MOST with analog sources

So I have a question about how analog sources are fed into a MOST system.

For example, in my Disco 3, I have AUX input which is analog. I assume that all data going into the audio amplifier in my system goes over the MOST system (will look through the documentation I have later today).

If that’s the case, does the head unit convert my analog AUX input to digital and then send it over MOST to the amp, which then converts it back to analog? Just curious how analog inputs work in this system when a MOST based amplifier is involved.

My assumption is that the AMP does not have analog input and is only provided data/audio feeds over the MOST optical bus. If I am wrong, then it probably just has an analog passthru over to the AMP.

Looking at some additional info in the MOST booklet makes it seem like I am correct in my assumption.

hi @urieal

I have no experience at all with MOST, but I’ve read a lot lately - and I guess I have to read much more :sweat_smile:

I think you answered your question yourself already but I can try to explain it in my words - hopefully someone corrects me if I am wrong:

I guess it depends on the setting of your car where the analog AUX actually gets transferred to MOST. In my car (second picture in SAAB 9-3 II thread) you see, that the AUX is connected (analog) to the Entertainment Head Unit (EHU) which incorporates the radio and I believe it also creates the sounds for the direction indicator, warning messages and so on.
In my case the EHU therefore incorporates some kind of sound card and it is a node in the MOST ring as well. I guess every node in the MOST ring, which incorporates some kind of sound card, could translate the analog AUX signal to MOST.
If I am not wrong every node in the ring

  • receives all optical messages on the MOST
  • transfers them into electrical signals
  • can read all messages which match to its own address
  • can add new messages addressed to other node(s) → like e.g. the processed sound from AUX
  • sends its new and repeats all the messages that it received initially (unless they are corrupt) in the correct order by sending out a new optical signal for the next node

Hope it helps and does not confuse you!