Sonos Beam optical adapter input format

  • 10 January 2021
  • 7 replies


I’m trying to set up my sonos beam in order to play sound from an analogical system. I bought an analog to digital adapter that is offering a sdpif output with the following characteristics : 2 channel, LPCM, no compression, 48 Khz.

However, when I plug in the sdpif adapter from the beam, it does not work. The adapter works with my TV, so I know it works by itself.

Does anyone know what signal is the sdpif beam adaptor expecting ? Is there any way to make my setting work ?


Thanks for reading.


Best answer by Corry P 12 February 2021, 11:59

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7 replies

Post a link to the AD converter that you bought.

Userlevel 7
Badge +23

The Sonos web site is really pretty vague on technical details, but it does say this:

Sonos Beam plays audio from PCM stereo and Dolby Digital sources
Mind you it does not explicitly say it supports PCM stereo over optical.

Post a link to the AD converter that you bought.

It is this one :

Userlevel 7
Badge +18

Hi @eltrai 

Welcome to the Sonos Community.

Thanks for posting the link to your AD device. 

As the device outputs LPCM stereo, and the beam only supports PCM, I assume this is why you’re not getting any sound from the Beam.

You can see our Supported home theater audio formats here.

LPCM is generally used for multichannel sound, so I’m not sure why the AD device is outputting LPCM when it only does stereo sound.

A different adaptor may work, but we don’t support this setup. 

The supported method of getting analogue sound to Sonos is to use a Sonos Port, a Sonos Amp or a Sonos Five - these all have analogue inputs and do their own Analogue-to-Digital conversion. Once one Sonos device has a digital stream, any other device (your Beam, for example) can play it too.

Alternatively, you could purchase a second-hand Sonos Connect, Sonos Connect:AMP or a Play:5. If you are using the Sonos S2 app, please make sure the device you buy is S2 compatible (the Play:5 gen 1 and Connect/Connect:AMPs made before mid 2015 are not S2 compatible). If in doubt, you can call our technical support team with the serial number of a device you plan to buy and they’ll double-check for you.

CD and WAV are 2-channel LPCM, as is stereo over S/PDIF.

Userlevel 7
Badge +18

As far as I can make out, @ratty is mostly correct. CD and WAV audio are LPCM but the S/PDIF standard is PCM only (we’ll ignore Dolby Digital and DTS for now as they are compressed and irrelevant to this conversation), and that AD converter seems to be operating out of specification for the S/PDIF standard.

This doesn’t make a whole lot of sense to me as I always (way back in the day of CDs) thought S/PDIF was a straight passthrough of CD audio, but perhaps there’s some kind of conversion done. 

I am, however, ready to be corrected.

Userlevel 7
Badge +18

LPCM and PCM seem to be interchangeable, to some extent, when talking about stereo sound. I think @ratty might be right about S/PDIF too, especially if the Wiki page liked above is using the PCM term in this interchangeable manner.

@eltrai You may get better luck with a better ADC device, but I can’t make any promises. I would aim higher than an €8 price tag. You could get in touch with our technical support team who will be able to tell you what format (if any) is reaching your Beam by looking at diagnostics but be aware this is an unsupported setup, so they are unlikely to spend much time on the problem (as in, that’s what unsupported means).