Not hardwire what? The Era 300, or the Port?

In general, I’d use a tape loop on the old amplifier to connect the Sonos Port to. Then connect the turntable to the phono input on that old Amp (not sure why we’re using this old amp, and not connecting the turntable directly, but I’m answering your question), and then direct the Port’s line in to play on the Era 300.

Not hardwire to the Era300 - thought the sentence structure would have given a clue - but thanks for your help 

If you connect the turntable through your phono-preamp input on your old amp, and on to the Port using a line-level output (like the tape jacks) it will share that input with all your other Sonos speakers.

Personally rather than using the old amp I’d get a dedicated phono-preamp as decent ones are fairly inexpensive.

@shamil23 I think @Airgetlam has learned that when giving an advice it is bettter to be certain, than to rely on clues….

When playing the turntable connected to the Port, try to choose “Line in” as a source for the Era 300.

Thank you