I am considering upgrading my car's stereo with a new Multimedia Receiver (Pioneer DMH-W4660NEX). I plan to keep the Bose amp and speakers and just use a MOST connection from the head unit to the amp. The question I have for folks is this. How does the volume control work? Do you preset the volume with the steering wheel control (max volume) and then use the volume controls of the head unit to adjust the volume within the set limit or do the head unit and steering wheel controls both adjust the Bose amp?

 

What year and model car are you retrofitting? You posted in the R230 section but show a 2021 car.

 

2007 SL550

Sorry for not being clear.

 

Your selected Pioneer Head-unit looks top quality. I bought a $180 Head-unit from Amazon and am very happy with it. With an adapter (as mentioned on the Pioneer description), my steering wheel "+" and "-" keys adjust the volume. My head-unit also has a volume control button so that I can quickly change volume if needed. See my post #19 here:
https://mbworld.org/forums/sl55-amg-...004-sl600.html

 

Your new headunit will control the volume.

The output from the Phono connectors on your head unit will be translated by the MOST converter and the BOSE amp will respond correctly.

Your steering wheel controls will do absolutely nothing.....

UNLESS.....

you use a CANBUS adapter which can connect your headunit to the Mercedes CANBUS. Then the volume controls, forward/Back and telephone buttons on steering wheel will control the new headunit.

Waiting for adapter fascia so I can fit my Pioneer head unit, that I removed from my old SLK, into my 2005 SL500. Hoping the SLK parts will fit the SL500 system

 

This is the CANbus adapter I used and which seems to be very popular:
I only got the Volume Up/Down buttons working, but I think that was a limitation of my cheap Head-unit.