gillatgh OP
At what point is an external D/A converter warranted or beneficial
Over a CDP, one good reason it becomes warranted is "if" the dac has clock output and the transport has clock input, so then the dacs clock can be slaved to the transport, so both run off the one clock through an extra bnc coax or even toslink lead.
As it’s always better to have one clock for both, that way transport and dac are in sync with each other, just like stand alone CDP’s are, as their transport section is running off the same single clock as the dac section.
Quite a number of transport, dac separates have this, usually reserved for flagship models.
Arcam had a toslink one they called sync lock out and in, with the front button called Pro, on their top dac the Black Box 500 the transport was the Delta 250
DCS have it, MSB have it, Esoteric have it ect ect.
Cheers George