Use the optical cable. The DAC inside your PMA‑600NE is noticeably better than the DAC inside your DCM‑390 CD changer. The PMA‑600NE’s DAC Wins because it uses a newer 24‑bit / 192 kHz DAC chip, has cleaner noise floor, better jitter control and is designed for modern digital inputs (optical/coax).
Hope this helps.

