Graham, the problem is not with the Bose - it's the adapter. Whether it's TRS or TS, it's still a parallel headset adapter and not intended to do what you want it to do.

Radio Shack has 1/4-inch to RCA cables, or you can also use a split 1/4-inch mono to 1/8-inch stereo and plug into the 1/8-inch input.

http://www.samash.com/hosa-cmp150-series...1g82xoCfPnw_wcB

I believe Radio Shack has this cable as well.

Good luck,

Gary cool
_________________________
PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!

K+E=W (Knowledge Plus Experience = Wisdom.)