Does Boulder use the convention that pin2 of the XLR is the positive phase or hot from an SE reference? Most do, but I have read that not every company does it that way. Like I said earlier, the Cardas adapters are of very high quality and based on my own use of them they do use Pin2 as hot, but "no adapter " is better.
Not to rain on Whest in any way, but from my reading Whest derives the balanced outputs by adding a device at the end of their otherwise SE circuit. (I don’t think it’s a transformer, but they are a bit mysterious on that subject.) I recall on my old Sony SACD player, the best one they made (SCD777?), they too used an add-on circuit to convert SE to XLR balanced out. The SE outputs always sounded better to my ears.

