The Sonos Connect is actually designed to play music from the Sonos system on an existing sound system. In this way, you can, for example, address your home cinema system via Sonos.
However, since the Play 5 and the Connect and Connect:AMP products have an input, it might be possible.

then you have to use an appropriate phono preamp, which you connect directly to the pc.
greetings andy

Hello elena
no, it doesn't work like that. the connect is made so that you can play music that you have already digitised, i.e. stored as mp3 or acc etc in the pc/notebook/server, instead of playing it on any sonos speakers, on your old stereo system with an amplifier and 2 speakers. you effectively turn the old system into sonos speakers that you can also operate via the sonos app. if you want to play your lp's directly