It’s an active speaker, however, I think you’re asking if you would need a preamp  to connect your turntable to the Era 300.  The answer is yes.  The USB port, plus adapter, is not a phono input.

Thank you! This was exactly the information I was looking for. I’ve got my dad’s old setup, which means I’m trying to connect a turntable from 2000 (that works great) to an integrated amp from 1980 (that works well, but definitely some odd issues from the many many many moves it’s lived through) to my new speaker. I’ve finally gotten all the right connectors and gotten it all cleaned up and working, which is fine for now, but knowing that it’s an easy/inexpensive step if I do need to just let go of my current integrated amp is great news. 

Those older integrated amps have a built in pre-amp, which is why they have specific ‘phono’ inputs. Sonos is looking for the more generic ‘line level’ input, such as comes from pretty much everything else except turntables.