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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K

Kumar

Not any more. That room has a pair of PLAY:5 Gen2 plus a SUB. Trueplay tuned of course, smoothing out what would otherwise be a very lumpy room response starting with a major peak at 30Hz.
.

Oh, ok.
Would I be right in thinking that this sounds better to you than the bit perfect ZP80 into the AVI actives - even if the Sonos Sub was to be removed for an apples to apples comparison?

ratty

Would I be right in thinking that this sounds better to you than the bit perfect ZP80 into the AVI actives - even if the Sonos Sub was to be removed for an apples to apples comparison?

I now longer have the AVIs (which had a subwoofer too) -- so can't make a side-by-side comparison -- and they were early ADM9s in any case, so several generations back. My recollection was that the P:5s sounded more natural in the midrange (piano, voice), and of course with Trueplay the bass response at the sweet spot is much smoother.

K

Kumar

Seems to me from conversation here that there are the following five categories of people for whom Connect has/had some relevance:
1. Those that don't care about bit perfect, and have moved on to play units/Sub for even serious listening
2. Those that don't care about bit perfect, but use the Connect for its other features on the input side
3. Those that don't care about bit perfect, realising that all that the lack of it does is the fuelling of Expectation Bias driven perceptions of sound quality degradation
4. Those with high end legacy tech kit who won't touch even a bit perfect Connect because they don't believe that Sonos kit is worthy of a place on their component racks, because it is cheap in price and looks
5. Those that are affected by this bit perfect thing.
The odds that Sonos will act to address the needs of just the last category don't seem very good, also because the change would have been made for valid reasons that may then have to be addressed in a different way.

A

amun

....also because the change would have been made for valid reasons that may then have to be addressed in a different way.

You have no idea why the change was made - this is pure speculation.

The thing that I find most ironic is that for years the fanboys have been yelling 'bit-perfect, bit perfect' (because it says so in a very old test of a ZP80) and shouting down people who claim that other dacs and conversions sound better. We now find out that, since 2011, people who care about sound quality could have been right all along...

jgatie

You have no idea why the change was made - this is pure speculation.

The thing that I find most ironic is that for years the fanboys have been yelling 'bit-perfect, bit perfect' (because it says so in a very old test of a ZP80) and shouting down people who claim that other dacs and conversions sound better. We now find out that, since 2011, people who care about sound quality could have been right all along...

You won't find anybody who "yelled" bit-perfect before defending Sonos on this issue. At least I won't be. Sonos, for whatever reason, screwed with what should be bit-perfect output, and that is not good. So can it with the "fanboy" nonsense, it's a weak and cowardly tactic to attack the messenger and not the message. Either you can defeat the argument, or you can't.

L

LeighB

Lyricist III

You won't find anybody who "yelled" bit-perfect before defending Sonos on this issue. At least I won't be. Sonos, for whatever reason, screwed with what should be bit-perfect output, and that is not good. So can it with the "fanboy" nonsense, it's a weak and cowardly tactic to attack the messenger and not the message. Either you can defeat the argument, or you can't.

Agreed, this is about being able to stream the original bits to my DAC. If they are transcoded before they get there, there is not much point, why bother to have two digital outputs, they could save the money and not confuse people.

A

amun

[quote=jgatieSo can it with the "fanboy" nonsense, it's a weak and cowardly tactic to attack the messenger and not the message.[/quote]

You do realise that you're not a mod, don't you?

jgatie

You do realise that you're not a mod, don't you?

So I'm not allowed to call you out on weak and cowardly arguments unless I'm a mod? Who makes these rules?

L

LeighB

Lyricist III

You do realise that you're not a mod, don't you?

So I'm not allowed to call you out on weak and cowardly arguments unless I'm a mod? Who makes these rules?

How about both of you move on so we can get back to the discussion.

K

Kumar

....also because the change would have been made for valid reasons that may then have to be addressed in a different way.

You have no idea why the change was made - this is pure speculation.

The thing that I find most ironic is that for years the fanboys have been yelling 'bit-perfect, bit perfect' (because it says so in a very old test of a ZP80) and shouting down people who claim that other dacs and conversions sound better. We now find out that, since 2011, people who care about sound quality could have been right all along...

Of course I do not know why the change was made, but I'd say it is more reasonable to assume that Sonos made the change for valid reasons, than to say that they did not have a valid reason to do so...or are you challenging this statement as well?:-)

And those that were saying "bit perfect" were doing so - AFAIK - to explain that the Connect was equivalent to any digital transport out there, and was therefore just as capable as any CD player for example, to supply bits to any external DAC for conversion. That - as I am convinced - the Connect DAC is audibly just as good as any other DAC was not being claimed by those saying "bit perfect".
I also take your last statement to imply that "people who care about sound quality could have been right all along", could also have been wrong; and if so, I agree with that statement:)

I agree with LeighB that if the digital output isn't bit perfect anymore, why have it there at all - except perhaps that it would mean a cost to even change the hardware to remove it such that may not be worth the corresponding saving.

Thunderous silence continues from Sonos on this thread...

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