Sonos Connect optical out max resolution

As stated above, I am not using Sonos Connect to decode or convert the PCM stream. I am bypassing the internal DAC.

Sonos Connect passes through MQA to my external DAC, which indicates that it is natively unfolding MQA (blue MQA LED on DacMagic). The issue is that the sample rate remains 44.1kHz.

Therefore, my question, once again: What is the maximum sample rate that Sonos Connect passes through its TOSlink and Digital Coax outputs?

Most MQA content on Tidal  is actually 44.1 inside a FLAC file, saying that fairly certain that the digital output gets converted to 44.1kHz, 24 bit.

may be of use to the OP

https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-sonos-connect-streamer.8038/

How relevant is the above URL, Bell M? It is dated 2019 and Sonos have updated the software many times since then. My Sonos devices are all up to date with latest versions.

Does current (as of 24 Oct 2023) Sonos Connect S2 pass through 24 bit/44.1kHz over digital out without truncating to 16bit?

It’s relevant as it still current / valid.

There is no current Sonos Connect S2, insofar as it was replaced by Port on September 12, 2019. The ASR article is therefore just as valid now as it was then.

Connect (and ZPx0 before it) has always had a 24-bit/44.1kHz digital out. In Fixed Volume it was found to be bit-perfect, which I guess is why the cherished blue LED is lighting on the DAC.

I have to ask though: if sound quality is the objective why on earth is MQA being favoured? Thankfully it’s now going the way of the dodo, and Tidal is finally replacing it with genuine, unbutchered HiRes FLAC.

I am afraid, you have it wrong, Ratty: My Connect uses Sonos OS S2, according to the Sonos controller app on my smartphone (which app is also the S2 version).

Version: 15.9 (build 75146030)

The Connect has been updated at every Sonos OS update roll-out, so it is CURRENT in as far as the latest software. In this context, I repeat my question: How relevant is the above article, dated 2019? Sonos could have updated the software not to truncate 24 bit to 16 bit.

Does anyone has authoritative, as opposed to speculative guesses, at the correct answer?

As for MQA - I am not particularly hooked on it, but rather the question is much wider than MQA: will the Sonos Connect pass through 24bit at 48 or higher sample rates of ordinary (non MQA) FLAC files to the DagMagic over digital out, or will it truncate and downsample before passing the PCM stream to the DacMagic?

I don’t know precisely how the ASR 24-bit test signal was delivered but, sure, it could have been truncated. Sonos currently only offers 24-bit support from certain sources, such as local files, Amazon and Qobuz. For Tidal Sonos only claims 16-bit support, so perhaps your little blue LED was being illuminated by (horror of horrors) MQA-CD files? 

My point about the Connect/ZPx0 digital out however stands. The S/PDIF has always been 24-bits wide, to allow for the volume adjustment of 16-bit samples down to -48dB without loss of information. 

On the format support question, Sonos doesn’t support anything over 48kHz sampling rate. Its native sampling rate is 44.1kHz, and I have a suspicion that it may convert 48kHz to 44.1kHz before sending it out the S/PDIF. I haven’t looked in a long while. To be frank, if you’re wanting a bit-perfect streamer at higher sampling rates you’d need to consider alternatives.

At last - I have come across an official Sonos article about Tidal on Sonos. They support up to 16 bit/44.1kHz. No luck with better sample rates or bit depth

From their guide document: “ Stream CD quality audio (up to 16-bit, 44.1 kHz) ”

https://support.sonos.com/en-us/services/tidal?language=en_US

Which leads into the argument over how much resolution is sufficient…

Don't begin with “human ears can't hear beyond 20kHz”. That argument ignores the principle of superposition. Even though one cannot hear frequencies above 20kHz, if the signal amplitudes of such ultrasound frequencies are not at zero crossing at corresponding sample points in time of frequencies that we can hear, these ultrasound signals will either add to or subtract from the total signal amplitude - in other words, still contribute to the overall sound colour and detail that we perceive. But it is a game of diminishing returns. For 24 bit (and 16bit), beyond 44.1kHz the improvement decreases non-linearly. At 48 kHz you should still hear an improvement. At 96 kHz less so, and at 192 kHz, my guess is that one will be hard-pressed or need exquisite sound equipment to hear a clear improvement. So, perhaps, I should settle for 16bit/44.1kHz and downgrade my Tidal HiFi Plus to HiFi. Or buy a network streamer that does pass through 24bit 48kHz to my DAC.

Seems like Sonos, which has never sold itself as a ‘audiophile’ company, may not be the right choice for you.