So you have a USB port that don't supply power? sounds like a spacial rare issue that could e solved like this.some DAPs fail to act as a power supply... the newer ones do. Like the sony-nwa45, one the DAP doesn't provide usb. I have to use an adapter but the usb connector only use the data portion of usb hence the need of power. Anyway taking power from DAPs drain its battery faster. Better to use the power supply.
Or the DAC could have 2 inputs (like i has now) and one is only power (like it is now)
but both are USB(C) and and the DAC shuld work with only one of the connected if the one has power.
Thats why there are Standards and the low voltage charge and power plug standard is USB(C)getting a proper power adapter (wall wart) can be challenging.