[ctuna]

The Signals sent from the Logic 7 head unit are non standard fiberoptic and
no aftermarket amp other than the L7 understands them. Mobridge makes
a preamp that deciphers them and changes them to toslink or analog pre amp signal but that is not what you are asking.

Unless somebody came out with one and didn't tell anyone.

Its not impossible to put in an aftermarket system in a L7 BMW stereo just
convoluted and expensive and you have to loose the L7 amp.
The whole BMW system has to go meaning the BMW HU and Amp.
Then you have to put in something like a ms-8(has l7 in it) and amps and speakers to get back to about the same number of channels you had with L7 if you liked
it. Also you should mount the old head unit somewhere in the car to avoid
error messages and for the ability to still get you car to talk to the repair computer without errors.