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Sound quality differences between NAS units
19-08-2016, 22:42
Post: #11
RE: Sound quality differences between NAS units
(19-08-2016 18:55)beckphotonik Wrote:  I am sorry but I have to disagree. Listening tests have proven otherwise to me. As a retired electronics engineer I am at a loss to explain how or why but I shall stand by what my ears tell me. How the digital domain is handled DOES affect sound quality! I suspect that in the end we shall have to beg to differ on our stances.

I'm aware that this topic never results in a fruitful discussion and I think that's the reason why discussing this topic isn't even allowed at some forums. However, I wonder how an electronic engineer might consider a personal listening test a prove.

I think that somenone who claims something against common sense and all scientific reasoning has the obligation to provide a real prove or at least some kind of logical explanation. The same applies to those claiming that homeopathy is effective, pink unicorns exist or that the earth is flat.
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19-08-2016, 23:16
Post: #12
RE: Sound quality differences between NAS units
There was some discussion about possible scientific reasons for this on the Linn forum last year. See this post, this post and this post.

I have consistently heard sonic differences between music streamed from a Melco N1 and music streamed from other NAS devices, with all other components identical. I cannot "prove" this but I am as certain of this as I am about hearing sonic differences when listening to different renderers (which for some reason seems to be generally accepted without demanding scientific proof).

It is OK to disagree but this should always be done with respect for other people and their experiences. The line has not been crossed yet on this thread but I am mindful of some posts on the Linn forum that did cross this line.
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19-08-2016, 23:33
Post: #13
RE: Sound quality differences between NAS units
Simon >> I have consistently heard sonic differences between music streamed from a Melco N1 and music streamed from other NAS devices, with all other components identical. <<

Simon, as a point of information, were the units connected by Ethernet or Wifi?

Mike
Portland, Oregon, USA
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20-08-2016, 00:16
Post: #14
RE: Sound quality differences between NAS units
(19-08-2016 23:16)simoncn Wrote:  There was some discussion about possible scientific reasons for this on the Linn forum last year. See this post, this post and this post.
The argumentation that analogue noise from the NAS or other components makes it over the digital transmission channel into the renderer and in further consequence to the speakers and the ear seems not very convincing to me. It is even less convincing when it comes from an official of a company which wants to sell its products to an audiophile clientele along with a quite basic and abstract explanation about how the digital transmission works. If this argumentation was correct,
1) I'd consider this rather to be a problem of the renderer than of other components like the NAS or the used HDD
2) the problem would be solved by a single audiophile highend switch just in front of the renderer.

Quote:I have consistently heard sonic differences between music streamed from a Melco N1 and music streamed from other NAS devices, with all other components identical. I cannot "prove" this but I am as certain of this as I am about hearing sonic differences when listening to different renderers
I do not doubt that some people may perceive a difference in sound quality when using a different NAS. But how can you be sure that this difference is not caused by the human brain and in particular by the expectation that more expensive and higher quality equipment must sound better? How can you be sure that this is not a variant of the placebo effect?

Quote: (which for some reason seems to be generally accepted without demanding scientific proof).
I think the reason is that renderers typically have a DAC which undoubted affects the quality of sound.
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20-08-2016, 01:44 (This post was last modified: 20-08-2016 01:56 by lyapounov.)
Post: #15
RE: Sound quality differences between NAS units
(19-08-2016 10:01)DavidHB Wrote:  I can think of 3 candidates for consideration...

I was to write the same thing roughly, but DavidHB did it brillantly !

Though I have a question, and I think Simon has the answer : how is the content transferred ?

UPnP says it sits on top of TCP but only for the discovery and other stuff (like the former channel D in the old telecommunication times), but when it is about sending the content, it seems to be based on UDP using unicast protocol.

Simon : can you confirm ?

If so, then it explains a lot : TCP guaranty that the content is exact when received, while UDP does not. This is why TCP is not a real time protocol, because if the receiver is not happy, it asks the sender to resend the same content; incompatible with streaming. Therefor, it could be that the communication is more or less corrupted depending on how the extremities really cooperate, or the quality of the copper in between, or other external problems, like load on the network, interferences on the copper (people would be suprised how much electronic pollution there is on earth...) wifi transmission etc.

As an exemple : wifi quality degrades a lot when humidity is high. Reason being that the wifi frequency is an open one, the one of the microwave oven, which is the absorption frequency of the water molecule. I remember talking to the city of Amiens in France, 8 years ago. They had built a wifi network in the city which worked perfectly; except that they built it in winter. And when spring arrived, the tree leaves grew, and water in the leaves absorbed all the wifi signal power, and the network was poor quality. You can even check this at home, under very rainy days.

So degradation of the signal means more error correction, more interpolation, more CPU power, jitter, and eventually less accuracy in the data stream itself. Again, TCP manages, but not UDP. Therefor the concept of QoS in UPnP AV.

I am not an expert in electronic. But for sure, the better is your sound system, the more you will hear / feel such differences.

The only scientific experiment I would see would be to record the data which are transmitted, and check if they are exactly the same or not depending upon different factors such as time of the day, different servers, etc...

Just my two cents.
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20-08-2016, 07:13
Post: #16
RE: Sound quality differences between NAS units
(20-08-2016 01:44)lyapounov Wrote:  Though I have a question, and I think Simon has the answer : how is the content transferred ?

UPnP says it sits on top of TCP but only for the discovery and other stuff (like the former channel D in the old telecommunication times), but when it is about sending the content, it seems to be based on UDP using unicast protocol.

Simon : can you confirm ?

The audio data is transmitted using TCP and there is no doubt that in all cases the renderer has received an identical copy of the bits sent by the server. The discovery protocol uses a mixture of UDP and TCP.
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20-08-2016, 07:55 (This post was last modified: 20-08-2016 07:58 by simoncn.)
Post: #17
RE: Sound quality differences between NAS units
(20-08-2016 00:16)winxi Wrote:  The argumentation that analogue noise from the NAS or other components makes it over the digital transmission channel into the renderer and in further consequence to the speakers and the ear seems not very convincing to me. It is even less convincing when it comes from an official of a company which wants to sell its products to an audiophile clientele along with a quite basic and abstract explanation about how the digital transmission works. If this argumentation was correct,
1) I'd consider this rather to be a problem of the renderer than of other components like the NAS or the used HDD
2) the problem would be solved by a single audiophile highend switch just in front of the renderer.

I have tried many renderers and I have heard a sonic difference from the Melco with all the renderers I have tried. One of the points that DanielE made was that when noise is introduced into the transmission chain, it cannot just be removed but has to go somewhere. This suggests that all renderers are likely to be affected to some extent, although some might be affected more than others.

The Melco N1 can be used as an audiophile high-end switch just in front of the renderer. I have tried doing this with the audio streamed by another server such as a QNAP NAS and I have noticed a sonic improvement when the Melco is in the chain. This seems to provide some scientific/experimental support for DanielE's explanation.

Perhaps one day someone will design a renderer than can fiilter out electrical noise from the server with no audible impact. I wonder how much such a renderer would cost. It might be more cost-effective to use a server that doesn't introduce the noise in the first place.

Quote:I do not doubt that some people may perceive a difference in sound quality when using a different NAS. But how can you be sure that this difference is not caused by the human brain and in particular by the expectation that more expensive and higher quality equipment must sound better? How can you be sure that this is not a variant of the placebo effect?

Before I tried the Melco, my opinion was the same as yours. I borrowed a unit not expecting to hear any difference as I had never heard any difference between any other server hardware. The sonic difference was a complete surprise and has caused me to change my opinion. This is a scientific approach, where theories are developed and revised in the light of real-world observations.

Quote:I think the reason is that renderers typically have a DAC which undoubted affects the quality of sound.

The DAC is converting one electrical signal into another. If something else upstream makes a difference to the input electrical signal, it is surely at least possible that the output electrical signal could be affected.
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20-08-2016, 07:56
Post: #18
RE: Sound quality differences between NAS units
(19-08-2016 23:33)Mike48 Wrote:  Simon, as a point of information, were the units connected by Ethernet or Wifi?

In all cases, the server and renderer were connected by Ethernet.
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20-08-2016, 10:02
Post: #19
RE: Sound quality differences between NAS units
(20-08-2016 07:55)simoncn Wrote:  I have tried many renderers and I have heard a sonic difference from the Melco with all the renderers I have tried. One of the points that DanielE made was that when noise is introduced into the transmission chain, it cannot just be removed but has to go somewhere. This suggests that all renderers are likely to be affected to some extent, although some might be affected more than others.

The Melco N1 can be used as an audiophile high-end switch just in front of the renderer. I have tried doing this with the audio streamed by another server such as a QNAP NAS and I have noticed a sonic improvement when the Melco is in the chain. This seems to provide some scientific/experimental support for DanielE's explanation.

Perhaps one day someone will design a renderer than can fiilter out electrical noise from the server with no audible impact. I wonder how much such a renderer would cost. It might be more cost-effective to use a server that doesn't introduce the noise in the first place.

Just imagine a community forum discussing a high-end pc monitor. The users are typically willing to spend a lot of money to be able to view there photographs in high quality and store these photographs on a NAS.
Then a topic comes up: user A says that his images are much more vivid since he uses another NAS, the images of user B are sharper because o a new power supply for his NAS, user C observes a better contrast since he uses new cables in his home network, and so on.
Then a technician of the company selling the monitor comes in and tells the users this is because of noise generated in the NAS that makes it over the home newtwork into the monitor and 'the noise has to go somewhere'.
What would you think?

Quote:Before I tried the Melco, my opinion was the same as yours. I borrowed a unit not expecting to hear any difference as I had never heard any difference between any other server hardware. The sonic difference was a complete surprise and has caused me to change my opinion. This is a scientific approach, where theories are developed and revised in the light of real-world observations.

Sorry, individual observations do not convince me. I wouldn't even be convinced if I heard a subtle difference myself.
I'd be convincend by a peer-reviewed scientific study, where the analog output of a renderer is acquired and compared for different NAS using an oscilloscope with a high enough sample rate. But I highly doubt that such a paper, if it ever exists, will show a significant difference.

Quote:The DAC is converting one electrical signal into another. If something else upstream makes a difference to the input electrical signal, it is surely at least possible that the output electrical signal could be affected.
Do you mean affected by the DAC or affected 'by something else'?
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20-08-2016, 12:01
Post: #20
RE: Sound quality differences between NAS units
(20-08-2016 10:02)winxi Wrote:  Sorry, individual observations do not convince me. I wouldn't even be convinced if I heard a subtle difference myself.

In this case, how do you decide about buying equipment? If you are considering a possible change to your system and you audition a new component that you are considering purchasing and you hear an improvement, do you buy the component based on your audition or do you wait until you have found a review containing the results of an oscilloscope test that proves the new component has superior measurements to your current equipment?

If you always wait for the lab test before buying, your approach is consistent. If you would buy some other component (such as a renderer, amplifier or speakers) based only on an audition. I don't understand why you wouldn't do the same for a source component such as a server.

Quote:Do you mean affected by the DAC or affected 'by something else'?

I mean if the DAC receives a different input, it might produce a different output. Remember that the DAC is not receiving "ones and zeros" but an analog electrical signal that is encoded in such as way as to convey digital information.
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