I've been told both: that an adapter is bad and that it makes no difference.
@stuartk , I am certainly no expert on the subject. There may be variables involved that have an effect on how one feels about it.. I remember when my old Canare RCA to BNC cable started acting up I was feeling pretty proud of myself for knowing where I had put the adapter that the manufacturer of my DAC had provided. I really wanted it to sound good, but it didn't, so that is why I wound up biting the bullet and buying another cable. I suppose this may be one of those YMMV things.