Try swapping channels at each connection to see if you can narrow down the problem.
Thanks - I tried that and also swapped out the cables. Unfortunately I think it has to be an issue with the left channel in the zone player.
Do you have any “shorting plugs”? If so, does the Line-In buzz with the shorting plugs inserted? Note that you could fabricate a shorting plug by stripping an RCA cable and twisting the inner and outer conductors together. Also, the unit is aware of the plugs, shorting or not, and you will not be able to select Line-In without the plugs.
Great tip but it didn’t seem to work :(
Hi @Withoutstars
Welcome to the Sonos Community!
If you determine that it is indeed your old Zone Player that is faulty, you can replace it with a Sonos Amp - with AirPlay support and 125W per channel, it’s a significant upgrade over your ZP and supports S1 so you won’t have any trouble getting it to work with your existing S1 system.
Be sure to check your upgrade options by signing in at https://login.sonos.com, clicking on the User icon in the top right corner then going to Upgrades - assuming you haven’t used the vouchers already, you should be able to get 30% off your purchase!
I hope this helps.