In my experience I could A-B Toslink and Coax connections between a player and a DAC. They had been roughly equivalent in SQ.
When I inserted an ipurifier2 before the DAC, the Coax hookup sounded far superior. I noticed that the iFi had a Toslink jumper on the side which I connected in parallel.
Now both inputs are superior.
At the price I think it’s probably worth trying to improve ANY priced unbalanced cable. It definitely improves on pure glass.
Thanks for info.