- Edited
well ... the output may be too hot, but if you divide it down with a a couple of resistors if should be safe enough ...
you probably don't want to mess around with getting the line out from the UA709, as that may affect the feedback behaviour of the instrument ...
Try something like this:
C5
-||----+---------------+
| |
| z 2k2
|_/| z
_ | LS1 +--------Bela audio in
| \| |
| z 1k
| z
| |
J5-----+---------------+-----Bela GND