a2dp via blueman does not work

[farinet at arcor.de]

A year ago i remember, sending audiostreams via bluetooth (using
blueman) to an amplifier worked like a charm. Now, i'm unable to set
this up (the receiver is a Dual BA1). Blueman pairs but only as headset
not as a2dp. When i'm trying the latter i get:

"Stream setup failed"

I checked, if the receiver is broken, but it isn't: from an android
phone i could easily send audiostreams.