I have one of the very first hardwired 6X5 B7 with no DSD as I have never really be a fan of it owning an SACD player beforehand - though don't get me wrong in can sound great in many ways, I think it lends itself better to classical music.
I'm interested in this as I came to the conclusion the USB interface wasn't as good as the optical one.
Can use a soldering iron...
I posted some details here http://www.computeraudiophile.com/f6-dac-digital-analog-conversion/jlsoundsi2soverusb-universal-serial-bus-industry-standard-cables-connectors-and-communications-protocols-between-computers-and-electronic-devices-spdif-adapter-board-and-galvanic-isolation-29001/#post563046 which should help, testing Diyinhk XMOS 768Khz USB card at the moment an sounds great as well, works fine on all PCM but I have not gotten DSD to work yet,