Connect no longer bit-perfect?

The bass punch I'm referring to is not minor. You are right that the digital and analog cases require different volume settings. I have tried subjective matching as I switch. Sometimes I get it too loud, sometimes too soft. The conclusion is always the same - analog output sounds punchier. So, I think this is a case where the difference is sufficiently large that small volume mismatches will not confound the comparison. But as a scientist I remained somewhat skeptical.

If you play the same track ripped via itunes, and streamed from Apple, do you notice a difference?

To the last easy part - yes I notice the difference, I think Apple Music is streamed to deliver a lower sound level in general.. This obviously isn't a problem when I am playing any one source - it just takes a one time setting of the volume control on the controller for the desired sound level to be consistently delivered - except for some CDs that are recorded hot. Now I haven't had the time to see if the same music, played via Apple also ends up louder to the same degree compared to other music from Apple, I need to get around to do this some day.

As to the first part - subjective matching doesn't work if test results are to be valid. A 0.2dB difference in sound level has been proved to yield punchier sounding results, so I am not sure this can be dismissed by saying that the punchiness is so large that it could not have been caused by sound level differences; seems like a cart before the horse thing to me, a non scientist. But more importantly, why are you stuck as you put it? Just use analog. And if you want to use digital for reasons of other conveniences, leave the volume control on the amp at a higher setting. No?

On the track volume issue, if you rip to wav format the songs will be louder because there is no volume normalization tag. When itunes rips to a format that allows metadata (I use Apple lossless - ALAC), itunes computes and stores the volume normalization in the track metadata and Sonos then responds to this. Turning off Sound Check in itunes only affects playback within itunes (the tags are always added to formats that allow them.) I wish Sonos had a similar switch! By the way, volume normalization almost always reduces the volume of a track. It couldn't raise the volume because most tracks have peaks close to the maximum, and a volume increase would lead to clipping.

Back to the listening topic. There is no way to use volume to make up for the bass difference I am hearing - I have tried. The attack of the bass cutting through the other instruments has a very specific frequency signature. Increasing the volume alters every frequency. I would like to use the digital input of the Peachtree to free up the only analog input for other purposes. Unfortunately I hear the sound as bent even though I don't want to.

This paragraph may be considered "too much information". My goal has been to record the analog and digital signals so I can demonstrate the difference. Recording the digital output is easy, and it can be lined up perfectly in my audio software with the original wav version. This is where I discovered the 1dB compression. Recording the analog output is also easy, but it requires A2D conversion. I use a fairly high quality audio interface with reputable A2D converters. I also sync the interface SPDIF clock to the Connect. However, there is a problem lining up the waveform with the original - the timing drifts. I didn't expect this, and I don't understand why it happens. It makes it much harder to compare waveforms objectively. I did try to reproduce my original plots and they had a lot of scatter, but I did see some evidence that the analog output also performs compression. When I get some time I will return to these issues.

When itunes rips to a format that allows metadata (I use Apple lossless - ALAC), itunes computes and stores the volume normalization in the track metadata and Sonos then responds to this.

This is where I discovered the 1dB compression.

My CD rips are all in ALAC, while iTunes purchases are in AAC, so the volume normalisation information is available to Sonos, I should think. I just don't think that Sonos is using this effectively in playback.

I hear what you are saying about bass frequency effects that you are seeing and how volume increases don't/won't work selectively. And if using Music Eq is what is needed to restore things - even if that is possible here - then the Connect has stopped being the straight wire, I agree.

A question though: do you think that the measured compression of 1dB that you are seeing will cause this selective frequency effect? Or is there something more that is happening here?

I also notice that Sonos still hasn't replied to my normalisation question posed elsewhere for a second time.

And is noticeably silent here. Either their engineers don't know what is happening or they are choosing silence.

I also notice that Sonos still hasn't replied to my normalisation question posed elsewhere for a second time.

And is noticeably silent here. Either their engineers don't know what is happening or they are choosing silence.

I get the feeling that they're choosing silence. I still don't know why they would remove the ability of a component with a digital output to provide the bit-perfect digital output that it used to be capable of, and was well lauded for. They should at least provide some kind of setting to allow bit-perfect digital output again, whether it's tied to the already existing "Fixed Volume" setting or a separate setting that can be enabled only when Fixed Volume is enabled.

Do I personally care about it? Not anymore... my Connect now serves as an input-only. But obviously there are others that do.

Now that's an interesting thought. I didn't realise that you have both ALAC and AAC versions of the same track on a local hard-drive. I thought you were comparing streaming to a local rip. If you have access to both versions locally, and they have different volumes, you can use mp3tag to look at the volume normalization tags. And you could also calculate the peak values and RMS. Better still, I could do that if you can find a song that exhibits this problem that I also have the CD for. Then I could purchase the itunes version and make a comparison. Best chance is a Miles Davis song - I have a lot of his stuff. I also have a fair bit of ECM jazz from some years ago.

I think it unlikely that the 1dB compression is causing this issue, but I can't rule it out either because I can't turn it off! However, look-ahead compression could theoretically act to reduce bass transients (which often have the most energy and hence largest peaks). My suspicion all along has been that the Connect DAC is better than the Peachtree, although most audiophiles would laugh at this statement. A slight confession here: I have recently bought an external DAC that comes highly recommended and is not too expensive (Schiit Bifrost). The idea was to settle the DAC issue once and for all (and this is all good fun as a retirement hobby). However, because the Connect doesn't pass the signal through unchanged, it makes this comparison much more difficult.

Cheers, Peter.

Now that's an interesting thought. I didn't realise that you have both ALAC and AAC versions of the same track on a local hard-drive. I thought you were comparing streaming to a local rip.

My suspicion all along has been that the Connect DAC is better than the Peachtree, although most audiophiles would laugh at this statement..

Peter, I am sorry if I did not explain correctly - I don't have the same track in both, I have bought AAC versions only of music I did not have in my now static CD collection. Now if you are referring to Miles, I have a lot of his music in both formats, but not the same in both. Something Else for instance is a ripped ALAC CD, while the other classic 50's album of his, Round Midnight, is a AAC iTunes purchase, and when both play from my NAS, there is no noticeable sound difference. But I recently bought a new HighNote album of Ron Carter and Houston Person, Chemistry, in AAC and that plays very noticeably louder. As do all other iTunes purchases of the same duo, a favourite. And as do other HighNote albums bought on iTunes - Person, as well as from other artistes on that label. Given this, if there is any purpose to be served in you looking at any of these files, let me know, I will be happy to provide them.

As to the Connect DAC - before I boxed my legacy audiophile kit after buying Sonos, I did a lot of testing, admittedly imperfect, but good enough for my decision making. I compared the sound quality from analog output of the Connect with that from my SACD player, both into high end amplification and Kind of Blue was one of the test albums. I found no difference in quality and decided that I did not need the SACD player. Nor have I heard of anyone that has been able to pick out the Connect DAC in a well constructed level matched listening test against any other DAC - not even ones with five digit price tags. I therefore believe that the Connect DAC is audibly straight enough. As are many others - indeed I strongly suspect that a modern DAC is no longer a factor, having become a reliable commodity at a low price point.

Ironically, going by your findings, it would appear that those that don't think so, and want to use the Connect into another fancier looking external DAC may be ill served by Sonos while doing this, with audibly poorer sound quality than they would obtain via the analog outputs on the Connect!

Do I personally care about it? Not anymore... my Connect now serves as an input-only. But obviously there are others that do.
I don't care about it either, for the same reason and in just one zone where I use it to drive the analog inputs of a legacy amp that is still working well.

But the inadequate way volume normalisation works just now affects all units and all zones, including those served by play units. That's the one I am looking for some response from Sonos.

When I read the thread over I found nothing definitive about why Sonos "degraded" the Connect. It can't have been for volume normalisation because that, as far as I can see, still doesn't work.

So why degrade the digital output at all?

And does this have any effect on sound quality where Connect is the first player in a group that is wirelessly broadcasting a digital stream to other players in the group? Is that stream not bit perfect any more? If so, this is a bigger problem than of being one only for such people that are using the Connect wired to the digital inputs of an external DAC? Based on my experience of the Connect used in that mode, I'd say that I haven't noticed any sound quality loss, but I don't have a reference baseline anymore, so I can't be certain!

I also notice that Sonos still hasn't replied to my normalisation question posed elsewhere for a second time.

And is noticeably silent here. Either their engineers don't know what is happening or they are choosing silence.

I just replied to that thread. We just hadn't read it yet.

When I read the thread over I found nothing definitive about why Sonos "degraded" the Connect. It can't have been for volume normalisation because that, as far as I can see, still doesn't work.

Normalization for tracks does work, but we'd be happy to help take a look with you to make sure it's working right with your system.

So why degrade the digital output at all?

We are talking about a minor change to the audio when applying normalization.

And does this have any effect on sound quality where Connect is the first player in a group that is wirelessly broadcasting a digital stream to other players in the group? Is that stream not bit perfect any more? If so, this is a bigger problem than of being one only for such people that are using the Connect wired to the digital inputs of an external DAC? Based on my experience of the Connect used in that mode, I'd say that I haven't noticed any sound quality loss, but I don't have a reference baseline anymore, so I can't be certain!

Short answer, no. When players are grouped together the audio that's sent across the system is the original digital file of the track, retrieved from the source by the group coordinator and then distributed untouched to the others. Each player uses its own DAC and settings on that original file once they receive it.