Sound quality difference between direct Qobuz and Qobuz via Roon on Weiss DAC502 MK2 (ref#PHM415)

Roon Software Discussion
43

Not directly related to the Weiss DAC, but when I did a comparison of Qobuz files, my own ALAC files, Qobuz directly or Qobuz via Roon on my T+A DAC, at no point did I notice any different audio quality. As far as I could tell, they came out exactly the same (and in Roon, the signal path always had the “purple” light). Of course, I have within Roon the option to adjust the sound or use volume leveling etc., all these options are turned off in my setup.

The Weiss is a high-end DAC, which means: there shouldn’t be any difference in audio quality, regardless of how the files are delivered, and regardless of where the PCM gets decoded. In theory, there should be no difference, period. In the end, it is the PCM that gets converted to analog in the DAC, and the PCM should be literally the exact same, regardless of whether Roon decodes the FLAC and sends the PCM to the Weiss, or the FLAC gets sent directly to the Weiss, because in the end, it is always the PCM that gets “played”.

So since you hear a clear audio difference, and since apparently “Weiss had received several similar reports regarding Qobuz Connect versus Qobuz via Roon” and are actively investigating the matter, this seems really a very interesting and even unusual case.

45

Thank you. That’s pretty much where I am as well.

I fully understand the theory and would normally expect both playback paths to sound identical. That’s why I initially questioned what I was hearing.

What made me pursue it further was that the preference remained consistent over multiple listening sessions, and then Daniel Weiss mentioned that they had received several similar reports and were investigating the matter.

Like you, I’m genuinely curious to see whether Weiss eventually finds an explanation or whether it remains one of those observations that is difficult to pin down.

46

Yeah, very interesting, which is why I’m in this thread: I am curious about the “resolution”. It’s like MusicD said: “If neither path alters the data, the actual PCM samples arriving at the DAC chip are bit-for-bit identical, and a DAC like the DAC502 reclocks everything to its own internal clock anyway.”.

That means, even if there were theoretical differences in the quality of the signal path of the decoded PCM from Roon or the direct FLAC stream from Qobuz, they cannot matter, because high-end DACs reclock the streams, that means they take the exact same PCM and read it at the exact same speed. There is no theoretical possibility for the sound to be different.

As far as I can see, the following options are there:

  1. Roon for some reason choses a different version/mastering of the album from Qobuz direct. Would easily be checked if that’s the case. That’s obviously not it.
  2. Roon is set to change the sound in some way via some DSP setting.
  3. There is some setting in the Weiss which can account for the change.

I have a T+A DAC which has options for the oversampling + digital reconstruction filter (“linear” and “impulse”), which may produce slightly different results. That is, however, a universal setting for all input. Is it possible the Weiss has similar options and they are implemented differently for Qobuz and Roon? This, I admit, is just a shot in the dark, as I am not familiar with the intricacies of the Weiss device, other than that it should be an excellent unit.

47

I ve noticed the same with Tidal connect and Roon untill I read a review stating that the differences diminue when you improve the source. I added a clock and an upsampler from Auralic. There are no more differences between Roon and other apps. The better the streamer and the smaller the differences. Now Roon sounds superb.

48

This mirrors my experience. More than that, with the best transports, Roon can actually sound significantly better then internal streaming via “Connect” apps.

49

I read that in a Dutch review. It said when you add a clock there are no more differences. I was planning to stop Roon but I loved the interface. I added a clock and the differences were gone. Roon sounded amazing. When I later added the upsampler it also sounded better. I compare with Connect and Bubbleds and Roon is the best but your source has to be very good or the Connect will sound better. It is strange that it does that.

50

If one looks for the root for differences in sound quality, unlike analog, where there are many theoretical and practical influences, and every mechanical step on the way may change and influence the sound quality, the digital domain is a binary. It’s either/or, black/or white, Zero or One.

Fact: the exact PCM stream should deliver the exact same sound. If the PCM that goes into the DAC is the same, sound will be the same. It doesn’t matter if the source is WAV, FLAC, ALAC, AIFF… the audio content that’s read is always the same.
To say otherwise would be the equivalent of saying the PDF manuscript of a mystery novel you read in Acrobat Reader is more suspenseful when you receive it in a RAR rather than a ZIP file.

So if the Weiss DAC502 MK2 sounds differently if one listens to Qobuz via ROON or Qobuz directly, there has to be a difference somewhere. Be it in DSP settings, be it in a different PCM stream, or be it in a different setting during playback.

It is not possible for Tidal, Qobuz or Roon to inherently sound “better” or “worse” or “more open” or “less spacious” or whatever from each other if they deliver the same PCM to the DAC (and why shouldn’t they?), it’s not possible for the same PCM stream to sound sometimes more like this, sometimes more like that, depending on how it is delivered.

The Ethernet or WiFi just transports packets, the Weiss DAC502 MK2 does not even “know” where the packets come from, the packets get “unpacked”, and the DAC just sees the resulting audio stream, and if the same PCM is delivered, the result will also be the same. Down to the last bit and byte. And bits and bytes don’t just change at a whim.

So if one experiences differences in sound quality, there are two options:

  1. The differences in sound qualitiy are perceived but not real. That would be a psychoacoustic issue, that can best be checked with double blind tests.
  2. The differences in sound quality are real. In that case, the fact that the domain is digital allows you to concentrate the search for the root cause to very specific areas where a difference in sound quality could even occur, and that’s basically down to two things: different PCM stream or different settings somewhere else (for example playback). In one way or another, it comes down to one of these two options.
51

Agree. My humble Zen Stream delivers exactly the same excelent sound via Roon, Qobuz Connect and Tidal Connect. Cheers

52

I have done A/B testing playing Qobuz connect direct vs via Roon all through a good quality SOtM streamer and a Vitus DAC and can 100% say there was absolutely zero difference in my system.

53

Yes, same here. As I noted above, I tested this earlier this year and played the same high‑res/lossless tracks from Qobuz directly, Qobuz via Roon, and purchased Qobuz files on my NAS (via a T+A device). I could detect absolutely no difference in sound quality, not even when switching directly from one to the other.

Of course, this doesn’t prove anything (maybe I have tin ears, who knows, could be), but if I did notice differences in sound quality, I would certainly be very interested in what caused them and how they originated.

54

There could also be different processor and network activity from the Qobuz Connect software compared to the Roon endpoint software embedded in the Weiss DAC. And if the DAC is poorly shielded, or the power supply isn’t sufficiently independent, or the clocking is differentially affected then the sound quality could be affected. Also we have learned in the support thread that Qobuz use different files from those that Roon use, so there is also a possibility that the digital data is different in some way, perhaps due to watermarking. Who knows. Plenty reasonable hypotheses. What is good is that Weiss have taken the issue seriously and are investigating, rather than just waving their hands and saying “can’t possibly happen”.

55

True, and that’s why I certainly didn’t say “couldn’t happen”. I’m always for analysis and going step by step to the root of things.

However, you will find that the potential issues you raise all fall into either category A (different PCM) or B (different settings… a different clock would certainly account for that, though as far as I know, the Weiss has ONE internal precise clock that it uses). It would be easy to zoom in on the issues to eliminate or confirm that any of them are the case.

56

I understand your reasoning, and that’s exactly why I found my own observation surprising.

When I started comparing the two playback methods, I didn’t go into it expecting Qobuz Connect to sound better. If anything, I would probably have expected Qobuz through Roon to have the advantage, given the maturity of the platform and how much effort Roon has put into its audio architecture.

Instead, I found myself consistently preferring the direct Qobuz playback on my Weiss DAC502 MK2.

That doesn’t prove that the difference is real, nor does it tell us what the cause might be. It simply means that expectation bias is not an obvious explanation in my particular case, because the result was the opposite of what I would have expected.

That’s one reason I’m so interested in what Weiss eventually finds.

57

If anything, processing a raw PCM stream should be easier than decompressing and processing a FLAC file. Regardless, if minor differences like that are audible then imo it suggests poor DAC design eg. isolation between the streamer and dac sections, and/or justifies separation of streaming endpoints and Dacs, vs all-in-ones.

This isn’t true. I have directly verified this myself. For a given Qobuz master/track, I have captured the raw PCM output from Roon and also captured and decompressed the FLAC file from Qobuz directly. The two files were %100 identical i.e. not a single byte was different.

58

We have learned that they use different servers, not files. The problem there was that some CDN edge servers that are used by third-parties had a broken file cache. This does not say anything about different files in normal operation.

59

Just my opinion, but I don’t think a person can control a subconscious bias with conscious thinking.

But I can’t say why you hear a diference.

60

Just to check the obvious, and I’m sure you’ve already done this, but have you checked that you’re using the same stream for both?

i.e. Roon can be set (Services — Qobuz — Edit) to request a lower-resolution file from Qobuz. Is it set to the maximum (24/192)?

If the Weiss has a similar setting, is that set accordingly?

61

Very interesting thread. Have you ever tried a blind test? (someone should randomly switch your chain between the two methods on one song without telling which is which, and note down your preferences at least 10 times)

Just to set aside the “bias” thing

g

62

Thanks for your comments

Yes, I’ve already checked that.

Roon is set to maximum Qobuz quality, and I’ve verified that I’m comparing the same album and resolution in both playback methods. So far, I haven’t found any obvious differences in the source material or settings.

I haven’t performed a blind test yet, but it’s on my to-do list. Once I’ve done it, I’ll let everyone know what I find.

63

The ‘bits is bits’ arguments are always persuasive until they are undone by the actual audition. No-one fully understands the subtleties of human hearing, which has astounding capabilities and keeps detecting things it shouldn’t. I trust Weiss a lot. Their equipment is excellent. No hype, just precision engineering of all known factors. So I am really curious what, if anything, they will uncover. When do you think we might hear back from them?