@donnylovely - that is very interesting indeed.
I have replaced my Amp and DAC and that has resulted in great improvements. I'm currently using USB into my Ares II DAC with an ifi USB iPurifier3. I have tested with and without the iPurifier3 and it definitely helps remove noise. I have also tested with a very expensive USB cable versus something for around £30 and noticed no difference once the iPurifier3 is at work.
As a continual tweaker, I have got a few components on order and will experiment with them in various combinations:
Audiolabs DC Blocker (will test on my Rega amp and the Denafrips DAC - may end up with two, one for each, or none if I can't hear a positive difference)
ifi GND Defender (as above)
ifi iSilencer+ - for the source end of the USB connection
Audioquest Cinnamon Coax - will try this instead of USB from the Zen Stream
ifi SP-DIF iPurifier 2 - will try it with the AQ Coax (with an iPower X for the 5V input)
Douk U2 Pro DDC - will try this with and without all of the above tweaks to see what gives in this super-budget device (I have a second spare iPower X 5V for this though reports say it is better with USB power)
An Intel NUC for ROCK - I want to evaluate Roon as I want to use Qobuz and Tidal in harness. Plus Tidal connectivity is intermittently glitchy to the Zen Stream.
If I like Roon I will try it direct to the DAC both via USB and via the Douk DDC - to see if I can eliminate the Zen Stream altogether. I will also probably buy a better PSU for the NUC.
Other than the NUC, everything is returnable (though I got the NUC for less than the barebones unit sells for new so I'm sure I can resell it).
I also have a pair of Cisco 2960's spare with SFPs and a short fibre optic cable that I can put in front of the NUC if necessary.
Believe it or not, my end game is to have as few boxes as possible but I want to experiment to find the best SQ with the "budget" kit.
If the DDC makes a big difference I will almost certainly try a Gustard U-18, Singxer SU-6 or Denafrips IRIS (if I can find an IRIS!)
With all of the above said, I'm also very interested in the new ifi Neo Stream but if Roon works well for me I will try to remove another network device and go direct to DAC. However, I suspect the galvanic isolation of either Wi-Fi to the Zen Stream or the Optibox into the Neo Stream will really help (plus the Neo Stream removes the need for a DDC and Coax/USB tweaks!)