Hi Gar, I understood this from the 'get go' when I initially auditioned the PAS a year and a half ago, and made sure to go out my Tyros in discrete stereo, utilizing 2 separate audio output cords, with each cord going into separate INPUT channels on the Bose PAS. Unfortunately, even with it setup this way, resulted in an unpleasant brittle dull sounding "Grand Piano" because the effects were now not heard (canceled out because of the classic stereo phase canceling phenomenom). My only guess is that perhaps Bose PAS's recent OS upgrade (of which includes new Preset EQ setting improvements) may have addressed and somehow been able to resolved(?) the prior stereo voice sampled phase cancellation problem. I'm keeping my fingers crossed and will let you guys know my findings after I've finally had a chance to audition at my local Guitar Center, the PAS with my Tyros once again. - Scott