Will, your response was very, very helpful. Part of my problem, as I am sure you can tell, is getting to a level of understanding where I can properly articulate my question.
Let me fill in a few details now that I think I understand what I am trying to ask!
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So here are my two questions.
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Sure, that helps.
I'll start with a couple of general comments...
First, you have a good quality system that you've obviously invested some time and money in selecting. However, I wonder if you might find the Benchmark DAC3 to be more in the same league quality-wise with your preamp than the Schiit products. So I do think there is a sound quality improvement to be had there. And of course when it comes to speakers, that's where 90% of any system's sound quality lies, and your opportunities for improvement there are limited only by your budget.
When one is generally happy with the sound of a system, getting improved performance can become a game of diminishing returns, though.
Second, as we go into the specifics of configuration, I'll say this. I've spent decades working in the technology industry, especially in networking. I know how digital computer systems move data. When it comes to high-end audio, and "audiophile"-quality components, people have a lot of beliefs. For an example, there are people who believe and assert that they can hear the difference between one USB cable and another. I don't know or care what sort of audio related beliefs you may or may not have, or whether you are completely measurement driven or completely ear driven. I have zero interest in debating those sorts of issues with people, or in trying to convince any audio lovers of one thing or another.
A couple of things you didn't mention but which are important: how are you connecting the DAC to the streamer (toslink? USB? BNC?), and what requirements do you have for how the PC may or may not be physically cabled in. I'll have to make some assumptions.
So, based on your checkbox experiment, yes you are having MC perform as both DLNA server and controller. This is common, nothing wrong with it, as far as DLNA goes. (You should know this as you configured your streamer, you told it where to get its music).
The path for the music data in your config is as follows:
1. Music data resides in files on the hard drives of the NAS. -->
2. MC transfers a music file across the network to the laptop running MC. -->
3. MC (as the DLNA controller) tells the streamer what music to request.
4. Streamer requests a file from MC.
5. MC transfers the file across the network to the streamer. -->
6. Streamer decodes the file, and pushes the bitstream to the DAC via either USB or Optical or whatever (I guess you're using the optical toslink cable?) You didn't say which input on the DAC you are using.
Whether you use MC as the DLNA server, or a bit of embedded DLNA server software on the QNAP, is irrelevant from a noise perspective. (You might be able to run MC in a container on the QNAP, but this will not improve anything for you.) In both cases, the file is transferred intact to the DAC, and the DAC decodes it. There is no impact on noise here. The sole source of noise any noise must be between the innards of your streamer, to the outputs on the preamp. MC and the NAS cannot contribute. I think that covers your first question.
For the second question...
My view is that connecting the laptop directly to the DAC, either through toslink or USB, and eliminating the streamer, is superior to what you are doing. I distinguish this from what you're calling scenario 2 above, because MC is not a "server" here. In what I'm describing, there is no server, as DLNA would not be involved. MC would load files directly from the NAS file share, decode it, and push the bitstream to the DAC.
Why is this superior? Well, if you want to pass totally unaltered, "bit perfect" audio, with no equalization or anything else, then the sound quality will be absolutely identical. However, your system will still be much more responsive. You will have much more control about things like track changes, fast-forward, rewind, and everything else, as MC can execute all those functions directly. You will not have any DLNA problems. I looked back at your somewhat brief posting history, and most of your posts seem to deal with DLNA related problems. That does not surprise me; remember my opinion about DLNA.
Furthermore, if you're not addicted to the mental concept of "bit perfect" audio, then the config I describe becomes vastly superior, because it allows you the full wealth of processing that MC can provide: volume leveling, room correction, equalization, etc etc. MC does all its processing as 64-bit data, so the quality level is extremely high.
Regarding your somewhat veiled question about cabling: you don't specify what "non-USB" connection you're using. Only Toslink (optical) provides total electrical isolation. Any other S/PDIF or AES connection over metal wire (whether copper, silver, gold or adamantium) has the potential for ingress of radio-frequency/electromagnetic interference. Except for badly designed components, data transmission issues that can affect digital audio primarily come down to the issue of jitter. How much jitter is created, and how it is addressed, is very much device/implementation dependent. It is not strictly a function of physical cabling. One pair of devices connected via USB may have lower jitter than over Toslink. A different pair of devices might be superior over Toslink than the first two devices are over USB. Before trying to assess/solve/minimize the problems of jitter in a system, you would need to gain a technical understanding of jitter and exactly how it is dealt with by the specific devices under consideration. This device-specific information is often not made available, and making useful measurements requires expertise. And all this is predicated on the presumption that you can really hear it in the first place. All of this jitter related stuff is beyond the scope of what we should get into further.
I hope this helps...