after more than a year of development, my USB audio class 2.0 interface finished.
it's complying the USB Audio Class 2.0 standard, will have native support in Mac OS X 10.6 (or later) and Linux (with the lastest ALSA). a custom (ASIO) driver for Microsoft Windows (XP and Windows 7) is also available. :-)
apart from standard S/PDIF (and AES/EBU) output, it also equipped with an I2S output.