That is exactly what every DLNA software does..
...lets you connect a server to a renderer.
1: the iOS device is renderer/player AND control point as well - to get sound send to your PM you must use the AirPlay function (of the iOS device and the PM) (= AirPlay function of the PM)
2: the iOS app (or webbrowser function) is nothing but the control point. - the sound is send from the server to the renderer/player (the PM) direct. Every DLNA app can acts this way! No AirPlay is involved! (= DLNA function of the PM)
There are several reasons, why I choose not to use the DS audio app.
Mainly because I do not like the interface - but also because I want to be able to pick a server of my own choice.
You may install different servers on the SynNAS - most of them are better than the one used by DS audio.
Try different servers/DLNA app's and choose the combination you like.
Greetings Millemissen
Location: Flensborg————Danmark