Has this been established to be audible in a controlled blind listening test? I have’t seen any reported anywhere.

And if you are concerned about sound quality in the abstract, there is the option of using the fixed outputs of the Port, or to go even further, an external DAC.

To avoid a religious war, let me rephrase: 

Has Sonos updated - or announced an update - to the variable output functionality?

My question was not directed just to you - there has been so much said even on this site on this “issue”, but as far as I know, there is no actual objective listening test that has been able to pick this out. 

Hence what was intended to be an open question to others here as well, out of genuine curiosity. 

When I tested early on, the soft-knee limiting was very obvious with Variable Volume when running sine wave test signals at, or near to, full scale. Significant odd-harmonic distortion, clearly audible and displaying the usual patterns in a spectral analysis.

IIRC the output limiting ceased to be apparent when the volume setting was below about 85%. This was with input samples peaking at full scale.

I have no idea whether Sonos have since issued an update making the limiting less aggressive. They tend not to mention such things.

It’s worth pointing out that any digital device with an S/PDIF output that’s capable of increasing the samples (by volume or EQ) will typically have a limiter of some kind, so as to protect the S/PDIF from hard clipping. With real music, the ‘soft clipping’ which might occur occasionally at high volume levels is far preferable to hard clipping.

Clearly audible and gross enough to rule out the need for any listening blind test?

Also, this issue does not arise with the analog outputs, either in variable or fixed modes?

Good heavens, yes. But we are talking about an artificial test signal, of a sine wave at full scale.

There’s no need for such level shaping with the analog outs. The digital signal can go straight to the DAC (an AKM AK4490EQ, which is well regarded) for conversion, instead of having to be squeezed out the fixed width S/PDIF. 

So, this issue then is ONLY when digital output is being used to feed an external standalone DAC or one in an active speaker or DAC equipped amp, and with the Port in variable mode - but audibly so only when the volume levels on the Port are more than 85%. That is what I gather from the preceding posts if I have understood them correctly.

But why then do digital outputs in fixed mode, which should be the equivalent of variable mode at 100%, not have this issue?

In Fixed mode the data is taken straight through from the decoder, with no risk of volume or EQ adjustment pushing samples over full scale. 

Ok - and on both my Connects I don’t use the digital outputs, but the problem needing to be fixed for variable digital outputs must have been there all the same. So if it is only the Port that has this issue, why did Sonos adopt a different solution for the Port, one that causes the issue? 

One also hopes that this discussion gives enough insights into this issue to the OP that allows him to stay away from Bluesound that by all accounts may cause many more real problems.

Kumar, genuinely would be very interested to know what problem you have experienced with Bluesound.

I haven’t; I don’t believe in spending more money than on Sonos in pursuit of more bits and bytes for my music play, which why I said - by all accounts.

There are many reports as to the clunkiness of the Bluesound app and instability of wireless music play that I have read both here and on some other discussion fora. For no objectively established gains in audible sound quality.

The soft-knee limiter is present on the Connect too. If you recall, it turned out that it was being misapplied in Fixed mode, as well as in Variable. That bug was subsequently corrected.

As for the limiter itself, presumably it’s a different DSP chip and new code on the Port. Quite why the algorithm apparently affects the sound more than in the Connect is not known.

Ahh yes; if I remember right, a member from Australia did a lot of research into that.

Recently, a Sonos moderator posted this in connection with the Port:

When using digital output, line out levels only affects how you control volume. For best signal-to-noise ratio, Fixed should be used, but volume can only be controlled at the amplifier. If you have a “works with Sonos” amplifier, Passthrough should be used, and volume can be controlled in app or at amplifier. Variable allows volume control at app or amplifier but they are not linked as with Passthrough - with low volume in app and high volume at amplifier, you’ll get more background hiss. Audiophiles would never do this due to the SNR, but you’d still hear music.

What is this passthrough mode - is it an update - and what effect does it have on the thread topic? And why will it work only with a “works with Sonos” amplifier and not any other amp?

In Passthrough mode the Sonos output is fixed, and the Sonos app directly controls volume in a downstream "works with Sonos" amp or receiver, ii.e. one that's able to accept network commands from the controller. 

Ahh ok...a nice best of both worlds solution then which also solves the thread title problem. Has that always been a feature of the Port since the beginning? And are such amps proliferating among the mainstream brands like Sony now?

I have a suspicion the Passthrough facility pre-existed Port, probably works on Connect and maybe even earlier. As for the breadth of “works with Sonos” support I haven’t a clue. Onkyo is the name that most readily springs to mind.

But how does one choose it, assuming the amp is compliant? Or is this an S2 thing?

It’s an extra option for the Line-Out Level. If it’s not there in S1 it must be an S2 thing. 

It is there in S1; I am pretty sure I didn't see it being there the last time I set this function for my Connect years ago.

But this is where it gets confusing - there is a remark in the app that pass through is only if you control volume using an external amp and third party control system. Presumably this is now also for amps that “ work with Sonos” where the Sonos app can replace the third party control system...but then for all other amps would one not just use Fixed?

I think the wording could be sharpened up. It really means to only use passthrough if you control volume using an external amp with a third party control system (e.g. via Sonos). 

What basically happens is that the player outputs at Fixed 100%, and the amp/recvr -- which has previously registered somehow -- takes commands from the Sonos controller. Whether it’s done locally or via the cloud I’m unsure. 

Try this for info: 

The video describes how to set up things using the Connect in variable mode with the amp set to a predetermined volume level. Even though the pass through option is seen. I wonder why…

But based on what you are saying, if the pass through was selected here, the Sonos app would move the volume levels on the shown amp up and down via the slider in the app. 

I also have this question.  And not sure if I have understood the potential issues fully.

I want to use the digital out with an external DAC which has a manual volume control - remember those!?

If I understand everything here correctly, using it this way will NOT have any significant sonic degradation.  Would  that be fair to say?

Further, if I were to use the variable digital output, it is considered by most that I will suffer some loss in fidelity.  I will be using a high end DAC/AMP/Speakers.

What HiFi slammed the Port a year ago, but I have heard nothing widely reported elsewhere.  As often the case with What HiFi, they focused on the bad analogue output and then glossed over the digital output.

As the OP suggests, I would have expected this could be fixed with a firmware update.  

Ideally would use the variable digital output because while I can accept old school, doing volume from your seat is preferable.

Why not go for the ideal and not let your comfort be dictated by subjective opinions of others, almost none of which are supported by a controlled blind listening test? 

This business of bad analogue output in a What HiFi review is as much drivel as most of what they put out. So even the variable analogue output is just fine.

Your only problem with doing this though is that it will make your “high end” DAC redundant and save you footprint, cable clutter and electricity. Only you can decide if you can live with that. If you cannot, use the variable digital output via the DAC.

Well I’ll give it a go.  I’ve got the ports anyway.  

DACs are not all made equal though.  

And I’ll have monitor speakers with XLR so the port isn’t ideal.

Digital to Digital shouldn’t be that hard to get right.