I think the flac decompression load on old streamers is a not totally implausible hypothesis for the local stuff.
“Signals across the internet” picking up anything makes no sense to me because there’s lots of devices in between. And such pickup (whatever it might be) would stop at the router. In any case, this would be stopped with 100% certainty by using wifi locally. And the data is just a large number, whether I deliver it by internet, CD, or a piece of paper by carrier pigeon 
When I first built a PC for music usage (with a less powerful processor than current) it was clearly audible that WAV’s were better than Flac almost certainly for the reason you have given. All my files on the PC are stored as WAV’s so this would fit your theory.
It’s in my humble opinion the best hypothesis that has been put forward in any case, and it’s probably given additional support by the fact that nearly no-one hears the same difference when using UPnP flac>wav transcoding with the much more powerful new streamers
With my Nds and local files stored on my Melco server, Flac sound better vs Wav for me.
When you are using Tidal with Roon, disable all the MQA none sense, you might find that uplifts the sound quality. I do find that Qobuz has the edge on Tidal, but then I have a “student” Tidal subscription, because i am an immature student.
Qobuz and Tidal work well with Roon, if your DAC will decode DSD, then you should try setting Roon to output DSD, it makes Roon worth every dollar you spend(t) on it.
My local music collection is on an SSD, with a NAS backup. When I have plenty of time to spare and a larger SSD, the FLAC RIP’s will be converted to DSD, the change is so day and night, assuming you have a DSD DAC
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That’s interesting. And funny that as soon as I have accepted that with old streamers it kind of makes a little bit of sense that wav might sound better due to the processing load, you experience the opposite that has no explanation whatsoever 
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On a PC as I understand it the Flac would have to be decoded for Windows audio stream hence more work for the PC processor to do - more noise etc. It would be interesting to know how Flacs are handled relative to WAV’s on the Melco (especially as they may feature on my future upgrade list)
Whatever the computing platform, flacs have to be decompressed before they can be played. The effort to do this is very low, though
In my system, local streaming sounds significantly better than streaming from Tidal. I use Tidal to try potential library acquisitions but almost always buy a download and copy it to my Melco.
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Rob Watts, Chord’s designer of DACs etc has stated that RF ground plane modulation in a DAC affects the audio output, and he has put great effort into minimising that. (Nothing to do with file format.) if he is right, and I can see no reason to think otherwise, then anything that affects the RF content of the digital signal reaching the DAC could affect the analog audio output. I found with Hugo, which doesn’t have any attempt at galvanic isolation of the inputs, there was a very clear improvement in sound quality inserting an isolator between a computer source and the DAC. With Dave DAC, designed to eliminate RF modulation as far as could be achieved, an isolator is unnecessary.
Whether internet introduces more RF than a local network I don’t know - though it wouldn’t be less as the signal traverses the local network as well.
I grant that this might be possible. But why does he apparently go to lengths to not have galvanic isolation in the Hugo, when every ethernet port has galvanic isolation by design?
This is the interesting part, and I do doubt that this intrudes from the internet via the router in any meaningful way. And if it does, just put wifi in between, problem solved
In mine, I detect zero difference
out of curiosity how do you stream? Direct to the NDS or via the Melco, as proxy(is this possible)? How is the Melco attached to your NDS?
I have no idea. I had a Naim Unitserve server before and I preferred a bit Wav.
Now, with Melco, it’s Flac or AIFF.
But it’s really really minor however.
Why do they need to be decompressed ? Flac is more popular generally, or more common as format. Qobuz and Tidal use Flac for online streaming. And mosts sites sell downloads in Flac too.
It’s only a Naim strange thing, perhaps even not true, to give that preference to Wav.
I find Flac airier and a bit nicer vs Wav. But prefer also AIFF vs WAW.
But it’s a matter of preference in my system, my ears, my room. I can’t say that one is better, but which one I prefer and find better sounding for me.
The same can be experienced with DSD. Technically, DSD should sound better vs 16/44. But it’s not always the case . We are several here to find DSD dull sounding. I prefer personally 16/44 or 24/96 vs DSD, with my NDS.
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Yeah, but the null hypothesis would be no difference at all. If there really is one, I find the question interesting why that would be, and I can’t imagine any reason
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Hugo is a DAC, not a streamer, so doesn’t have a network connection, instead needing to be fed with a rendered digital music stream not data files. Aside from that, IIUC the absence of GA is because Hugo was designed to be used as a portable device, fed from a smartphone, and galvanic isolators demand too much power from the phone for such use. It is interesting that people then found it sounded so good that they used it in home systems! That of course led to the Qutest which does have galvanic isolation. (But of course GA of the port doesn’t of itself ensure ground plane modulation is completely stopped as any other coupling of source to the ground of the DAC would provide a path.)
Same answer to those who find internet cables make a difference with local sources, then fussing over which cable is best!…. Interestingly there still seems to be a view that using wifi degrades the sound - but perhaps it is to do with RF from the receiving end? Not something I’ve ever looked into or tried (I don’t stream files across a network or wifi, but feed direct from store to renderer in the same device.)
The Melco is connected to the switch ( PhoenixNet) and the Nds to this same switch. The streaming is using UPNP.