Skip to main content
Peter Mc
Peter Mc
August 23, 2016
Question

Connect no longer bit-perfect?

  • August 23, 2016
  • 450 replies
  • 29770 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.
      This topic has been closed for further comments. You can use the search bar to find a similar topic, or create a new one by clicking Create Topic at the top of the page.

      450 replies

      Show previous replies
      Kumar
      March 7, 2017
      There is at least a breakdown in communication between Sonos and some of their dealers. .
      Not necessarily; not if - as you also say may be the case - Sonos did not specify the Connects as bit perfect, and if they did not also say this in any way to their dealers in any communication. Your dealer may have a better handle on where he got the bit perfect thing from and it may not be from Sonos.
      Peter Mc
      Peter McAuthor
      March 7, 2017
      As far as I know, the bit-perfect reputation of the Connect relies on a single test of its predecessor, the ZP80, found here. That test was published in Sep/Oct 2006.

      It would seem the Connect's reputation as a bit-perfect transport is no longer deserved.

      My preliminary tests indicate that the analog output of the Connect likely has the same brickwall limiter applied, and by extension, this probably applies to every bit of Sonos gear uniformly. Ryan from Sonos can chip in if this is not the case.
      "The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett
      Kumar
      March 7, 2017
      As far as I know, the bit-perfect reputation of the Connect relies on a single test of it's predecessor,
      The Atkinson review in Stereophile - is that the only place where this was stated and then relied on in word of mouth?

      By the way, I had picked up a very interesting "tell" in that review in this statement of Atkinson:
      "It's just a shame, I guess, that these groundbreaking audio products didn't come from an established high-end audio company."
      ratty
      ratty
      March 7, 2017
      As far as I know, the bit-perfect reputation of the Connect relies on a single test of it's predecessor,
      The Atkinson review in Stereophile - is that the only place where this was stated and then relied on in word of mouth?
      The tests here provide corroborative evidence. The S/PDIF lowest byte would not be zeroes if the samples had been adulterated.
      Majik
      Majik
      March 7, 2017
      Arguably, if there is any misselling involved it was from the dealer. However, the dealer was operating on what was, at the time, correct information so I don't think they missold.

      As has already been stated, the information on the Connect being bit-perfect doesn't seem to come from Sonos. So no misselling there either.

      However, what I think is a bit disappointing is there was an implicit view in the industry that the Connect was a bit-perfect transport and, whilst they didn't specifically make this claim themselves, Sonos were aware of it and did nothing to correct that view when they made the change.

      This all makes me think this was a misstep rather than a deliberate strategy and I'm hopeful that, now it has come to light, that Sonos will be doing something to correct the issue.

      I'm normally the first person to point out that software developments are not as straightforward as many people claim, but in this case, reverting to a bit-perfect output should be an easy thing to do, as the code is already there and has been for most of the last decade.

      Implementing a user-selection may take a little extra effort and testing if they want to retain the ability of Connect's to support volume normalisation under user-control.

      Cheers,

      Keith
      Peter Mc
      Peter McAuthor
      March 7, 2017
      The tests here provide corroborative evidence. The lowest byte would not be zeroes if the samples had been adulterated.
      Can you explain a bit more what you mean here Ratty? Corroborative evidence of what? What is potentially doing the adulteration? Sorry but I'm having trouble cluing in to what you mean - perhaps the G&T with dinner 🙂
      "The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett
      ratty
      ratty
      March 7, 2017
      I have a sneaking suspicion that this may have crept in around the time of Trueplay.

      In the case of PLAY:1 the effect of Trueplay's EQ could, when added to the existing EQ to make it sound 'big', on rare occasions result in bass clipping upstream of the volume control. (This was often dismissed as 'hardware fault'. It wasn't: I witnessed this on multiple PLAY:1s requiring the same, possibly pathological, room compensation.)

      A quick solution may well have been to implement a soft knee limiter. Certainly something has largely resolved PLAY:1s earlier difficulties. If true, it's a tragic irony that this was carried over into CONNECT, when the unit doesn't even support Trueplay.
        ratty
        ratty
        March 7, 2017
        The tests here provide corroborative evidence. The lowest byte would not be zeroes if the samples had been adulterated.
        Can you explain a bit more what you mean here Ratty? Corroborative evidence of what? What is potentially doing the adulteration? Sorry but I'm having trouble cluing in to what you mean - perhaps the G&T with dinner :)
        My point was simply that in those 10-year-old ZP80 tests the samples must have passed through unsullied, otherwise the lowest byte of the 24-bit S/PDIF would have been populated -- as it indeed was when the tester dropped the volume below 100%.
          Peter Mc
          Peter McAuthor
          March 7, 2017
          My point was simply that in those 10-year-old ZP80 tests the samples must have passed through unsullied, otherwise the lowest byte of the 24-bit S/PDIF would have been populated -- as it indeed was when the tester dropped the volume below 100%.
          OK, I get it now. Took me a while 😛
          "The presence of those seeking the truth is infinitely to be preferred to those who think they've found it" - Terry Pratchett
          gizze
          Enthusiast II
          March 9, 2017
          Not sure what models were specifically affected. Sonos would have to answer that.

          As to your trying to get this thread back on topic; I have been chuckling for the past couple of days at the outrage directed at me for "derailing" this thread. Outrage which came from a poster who ignored everything about the Connect being bit-perfect and instead shot us off the rails into Hires/MQA land!

          I said I didn't understand why the same few people come into every thread where people are discussing getting more from their system and call those people fools.

          I said that we could do with Sonos offering an "audiophile" product (Note audiophile for their marketing reasons) that offered Bit Perfect output and with MQA now coming to Tidal and talk of Spotify getting on board it would be a nice option that I am sure they would do incredibly well with.


          The only reason I came back on was because I searched for "Sonos Connect Modification" on google to look for something, and what was the first hit?

          You, 4 years ago calling any Sonos Connect mods snake oil. :D

          https://en.community.sonos.com/advanced-setups-229000/zp90connect-modification-comparison-27830/index1.html#post177195

          At least you're consistent.

          The whole gang is there too, Kumar et al.



          I agree with much of what you say, but there is also loads I don't agree on, but hey ho, such is life, it would be boring if we all thought the same.
            Show more replies
            Terms & ConditionsAccessibility statement