About the signle es9218p of 3.5mm output
As for the single es9218p of 3.5 output, do you know that Shanling up4 can freely choose to use single es9218p or double es9218p when outputting 3.5? Have the option given to the user been considered? I know that the single es9218p solution can have a longer service life, but some people still hope to try to use double es9218p freely under 3.5 port, do not know if this is difficult to achieve, or Other effects of sound quality and design circuits?
It's not difficult to achieve, and it's just a matter of design choice.
To support those HW options, we need to add a switching IC between the jack and DAC/AMP output.
And every switching IC has some amount of resistance even at the ON-state. We want to deliver the pure signal out of ES9218p directly to the jack.

Thank you!