Command replacement - Most converter to use existing Amp. No sound
 

I am replacing my Command with an aftermarket head unit and want to use the existing amp and speakers.
I purchased a Xtrons Most Converter that is supposed to work with 2005 CLK Command and Harmon Kardon Most amp.
The fiber is lighing and flickering, but no sound through the speakers. I have a feeling the amp is not waking up.
Does anyone know what I need to do to wake the amp?

It requires a proper signal sent over the fiber to wake up the amp. I tried to do some research on that Extron product, but I don't see anything they make for Mercedes MOST. What model is that you have? Any links to its product page?

BTW, the MOST interface units I've seen don't offer multi-channel support - they only output left and right with no fade control, like tghis:

https://avinusa.com/most-fiber-optic...edes-benz.html

This is the link to it on Ebay:
http://www.ebay.com/itm/Car-Optical-...72.m2749.l2649

XTRONS Model: FOB03

MPN: 5055869117388

Supposed to be plug and play. Wasn't sure if there was a 12v wake up line for the amp.

They are only 2 channel. The HK amp will distribute the sound to all the speakers.

The Xtron is supposed to work just line the Avin unit. The HK amp takes the 2 channel signal and distributes it to all the speakers.
The fiber flashes but no output. I have a feeling it is missing the turn on command. There isn't even a bit of hiss through the speakers.

Just a shot in the dark, but I see it has leads for Battery+, Accessory and Ground. Where did you attach those? I know there is only constant +12v in the vehicle wiring harness for the radio. You's have to pickup the accessory power elsewhere - say from the cigarette lighter.

I contacted Xtrons. They are sending a different model, FOBB01, that they say should work. I will keep you posted.

Please do let us know. I think even though you don't get fader control, that would not matter to me - I never adjusted the fade in the CLK. I always kept it centered. I do wonder if it does the Logic7 processing, though.

As I understand the processing is done in amp. It includes electronic crossovers for the tweeters and the subwoofer as well as the Logic 7 processing. We just don't have the code set built in to manipulate it - fader etc.

On Xtrons site they are now including the Most fiber decoder as part of the package with their Android radios. Only problem is they don't have the faceplate size to fit our car. They have the 260mm x 240mm and we have 254mm x 238mm. Which I found is hard to get.
http://xtrons.com/pb76m209ap-fobb03-...r-decoder.html

I bought an Android radio that does fit. It has very good bi directional Can Bus. I can use the steering wheel controls and the display in the center of the speedo show the radio station, CD track info, etc. It surprised me how well it works. I can't recommed it yet. I ordered it with Android 7.1 and 2 gb ram. They shipped a unit with Android 5.1 and 1gb ram. When its straightened out I report back on how it is working. Currently fighting with them on shipping return charges.

I have been working on this and tried a different model of the Most adapter and it didn't work.

I have a hunch that the problem is the amp is not turning on. I have attached a schematic of the most bus and it shows seperate turn on lines. They call them Wake up.

I think when the Command goes on it sends a signal over the wake up line to turn on the Amp and the CD changer etc.

Can you tell if it is just a 12 v signal or some type of code? I was going to test it but not sure of pin out of the radio connector.

Or from the schematic can you tell what wire color is from the way it is names? I have indicated what the wires are with blue arrows.

Thanks!

BUBK = Blue w/ Black tracer.

Thanks, there is a blue / black at the connector for the Nav and the power connector for the CD changer. I first checked them for continuity and they are connected.
Then I checked for voltage. They have 12v. on them with the radio disconnected. When the ignition is on they have 12v. I was hoping it was a 12v trigger from the Nav to turn on the other devices (amp and cd, etc), but it is not. Nothing is simple in these cars!
The set up in the CLK500 from 2005 - 2009 is unique in both size and how the amp works. The Most adapters for the other models just do not work with our cars.
I guess I am going to have to put in a new amp to use the existing speakers.

Hi,

Do you have WIS wiring diagram for the H-K amp and speakers in the CKL Cabriolet? I have been searching for it and can't find it.

I want it to determine how many amp channels I will need. I think 5 so far - 2 - Door front, 2 - Door rear and sub. Not sure what the tweeter in the base of the A pillars are wired too. Do they currently have their own amp channel? I was thinking if they go back to the amp to then use a small cross over to connecing them to the door front speakers.

I know there is a center speaker in the middle of the dash. Just going to abandon that one.

Any ideas for me?

Try this:

http://benzbits.com/w209/SoundAmplifierWIring.pdf

amp question on clk350 06
 

Good luck OP, and I apologize for jumping on this thread, but my 06 clk350 sometimes will not have sound, even though I can see the iPod track playing or radio is "on"... is this because the amp is not waking up or I turn the car on with the radio on, or what?

Again, once I read about the amp turning on or off, I suddenly realized this could be the trouble in my car; it happens one out of every three times I am driving and want to play music. Sorry to OP and Rudeney and again good luck with that new system...

Does it happen if you are on Radio and the iPod input?
If it doesn't happen when you are on Radio then it isn't the wake up line.
Most probably an issue with the iPod cable. It isn't connected properly to the iPod or has an intermitant connection to the wiring of the connector.
Try another cable to see if this solves the problem.

Hi, thanks for the response...

No, it happens both with the radio and the iPod sound.

I get nothing at all and it happens when I start the car... it won't suddenly come on later while I'm driving...

just no sound at all on that trip.

I came across the same issue with my 2009 w211 and COMAND NTG2.5. I was able to wire everything up, the radio comes on and sound is going to the harness outputs instead of the RCA cables. I guess its because the amp is not on and I could verify that it doesnt come on. On the factory harness pin 16 is the MOST wake-up signal, when turning the ignition on it sends 3 grounding signals over that pin, the aftermarket unit does not! I don't know how to fix it, but I was hoping there is a way to power on the amp without the wake up signal and use the ignition ON clamp from the SAM in the trunk. Did somebody successfully replace a NTG2.5 with an aftermarket unit? What am i missing here? Thanks

Hi. So what came of this? I'm stuck on this same thing on my w219

I tried several Most adapters from 3 different sources with my aftermarket radio and none would get the amp to turn on. I was able to return them all. Then gave up.

With the low cost of a replacement amp I ran 5 RCA cable to the trunk and installed an after market amp. I cut the speaker and power wires off of the old amp and connected them to the new amp. It wasn't difficult to run the audio cables to the trunk. The entire install of the amp too less time than mucking around with the all the Most adapters.

It works great. The whole system with stock speakers sounds much better than I expected.
I used a Soundstream PN5.640D Picasso Nano 640 W 5-Channel Class D digital Car Audio Amplifier I bought on Amazon for $139.00. It's been over a year and still going working and strong sounding great.

Hi OP,

I am currently in the same boat, have a 2007 with the HK system and just bought a Pioneer AVH-w4400nex but struggling to figure out the fibre optic bit.

At the moment, I am waiting to hear back from connects2 as this: http://www.connects2.co.uk/Product/P...tem/CTSMC013.2 might work, but not sure yet.

From the pics, it seems to have a similar box to the xtrons FOBB03 and the one AVINUSA sells. So you had no luck with them even though you did feed them a constant 12V?

If I am do go the same way you did, replacing the amp, are the HK speakers 4ohms as well? My fear is that they might be lower, thus making it hard to work them with an aftermarket amp. Is your setup as loud as the factory setup was? Cause I've heard the volume might suffer.

Many thanks!

Jason

So you kept the HK system or swapped the amp out?
Do you have a link to that Metra harness, or the part number handy?
Thanks!

I can only see harnesses for non-amplified systems on axxess's website, like the AX-ADXSVI-MB2.
To keep the HK amp, there must be a MOST module that converts RCA to fibre optic.

I am sure your car is the same. Did you perhaps bypass the amp and wired the speakers to the aftermarket radio, using the built in amp?