I'm shopping for a MOST adapter to enable the installation of an aftermarket head unit in a 08 GL550 with the HK system. There seem to be a couple of options:

The cheap one (looks like the same one Avin uses and sold under a variety of names): for $99

or

A more expense Scosche (out of stock) or Axxess: https://www.crutchfield.com/p_120MC9...Interface.html for $300+

it looks like the more expensive version is more of a plug and play proposition, but is there any functional difference?

 

Check this thread:
https://mbworld.org/forums/gl-class-...on-system.html

 

The one from amazon only converts rca output from head unit to optical signal to factory amplifier. It won't do anything for wiring an aftermarket head unit to factory wiring. You'd still need a wiring harness and something for steering wheel controls. The one from crutchfield is harness, steering wheel controls converter and optical output converter all in one package.

 

Thanks. Wiring the +12V/ground isn't a big deal, but the steering wheel controls are the thing I worried about although one of the amazon reviews claimed they still worked with the cheap one.

 

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With respect to the MOST adapter (not steering wheel/CANBUS) there are some adapters on ebay that have an unusual 4 RCA speaker input. If your aftermarket head unit has both front and rear left and right output and a fader control, you can hook up one of these other units and have a 'fader-like' ability via your HK amp.. They are almost twice the cost of the 99 dollar units that do not have the fader. I installed one of those with an Android head unit. They work, but you can tell it is not like a normal analog amp where the response is instantaneous; the digital signal in the MOST adapter must go through some type of microprocessor & software to simulate the fader, so there is some lag time and some music (with big fade ins) sometimes causes a glitch like you might get when playing music on a phone app. It would be interesting to see if they have improved this over the past few years, their latest version is version 4, and I have a version 2.

 

Thanks. I didn't see the 4 channel units, but I'm happy with the default F/R setting you're stuck with if you use a 2 channel adapter. I ended up using the Axxess adapter linked above to install a Pioneer DMH-2660NEX. Pretty straightforward installation although the directions included with the module that allows steering wheel control were incorrect. The included directions said to hold down the up volume button on the steering wheel down during the learning process. The unit correctly identified the brand of head unit, but couldn't identify the vehicle, which left the steering wheel controls inoperative. I found more directions on the manufacturers website, which said to tap the volume up button over and over while learning was occurring, which did the trick. The only issue is that the track buttons operate opposite of how they did with the factory head unit. You can go through a manual learning process to remap buttons and make them behave like they did with the stock head unit, but I'll just re-train my thumb.

Also for anybody doing an aftermarket head unit installation with a Command 2.0 head unit (<2010?), there is no Fakra connector for the backup camera, so you have to find the video cable from the camera, cut it and attach a cable with a RCA connector to connect it to the head unit. https://www.benzworld.org/threads/av...ation.2375585/ (post #13) has pictures of the relevant wire, although note that the connector shown isn't the one that connects to the factory head unit/connects to the Axxess harness, but is one connector upstream of that one.

Overall I'm very pleased with the installation. The Metra install kit made for a simple and clean install in the dash and since I could adjust frequency response with the included equalizer, I looked at it with a RTA program. The frequency response with the stock HK amp/speakers is surprisingly flat. Big mid-bass bump around 250hz, and response falls off a cliff above about 8k, but not bad at all for a factory setup.