Five would be the better option. You get both the line in, and an excellent speaker that he can use, and group with his One SL.  
 

The Port has the line in, but no speaker. It’s really designed to connect the Sonos ecosystem to an existing receiver/amplifier/stereo system. it would work, certainly, but the Five would probably please your son more. 

Hi @Wildjt.

Welcome to the Sonos community and thanks for reaching out to us. I understand that you are looking for answers on how to integrate a turntable with a built-in pre-amp to your son’s Sonos One SL. Let me help you out with that.

The Sonos Port and the Sonos Five both have a line-in port feature that would allow you to integrate your turntable into your Sonos system. However, the Sonos Port uses an RCA connection while the Sonos Five uses a 3.5mm headphone jack as a line-in connection (same as your headset or earphone jack/connector.

The most ideal product you would need to connect the turntable to Sonos would be the Sonos Port. as the turntable uses RCA connection that would be an auto fit to the Sonos Port and then using the group and ungroup feature on the Sonos app, your son can group the Sonos Port with the Sonos One SL through the Sonos App to have the audio come out of the Sonos One Sl.

@Airgetlam has a good point. The Five already has a built-in speaker while the port does not.

Let me share with you a topic here in the community that discussed more details about integrating a turntable to Sonos.

I hope this helps.

Please let us know if you still have further questions or concerns. We are always here to help.

Thanks,

This is a complete no brainer. I agree with @Airgetlam . The Five would make a much better present than the Port. 

There would be no difference in performance of tbe turntable. Assuming the turntable has an RCA out connection, you would just need an RCA to 3.5mm stereo jack cable.

Here are examples of the sort of cable you ought to include with the Five. 

https://www.amazon.co.uk/RCA-Cables-3-5-mm/s?keywords=RCA+Cables&rh=n%3A4085681%2Cp_n_feature_keywords_browse-bin%3A1055633031&c=ts&ts_id=4085681

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Thanks for all the input.  One last question on this.  I see that the Port has the ability to airplay from the IPhone, is that worth not getting the Five.  I was kinda leaning to the Five if would accomplish integrating his turn table into the speaker.  And that would give him 2 speakers vs just 1?   Thank you again

Hi @Wildjt.

Thanks for your immediate response.

The Five is also an Airplay 2 compatible device with the + on the built-in speakers. Yes, you’re correct choosing the Five would result in your son having 2 speakers instead of having only the One SL. I only recommended the Port for the sole purpose of integration but the benefits of having the Five would be much greater than having the Port. 

Please let us know if you still have further questions or concerns. We are always here to help.

Thanks,

Thank you all for your input it was most helpful.  Just wanted some clarification on things before spending that kind of money. 

Ditto on the Five - the best turntable solution for someone who doesn’t already have a HiFi setup near where the turntable will logically go.