Question

Connect no longer bit-perfect?

Forum|Forum|10 years ago
August 23, 2016
450 replies
29769 views

It looks like the Connect is no longer bit-perfect. Here's my evidence: let's discuss this.

First, I constructed a wav file of pink noise with amplitude ramping up from zero to digital max and back to zero.
I play this through my Connect and record the SPDIF output from the coax output into my PC.
The recording uses a Scarlett 8i6 audio interface set to use the Connect as master clock.
I record into a DAW (Sonar) multiple times - all instances are identical.
However, this recorded signal is not quite the same as the original wav file - it can be up to -21dB different.
See https://www.dropbox.com/s/t8od479xo9hi5el/connect_diff.PNG?dl=1
Note the expanded scale on the difference (third) track.

It looks like the difference gets larger when the signal is larger. To confirm this, I import the
original and difference files into Matlab and plot the raw data (difference vs original). There is clearly audio compression
happening here. See https://www.dropbox.com/s/p1yq6wcqafvnhaj/diff_vs_orig.png?dl=1
The scale is such that digital maximum is 1.

There also appears to be a slight bias when the waveform is negative and the signal is below the
compression threshold. See an expanded version of the previous plot
https://www.dropbox.com/s/9001tl9mkle4wly/diff_vs_orig_zoom.png?dl=1

Happy to answer questions about the method and conclusions.

Cheers, Peter.

p.s. Volume is set to fixed - I haven't tried variable.
In a loopback test (8i6 out from DAW to 8i6 in, no Sonos gear involved), I get bit-perfect cancellation.

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Peter McAuthor

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

Normalization is ALWAYS applied, therefore the minor change (compression) is also ALWAYS applied. I can defeat normalization by either removing the tags or using wav files. I CANNOT defeat the compression. It applies to everything I play through a Connect, and presumably every other component of Sonos.

Surely any hi-fi gear that forcibly altered the signal in this way would be reviewed poorly and eventually fail in the hi-fi marketplace. The best audio gear tries to reproduce the signal without adding its own coloration. Surely the Connect should be capable of passing through the digital signal faithfully and unaltered.

Please consider adding a switch so we can choose to disable the coloration, or at least return to the old setting where fixed volume output bypassed it.

Cheers, Peter.

"The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett

K

Kumar

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.

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.

Ryan, very good, thank you. How do we proceed with seeing if things are ok with my system? It will be easy enough for me to set up a playlist with just two ripped tracks, one of which plays louder than the other. Do you need to know which tracks I will be using in advance?

Peter, to the second paragraph in the quote, this should mean that in grouped mode, your weakened bass problem ought to disappear when the Connect to digital input on Peachtree set up is in use and reappear when the Connect is not in grouped mode? Although Ryan confuses me by saying each player uses its own DAC. In your set up, the Connect obviously will not. Or does it mean that you will still see the bass issue via the Connect fed zone, but the other zones won't see it even if the Connect is the group coordinator? And in a later post you refer to this being a minor change - going by your description of how it affects bass quality, it is a MAJOR issue even if the compression may be minor?

Ryan S

Retired Sonos Staff

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.

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.

Ryan, very good, thank you. How do we proceed with seeing if things are ok with my system? It will be easy enough for me to set up a playlist with just two ripped tracks, one of which plays louder than the other. Do you need to know which tracks I will be using in advance?

I just opened up an incident for you with the support team to take a closer look into this. They'll want to see a couple tracks where you've noticed trouble like you described above and will likely want to remote in to take a look at the metadata of the tracks themselves. The reference number is: 160913-001584. I'll see if a technician can reach out to you directly, but feel free to give us a call on our support line with that number too.

Peter, to the second paragraph in the quote, this should mean that in grouped mode, your weakened bass problem ought to disappear when the Connect to digital input on Peachtree set up is in use and reappear when the Connect is not in grouped mode? Although Ryan confuses me by saying each player uses its own DAC. In your set up, the Connect obviously will not. Or does it mean that you will still see the bass issue via the Connect fed zone, but the other zones won't see it even if the Connect is the group coordinator? And in a later post you refer to this being a minor change - going by your description of how it affects bass quality, it is a MAJOR issue even if the compression may be minor?

My comment in regards to the DAC was if you were grouping the CONNECT with a PLAY:5 for example, the PLAY:5 would do it's own conversion. In short, when you group players they each get the same starting digital stream from the original source without any alteration done. Once the player gets it they will take it from there as if you'd played the audio right to the unit. tl;dr Grouping doesn't affect audio quality of a stream.

Mark good posts by pressing the like button, and select the best answer on questions you've asked to help others find solutions.

Peter McAuthor

Hey Ryan - Thanks for the clarification. Please note that I think it unlikely the Connect DSP is responsible for the bass issues I hear, but I can't rule it out because I can't turn the DSP off.

How do we make progress on this issue? Should I open a support ticket?

Cheers, Peter.

"The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett

Ryan S

Retired Sonos Staff

Hey Ryan - Thanks for the clarification. Please note that I think it unlikely the Connect DSP is responsible for the bass issues I hear, but I can't rule it out because I can't turn the DSP off.

How do we make progress on this issue? Should I open a support ticket?

Cheers, Peter.

We're looking into it on our end here right now. We may want to get a ticket started up for you as well, but I'll let you know on that.

Mark good posts by pressing the like button, and select the best answer on questions you've asked to help others find solutions.

Peter McAuthor

That's great news. Thanks Ryan.

"The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett

K

Kumar

I just opened up an incident for you with the support team to take a closer look into this. They'll want to see a couple tracks where you've noticed trouble like you described above and will likely want to remote in to take a look at the metadata of the tracks themselves.

Thank you, Robbie is in touch with me and I will post outcome details, once there is one.

J

JRausch

Lyricist III

It's been plenty long enough to fix this. First proven in July of last year. I have made up my mind to sell my Connect and get something else if I don't see this corrected (or at least an announcement) by the end of this month, January 2017. Along with it will go all recommendations of Sonos as a serious music system.

There are plenty of good solutions to play my music library and one of the lossless streaming services (I use Tidal) for serious listening. For the sources that Sonos is devoting all of their resources towards (Spotify, Amazon Alexa, etc.), I can play with my PlayBar in the great room as background music. Or on a Bluetooth speaker wherever.

Just guessing, but I think the Connect was just an afterthought anyway, likely sharing a subset of the software in the Connect Amp, which is why we have the output stream being mucked with. Sonos has not demonstrated they are serious about audiophile systems.

ratty

Just guessing, but I think the Connect was just an afterthought anyway,.

You are guessing. ZP80 (from which CONNECT is descended) was the second ever 'ZonePlayer' after the ZP100. Specifically designed to link to existing amplification, with or without an outboard DAC. It's been around since 2006. Hardly an afterthought.

J

JRausch

Lyricist III

Just guessing, but I think the Connect was just an afterthought anyway,.

You are guessing. ZP80 (from which CONNECT is descended) was the second ever 'ZonePlayer' after the ZP100. Specifically designed to link to existing amplification, with or without an outboard DAC. It's been around since 2006. Hardly an afterthought.

Okay, bad guess, but the issue remains.

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