The answer to yesterday’s guess what this cable does is as follows – 
It is an iBasso burn in cable for their new Digital Audio Player (DAP) the iBasso DX80 which I will be reviewing once I have had more time with it. 

The cable is plugged into the headphone socket with the music playing. This allows the burn in process to take place. What does this mean ? The DX80 can reach its full sound quality potential by forming the capacitors and stabilising the electronic components used. 

Another way of burning in the DX80 is plugging normal headphones in with music playing. The cable allows for the process to be done as effectively as possible. 

Some of you were very close guessing it was a burn in cable but suggested it was for the DX90. I’ll allow that as a correct guess 🙂