Yeah, isolation won’t make much difference there. At the moment I’m running my Spring 3 from UP Gateway based NAA straight (CUI Inc medical grade 5V PSU) and it measures fine. And Spring 2 straight from my HP Xeon server and that measures fine that way as well…
I’ve tested both with Intona too, as it also works and measures fine that way.
On T+A DAC 200 I’m using Intona 7054 and it makes measurable improvement. And on T+A HA 200 I’m using 7055-C and it makes measurable improvement there too. In addition, with Accuphase DAC-60, I’m using Intona 7054 and it makes big measurable improvement there as well.
On Marantz SA-12SE, I’m using 7054 too, but there the difference is smaller but still worth.
My Holo Red is paired with TEAC UD-701N and it is pretty good for that, alternatively I would recommend USB isolator with that DAC.