[Gogar]

Supe if I were you i'd...........

Anyway, leave the TV as is, it's fine.

Buy a SONOS Connect (gen 2) used for between $100 and $200 on ebay.

Put Sonos S2 app on your phone and also on the macbook.

Play music from the app on your phone OR on the macbook, doesn't matter.
You don't need any USB cables,
You don't need any 3.5 cables,
You don't need any adapters,
Nothing. Done. Plug the RCA outputs of the Sonos into an RCA input of your preamp.

Sonos app can play pandora, spotify, or the music stored on your computer or phone. If you create a playlist on your phone, walk over to your computer and it will be there too.