resolved but i think we can write this one down to extra terrestrtial activity..........OM's suggestion was worth a try - yes its a mini jack on the front panel - and the cheapie headphones gave me both channels. then plugged in my quality phones and got both channels. but it still doesn't explain why all other sound programs worked with the quality headphones apart from RB. i could get BIAB on both left and right and then only left on RB with the phones plugged in and not moved or adjusted in any way...........

thanks OM and rharv for the suggestions but i think this goes in the same box as 'what happened to the Marie Celeste........'