I play my B2 through a Bluesound Node 2i streamer via optical cable, which is similar to what you want to do. If the Mu-So has an optical input, which I think it does, you could do the same. You'll need a "mini toslink to toslink" cable just long enough to do the job without putting any sharp bends in it.
As the B2 is so small, the rear panel doesn't have room for a full size toslink (optical) socket, instead it has a combined 3.5 mm (analogue) jack output and optical (digital) output. It's marked "line out + SPDIF" .The mini toslink plug fits that, with the full size one at the other end of the cable going into the streamer. There's more information on the Brennan website: