Do Streamer only devices really impact sound quality?

Ok. I am a software engineer with 15 years of experience. I have built streaming services for my day job in the past. I have pretty deep technical knowledge into how streaming services work. 
 

The idea that you might be losing bits through low quality components is simply not true. When data is transmitted from a server like Spotify’s, or even when data is being transmitted over a cable via USB or Coax, the data is sent in packets. A packet is a bunch of bits. For Spotify, a single packet is 512kb for example. In TCP, receiving device (we call them clients) sends an acknowledgement message back to the sender (we call them hosts) if and only if that packet is not corrupt.

Another poster basically mentioned that you skip the ack for streaming. That’s not true. You skip the ack for live broadcasting like Twitch, but not for streaming like Spotify or YouTube. If you lose a packet, the music just stops and waits for you to get the packet. We would rather stop the playback than just skip 512kb of a song. That would be a huge part of the song just cut out.

Transferring data over USB or Coax is not all that different. It uses a checksum to ensure the packet isn’t corrupt. I won’t go into how checksums work, that’s way too overkill for this post. Over TCP, the checksum is actually pretty weak. It has a 1 in 65536 chance to have a corrupt bit. That’s pretty high. But it’s ok usually. Even if you have a corrupt bit, it’s very very unlikely to affect anything at all. It’s unlikely that corrupted data is even a part of the audio file. It’s probably something else, like a header, or the checksum being corrupt but not the data, etc.

USB and Coax uses a different checksum. It uses Cyclic Redundancy Checksums (CRC). If a single bit is ever wrong, it will be rejected. Again, I can’t go too deep into all the details here of all the ways data over USB or Coax could become corrupt, because the chances are non-zero for a variety of reasons, but typically we are talking like, once a week or something where a single bit could somehow flip, and even then it’s unlikely to change anything about how the music plays back.

For this reason, I can say pretty confidently that your streamer is not losing data between it and a DAC. There’s basically no way. 
 

Jitter is not at the level of bits. We’re on a much higher layer when talking about Jitter. I don’t have quite as much familiarity with this to be honest, my experience has to do with transmitting data, not the actual playback, or the exchange from digital to analog.

On the grand scale of what things affect the sound most, streamers certainly can if done wrong but not so much when done right and that need not cost much these days.   It can be done right these days using most any platform including home computers but there is more that can go wrong there for those less computer literate. 

I agree, don't have to spend a fortune on streaming equipment to hear differences. I've been streaming for many years, started with most basic, laptop to dac with Foobar, been incremental improvements all along the way.

I made the following budget minded changes to the front end after initial  setup.  I have BS Node 2i and Topping D90 with AKM chip. Took some time research and learn.  Discussions such as this are very helpful.

1.  Better power cords for Node and D90.   $200

2. Hardwired ethernet cable to streamer. $40

3. Dedicated power circuit for audio system. $500

4.  Upgraded power supply to Node.  $130

5. COAX  from streamer to DAC. $40

6. DX Engineering EMI/RF filters on ethernet. $50

7. New cable modem router combination.  It included a LPS and eliminated  an older router and wall warts.  FREE

8. Herbies firm fat dots.  $80

Cumulatively,  these changes made nice changes.  Depth of soundstage,  transients, sense of space, details revealed in bass, etc.

Then I  added a Add-Powr Symphony IO.  This improved the sound even more.

Sure, each step could have cost more and would probably improve the sound even more.  If you upgrade the above steps, the cost goes from 100s to 1000s.

Keep an open mind and audition some models. I don’t notice any difference with them and am content to play directly off the streaming stations. Put the money into speakers.

New custom streamer goes in, great attention to noise and latency issues. Revelatory is only word I can apply to what I'm hearing, much greater sense of ease, I simply relax into music, its like the music has slowed down and come into its own natural flow, far more like the top tier vinyl setups I've heard. There has been substantial reduction in noise floor as well, but the newfound sense of ease is the revelatory thing.

@sns  Very well said as to the incredible improvements that can be achieved by upgrading to better components in the streaming chain. 

Lost my chain of thought here. I agree harshness, sense of hardness can be attributed to streaming chain and/or system. So, assuming one has rid themselves of this and still has fatigue. This is very likely fatigue due to jitter. I eliminated vast majority of harshness/hardness some years ago, eliminated minute residual over the years through streaming and system tuning. Still remained this slightest sense of fatigue,  like excess precision, a bit analytical presentation, very hard to put finger on although I began to hear it as timing issues over time. New custom streamer goes in, great attention to noise and latency issues. Revelatory is only word I can apply to what I'm hearing, much greater sense of ease, I simply relax into music, its like the music has slowed down and come into its own natural flow, far more like the top tier vinyl setups I've heard. There has been substantial reduction in noise floor as well, but the newfound sense of ease is the revelatory thing. I attribute this to great reduction in jitter vs past streamers.

I would definitely agree that the ethernet stage can be the most complex, and certainly seems to allow the most possible upgrades, warranted or not.

And I would certainly agree with @sns , that a decent switch can make things worse. I tried the Network Acoustics Muon between my Netgear Orbi router and my Zenith streamer and liked it a lot, until I experienced severe drop-outs (the NA guys suspected the router wasn’t very good at “auto-negotiating down to 100mb/s”). On their advice I added a bog-standard TP-Link switch with decent iFi power supply between the router and streamer. The drop-outs disappeard but it sounded awful - really brittle and bright.

I currently have an SotM ISOCAT7 and dCBL-CAT7u.

@jjss49  No doubt!

One has to address both noise and jitter in order to get optimal streaming sound quality. In most cases one will have treated noise issue first since more easily addressed with more affordable devices. If still residual fatigue this very likely due to jitter. Jitter is more difficult to address, add on timing devices can't correct timing, latency issues within streamers/dacs. The jitter has already contaminated the signal, band aids don't close the wound, you could say the same about noise contamination.

So, the point is to do the least harm at each and every point of streaming chain. Per @lollipopguild every single component in chain is important and needs to be optimized. And I do observe those claiming to hear least fatiguing, most optimal streaming quality do have top tier components across entire streaming chain. I observe the best quality streaming comes from the least complex streaming setups using these top tier components, no band aids or add ons. The one exception to this is the single add on of the network devices such as Muon, in my case JCAT net XE. This seems to be critical component as routers certainly noisy and seem to be effective even for those using audiophile switches. By the way, adding audiophile switch was single worst addition to streaming setup ever experienced, YMMV.

There is interesting post here with individual going to second modem/ISP service to exclusively serve audio system. Modem direct ethernet connection to streamer and remote device such as laptop or tablet. Perhaps this setup negates need for network cleaner/filter devices?

Fatigue in the digital realm is caused by jitter, I’m really beginning to believe humans can detect extremely miniscule levels of jitter.

i agree but would add that electrical noise is also an important contributor to a perceived sense of harshness to the music - this is why filters and cleansers such as network acoustics, etherregen, optical modules and so on are able to make such patently audible improvements

@lollipopguild  Amen. The one nit is high level of detail can co-exist without fatigue. This is the plateau I finally surpassed after well over 30 years of trying. Fatigue in the digital realm is caused by jitter, I'm really beginning to believe humans can detect extremely miniscule levels of jitter. Some claim we've already attained levels of jitter below threshold of hearing, don't observe any evidence for this.

@dvdgreco When I started off on my recent complete overhaul of my hifi, I was similarly convinced that surely 1s and 0s are sacrosanct, and what is the point in buying better than a budget Cambridge streamer/DAC.

It wasn't until I tried several different USB cables between my new Zenith and Hegel H390 did I fully accept that such a thing as quality exists in the realm of digital signals.  Not only that, and this surprised me, USB cables to my ears have definite characteristics, which myself and other reviewers could agree on.  For example, the Laboga Emerald USB has a lovely warm and rich tone to it.  Why?  who knows - maybe not even the cable designer.  

In my experience, everything between the router/switch and the DAC's input affects the SQ to some extent.  Filters, regenerators, ethernet cables, USB cables, power supplies and, yes, the streamer.

Of course, the impact of each will depend on partnering equipment, and I would expect that some DACs are more sensitive to noise and jitter than others.  

Thankfully, most suppliers have a returns policy - though burn-in can be an issue, and eventually you'll just get tired and even a little neurotic by continually performing A-B comparisons and "staring" at the music, rather than just listening to it.

My advice: aim for a warmish sound, then stop and enjoy.  High levels of detail, in the short-term, is impressive, but can soon fatigue.

@adasdad

Very funny.

@sns 

I'd only say believe those with top tier streamers, they are indeed hearing what they claim to be hearing, they are not delusional! I don't care about the damn theoreticals, audio is for our listening pleasure, not meant for some listening bot or textbook.

indeed... nor for "measurements are everything" geeks

@tk21 You got it, context is everything.

@adasdad Not going to speak for ghdprentice, but my custom build streamer has been directly compared to top tier streamers such as his Aurender, Taiko Extreme, as well as to many lower tier, and it rightly belongs in that tier as both previous owners only sold after comparing and purchasing Taiko Extreme (and this prior to JCAT LPS I power it with).  The top echelon streamers pay extreme attention to noise reduction via top quality power supplies, jitter reduction via latency optimization and rendering via clocking and noise reduction of various ports. So, these are some of the theoretical reasons  for improved sound quality.  And then we have the listening portion, some may not consider that to be valid, but between what others report and what I've experienced with streamers, sound quality is extremely variable, at least on par with dacs. I can only say, try various steamers for yourself, assuming your system has sufficient resolving powers, the value of top tier streamers will be patently obvious.

I also have the ability to directly compare various protocols via drop in PCIe cards from Pink Faun and JCAT, top flight cards are available for network, coax, I2S, AES/EBU, USB. Presently using JCAT net XE to Sonore setup (FMC to USB), sound is simply sublime! I could stay here for the remainder of my life, never heard higher resolving, greater sense of ease with digital. Had to greatly upgrade my vinyl setup to keep up. Perhaps I'll compare other protocols over time, simply not motivated at the moment.

I'd only say believe those with top tier streamers, they are indeed hearing what they claim to be hearing, they are not delusional! I don't care about the damn theoreticals, audio is for our listening pleasure, not meant for some listening bot or textbook.

I wonder how many people have compared I2S with USB in a well-controlled A/B test.  I2S still isn't all that widely available.  My streaming DAC does have an I2S input but I've never used it.  In my system, the most likely path into that IIS port would be from my Mac's, uh, USB port, via a converter box such as the Sonore ultraDigital or the Matrix X-SPDIF 2.  I've been slightly curious to see if that would produce a noticeable improvement, but don't really want to add another little converter box into an already cluttered system. Besides, the SQ already is pretty darn good.  But I do wish my music server (the SGC sonicTransporter) had an IIS output port. My DAC with IIS input can support 16-32 bit PCM, while its USB pipeline supports only 16-24 bit.  Perhaps more importantly, IIS might eliminate the annoying USB handshake problems I sometimes experience.

IIS from the Matrix X-SPDIF seems to be popular among users of the PS Audio Direct Stream DAC. I wonder if this popularity doesn't stem from limitations of PS Audio's USB implementations, or from problems with the Direct Stream's network bridge card. Point is, again, that if we're going to compare USB to IIS, I think we need to specify the context of how USB is being implemented in the system we're comparing.  

So @ghdprentice, you’re saying that if I put a $22K dedicated streamer somewhere in my listening chain, only then will I hear the benefits of what digital can do?

I have (and love) a BlueSound Node 130. It has a great interface, and is easy and intuitive to use. For a while I thought about upgrading, but instead went with a DDC (Denafrips Iris DDC). It isolates the signal galvanically and optically, so the signal gets sent to the DAC (Denafrips Pontus II) cleanly.....I've done a review elsewhere here.

I'll keep what I have now as I'm completely happy with it, but at some point will want to compare the quality of that pair with higher end streamer. Price will be hard to beat, $600 for the Node 130 and $500 for the Iris DDC; damn good pair for $1,100

Point is not to generalize about inputs/outputs, each case is different...blathering objective statements only further confuses people.

@sns Oh, you mean blathering like this?

USB inputs are optimized in many dacs, preferred by many.

Really? Where’s your proof? Didn’t think so. Of the hundreds of posts I’ve read on the subject yours is the ONLY one I recall where USB was preferred to i2S with the exception of Holo DAC owners where it’s well known that those DACs are optimized for USB, which seems to be much more the exception than the rule. By contrast, I’ve read many, many posts where i2S and/or AES/EBU were superior to USB or SPDIF. Maybe your DAC sucks and can’t realize the benefit of an i2S connection, or maybe you used an HDMI cable that was too long — I dunno, but I think you’re in the distinct minority on this unless you can quote others preferring USB over i2S besides, apparently, people with your specific DAC (or Holo, obviously) because I sure ain’t seen them but can cite many (including me) who’ve found i2S to be vastly superior to USB. Your move chief.

@tk21 Good points.

Another thing that needs to be pointed out. The optimal mode of transmission depends a lot on the quality of the rendering in streamer. Some streamers take great pains in optimizing usb in use of high quality clocks and power supplies on dedicated circuit boards, ,others take usb directly off relatively noisy motherboards.

Point is not to generalize about inputs/outputs, each case is different. Research both dac and streamer for optimized ports and purchase compatible components. USB has some theoretical disadvantages, but implementation has been continually improving, blathering objective statements only further confuses people.

Individuals use usb because it has best SQ vs other inputs/outputs available to them. I've observed many trying coax, AES/EBU, I2S inputs on dac, finding them inferior and returning to usb.

I don't know that the channel itself necessarily makes that much difference, to my ears. What makes a SQ difference, to me, is the various DSP options I can get (or cannot get) via one channel or another.  I need a USB connection to a Macintosh computer in order to run BAACH4Mac (a spatial audio processor). I need a USB connection to a Mac, or to a dedicated music server (with an ultraRendu in the middle), to run HQPlayer (which offers many filtering and upsampling options).  If I want multi-room playback, I cannot run either of those processes, so in that case I use ethernet (or, in the past, coax or RCA analog).  If I want to play TV sound through my HiFi, I need Toslink (because my system does not have a complete HDMI ARC path from HiFi to TV and back).

IOW, functional requirements  (as well as SQ) dictate the choice of streaming signal path, for me.  I've had at least 4 different streaming pathways in my system. These include the Bluesound Node 2i (which FWIW has one of the worst ASR measurements for a device of its kind) and also a Matrix Element X (which FWIW has one of the best ASR measurements for a device of its kind).  I haven't noticed enough SQ difference among those paths, per se, to override the functional differences.  And without going to a ~$30K T+A streamer/DAC (one  that supports  the NAA protocol), I doubt any of them delivers enough SQ improvement to justify doing without HQ Player (or BAACH4Mac).  Which I'd like to do, just to simplify the chain. But I'm skeptical that a change of streamers alone can make my soundstage sound about 50% wider, as BACCH4Mac can for some content. 

@soix Do a survey, how many using usb vs other inputs. I had Singxer SU6 in order to try I2S with my present dac, a couple other individuals with same dac tried I2S, returned to usb after less than satisfactory results, I didn't even bother, sold the Singxer. USB inputs are optimized in many dacs, preferred by many. Do you have proof that other inputs superior to usb on all dacs? I didn't think so.

Didn't Alvin Lee state that when using the Node with any of the Denafrips streamers that USB was the preferred connection? I think I read that here on AG, but can't find the specific post or remember the reasoning for his comment .  

Individuals use usb because it has best SQ vs other inputs/outputs available to them. I've observed many trying coax, AES/EBU, I2S inputs on dac, finding them inferior and returning to usb

@sns IME no…just, no.  That may be your individual experience and can always be gear dependent, but other than Holo DACs I don’t know of any other DAC manufacturer that recommends USB over i2S or AES/EBU.  For example, I fed my Musician Pegasus DAC via a high-quality USB cable and then bought a Denafrips Iris that let me use the Pegasus’ i2S input and it was a whole new world of performance and I ain’t no way going back to USB.  What USB versus i2S or AES/EBU connections have you tried personally and with what equipment?  You can cite “other people’s” experience all you want, but unless you’ve done it yourself, as I have, you’re just propagating hearsay and nothing more.  Back up your, frankly, controversial contentions with actual experience or this is just audio flimflam based on nothing and counter to what most have experienced here. 

The DAC is much more important. I like to go optical off the streamer to prevent noise from being transmitted from the streamer. 

Individuals use usb because it has best SQ vs other inputs/outputs available to them. I've observed many trying coax, AES/EBU, I2S inputs on dac, finding them inferior and returning to usb. Theoreticals are one thing, hearing is another. USB continues to be used because both manufacturers and consumers find it preferable to other formats.

As for software vs hardware, I've heard great variability with both.

My take is optimized streaming only achieved when all components, software, software and hardware configurations are optimized. Everything matters. Based on reports of others I observe great correlation between optimized streaming setups and great sound quality. The most experienced streamers report their findings, others follow their recommendations and experience better sound quality in vast majority of cases.

If you are going to use usb to a dac (why anybody would is beyond me), then a server will probably make a difference. If you use Ethernet then IME they don’t and you don’t have any issues with jitter or clocking. It’s only with usb that you have to buy all the tweaks/gimmicks to try to get usb to sound good. 
You still have to provide a quality internal network infrastructure with top quality cables to get good quality sound using Ethernet.

For over a decade, the software that is used to read the data has more influence on sq than the hardware. Even when I used an external server years ago, the Auralic Aries, I preferred the sq when I used the Lumin software to access the Aries. Same goes for iTunes, pure music, amarra, audirvana, and Roon. 

Funny you should mention these two particular streamers.  I’ve had both, and much preferred the sound of the Cambridge.

@soix - I was just trying to point out that something outstanding and fantastic could be had for thousands of dollars less than the Innuos Zen Mk3. Didn't say it sounded better.

@navyachts Just as he did with the Sueezebox, he left out the qualifier “for the money,” but he did say it’s not on the level of better/pricier streamers.  Just highlighting a few words from his review without context is misleading. 

@soix ​​@tk21 Speaking of Darko, on the other end of the spectrum, here he calls the WiiM Mini "Outstanding" "Fantastic" & "Favorite streamer of 2022" all for $79.

https://darko.audio/2022/11/introducing-the-wiim-pro-network-streamer/

@dvdgreco , There is no doubt that adding a good quality streamer to a good system will make a big difference.  It is likely that the Node and the Cambridge are not all that different.

I added an Auralic Aries G2.1 in front of my already good sounding Tambaqui DAC and it made (to me) a noticeable improvement.  I did not want to believe this, as there is a good streamer in my Tambaqui.  But it did.  I use USB from streamer to DAC, and also enjoy the Muon Filter in front of the streamer.  I also upgraded my network cables to Supra shielded Cat 8.

Correct. Bits are bits. And jitter in today's equipment is so small it cannot possibly be audible. And error correction has been perfected for decades. Even as far back as when I was doing network programming for banking systems in the 80's.

Simply put…

they can all sound different from one another. If you cannot hear the difference between one streamer and another, then it could be a question of the associated equipment? But even a low cost system should reveal the difference.  I used an Allo Digione with Volumio as the OS. I thought it sounded pretty spectacular. Especially with the coding mods and upgraded ps.
Then, I upgraded to a Pi2 design Mercury Streamer. My mind was simply blown by the improvement. It was immense. My system was instantly elevated (and it’s not all that special a system). To the point that I had serious trouble staying away from it.

So my answer is that there can be a major difference between transports.

@soix Like you, I'll use my ears to test, but I also want to try to understand some of the "why" behind what I'm hearing. My understanding is that for coax and ethernet applications, solid core copper is the best industrial option vs stranded copper or copper coated aluminum. E.g. solid core is best for power over ethernet applications like cameras or wifi access points, and solid copper products can also transfer over longer distances. It would make sense to me then that solid core products would benefit sensitive A/V components too. So if you're looking for affordable ethernet cable to test, you may be interested in this oxygen free, solid core copper ethernet cable I found on Amazon. I wired my whole house with it. Once I started buying enough to wire an entire house, it cost about twice as much as the stranded copper alternatives, but I didn't want to skimp out. Hit me up once you start testing ethernet cables. I'll join you. 

Cat 8 Ethernet Cable 1.5ft Shielded, Indoor&Outdoor, Heavy Duty High Speed Direct Burial 26AWG Cat8 Network Wire, 40Gbps 2000Mhz SFTP Patch Cord, in Wall&Weatherproof RJ45 Cable for Router/Modem/Xbox https://a.co/d/4ZcnKcR

@classdstreamer I haven’t compared Ethernet cables yet.  I have a Wireworld Starlight 8 I’m gonna run from a TP-Link extender to my streamer when I get situated, but I’m also gonna try a generic and a CAT7 cable to see how it stacks up for less $$$.  I’ve heard Ethernet cables, like everything in streaming, make a big difference and that’s been my experience too thus far, but if a CAT7 outperforms my WW cable at less cost so be it.  The Supra 8 has a lotta supporters so not surprised you’re happy with what you’re hearing.  I’m agnostic and just use my ears to make my decisions.  

@soix The switch I use is the TP-Link TL-SG108-M2. It’s the backbone of my home network. Not audiophile, but it’s fast. My wife didn’t like the idea of a network closet, so I needed something small and fanless to hide behind furniture. It fit the bill.

My current ethernet cable is a Supra 8, because it was highly reviewed and affordable. I haven’t started A-B testing ethernet cables yet. I’ve been putting the bulk of my budget into components and component upgrades. What have you found with ethernet cables?

@classdstreamer Interesting.  I would’ve thought upgrading to a better power supply would’ve made a bigger absolute difference, not that the improvements you noted are at all insignificant.  I might try something like a Teddy Pardo LPS in the future, but given your impressions I’m not in all that much of a rush.  BTW, what Ethernet cable are you using into the ZS and what switch?

Aside from the great sound quality, I really like the slick display and the fact it has transport keys.     The component form factor is appealing to me also , as is the insanely good build quality. 
 

I am ok with having to spend for all those things if a component is really good

@soix Yes and yes are the short answers. 

As you likely know, iFi has 3 levels of power supplies, and it shipped the first level with the Zen Stream. I had an extra iFi iPowerX lying around, so I used that for a while with the ZS. Then I got the itch to try their highest tier of power supply, which I'm currently using. Their highest PSU gave a little extra refinement to the sound. 

I haven't tried the ZS with the wifi antennas. I went hardwired out of the gate.

Farther upstream, I recently upgraded the home network to multi-gig LAN and WAN. Because no audiophile companies have a multi-gig switches out yet, I'm using a TP-Link multi-gig switch directly into the ZS. I wanted to get used to the sound before I reinstalled the optical converters to see if there was any difference converting the network from ethernet to optical right before entering the ZS. Speaking of iFi and optical, have you seen iFi's latest streamer?--the iFi Neo Stream? It comes with a low noise optical converter and optical cable to connect to the optical input on the Neo Stream. I'm interested, but I'm uncertain whether it would be an upgrade for me. 

@classdstreamer Wondering if you’re using an upgraded power supply with your ZS?  Also if you ever went hard wired from a switch/router to the ZS?  Both are supposed to yield significant improvements.  BTW, I also own the ZS with upgraded iFi iPowerX power supply.  

For me, swapping out streamers was one of the biggest improvements I've had with my stereo system. I recently upgraded my amp for something 1k more expensive, and it didn't make as big a difference. Here's my streamer post:

@audioguy85 

Very funny…🤣. 

NO! I guarantee my 179 dollar grace digital streamer sounds identical to a big buck over priced streamer in a blind test. It's all bull to sell you something you do not need.

But the Node is not only a streamer/file-player, it’s also a DAC. It can be used for volume-control, too. I’ve seen reports that it’s quite good when used only as a streamer (feeding digital output to a downstream DAC). If that is our baseline, how much SQ improvement can one expect by switching to a much more expensive stand-alone streamer (such as the Auralic Aries G2.1)?

@tk21 A ton of improvement is possible. Reports that the Node is “quite good” should not be inferred to mean that it’s anywhere near even not much more expensive alternatives. Example, an Innuos Mini Mk3 with LPS power supply upgrade is near the upscale Zen Mk3 in performance (and no one would put the Node, even with upgraded power supply on the level of the Zen Mk3), and even its DAC does a very good job with the LPS. Innuos has trickled down tech from its upper models that the Node can’t match even with an external power supply, and the Zen Mini will scale up much better if/when you upgrade to a better DAC. Yes, it costs a bit more, but you’re also getting a lot more. Underestimate the role/impact of a streamer at your peril.  Here’s Darko’s review of the Zen Mini both with and without the upgraded external power supply and with/without its internal DAC FWIW…

https://darko.audio/2019/11/innuos-zen-mini-mk3-review/

Not sure what to make of that title.  I suppose Darko might be saying that the SBT was a relatively affordable engineering marvel, not that it's the best-sounding such device ever made, regardless of price. The same might be said of the latest Bluesound Node. But the Node is not only a streamer/file-player, it's also a DAC.  It can be used for volume-control, too. I've seen reports that it's quite good when used only as a streamer (feeding digital output to a downstream DAC).  If that is our baseline, how much SQ improvement can one expect by switching to a much more expensive stand-alone streamer (such as the Auralic Aries G2.1)?

I did a quick search for Darko's streamer reviews.  Not sure I found the one @soix cited.  Anyway, Darko's highest praise seems to go to the Logitech Squeezebox Touch. 
 

@tk21 The title of the Darko Squeezebox video is unfortunate and misleading.  If you watch the video he compared the SBT to a Bluesound Node 3 and finds them comparable — hardly high praise in the scheme of things.  Here’s the video I was alluding to in my prior post that is a bit dated but still relevant for pointing out differences between streamers…

https://darko.audio/2019/02/a-short-film-about-the-innuos-zen-mk3/

@tk21  @soix  I think two different setups are being discussed here.  My take is that tk21 is talking about not hearing the impact of a streamer in an all in one unit. So yes who knows if any difference is due the DAC or the streamer, or parts , or implementation within the "streamer".  Most of the other posts have been about streamers separate from the DAC , so  if one is using the same DAC, streamer output to it, and cables  it obviously allows for a notable comparison.