ULF Bluetooth Volume problems/Error Code 204

[Mangozac]

Well lately I've been less than excited about my ULF OEM Bluetooth retrofit I did last year. I suddenly realised I'm not using it as much as I should because it's simply not loud enough at highway speeds, making conversations too distracting from driving. I've been through all of the usual processes to increase it:
- Volume up MFSW button while in-call
- Volume up on radio knob while in-call
- Bluetooth volume up on phone (Galaxy SII) while in-call
- GAL set to 6 (this makes no difference and is a bit annoying as it makes the stereo drop in volume too much when at traffic lights)
- TPV set to 9 (no effect)

For reference it's a 13th gen ULF and I've only got basic 6-speaker audio.

I decided last night to plug in my laptop via diagnostic cable and INPA to have a look and see if there were any settings that could be adjusted that way (both in the ULF and radio). While I didn't manage to find any settings to tweak, I did find an error:

Date:      05/24/12 17:55:25
ECU:       ULF
JobStatus: OKAY
Variant:   ULF
---------------------------------------------

RESULT:    1 errors in error memory !
---------------------------------------------

204   Mikrofonfehler/Audiofehler

Error frequency: 1

   Fehler momentan vorhanden
==============================================

Translating to English still gives a pretty cryptic result:

204 error microphone / audio error

Error frequency: 1

    Error exists at the moment

So is it a microphone or audio error? What is the error? When did the error occur? I'm assuming the physical error doesn't still exist? Perhaps that was just from when I was playing around during installation?

I figured I might as well post on here and see if any of the technical gurus knew what it might mean. Probably a long shot...

In any case clearing the error has not helped the low volume problem. I think I'm going to have to build a little op-amp based preamplifier circuit to install in the harness behind the radio (rather than hack up the harness at the ULF main connector). Does anybody know if the phone audio signals are just line level (so the radio would amplify them)?

Thanks!

 

[VvrooomM]

I have exactly the same issue, if I turn volume on radio up before a call it's fine and I can adjust downwards. But if someone calls me the volume is barely loud enough to be heard above low speeds. Never found a solution, I have DSP and put it down to that.

In the states a little audio amp 10w or so is available or was but cannot find anything similar elsewhere.

Keep me informed please if you succeed.


Tapatalking on my iPhone.......

 

[Mangozac]

Interesting that you have DSP. I was under the impression that with premium sound systems the extra amplifier could make the bluetooth louder...

I have seen that ELK800 amp that people one of the BMW sound specialists recommends installing, but the install looks really hacky and the amplifier itself larger than necessary. I've read that the preamp volume knob doesn't need to be set more than 25%, which suggests overkill. I reckon it could pro ably get away with just 2W instead of 10.

Sounds like I'll have to get the oscilloscope out and measure the signal level myself. The idea then is to make a tiny module which plugs in line at the back of the radio...

Will keep you posted for sure!

 

[VvrooomM]

If your making one, to make two would be hardly any more effort!!


Tapatalking on my iPhone.......

 

[Mangozac]

If your making one, to make two would be hardly any more effort!!

Indeed, I would most likely make a handful of them

 

[jim80]

So you thought you would post and ask the experts! You sound pretty 'expert' yourself! I have this same issue and was also wondering if it could be sorted. If you manage to sort it out please post all details!


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[jim80]

Anyone else know if there is a difference in quality between Bluetooth connection and using a dock for the iPhone. Just wondering whether I should bother buying one or not? I have an aftermarket iPod connection in the glovebox which does the music stuff but doesn't charge the phone. Would they have messed up the wiring for the phone dock when wiring in the aftermarket dock??

Sorry for the high jack!!!


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[Mangozac]

So you thought you would post and ask the experts! You sound pretty 'expert' yourself! I have this same issue and was also wondering if it could be sorted. If you manage to sort it out please post all details!

Haha thanks mate. My electronic engineering skills make implementation straightforward enough, but before I can implement I need to know the specifics of what I'm doing

I'll try to find a chance to plug an oscilloscope in and test the signal levels later in the week.

Anyone else know if there is a difference in quality between Bluetooth connection and using a dock for the iPhone. Just wondering whether I should bother buying one or not? I have an aftermarket iPod connection in the glovebox which does the music stuff but doesn't charge the phone. Would they have messed up the wiring for the phone dock when wiring in the aftermarket dock??

Are you referring to BMW bluetooth/dock or aftermarket? It's quite possible that older dock systems can't charge the newer iPhones (I know that there is an issue like that with iPods).

 

[jim80]

I have an aftermarket dock in the glovebox but was considering a BMW insert for the communication thingy!


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[Mangozac]

I doubt that plugging the phone in via a snap-in adaptor is going to give you much better audio quality than using Bluetooth. Once the signals reach the ULF module they both use the same microphone and audio output channels anyway.

 

[jim80]

Yeah, I understand that. But is it worth buying one for the charging facility and the use of the cars aerial? Does anyone have the snap in connector? And is it any good?


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[Mangozac]

That's purely up to you

Sure, charging would be handy and if your phone carrier is that bad I guess the car antenna would be better. Check that you have the car antenna though - something tells me that might be an additional part that needs to be wired in.

 

[jim80]

Thanks for that, I'll have a dig around!


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[Mangozac]

Just posting an update on this

This afternoon I pulled the radio out (man removing the vents still isn't getting any easier and takes ages!) in order to make some measurements for the small telephone preamp I'm going to make up for it. The plan is to splice the preamp into the wiring at the rear of the radio. I have an adapting harness as part of my Dension Gateway 300 system which will allow the system to be returned to factory spec simply by removing the Dension harness.

Anyway I did my measurements (the telephone audio signal uses a 4.5V virtual ground for its signal -ve) and put everything back together. Driving home later I received a phone call via bluetooth - the track that was playing stopped and the radio display said "Phone", but it didn't actually ring. I answered but then couldn't hear anything. When I got home I called back the caller and they said that they could hear me. I went back into the car and tried it out (with the engine off) and discovered that it was in fact working, but the volume was extremely low. Both with making phone calls and using the voice command.

So this has left me wondering if I have a poor connection in the system giving me the low volume. I'll pull the radio out again tomorrow afternoon and re-seat the connectors to see if it helps. Of course now I'm wondering if the less than ideal volume issues I've always been having are also due to such a problem...

Will report back!

 

[Mangozac]

I know I'm talking to myself but this may be helpful to someone in the future

So as per my last post I suddenly had no volume at all after I had the head unit out a week or so back. Well this weekend I pulled it out and found that the problem was that the connector used for the telephone connections had not seated properly. I plugged it in properly and everything was back to normal. Still poor volume levels though.

Out of interest I actually discovered that the telephone audio is coming from the footwell speakers. I don't know who decided that would be a good idea! :?

Anyway so the next step is to make up my little amplifier PCB. I've been tossing around a couple of design ideas in my head but think I may just be overcomplicating things so will sit down and churn out a simple new design this week some time.

 

[Mangozac]

Update time: the plot thickens!

Over the last week I finally put together a little bluetooth amplifier board I designed. I finally got it installed last night and tried it out but have had disappointing results. While the amplifier does work, anything more than a gain of about 2-3 just causes distortion without any real increase in volume.

This would indicate to me that the problem is now with the audio level coming out of the ULF but rather that the head unit doesn't apply enough amplification to the signal before sending it to the footwell speakers. I considered that maybe in phone mode the head unit connects the speakers directly to the ULF audio signal, however if that was the case then with my tiny little amplifier in line there would be no audio at all (it doesn't have the grunt to drive speakers and is only a line level voltage amplifier).

So obviously this is quite frustrating. I'm not sure what to try next...

 

[bcworkz]

Thanks for the updates. There may be a limited audience, but you're not talking to yourself. Good effort despite disappointing results. My immediate thought is to forget trying to find the cause, just address the symptom. Like an inline speaker amp on the kick panel lines that only switches in when in phone mode? Easier said than done I fear. How to detect phone mode? I believe the ULF sends out status on the digital K-bus. Well beyond my knowledge how to capture that.

I suspect the kick speakers are used for phone because most of the voice signal would be filtered out by the x-over if fed to the tweeters. If fed to the rear speakers, there's a chance the voice would be muffled if the seat is all the way back, essentially blocking off the speaker. Kicks are all that's left.

 

[Mangozac]

No problem; glad to know that someone is finding them edifying

Of course, I forgot that being the base sound system there isn't actually a speaker in the door (other than the tweeter)

While your suggested solution is feasible, it is overly complicated and ultimately I'd be better off just swapping the ULF system out for a Dension bluetooth system. Phone on detection is easy - the ULF does send a discrete "phone on" signal to the back of the head unit. Switching in an amp would suck though.

The thing is that there's no reason why this shouldn't be working well - it's only some people that have this problem. There's stacks of others on here with the same OEM system in their E85 which works just fine. 13th Gen ULFs (like I have) are supposed to have great volume output levels (as opposed to some of the other generations).

Apparently although the car came pre-wired for phone, the phone option was apparently only actually available from 2004 onwards. Mine is a September 03 build and my business CD head unit doesn't support MP3 (I believe that was introduced in 2004 also). I'm wondering whether this is just a quirk of that generationhead unit? It would be great to swap it out for a newer one to try but they're much too expensive to buy for an experiment

 

[bcworkz]

I think you may be onto something regarding head units. Early phone options could easily have different interface levels than newer bluetooth units. I would lend you mine (which works just fine as well) for testing if we weren't half a world apart. Easy enough to take out once you know the "trick" vent release. Maybe you can find a willing owner closer. I understand E83 X3s have the same radio, so the potential pool expands a bit.

 

[Mangozac]

Unfortunately I don't know any BMW drivers who would have the suitable head unit to try out

Out of interest, is there any chance you could tell me the part number of yours? Maybe next time you've got the vents out

My understanding is that all of the Business CD units are the same and they just have a different front plate to suit the car. So I could probably get any one from 2004+ for the matter of testing it out. Unfortunately I don't know anybody with a 2004+ BMW well enough to ask them if I can borrow their head unit!