MacMini –> Audirvana 3.5 –> Sonarworks –> UpnP –> Golds (DOS2) = BLISS!

[Pwalder]

Thanks for spending so much time on this. The current situation is that I have a working system as a result of creating a separate wifi network from my Virgin Media cable modem. This gives an average of >70Mb/s speed. Both my iMac and iPad (remote) are now on this network and I have also configured the Phantoms to this network  and everything seems to be working with the exception of 24/192 files which still skip. Files are being streamed from Qobuz Studio and Tidal Masters trial accounts (I understand that Phantoms don't support MQA so Tidal Master files are being rendered after just one 'unfold' in Audirvana......as I understand it!). I have restricted the input from Qobuz to 24/96 to stop the skipping on native 24/192 files.

The question you asked relate to the old network which is still working ok for non Audirvana applications. Here are my attempts to answer them.

1.  What network equipment do you have?  All-in-one modem/switch/access point?  Model/vintage?  Please describe the topology if simple or draw it if not.  Please describe how far away anything connected over wireless is from the access point and how much, if anything (e.g. walls, etc), is in the way.

Answer: The Virgin Media cable modem is a very recent acquistion from my ISP and I believe has up to date spec but is not a MESH modem. On the 'old' network the cable modem  is linked to an Apple Extreme Time Machine which then effectively becomes the router.......Apple Support helped set me up the precise configuration of the Apple Extreme and I am afraid the details are beyond my knowledge. The Apple Extreme supples both 2.4 and 5.0 networks and I tend to use the 5.0. The Apple Extreme is also linked via a Powerline system to two Apple expresses elsewhere in the house and garage to increase coverage. One of these Apple expresses is in the same room as the Phantoms and an ethernet link goes from the Apple Express to the 'legacy' Dialogue and this is still active and in the old network was recognised by DOS 2 as being present.....plan was to use the Toslink port for my Arcam CD player. I did test this and it worked although if Qobuz/Tidal prove reliable I won't need it.
2.  How is your iMac connected to your network?  Ethernet wifi? both?  If wifi, how good is the wifi signal strength seen from your Mac (do you have the tools/knowledge to measure it?).
Answer: .....See above.. Effectively both on the 'old' network but under the new configuration just wifi via the Virgin Media cable modem and that pathway doesn't include the Apple Extreme or Powerlines etc. Just to note the Mac and Phantoms are in different rooms. Mac upstairs and Phantom downstairs so no 'line of sight possible'.
3.  You say your Phantoms are not connected via Ethernet (correct?) but your Dialog is (correct?)
Answer: Yes that is correct in both instances... (see above)....Dialogue and Phantoms are all in the same power block.
4.  How good is the wifi signal seen from your Phantoms (do you have the tools/knowledge to measure it?) averages > 70Mb/s
5.  How are your Phantoms connecting to your Dialog? (in the app click on the cogwheel, each speaker and then Network Interfaces)......The interface is 'Auto' in both Phantoms. Just to note that both Phantoms are running 2.8.5 but the Dialog is running 2.8.3. I have been in regular communication with Devialet support for about 3 weeks as they said they should all use 2.8.5  and they have promised an update for the Dialog but it hasn't appeared yet...I've been nagging!!

As you can see the 'old' system is pretty complicated but up to installing Audirvana it 'just worked' consistently. We are expecting to move house in the next month so I am now starting to think this is the opportunity to start with a blank slate and build up from the new wifi network. This may well mean retiring the Apple Kit which has been super reliable and for a non-techy like me the Apple Support (like your own!) has been fantastic and a very reassuring back stop.
Once again thanks for spending so much time on this and if you do have any suggestions on the best way forward I am very happy to listen.......I have learnt a lot from this exchange.

This afternoon, after yesterday’s success, unfortunately the skipping has returned. Internet speed was not the issue at 100 Mb/s and was present on 24/96 which was working yesterday  ☹️

Aaaargh, so close!  @Pwalder I has suspicions that your network was somehow to blame, and there are indeed a couple of factors in your description that could be causing issues (see advice below).  However given the above I am now leaning towards a firmware problem as the most likely culprit.  The optimist in me would love to think this could be rectified by updating your dialog to 2.8.5, let's hope so, but unfortunately the realist in me says the optimist is a fool and that the upcoming 2.9.0 is more likely to provide the solution.

A couple of observations about your network:
1.  PLC bridges, like the ones between your Virgin modem and your Airports, can be problematic.  If there is a device (usual culprits are washing machines and driers, especially old ones with mechanical timers) that is sending noise back into your mains, PLC connectivity can be the first to suffer.  It is hard to control the quality of your mains so PLC is really for last resort only.
2.  Wifi antennae radiate perpendicular to the antenna in a circular pattern.  Imagine holding an LP on a pencil.  If the pencil is the antenna the signal propagates in the direction of the vinyl.  In other words if your antennae point straight up you will get best propagation (i.e. coverage) horizontally.  But if you want coverage in the vertical plane, such as in a multi-story house, you will want to angle the one or more of the antennae appropriately or use a mesh system with one unit on each floor.  
3.  However it is also hard to control the quality of your wireless environment, especially if you live in an apartment building or other multi-unit dwelling where your mains and your airwaves are at risk of pollution by others outside your control.  For that reason Ethernet is still more reliable than either.  If you are moving house please consider getting it wired!  
4.  Finally, Wifi dropouts are not always due to poor coverage causing poor bandwidth.  Radio spectrum is a living organism and even if the architecture is pretty fixed sources of congestion and interference come and go.  So measuring bandwidth at the endpoint tells you something, but unfortunately you may never know how much it is actually telling you.  Hence point 3 above.

Sorry, I've failed you here.  But with your latest datapoints I am tending to the view that your problems are not user-solvable.  Sorry.

Thanks once more. Its playing 24/96 without a hitch as I write this on the 'new' network i.e. which only uses wifi directly generated by the Virgin Media modem - no plc. I didn't know any of the information you've provided about wifi propagation or washing machines (which actually was in use yesterday so just might have been influential). Like you, I think the Dialog firmware mismatch is almost certainly a red herring. I am certainly not giving up on this, as when its working it's something I really enjoy and as the new house we are buying is going to need some electrical work I will seriously thing about getting some ethernet wiring. I've read about  different CAT wiring standards, so if I go down the ethernet route (which now seems likely), what standard wiring should I specify in order the wiring is reasonably future proof ...CAT 7? Could I also ask one final question.....given the comments about router antenna, and the fact that my router is on the first floor (but immediately above my Devialet Phantoms on the ground floor), would simply changing the orientation of the modem/router (ie lying it flat rather than upright)  make a difference. I appreciate I can just try, but wasn't sure if modem manufacturers already have thought of this and build in two perpendicular aerials to in effect create a sphere of wifi rather than a two dimensional disk (LP in your explanation)? Thanks again for the time you've spent on this. I continue to learn and I have no plans on giving up on this until I get a stable system.