When using it with an external DAC from a third party.
i.e not the Naim DAC, in which case you would probably connect the PSU to the DAC itself, as opposed to on the transport section (NDX2).
If the addition of the external PSU to the transport makes little difference, when using a third party DAC in this way, then the ND5XS2 is probably almost as good … unless you want a nice colour screen of course
Having never used an external Naim PSU on the transport section only, I’m genuinelycurious …
In my old NDX days, I used to use it as a S/PDIF source for a DAC. I had a Cuddly Toy XPS which had made a rather nice upgrade when using the analogue outputs (not surprisingly) but no difference when used as a S/PDIF source. I assume the same with the NDX2. I’m curious as to whether Naim could supply a modified link plug for users who are using the NDX2 as just a digital source to disable the unused analogue section which may provide a slight benefit. I know Simon @Simon-in-Suffolk uses an NDX2 as a source for his Chord DAC but am not sure if he’s using it bare so maybe he’ll able to comment on his experience.
I use the NDX2 and it’s digital output using its own inbuilt power supply.
Will an external powersupply make a difference, well there might be a slight sonic difference but very doubtful there will be a meaningful improvement.
James the new streamers have a mode option in setup which configures the streamer for digital out or analogue out, but not both at the same time … so it appears there is some internal optimisation on which mode you want to operate the streamer in.
I don’t know, but I doubt that goes to powering on or off different parts of the circuitry.