTunes to manage flac or alac files plugged into Schiit Modi 2 via USB cable and then into preamp via USB cable.
I believe you meant to say into preamp via RCA cables.
I would never use iTunes for playback. Use Foobar2K, Jplay, Jriver or Amarra instead. Amarra will give you the best SQ IME.
The better the USB cable you buy, the better it will sound.
Steve N.
Empirical Audio