few

TLDR: RCA-to-MOST adapter, does it work?

Hi all,

I'm new here, but recently picked up a 2007 C280 W204 with Harman Kardon sound system. I like the car, and the stock sound system is good, but I wasn't happy with not having any interface for plugging in my phone (I want support for podcasts, music, Andoid auto/maps nav, & backup camera). I would have been fine with a 3.5mm aux input, but my car doesn't support it, and it looked like it would cost a lot to install one of the stock MB phone adapters (because mine doesn't have the cradle piece, and MB doesn't sell these anymore).

I spoke with folks at Crutchfield, and ended up installing a Sony head unit (XAV-AX100). The head unit is very nice & I love android auto. I'm not thrilled with the resistive screen (I have to push hard and the sliding motion doesn't work great), with the fade/balance controls, or the backup line configuration options. But overall it's a good unit, and I'm happy (I'd rate this 4/5).

Crutchfield also sold me a bunch of other stuff:

• For fitting the double DIN / 2DIN head unit into the MB C280 dash: American International MBK102 Dash Kit, which seems fine, although I haven't finished putting the trim back in place yet.
• To connect the stock radio antenna: Metra 40-EU10 Antenna Adapter. I'm not thrilled with the FM quality, it seems to have worse reception than it initially did (I suspect the antenna might not be getting power?). If anyone has an idea about how to improve this, I'd love help/feedback!
• To adapt the MB W204 harness & steering wheel controls: Crux SWRBM-57 Wiring Interface. This was really annoying to install. At first the wiring interface wouldn't power up the AUX power wire when the key was inserted & ignition started. It turns out that the CAN BUS wiring was backwards for the C280 W204 Harman Kardon vehicle harness. I had to cut & reverse the wires for the + and - CAN bus signalling. Afterwards it worked, except it only handles the volume up/down controls on the steering wheel, not the steering wheel phone controls. Super disappointing, considering that it was labeled as ready for my vehicle model. I'm a noob: I didn't realize that 'steering wheel control function retention' doesn't mean retaining all the steering wheel controls... Buyer beware I guess. I'll post a picture & diagram in a later followup message.
• Backup camera: Boyo VTL17IRTJ, I installed this by drilling a small hole right above/behind the license plate. There is a small hole through the plastic trunk fascia that the license plate attaches to, and another small hole that goes through the main trunk wall. I used some self-sealing rubber tape to act as new grommets in both locations. The camera quality isn't amazing (the picture is washed out in bright light, but it's fine for the 20 seconds that I use it. I'm not taking family photos with this thing, and it should help ensure I don't miss any kids walking behind the car. I haven't used it at night yet, but I'll check on that later. The installation instructions included with the camera are really lousy. I ended up powering it by t-splicing into the reverse light harness right at the rear right tail light. The red wire on the RCA video jack is meant to be hooked up to the reverse signal at the head unit- it works fine. I'll post a picture & diagram in a later followup message.
• I used the stock SONY male to female USB A cable to run from the head unit into the arm rest. Then I used a second usb cable (overpriced) to plug in my Andoid phone in the upper arm rest. uLinxMAXT USB to Micro USB. I might eventually 3D print a holder for my phone so that my phone fits snugly in the arm rest pocket.

Here is where things kind of go off the rails, and I'm really looking for advice.

I realized that the stock Harman Kardon amp wouldn't work with the head unit. Crutchfield advised the following to get the speakers connected:

• A 9 conductor harness to run the 4 speaker outputs (front/rear left/right) from the head unit to the car rear. EFX 9-Wire Ultra Flex Speaker Wire 20 feet. It's a great cable , I love the clear silicone covering, and it's easy to work with, but I should never have used this approach in this car in the first place!
• Connectors for connecting the SONY head unit wires to the new 9 conductor harness. Posi-Products Car Stereo Wiring Harness Connectors. I love these connectors , which I had never seen before. I should have bought 2 or 3 packs, as the 1 pack I had is not enough for the install I was doing.
• A mono amp to power the subwoofer: Alpine KTP-190U Power Pack.
• Power cables to run from the battery to the new amp: Crutchfield CK12. Once again, great cables , but I ended up not needing them at all.
• A cable to run the signal from the new amp to the subwoofer: Crutchfield Speaker Wire 12-gauge. Nothing special. This was totally useless for me. I don't know why this was ever recommended by Crutchfield sales.

I was eventually able to connect up the harness to the four door speakers. I also hooked up the amplifier. What I hadn't realized when purchasing all this was that I lost a bunch of speaker outputs, and this doesn't sound nearly as nice as the stock amp. Again, I'm a noob. I lose all outputs from the tweeters and base in the two front doors, the center dash speaker, and the rear most speakers.

I also basically can't hear the subwoofer at all, and I don't have control over the sub. This doesn't use the signal from the head unit sub output, instead it uses the front right/left head unit speaker drivers to generate the subwoofer signal. The subwoofer is a dual-coil system, so this new setup sucks.

Crutchfield were great about accepting returns, and they were very supportive in solving the issues I ran into (for example helping me to figure out the backwards CAN bus wiring on the CRUX adapter).



So, now I'm trying to find a better path forward. Here's where I really need help.

This RCA-to-MOST adapter for using the stock Harman Kardon amplifier looks great: https://avinusa.com/most-fiber-optic...l-r-clk-c.html

Is it too good to be true? Or does it actually work for the W204 C280? Has anyone seen AVIN RCA to MOST interface reviews for the 2007 C280?

It should adapt from the head unit RCA output to the M.O.S.T. fiber optic bus and allow me to use the stock amplifier to power all the speakers. At 99$ it's very worthwhile, if it works. AVIN does specify "Mercedez-Benz C 2005-2008" as being compatible. But AVIN also has a policy of "no returns for this product only exchange", which would leave me out about 150$ (because I would also need a couple of fiber optic bypass loop connectors where I'm taking out the stock CD changer and satellite radio). This solution would give me left/right balance control, but because the unit only uses the front RCA stereo outputs, I wouldn't have front/back balance control with this adapter. The front RCA connections are apparently used because that's the speakers that phone bluetooth sound is projected through. I'm fine with those limitations, if the unit works.

The reviews online for AVIN seem to vary widely. Some people have posted pretty negative things about AVIN (that site seems a bit racist, but they indicate that the units never worked for them), and some people seem happy with the products as working fine. I'm waiting to hear back directly from AVIN (I only sent a message last night - this is not a complaint!). I haven't seen any reviews or feedback specific to the 2007 C280 W204. Does anyone have experience with this product or company?

What looks like the same unit appears to be sold by a bunch of places. I think the original manufacturer is this Taiwanese company (Long MK Trade Limited): www.autoaux.com. They sell it directly through Aliexpress for 90$. I contacted autoaux.com, and Polo stated they have not tested it with the 2007 C280 (I'm guessing any W204 C class vehicles).

I think that their Type B model is the same as what AVIN is selling (rebadging?). AVIN lists the unit as compatible with the C class vehicle.

EBay has a listing from ACR-hof (in Germany?), that seems to show the same adapter for 250$ (pretty steep markup if the same unit!), and they list it as being compatible with the Mercedes C-class W204 vehicles.

There are also a bunch more EBay listings for units that look essentially identical (designed in Germany, made in China)
Here: Listed for W209 & W211 (99$)
And here: Listed for Mercedes Benz ML GL R Class W164 X164 W251 & Porsche < 2011 (99$)
And here: Listed for Mercedes Benz CLS E SLK/SL W219 W211 W171 <=2008, and S/CL W220 (99$)

Real & works, or not?

I still have my car ripped apart, as I don't want to reinstall all the trim until I'm done with this mess... Please help this MB ASAP!

Thanks in advance for your help!

few

I guess no one else has replaced their stereo or tried one of the RCA-to-MOST adapters?

If it works, it should be a huge convenience improvement in the car.

few

I'm adding some details here about the Harman Kardon amplifier wiring in the trunk of my 2007 C280 4Matic (W204).

Rudeney had posted a wiring color label that seems to be correct for my amplifier (also see my photos below):

few

Here I'm detailing the wire I used to power the reverse camera. I used a BOJO camera.

The ground supply lead for this is easy to hook up (ground screw is easily accessed on the vehicle chassis between the fiber optic amp and the satellite radio controller near the rear right tail lights).

The 12V reverse-enabled supply is not so obvious, it needs to be hooked up to a wire on the rear tail light assembly. I show it in the following photo. The yelloy/grey wire is the reverse light power supply that should power the camera when backing up (you can see that I spliced the red supply wire to the camera onto the yellow/grey wire).

Adi-Benz

Not many people, VERY few have changed the head unit, so there's not much knowledge on this. Post pictures of the new unit when you're done!

few

Here are some photos of the Sony head unit installed in my C280.

Sorry the dash is still dirty / smudged, I haven't cleaned it up yet after reinstalling the panels. It isn't a perfectly flush fit, but it is almost completely seamless.

few

I love having Android Auto on my C280!

few

Here are photos of the Crux adapter cable.

I described this earlier:


I have slightly pulled out the brown/pink and pink cables that I needed to swap before the CANbus communications worked in my 2007 C280. To swap the wires, I cut them, and used a short tie Western Union splice to connect the pink of the first connector to the brown/pink of the other connector, and vice versa. After I did this swap, the steering wheel volume controls worked correctly (and the aux power from the Crux unit started working). Before the CANbus wire swap the Crux interface didn't do anything other than waste a bunch of my time. Everywhere I made a splice I covered it with a self-fusing silicone tape.

few

Here's some information that didn't work with my C280.

This is what the MOST cable connectors look like. Except mine also have a few electrical conductors in the MOST cable connector.


FYI, I received the following information from a support line, but it didn't match what's on my C280. The connector on my AMP looks nothing like this. I'm not sure what model it might correspond to. I think it's some different C class model. Maybe the stock non-optical version?


FUNCTION
PIN
COLORNoise Canceling Mic In (+)
1
WT
Noise Canceling Mic Shield
2
BARE
Noise Canceling Mic In (-)
3
BN
MOST-Bus Wake Up
8
BU/BK
Chassis Ground
9
BN
Sub Coil 1 Output -
11
BN/VT
Sub Coil 2 Output -
12
BN/YW
LF Speakers +
13
L.GN*
RF Speakers -
14
BN/OG*
LR Door Speaker -
15
BN/PK**
Center Speaker +
16
GY
Amp is located in right rear corner of trunk behind side panel
FUNCTION
PIN
COLORRR Door Speaker -
17
BN/WT**
Sub Coil 1 Output +
19
VT
Sub Coil 2 Output +
20
YW
LF Speakers -
21
BN/L.GN*
RF Speakers +
22
OG*
LR Door Speaker +
23
PK**
Center Speaker -
24
BN/GY
RR Door Speaker +
25
WT**
Constant 12 Volt
26
RD/VT
*Front door tweeters and front door woofers are wired together in parallel.
**Rear deck tweeters and rear door woofers are wired together in parallel.
All factory woofers are 2Ω impedance. Reverse Light ( + )
Pin #8 of 16-pin plug (C14) at trunk fusebox
GY/BU

few

Confusion, and perhaps some encouraging information...

I found an aliexpress site that indicates that the C280 MOST cables will not fit the most common model of RCA to MOST adapters...



This seems to have the part number JN1702001563BP56.

That is definitely what the MOST adapter on my vehicle looks like:



The dual fiber optic cable connector and 4 pin electrical connector are held in a larger connector, and can be easily removed by pushing on release-tabs.





My Harman Kardon amp and Sirius unit have the following connectors:





The unit that AVIN sells as "Mercedes MOST Fiber Optic Amp Interface for ML GL R CLK C" has the following product photo:


The unit that AVIN sells as "Mercedes MOST Fiber Optic Amp Interface for E-Class CLS SLK S CL Mercedes-Benz" has the following product photo:

From the look of the connectors, the "CLS SLK S CL" type probably does not fit the MOST connector in my C280, but I'm pretty sure that the Type B "ML GL R CLK" type probably will fit the 2007 C280 after disconnecting the fiber optics from the larger connector. This matches the explanation from the 250$ ebay listing for what looks like the same product. They state that it will work if the connector looks like either of the two following photos. They also say that for the larger connector, the fiber optic cable just needs to be pulled out of the larger housing. Aha!



As I showed above, with my connector the fiber optic pops out easily. I'm getting more confident that this will work, but still not 100% sure.

I'm very disappointed that the aliexpress stores seem to be unwilling to accept returns on the units. I'd love to try this to see if it works, but am hesitant to drop 100+$ on testing (anyone else feel like splitting the risk?).

I haven't heard back from AVIN since 4 business days ago, which reduces my confidence in their store. The aliexpress stores at least reply via email...

Adi-Benz

Nice job! But, also, I'm pretty sure your car is a w203, maybe more people know extra info over there.

few

Oops! You're right, my model is a W203. https://en.wikipedia.org/wiki/Merced...C-Class_(W203)

Is there an easy way to move the whole thread to the W203 forum?

Thanks!

few

EDIT: I think that the only difference between the "Type A" and "Type B" RCA to MOST adapters is that the connector here is included with the "Type B".

---

I think that to be able to connect my fiber optics to the RCA to MOST adapter, I might also need one of these 10$ adapters:
https://www.aliexpress.com/item/MOST...865086988.html

I think that is the retaining clip for going from the tiny 2-fiber connector to the MOST clip in piece. On the left is my unclipped fiber optic connector, in the middle is what should connect to the RCA-MOST adapter, on the right is the 'MOST Fiber Optic Male Connector'.

Adi-Benz

You might have to pm a moderator, I'd check by the sticky section and send from there.

few

A small update.

I have now cancelled my purchase of the MOST to RCA adapter with Automirr / Longate. Despite the product page stating that they will refund the product cost (but not shipping), they emailed me telling me that they won't honor that. They would only refund 70% of the product cost. This is pretty sneaky, considering that I had already placed the order.

See the screen-captures below. Trying to purchase this MOST to RCA adapter is like shopping online in 1995.

I placed an order with AVINUSA, despite not hearing back from them for 7 days now. I'll see if the product ships... hopefully the fulfillment is better than the customer service. It was charged via paypal immediately, so at least it seems they're still open for business.

---

few

The loopback connectors are easy to find at or https://www.aliexpress.com/item/MOST-Optic-Fiber-Male-Connector-1-1355426-1-Use-For-Audi-BMW-Mercedes-Benz-2pcs/32863857410.html...

For eliminating the satellite radio from the system, I need to connect to a female loopback cable, which will also mean I need a 2-position connector to MOST male adapter. For eliminating the CD changer, I'll need another female loopback cable.

I looked up the connector information. So the MOST (M.O.S.T., media oriented ) connectors are made by AMP / TE Connectivity. Bones-Electronics provides a great diagram of the different MOST connector components and their TE Connectivity part numbers.

2 position connectors: TE AMP 1-1355531-1 (female), and TE AMP 1-1355531-2 (male). I can't see any difference between them, but TE has 2 part numbers (for male and female terminals).


The 2 position connector that goes into the larger mercedes optical + 4 electrical wire adapter (TE AMP 1-1355639-1) can be inserted into a MOST male connector. These connectors are TE Connectivity Part # 1-1355426-1. Those connectors can be purchased from Mouser or Newark (online electrical parts distributors). They're around 0.50$USD to 1.00$USD.



Cover assembly for MOST optical + 4 electrical wire adapter (TE AMP 1-1355639-1)



And here is the other style of optical + 12 electrical wires (TE AMP 1-1355795-1)

few

AVINUSA did ship the adapter to me quickly. It works on my 2007 C280 W203. It sounds much better than the bypassed amp situation (drives all the speakers).

I also disconnected the satellite radio unit. The 2 position connector did fit into the TE Connectivity Part # 1-1355426-1 MOST male adapter from Mouser. I used that with a bypass loop from Amazon.

I tried to use a loopback connector to remove the CD changer, but the amp wasn't working. I'm not sure if that was because the AVIN MOST adapter hadn't yet configured itself, or if the car wanted the CD changer in the loop. I still have the CD changer plugged in (it's not useable), and things are working.

I installed a parking brake bypass, because I was having trouble connecting new phones to android auto. That's working fine also.

Finally, I installed the nag screen disable patch from https://forum.xda-developers.com/and...sable-t3712190. This works well on the stock firmware that I have on the unit (XAV-AX100 v1.02.06.0). I haven't tried upgrading to the latest Sony firmware (XAV-AX100 v1.02.07.0), as I'm not sure the nag screen disable patch would work properly. I may end up changing the stock Sony splash screen to something more interesting. When applying the patch, it says the new firmware will be 1.02.07.0, but it actually stays 1.02.06.0.

Now I'm very happy with the setup, and very happy with the AVINUSA turnaround. It was a really long time for hearing back from them regarding the initial support question, but it turned out well (despite the misadventure with the AliExpress order).


Firmware updating...


As I thought, the MOST box for this model includes the 2 connector to MOST male adapter. That's necessary for the 2007 C280 head unit fiber optic connector style.





I happened to park next to another C280 when picking up a pizza.

keshaun

Which components should I use the bypass loop for? Also did you connect the factory amp fiber optic wire to a bypass loop? (Thanks for responded to my pm btw )

few

You will need the amplifier to be plugged into the fiber optic (MOST) network, that's how the sound gets to the speakers. Anything you disconnect (like the CD changer, and the satellite radio receiver) needs to be bypassed with a bypass loop. You can also leave those components in place, they will just use electricity if left connected.

keshaun

Where's the fiber optic cable for the cd changer? Also not exactly sure where the satellite antenna is, should that be capped also?

few

I'm not sure what you took pictures of. I think the first picture is the cable that plugs into your head unit. You need the adapter for your head unit. You can also see the fiber optic bus, that will plug into the most adapter.

I'm not sure what your second photo is.

The third photo shows the CD changer unit. The back of it has two fiber optics, and some electrical wires.

The fiber optics make a loop. There are two connectors at the stereo head unit, and two at each other device. The CD changer in my car is in the glove box. To disconnect it, you unscrew it and the cables are plugged into the back. You don't need to disconnect it. The satellite radio receiver in my c280 is in the trunk, on the right sidewall, near the tail light. It's behind the fabric lining of the trunk. You do not need to disconnect the satellite receiver either. But if you do, then you need to put a bypass loop in the place of the removed equipment. The amplifier is below the satellite receiver, and slightly closer to the back seat.

keshaun

My bad I probably should have said what the pics are lol, the first are the two that plugs into the amp and the second is the module that sits in the back of the trunk in the middle. Where did you use your fiber optic bypass? I saw higher up in the thread you used a bypass loop for something

few

The only place I used a bypass loop was on my satellite radio receiver. In the trunk. On the right side above the amplifier, near the tail light assembly. You can probably just leave everything else in place.