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Sound quality differences between NAS units
20-08-2016, 12:13
Post: #21
RE: Sound quality differences between NAS units
(20-08-2016 07:13)simoncn Wrote:  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.

If this is the case, then the fault must lie in the renderer or in the subsequent amplifier or loudspeakers. Now the renderer is a small computational device which must contain its own clock that drives its switching circuitry, and I find it hard to see how controlling this "noise" could be possible, but that noise from the Ethernet or wireless could get through. Digital audio is based on mathematical theory which shows us that we should be able to reconstruct a bandwidth limited digitised signal correctly, i.e. for any given digital stream there is one correct analogue output.

So, I think that winxi is right and these are differences in human perceptions. If I'm wrong, then either much "Hi-Fi" equipment is badly implemented, and that's the problem, but because noone measures or tests it we don't know this. Or there are effects that we can't measure or explain, which makes designing the equipment hard, and also means that the manufacturers of our audio equipment have no useful method of ensuring sound quality control, if they can't take a sample device and perform objective tests on it to check that it meets its sound quality specification.

But I know we'll never agree about this, so I should be happy that I can enjoy listening to streamed music through a basic Sony Blu-Ray player, and an equally basic Yamaha amplifier with built-in DAC.
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20-08-2016, 15:09
Post: #22
RE: Sound quality differences between NAS units
I will sign off from this debate with a final update. As implied earlier, I came to this with no axe to grind to say for example that my new higher-spec NAS sounds better, so I reject suggestions of placebo effect. I happened to observe differences, then sought to ascertain what they were attributable to. I've just done some careful listening against 3 Minimserver sources: a Win7 PC, my Synology DS and the MyBook. The observations are completely reproducible across material: in my home (it may be different elsewhere), the Synology has controlled bass-line but slightly shut-in vocals. The MyBook has better vocals but once you listen past that the bass-line is actually quite muddy and boomy. The PC has all the strengths and none of the weaknesses of the other two.

Yours in music everyone.
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21-08-2016, 12:17
Post: #23
RE: Sound quality differences between NAS units
Did you do a blind test? That would be interesting. Put tracks from all three sources into a playlist and play it shuffled. Or better shuffle it once so you can check the played order later on if you were right in guessing the source.

Are there audiophile switches available similar to the LAN port that is integrated into the Melco NAS? The whole NAS is a lot of money. And the question is how big the sonic advantage will be for me personally.
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21-08-2016, 19:11 (This post was last modified: 21-08-2016 19:31 by winxi.)
Post: #24
RE: Sound quality differences between NAS units
(20-08-2016 12:01)simoncn Wrote:  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.

My point here is that I'm sure that there is no causal link between sound quality and a different NAS and that's why I say that I could only be convinced by a lab test. But of course it's not your job (or the job of any other customer who is obeserving sound quality improvement) to provide such a test or a prove. But I would request such a test before buying from a manufacturer or vendor who claims that his NAS improves sound quality. Do they provide such tests? If not I think they may have good reason to do so.
I would not request a lab test for products which obviously affect sound quality like renderers, amplifiers and speakers. There I rely on data sheets and also personal listening tests.

Quote: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.

The signal passes through various stages in the renderer before it comes to the DAC. The network interface demodulates the received signal and converts it to 0s and 1s which are buffered in a volatile memory. An internal logic (which is driven by its own clock, btw) fetches the buffered data and applies it serially to the DAC. All these stages contain various active digital comparators which are designed to produce a stable output signal. Also, a good DAC is designed such that its ouput signal does not depend on the input signal level, as long as the input signal level is in well defined limits.
However, since the DAC is the interface between the digital and the analog domain, it has some inherent sources of error and noise and its performance is determined by its design. A great majority of people who have some experience in electronics engineering will tell you that the DAC largely affects sound quality and that, on the other hand, it is extremely unlikely that noise generated in the NAS makes it to the DAC to such an extent that it noticeably affects sound quality.
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21-08-2016, 22:49
Post: #25
RE: Sound quality differences between NAS units
I have tried different NAS drives including different Melco models and have found Melco to be the best sounding and their more expensive model to sound better than the entry level.

I have swapped drives on visitors without telling them what was being tested and they have consistently found Melco better.

So I would dispute your statement there is no causal link to sound quality and different NAS drives.

Have you tried this yourself?

Peter
________________________________________________________
Linn Klimax DSM Katalyst & Solos, Wilson Benesch ACT C60s & Torus
Linn Klimax Renew DS/1, Klimax Twin & Wilson Benesch P1.0
Linn Klimax Renew DSM, Chord Mezzo 75, ProAc 1SCs
QNAP 559 ProII, Melco N1ZH, MinimServer, Lumin & Kazoo
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22-08-2016, 09:38
Post: #26
RE: Sound quality differences between NAS units
(21-08-2016 22:49)Peter@57m Wrote:  I have tried different NAS drives including different Melco models and have found Melco to be the best sounding and their more expensive model to sound better than the entry level.

I have swapped drives on visitors without telling them what was being tested and they have consistently found Melco better.

So I would dispute your statement there is no causal link to sound quality and different NAS drives.

Can you be sure that you didn't (unconsciously) influence your guests?
Have you already tried a blind test, were another person being in another room plays a track from a highend NAS or a regular NAS and you guess which NAS is used? To get a significant result, this experiment should be repeated at least 20 times for the same track. I'd be interested in the results of such a test.
Did somebody other do such a blind test?

Quote:Have you tried this yourself?

I've tried two different NAS and also streamed from a PC and I observed no difference in sound quality. But I had not the chance to try a highend NAS yet.
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22-08-2016, 14:18 (This post was last modified: 22-08-2016 14:21 by lyapounov.)
Post: #27
RE: Sound quality differences between NAS units
http://docwiki.cisco.com/wiki/Quality_of...Networking

For me, the idea that "Protocol is based on TCP means that it is bitperfect at the end" is OK in an asynchroneous world, but how does it fit into streaming ?

Simon, you are a top level engineer : you know that TCP compatibility with streaming goes through buffer management. Youtube streaming is based on TCP. Fine. But how do we care about latency when watching a movie on youtube ? We don't. Because there not in the video world an equivalent of our top level amplifiers and loudspeakers (me : Karan and Tango).

Many people here have a hifi system which is like a Pleyel or a Bosendorfer : any error by the pianist is hyper amplified. There is no equivalent in the video world. So, OK bit perfect, but latency, jitter, etc... Maybe at the level of a micro second. Could that make a difference ? Obviously yes. I can't see any other reason.

Yes I can see one : psychology. My son is a top sound engineer, graduated from Paris Department of sound engineers in the national conservatory (http://www.conservatoiredeparis.fr/en/le...ervices/). And yes, he experienced professor changing a parameter, and everyone heard a difference. Till everyone realized that the changed parameter had no impact on the sound produced. Bitwise perfect, exactly the same. But again, one should not put too much on psychology.

What we should not forget is that the mixt of digital and analog is very recent in music (and elsewhere), and that there is still a lot to discover.

Fortunatly !
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22-08-2016, 14:30
Post: #28
RE: Sound quality differences between NAS units
(22-08-2016 09:38)winxi Wrote:  Can you be sure that you didn't (unconsciously) influence your guests?
Have you already tried a blind test, were another person being in another room plays a track from a highend NAS or a regular NAS and you guess which NAS is used? To get a significant result, this experiment should be repeated at least 20 times for the same track. I'd be interested in the results of such a test.
Did somebody other do such a blind test?

Quote:Have you tried this yourself?

I've tried two different NAS and also streamed from a PC and I observed no difference in sound quality. But I had not the chance to try a highend NAS yet.

The difference was pronounced so did not do 20 tests.

Please post back when you've tried a Melco type NAS as we all know the theory why there shouldn't be a difference.

Peter
________________________________________________________
Linn Klimax DSM Katalyst & Solos, Wilson Benesch ACT C60s & Torus
Linn Klimax Renew DS/1, Klimax Twin & Wilson Benesch P1.0
Linn Klimax Renew DSM, Chord Mezzo 75, ProAc 1SCs
QNAP 559 ProII, Melco N1ZH, MinimServer, Lumin & Kazoo
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22-08-2016, 14:57
Post: #29
RE: Sound quality differences between NAS units
(22-08-2016 14:30)Peter@57m Wrote:  The difference was pronounced so did not do 20 tests.

Please post back when you've tried a Melco type NAS as we all know the theory why there shouldn't be a difference.

As I've stated above, I would still be sceptic even if heard a difference myself. I would then start a blind test to be sure that it's not my imagination.
It's a pity that you are not willing to do such a test, the results may have surprised you.

Has another user tried a blind test for a Melco NAS vs. a regular NAS?
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28-08-2016, 18:50
Post: #30
RE: Sound quality differences between NAS units
As other posters have indicated I suspect the differences heard are due to variations in the level of noise/interference transmitted with the ethernet music packets. When I bought a stand-alone renderer (the Sonore Rendu) I was told by the designer that it had built-in isolation, however because it was inexpensive to do I added external optical isolation in the last ethernet link to my DAC and this made a small but audible improvement in sound quality. I found this surprising as I have a wireless bridge between my NAS, computer etc and the hifi equipment which I thought would prevent any related noise/interference reaching the renderer and DAC. I can only assume that power supplies etc local to the hifi equipment was introducing noise/interference. The mains for the hifi is a separate dedicated spur from the rest of the household mains (including computers, NAS etc.), and I use linear power supplies for the hifi kit.

System: ALAC iTunes library on Synology DS412+ (running MinimServer) > Airport Extreme bridge > Optical isolation > dCS Network Bridge (controlled by Galaxy Tab S2 tablet running BubbleUPnP&Mosaic) > PS Audio DirectStream DAC > Primare A60 > Harbeth SHL5plus 40th Anniversary model
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