DirectStream: USB Sound Quality better than Bridge II


#21

Both amplitude noise and time noise (jitter) can potentially matter. The DS is less sensitive to input jitter than most other DACs so this is less of a problem. But amplitude noise can become jitter and jitter can become amplitude noise any time a clock interacts with the signal (both illustrations are qualitative not quantitative):

Any ground loop (which is hard to avoid with non-optical connections) can transform the flux in the loop into a current around the loop (and vice versa: noise in a loop can radiate via the ground loop.)

Any noise that get’s superimposed on any analog signal in a system can become audible: low frequencies simply raise the noise floor, higher frequencies get modulated down into audio frequencies by any non-linearities in the following circuits (e.g. the parasitic diodes in the input transistors, etc.) (E.g. like a crystal radio.)

Just because an Ethernet connection uses a transformer on each end doesn’t mean that it doesn’t transmit noise: noise near DC is certainly attenuated a great deal but noise near the frequency of the nominal signal frequency passes right on thru the transformer (and hopefully is mostly dealt with by the common mode and differential mode chokes in the Ethernet receiver and transmitter connectors.)

USB’s noise is a little worse, there is ground noise that’s hard to get rid of, but there’s also noise on the VBUS line (which needs to be there for proper signaling when a device or hub is added or removed.) Also the data lines run parallel to the ground and VBUS lines so there’s more cross talk than one would like.

None of these issues normally cause any data errors, but when you want 120dB S/N in your audio, the results of any of these effects have to be less than 1 in a million relative to the audio everywhere.

There are ways of dealing with all of this and various systems will have different needs re. that noise - you’ll find some here who get better sound with Ethernet and others with USB.


#22

Therein lies the rub. If there are no data errors, then there would have to be another explanation for how “noise” other than jitter affects anything whatsoever - in the DIGITAL realm. Which leads me to a newbie type question:

What difference does S/N make if we’re talking about your DIGITAL domain transmission so long as the receiving end is able to correctly parse/discern all intended bits in and timing of the source signal (using checksum, reclocking or what have you)?

I ask because I was halfway expecting an answer that the “noise” somehow makes its way into the other areas of the DAC’s circuitry - and you did mention ground loops, but external - NOT that this “noise” in any way affects the DAC’s ability to convert the original digital signal (over Ethernet or USB) into analog presuming there are no transmission errors (lost or corrupted bits/packets).

So the question here is still the same - how does alleged noise in either USB or Ethernet transmission make its way into the ultimate analog signal if said noise/distortion in the digital domain does not actually result in any errors?

Isn’t all of this really on the surrounding buffer/amplification circuitry and therefore independent of the means of digital signal transmission so long as PS Audio has designed their products well? That is to say, wouldn’t the ultimate “noise” factor be the SAME for any input source other than optical if we’re saying that, other than jitter, all noise should be filtered/attenuated in the same manner/amount by the “next step” in the circuitry within any decent DAC?

Thanks again!

P.S. If I misread you I apologize. Were you indeed saying that the “noise” inherent to the Ethernet or USB ‘circuit’ or ‘transmission line’ somehow affects the NON-digital aspects sonic reproduction (i.e. D.C. power supplies, grounding, etc.)?


#23

Digital data isn’t corrupted often enough in a functioning system to effect the output audio over any of the standard interfaces.

All this thread is talking about is the non-digital effects of amplitude noise and timing noise. Because each can become the other trivially anytime a clock is involved and because jitter and high frequency noise travel over/around/thru caps transformers, resisters, etc. easily, simple things like a transformer or cap is not guaranteed to attenuate all noise enough to not become something that’s heard or not become something that at least raises the S/N of the end result.

My previous post attempted to explain some of the mechanisms at play, do you dispute any of them? If not you have your answer. If so we can attempt to clarify.

[P.S. All of this is true for any audio system and not just PS Audio…]


#24

OK. So we are at least on the same page with respect to the data that is being received and decoded. That is not going to be corrupted or dropped except in extreme cases of interference which are not the subject of this thread.

I guess my original question then still stands – What did PS Audio experience during various stages/phases of development and what should the average user expect in terms of ultimate sound quality - as many variables as possible ignored or held in common - in terms of sound quality between the USB and Ethernet Bridge II inputs?

If I knew what specs or measurements to ask for I would, but what I’m looking for is an “official” non-proprietary laymans explanation for how much “noise” was actually measured and/or accounted for in each of the two above respective inputs given various testing parameters.


#25

The problem is that (as often is the case in hi-end audio) the relative effect of all of the forms of non-ideal behavior is system dependent (and for that matter listener dependent.)

If your system has any ground loops (almost impossible to avoid) then the flux of radio, etc. in your vicinity (cell phones, mobile phones, Wi-Fi, AM, FM…) will cause a calculable ground loop current. Whether you use balanced cables or single ended cables will greatly affect your system’s sensitivity to said current.

With Ethernet, RF interference more easily gets thru to the guts of all of the equipment. With USB noise on the wires is probably the biggest problem.

With enough careful measurement and modeling all of this can be calculated, but almost all of that work is not valid for any other system. The pragmatic thing to do is to listen.

My personal suggestion re Ethernet and USB is to pick the one that gives the user experience you like. Then optimize it if the sound quality isn’t what you wanted. All inputs can be made to sound great.


#26

Right, OK. And inherent in that answer is the notion that ANY of this noise we’re discussing, whether over USB or Ethernet, is also situation dependent - but not only that - unless a user has isolated virtually every other variable associated with “noise” (aka an extremely isolated, efficient and expensive system) there is likely no way that they’d be able to usefully distinguish between the “better” of the two inputs based only on “noise” - especially from the context of being able to advise another user or potential buyer. So I’m left right where I started.

Getting even further down the rabbit hole, I’d even be willing to accept that SOME “noise”, rather distortion, actually makes the system sound better to some people.

But I’m still just curious about PS Audio’s take on it and was looking to put to bed the idea that anyone in comments can reasonably or accurately - much less definitively - state that one of the two inputs under discussion is more noise-prone than another, which I have seen at least a few people do here in this thread, not isolating for EVERY possible other variable.

Does that make sense? Let’s at least establish SOME kind of technical or quasi-technical baseline rather than allow for misinformation or mistaken inferences/conclusions to perpetuate.


#27

I try to get people to not make categorical statements. I try to suggest parameters that may not be taken into consideration. (e.g. I always recommend that one should disconnect all cables except the ones being used to compare two possible cablings. But this is a big pain in the neck in most of our systems especially for those who like to do quick A/Bs…)

It’s a loosing battle: people get excited and want to share their positive experiences. Any audiophile should have learned long ago that anything they read (especially on the internet) is most useful as a hint rather than a definitive statement. Most manufacturers try most of the time to do the best they can to minimize system dependencies within their cost structures and the unit’s price point.


#28

Yup. OK, well thanks for the dialogue. :grin:

Now, off-topic, I need to find out how the heck to get rid of this MControl app and still be able to use MQA Tidal Masters - preferably with a Windows PC. Any suggestions on what threads to check? Am I pretty much relegated to Roon?


#29

Hopefully someone will help on that account, you might ask in a new thread if searching doesn’t get you what you want. I don’t use the Ethernet input (compared to other inputs it does little that I want and a whole lot that I don’t want.)


#30

“I don’t use the Ethernet input (compared to other inputs it does little that I want and a whole lot that I don’t want”

Oh my!
Dear Mr. Smith, did you just open up a whole new can of worms? :worried:

That comment sounds like you are discrediting the Bridge II. Can you elaborate on
what you meant by that?


#31

Not at all - It’s the basic interactions available in DLNA / UPnP that don’t work for me. I.e. Streaming based interfaces don’t (usually) support the kinds of navigation I typically want to do with my collection of music. I do ah hoc searches for things I want to play next and/or want to better tag. I can’t stand interface that doesn’t treat a new tag that I make up just as well as say, Title.


#32

FWIW, I wanted like to contribute my own data point to the pool of Bridge II vs. USB observations (in the spirit of good data science and striving for reliable statistics :grinning:).

I’ve been using a heavily tweaked USB setup with my DS for a number of years (Ethernet -> Auralic Aries with S-Booster BOTW power supply, Uptone Regen ISO, UltraCap LPS1, good Shunyata USB cable). A week ago, the Aries failed and I was faced with the decision whether to repair or replace.

I’ve been attracted to the idea of the Bridge for some time due to the setup simplicity, the idea of I2S vs. USB, and just plain stepping off the endless tweak escalator. However, I was hesitant given the mixed reviews; further, conceptually the idea of putting a noisy computer inside the DS chassis also seemed so wrong (seemingly completely counter to the obsessive “noise elimination” ethos of the USB camp).

I decided to try anyway (good return policy). I was hopeful, and was very motivated to “like the results”, but I couldn’t – the initial impression was really really disappointing, exactly along the lines noted above: “less bass, thinner, harsher high frequencies.”

Fortunately, fairly quickly I discovered that the default Roon settings for the Bridge had the DSP engine, as well as Roon Volume control on. Turning all that off was transformative to the sound, and the improvement in transparency, dynamics, imaging, and even bass over my USB setup is not subtle.

After many years of being immersed in the discussions about audio digital protocols, I still really have no idea why this all should matter (ground loops? Different types of digital noise influence audio differently?)

Notwithstanding, I am thoroughly pleased, and wanted to congratulate the designers of Bridge II for having developed a great product.