The Sonos app doesn’t generate any sound, either SPDIF or PCM. There are other apps on your Mac that do, but you might want to start your troubleshooting by looking at your control panel for Audio in the Mac’s OS. 

Thanks Airgetlam, I don't think there are any apps sending sound to the Sonos Playbar as no sound can be heard from any App as for some reason the Sonos app is now stuck on SPDIF… and I can't change it with an out put from any app...

Even when I unplug the optical connection to the Playbar the app remains stuck on SPDIF…

Again, the Sonos app doesn’t output any sound. It merely is a remote control to show you what is happening on the PLAYBAR (and other Sonos devices). If it is reporting SPDIF, that is what the PLAYBAR is receiving across the optical cable. 
 

You’ll need to adjust the settings on your Mac to send the PCM (stereo) signal, not any settings on your Sonos. 

Yes thanks, but it is strange as the Playbar settings says that it is not receiving any signal and I am at a loss to find any control setting that allows me to change the output signal from the iMac - I also haven't changed anything from the iMac to catalyse the change in output signal...

I’m not near my Mac, but on an iPad at this moment. I’d be looking at (I think) Apple’s Settings  > Sounds as a start, for the sounds from MacOS, but from other applications, you may need to check their individual settings, too. 

Thanks Bruce. I disconnected the Playbar and rebooted it. I removed the optical input cable. I think deleted the Sonos App on my iPhone and reinstalled it. I then reconnected to the Playbar using the newly re-installed Sonos App. The Playbar was successfully installed and could play Music/Radio broadcasts from the IPhone App. However when i changed to play TV (with no optical cable in the Playbar) the App once again displayed the TV Audio as SPDIF and when I connected the optical cable to my iMac via Bluetooth no sound from the iMac was apparent. Totally mystifying and more so as my set used to work and only gave up the ghost yesterday…

Very strange: reconfigured the entire setup with no optical input into the Playbar yet the Sonos App still shows TV audio input as SPDIF - does anyone know why this is?

Nobody seems to have an answer here… maybe it’s a glitch with the Sonos app upgrade? Surely there should be an easy fix! Does anyone have a suggestion on how to play audio from an iMac through a Sonos Playbar? 

Carried out an OS upgrade on my iMac and replaced the optical cable going from the DAC to the Playbar. The DAC is connected by bluetooth to my iMac (and optional but working headphone jack). Still no sound from the playbar. Even with no optical cable connected the Sonos app shows input as SPDIF - why is this?

Hi there—I’m having the same exact issue now with my Playbar. Did you ever find a solve here?

I gave up. But last week I once again deleted the Sonos app and re downloaded it on to my iPhone and the Playbar started playing sounds from my iMac. No idea why this now worked as I’d previously tried this and it didn’t work then. The input still shows SPDIF. I didn’t alter any settings on my iMac. Totally mystifying.

Hi @MstaggieM 

In case anyone has not tried this functionality in a while, all Sonos products should now be able to play from an optical input.

If you are still having this problem, please ensure your Sonos system is up to date: Settings icon » Manage » System Updates » Check for Updates

I hope this helps.