I'm sure I'm risking a torrent of vitriol, but I'm sorry, I just don't buy it. If you hear that much of a difference it would mean that the DAC was in constant error-correction mode with the old cable, and if that were the case the effect would be much greater than a loss of air around acoustic guitars.
The good news is you only spent $30 for your placebo, others have spent hundreds (or thousands).

I do not think you are totally wrong: there may be a lot of voodoo and autosuggestion in hifi cables and I am sure I am not free from it. Additionally I am a cable DYI so I am engaged in “cable sound”.
 
With analog NF interconnects I am 100% aware that there is an audible difference from a €5- to a €50 cable!

In digital interconnects I am pretty unsure that there will be differences from €30- to a €300 cable and I think it is a matter of the protocols used to transfer the data blocks: that is why I am taking a good cable for S/PDIF and cheap one for USB.
 
But long story short: I am noticing an audible,  positive difference replacing the €3- by the €30 cable.