So beforehand let me say i know the answer is nuanced and changes from device to device etc.

Basically if i have an output device and input device with independet volume controls, how do i best balance them for optimal sound quality?

In my case talking about a Samsung Galaxy Smartphone using Poweramp to send music via Chromecast to my Denon receiver. (DVC is disabled)

Or alternatively, what volume level do i set in Poweramp to send the original volume file over to the output device? Right now i’ve settled on using 80% on my phone and adjusting the volume on my Receiver.

I’m even just looking for a general “scientific” discussion or article about the topic since google is anything but helpful.