counciltime

Anyone have problems with speaker balance problems (bias to the left or right side) when using the 3.5mm connector plugged into the glovebox AMI interface? This is a 2011 B&O MMI3G unit. Initially I thought it was a problem with the new Android screen unit I installed but I'm now wondering if it's the cable itself. I've now tried a couple of different audio sources in that 3.5mm input and the right front (especially the door mid and tweeter) are hardly producing sound even when I adjust the balance and fader in MMI. But don't want to waste $70 on a new OEM cable if there is another way to check first.

Any ideas?

SMac770

I don't know any way to view signal strength or such in the MMI interface. The AMI port for MMI 3G is just a dumb connection with wires back to the J794. There's no electronics. So the three wires used for the analog AUX connection are just run back to the J794 back panel. It could be the pass-through block that the third-party devices tend to use is not making a good connection on the pin for the right signal. You'd have to remove the third-party intermediary and plug the Audi harness quad-block directly into the J794 again and see if the issue persists.

The pins for the AUX is T12y pins 1, 2, and 7. Can't recall which pin is which L, R, and gnd. T12y is the green plug in the quad block.

counciltime

Ah, thanks for that! - hadn't thought of removing the 3rd party pass-through and testing to isolate that. Will do today. You seem to be knowledgeable regarding the wiring. Are there any resources that point out the location of L,R, and ground on the quadlock ? also I presume the numbering of pins is left to right and top to bottom?

SMac770

You'll need to look at the green plug, it'll have the 1, 6, 7, and 12, or at least 1 and 12, on the plastic molding.

counciltime

Thanks Smac770 - you seem to have solid knowledge on the wiring (saw some of your other posts).

I removed the passthrough for the quad-block and gave a glance to the original and 3rd party quad-block connectors - I couldn't see any issues with a visual inspection. I then tested using the original connections and no change. The balance is heavily biased towards the left which makes me believe that it's (hopefully) the cable to the AMI port. Couple of questions for you:

1. In your opinion, what are my chances with a cheaper 3rd party AMI 3.5mm input cable vs. the $70 genuine Audi version? I'm thinking of going the cheap route next.
2. It seems as though most of the Android screen units don't use the 3.5 AUX/AMI but rather have to activate the AUX via the "green screen". One difference between my unit and others such as RSNav is that there is a CAN connection made via the glovebox whereas mine is connected via the backside of the A/C controls. And the previously installed CarPlay adapter interfaced with that same A/C route and there was nothing plugged into the AMI port. Is there any major difference between the two connections (glovebox vs. behind the A/C panel)? It seems (in my cursory research) that both are tapping into CAN and therefore both would/should be able to go the non AMI port route.

Thanks for your really quick responses - this type of stuff kinda eats away at me.

PS - I've gone ahead and purchased an OBDEleven interface to try out the green screen route.

SMac770

I wouldn't bother with a non-genuine AMI cable. But that's me. If there's any cable that would be least likely to be a problem, it's the AUX one.
I'd plug a 2xRCA to 3.5mm test cable into the AMI AUX cable port and test the resistance between the AUX pins on the harness to the J794 and the contacts of the RCA plugs and see if there's an obvious difference between left and right. Try to confirm if there's an electrical difference between left and right.
The green menu would only be if you needed to enable AUX or AMI on your MMI system. There is no green menu on the radio (Concert) system. Your AMI port is connected exactly the same as every MMI 3G system in the world. Either your unit is for MMI 3G or it's not. The AUX port is going to connect to the same pins on the J794 as the AUX port wires for the AMI port. So I don't really understand the intention of question 2. If the audio is wrong with the factory harness plugged into the factory J794, then you simply need to resolve that issue and not presume issues you don't necessarily have.

counciltime

Thanks SMac770,

You're definitely more knowledgeable about auto electrical than I am. I do have a multimeter though and will check it out. I'm presuming you mean that one part of the multimeter lead goes on the left pin on the J794 harness and one goes on the corresponding RCA contact connected to the AMI port. Correct?

I believe I have the MMI 3G High system (it's a B&O system). That said, there is no AUX port in the center console so I'm wondering if AUX input was an option and not standard? So the only 3.5 input I have is via the AMI port. My thoughts on the "green screen" were that the previous Carplay adapter had the same wiring connections as the Android screen version I'm trying to install. They are both connected via pass-through to the quad-block and then a separate connection via a pass-through behind the A/C panel. In the other carplay adapter, there was no need to plug into AUX (not present anyway) and there was no connection to the 3.5mm input on the AMI port in the glovebox. What is interesting is that the older carplay adapter, while it had some bias towards the left speakers, wasn't nearly as bad as the sound coming from the AMI port.

Yet the new Android radio rep is saying I need to connect the 3.5mm audio output of the system into the AUX input. Not sure why. I'm just wondering why the rep for this new radio isn't providing instructions on how to funnel audio via the direct pass-through connection to the J794 - that might help it a bit.

But I now understand what you mean - the AMI port input and the AUX (that I don't seem to have) both are routed through the same portion of the quad-block connector to the J794.

Thinking ahead, if I do find different resistance between the two channels, what are my options? I'm thinking that replacing the cabling between the AMI and the J794 is not trivial nor cheap. Also wondering if it may be the J794 itself?

Thanks again for sharing your extensive knowledge!

Greg

SMac770

Yeah, if it does resistance measurement. If you have diode mode, that might be more interesting to get a voltage drop reading since then at least it has some current applied. But you're just trying to see if the left and right connection paths have some measurable difference. If so, then you have a hard something to correct in either the wiring from the green plug to the AMI port or in the AMI cable itself. But if not, then "why the issue" remains, and yes, possibly a problem inside the J794 is a scenario.

AUX is never there if you have AMI. AMI supersedes AUX. It's possible to not have AMI or AUX. But you can't have both. From a front end unit perspective, AUX and AMI with an AMI-AUX cable are functionally identical. If the instructions say to plug the device into the 3.5mm input jack, then that's what you do. Be it the jack on the AUX port mounted in the center console or the jack on the AMI cable in the glove box. Then picking that input for audio in the front end unit.

counciltime

I've got a cheap meter but it has both resistance and diode. So for the diode, I would take a reading for both sides and note if there is a discrepency in voltage between the two correct? And for the resistance, again, note if there is a discrepency?

SMac770

Yeah, you're just trying to find out if there's a difference in the electrical connection from the 3.5mm jack to the pins of the J794 (or, specifically to the terminal pins on the wires in the harness connector to the J794). Could be a terminal pin backed out of the connector, etc. So check everything looks visually correct at the 12-pin plug, etc.