Sorry but we don't have any data yet at the moment.
ES9218p DAC/AMP output directly goes to 3.5/2.5mm audio jack.
So it mainly depends on ES9218p HPAMP output impedance, same as other ES9218p applications.

Ok, looking forward to seeing the full specs when you have them. I hope you can keep the output impedance as low as possible, to avoid adversely affecting the frequency response of headphones with largely varying input impedance with frequency.

@B0b:
That's why we have NO part between ES9218p output and 3.5/2.5 audio jack. We want to have the pure output from ES9218p go to the audio jack directly.
Please note that some application products have switching IC between them, which works as a resistance even at ON state.
Every semiconductor switch IC has some amount of resistance at ON state, which is called Rds-ON resistance.
Anyway, we always keep that in our mind when designing 5k.

Brilliant, thanks!