[gtmax500]

Hello everyone,

I am planning on upgrading the sound system in my H/K equipped M235 and have some questions about the amp wiring and MOST bus ring.

I have decided to forgo the LOC and high level input DSP and instead use a mObridge DA3. This will allow me to utilize the higher sound quality optical MOST bus interface and a DSP all in one device all while maintaining factory volume and owner controls, where I can purchase said DA3 as a direct consumer is a different story.

Anyway, I took out the trunk liner today to inspect the stock H/K amp wiring harness but could not find the MOST optical ring connections to the amp or ASD module. I did however find 3 optical connections into the (I believe) Bluetooth combox to the left of the fuse box under the trunk liner. My question is, is the HK amp not in the MOST ring and getting just an analog audio signal from some other module, and why are there 3 optical connections into the Bluetooth combox?

The mObridge website says the f22 is supported with the NBT iDrive but I guess that means I'll just have to install the DA3 before/after the Bluetooth module.

Any insight into the ways of the MOST bus interface would be greatly appreciated! Thank you.

[Gabrola]

The HK in the 2 series is a different one than the ones in the 3 series and higher, and it is analog and has no MOST connection.

[Viffermike]

Originally Posted by Gabrola

The HK in the 2 series is a different one than the ones in the 3 series and higher, and it is analog and has no MOST connection.

Correct. Basically, with a few relatively minor exceptions (example: the output from the HU is balanced, so any amp added to the system must have differential balanced inputs), the 2 Series audio systems operates like a traditional/typical wired car audio system. Your best course of action is to get your hands on the wiring diagram for it, then plan accordingly.

[Gabrola]

Originally Posted by Viffermike

Correct. Basically, with a few relatively minor exceptions (example: the output from the HU is balanced, so any amp added to the system must have differential balanced speaker outputs), the 2 Series audio systems operates like a traditional/typical wired car audio system. Your best course of action is to get your hands on the wiring diagram for it, then plan accordingly.

I believe you meant balanced signal inputs not outputs.

[Viffermike]

Originally Posted by Gabrola

I believe you meant balanced signal inputs not outputs.

Yep! Post edited. Thanks!

[gtmax500]

Okay, thanks for the info guys. I guess ill give mObridge a call since they say it's compatible.

Any pointers on where to find the wiring diagram? My cursory Google/forum search did not yield anything.

[zipphreak]

Scroll down a little in my post. Probably doesn't help, no MOST, just copper wiring.
http://www.2addicts.com/forums/showthread.php?t=1124786

[Gimmethecash]

I'm planning to completely bypass the factory audio system in this car - I'll run digital coax from my FiiO X7 to my Helix DSP Pro and the rest of the system I'm taking out of my Audi.

[Gabrola]

Originally Posted by gtmax500

Okay, thanks for the info guys. I guess ill give mObridge a call since they say it's compatible.

Any pointers on where to find the wiring diagram? My cursory Google/forum search did not yield anything.

The mObridge DA is actually compatible, but you will, however, need to add the mObridge into the MOST loop, making the install a little bit more involved, and code your headunit.

[gtmax500]

Originally Posted by Gabrola

The mObridge DA is actually compatible, but you will, however, need to add the mObridge into the MOST loop, making the install a little bit more involved, and code your headunit.

Thanks for the info. Got my DA3 on order but unfortunately they are having manufacturing problems so they said it will be another week ?

Quick question, does it matter where I add it to the MOST loop or anywhere is fine? Maybe ill start a build log when I get all my parts in.

[zipphreak]

How do you add it into the MOST fiber optic loop if the HK amp is not part of it.. Where do you plug the pre-amp in? Is the MOST output directly on the HU ?

[gtmax500]

Originally Posted by zipphreak

How do you add it into the MOST fiber optic loop if the HK amp is not part of it.. Where do you plug the pre-amp in? Is the MOST output directly on the HU ?

If I'm understanding it correctly, the MOST bus is a loop so if you attach a device anywhere in the loop they should all communicate with each other. I think the two main connection ports are the head unit and the amp. Unfortunately our amp only receives analog so that is out. When I had my trunk liner out I saw a fiber connection into the Bluetooth combox. That means we should be able to add a MOST accessory to that or the head unit. That's just my understanding of it so it could be wrong.

Since our head unit outputs analog sounds we will have to code it to output digital sound.

[zipphreak]

Very interesting project you got. Keep us updated, alot of good information could be gathered from your experiences.

[Gabrola]

The devices on the MOST loop are the headunit, instrument cluster and the combox for older cars (the TCB on newer cars isn't on the MOST loop). So you'll have to add it into the loop with the input and output going to the devices you are going in between. Diagrams added for clarity.

Before:


After:


Oh and if you don't have navigation/NBT headunit in your car then you probably won't have a MOST loop in the car at all, and the headunit will probably not have MOST sockets.