[drfeelgood]

Originally Posted by gblaue

Ok, let me bring some clarity to what’s going on.

First, the MOST network is a ring topology. When you add the Nav-TV, it is being added to the ring in front of the Bose amplifier. Everybody on an unmodified ring has a node address that is assigned when the ring starts up.the head unit, which is the master (node address 100), know that the amplifier is(or supposed to be) at node address 101. The Bose amp will take address 101 at ring startup. And the next device would 102, and so on. When you insert the Nav-TV in between the head unit and the Bose amp, the Nav-TV grabs node 101. The head unit doesn’t know that the Bose amp is now at node 102. The head unit make the audio sink connection to node 101(which it hardcodded to know that is the Bose amplifier, in this case), so the Nav-TV takes the audio packet off the ring and processes the audio, which were intended for the Bose amp.

Second, why do chimes and beeps only work when the Bose amp is installed? The Bose amp generates the tones internally. The commands of what tones to generate for a specific function are sent to the Bose amp via the CAN bus. Cars used to have chime modules. With DSPs, it’s just a software function now.

Third, and last, whether you are listening to the stereo, or not, the Bose amp is always listening with the microphones, and generating an interference signal to the speakers. The ANC is always active, whether the head unit is on or off.

Hope this helps.

Thank you for the clarification!