I recently purchased a used SMSL SU-9n on audiogon and long story short the optical/toslink input is malfunctioning but the USB works well. I tested multiple cables, sources, and I looked through the menus for simple solutions to no avail. All of my other cables and components work as intended with the SU-9n taken out of the system. However, when the optical input is selected on the SU-9n the audio cuts in and out at different intervals. Have any of you had this issue?
Here is a link to a YouTube video so you can see and hear the malfunction.
SMSL DAC malfunction
A list of the gear I used for testing.
Rogue Sphinx v2 amp
Elac UB5 speakers
Caldigit TS3 plus - USB hub
LG C3 - TV