Sorry if this is a silly question, but I am really in the dark with current music source technology and Googling just leaves me more confused.

I have a Denon standard HiFi amp, plugged into which there is a turntable, cassette deck, CD player and the TV (via the aux input) and then out to two floor-standing, column speakers. When I listen to Spotify I connect my phone to the tuner input of the amp and it sounds OK.

But, would it be sensible/advisable/a massive improvement/a stupid idea/a waste of time to plug the phone into a DAC and then connect that to the amp? And what about a (cool looking) valve DAC?

Any views gratefully received.