I think the "airy sound" is what you get with a tube amp that doesn't stick to tube amp design criteria that have made tube amps famous.
To get the classic tube amp sound you use point to point wiring, simple signal paths, and great power supplies. the ones that are being mass produced use printed circuit boards, have complicated circuits with lots of things attached to the signal path, a swiss army knife of features, and the sound suffers.
Jerry
