Many, but not all TVs have an option in their setup to output a stereo signal via the optical S/PDIF output. The normal consumer setup is to plug this into an optical input of an AV receiver, which can decode a multichannel Dolby Digital or DTS signal.
So make sure the TV has a stereo PCM output option, as external DACs cannot accept a multichannel digital signal (except for a few rare non-audiophile DAC gizmos).
Steve