Changing the output device Volumio

I’m using an iPad to control the Volumio app and at the same time would like to connect it to a DAC preamp for headphone listening. However in my Volumio Primo Settings> Playback Options> Output Device the options are only Analog RCA Output and SPDIF and name of DAC preamp if it’s connected to the Primo. There’s no sound coming out from the DAC preamp if connected to my iPad.
Connecting the DAC preamp to my Volumio Primo works perfectly but is it possible to connect and listen via my iPad instead?
Thanks for any inputs.