I was using the mini jack out on my TV to a simple 2 channel system. On my TV the menu gave me options for this output to set for headphone or line out and fixed or variable. Setting this to line out/fixed worked fine, however I got to wandering about the optical out. Sure, an expensive DAC should sound better, but could a cheap DAC improve the sound? After looking at some, I bought the Fiio D03K,
It seem to get better reviews than all the others. Build quality was impressive for 20 bucks. Then comparing the sound, it was better, not dramatic, but definitely better and absolutely worth 20 bucks. Your TV will need to be set to PCM on the optical output.