So I will disagree here. It depends. The DAC in the Node may or may not be better than the DAC included in the amp. And the phone may or may not be better as a digital transport into the DAC. I was using an LG phone in exactly the same way your son is. I replaced it with a Node because I didn’t want my phone tethered to my system. There was no obvious sonic improvement
1. Sony STR da5700ES Pre / Amp only as before...
2. Sony Pre into Bel Canto AMP (Theater Bypass)...
3. Bel Canto Pre / Amp on it;s own.
Not knowing anything different...1 was very enjoyable.
2 improved the top and mids....much cleaner / clearer, better soundstage, depth, lower mids into bass more "fuzzy / whooly" by comparison to 1.
3 initially sounded very bright on top....fatiguing...almost unlistenable on some tracks.
Left Bel Canto on with CD repeat for 100+ hours...
3 now is far better up and down the frequency range including the bass with bass cabinets set at "0". Rocket 33 speaker cables gave a nice boost to mids and tampered down the top just enough.