the probNew Stereo, original Bose. What's lem!!!

[Nuri]

Hi guys,

Pretty new to the site, and infact the audi scene for that matter. Just like to start though by saying this has definately been the most informative Audi forum I have come across. Great work, keep it up guys.

I picked up my 2001 Facelift S3 a couple of weeks ago. At the weekend I went to town and thought I would treat myself to the new Alpine IVA D105R with navi, digital TV, bluetooth phone connection and a 6 disc changer.

The car currently has the concert 1 with the Bose upgrade. I bought the required wiring loom that converts the pre- outs (on the HU) to the iso connector for the Bose. Now i expected the connecting of the HU to the Bose system to be rather siple! How wrong was I!!!

If the Alpine HU is on 0 volume and I turn it to +1 then I get a 'pop' sound from the speakers. They then continue to play normally. Same happens if I go from 1 to 0 and if I skip a CD track. I'm presuming I have some major interference and so did a search on hear for remedies. Most of the posts refere to a hissing sound and not the POP that I am experiencing. My questions to the wise and knowledgable are:

1. Has anyone experienced this POP too?
2. If so what did you do about it, and have you been able to cure it?
3. Any suggestions are most welcome.

I took the HU back to the shop and had them swap it, so its definately not a faulty unit. They also said that they had never experienced this before.

Please help guys. Tell me I didn't just throw away a shed load of cash on a downgrade!!!!

Thanks

Nuri

 

[Nuri]

Great, First post and I screw up the title!!!

Wahooooo

 

[timps]

This link describes it best along with a cure.

http://www.audi-sport.net/vb/showthread.php?t=26307

 

[Nuri]

Thanks for the speedy reply. That link was very enlightening, however i find something quite strange!! The previous owner had a Pioneer AVIC X1 screen in the car previously and did not have this problem. I also have a friend with an S4 Avant with the Bose and an AVIC X1. He also has no problem with it.

Is there something i should know abou the Alpine unit? I find it strange that it did not make this noise with the AVIC if it is the Capacitors in the Bose Amps.

I also tried a simple Kenwood unit in the screens place and did not get the pop!? Are Alpines really sensetive, or do i need to ground the casing of it or something?

Any further help would be really really appreciated!!

Thanks

Nuri

 

[AndyMac]

You won't get the pop if you use the speaker input adapter as opposed to the RCA input adapter. Although not as "clean" as it uses hi-lo converters to take the speaker inputs down to RCA level.
It's all to do with how the new HU deals with electrically noisy activity such as selecting tracks on CD's. Alpines seem to suffer the worst as they mute the RCA's so you don't get annoying clicks, unfortunately this discharges the capacitors on the Bose amp which results in the pop. It's also worse if the HU has high voltage RCA's, which most Alpines do (4v+)
Alternatively, upgrade all 4 speakers, run them directly off the Alpine and use the RCA adapter on the sub out of the Alpine to drive just the sub.

 

[Nuri]

Thanks for that Andy. I've got it wired up using the speaker outputs at the moment as a quick fix, but really wanted to use the Pre-outs.

Just been to Prestige Audio in Rickmansworth, (its near work), and they have made what i consider to be sensible reasons for the pop and also a solution.

Apparently the Bose package i have is only amplifing the rear speakers and the sub. The fronts are apparently just running from the HU. (Not sure if this is true but if it is the rest makes sense). The guy seemed to think that the pop could be the fact that i was running the front RCA into a non amplified speaker!!
He recommended that i use the speaker harness that is in there at the moment, as it has a signal suppressor to reduce the amplified signal going to the Bose amps.

He had a listen, and although there is a slight bit of white noise when the volume is low, its probably just the location of some of the wires, (that will change when i complete the install), he thought its sounded well.

I will update you guys once its all finished and let you know if it gets better, worse or no change.

Thanks a lot for all your help guys. Again, the besty Audi forum i know.

Nuri

 

[AndyMac]

If you have Bose then all speakers are amplified, if you don't then only the rears and sub are amplified. There is nothing in the middle.
If you've managed to plug the front speakers into the new HU then you definately don't have Bose, as the Bose system does not have any speaker wiring at the HU (it's all in the boot).
Look at the sub in the boot, non Bose has a single 6.5" speaker, Bose uses 2 x 4" speakers.
If you don't have Bose then run all the speakers off the HU's amp - you will get more power and better quality and no interference. You will need to rewire the rear speakers back to the HU to do this.
Then just use the RCA adapter to drive the sub off the sub out on the Alpine.

 

[Nuri]

Strange that you say that!! The speaker grills are bose, but that does not necessarilly mean anything! I shall have to have a look at the sub when i get back home tonight! Sure it is Bose but the guy in the Audio shop seemed to think that after he looked at the OE HU that i only had rear amplification.......

Thought his explanation of the "pop" coming from the pre out being connected to a speaker without amp was plausible.


The Alpine is currently hooked up using the speaker adaptor/ signal suppressor thingy to connect to the Bose as opposed to through the Pre outs as originally wanted.

Am i just going to have to live with this then!!!

Cheers,

Nuri

 

[AndyMac]

A pre-out connected directly to a speaker wouldn't cause anything other than silence, speakers need an amplified signal.
The pop has already been explained.
1. You need to clarify if you have the Bose sub which will confirm you have Bose
2. Take a picture of the wiring at the rear of the HU, the adapter that causes the popping is just purely a wiring adapter - takes standard RCA's and connects them to mini ISO which plugs into the Bose/Audi loom. There's no electronics in between.
There are numerous ways to overcome the issue, but I need to know what's been done already & what type of system it is.

 

[Nuri]

Thanks Andy,

I will get on it tonight and come back with pics and more info. Where abouts are you located? I'm in SW London. Just wondered if you were near at all.

 

[Nuri]

Hi Andy,

I can confirm that it is indeed the Bose system we are dealing with. There are 2 subs in a Bose box.

So much for the guys at Prestige!!!

I have enclosed some pics of the wiring behind the HU. The first is of the speaker wiring adaptor and the second of the RCA harness causing the popping. Just noticed that the popping also happens when you turn off the HU.

You mention that there are a few remedies to this. I would really like to use the pre outs instead of the speaker out puts if poss. Do your stuff miracle man.

Cheers,

Nuri

 

[AndyMac]

There are a few remedies for the overall problem, unfortunately there aren't that many for the issue with the Bose system.
You're already using the speaker input adapter which is the easiest remedy.
The others are a bit more involved:
1. Replace the 4 Bose speakers and run them directly off the HU, using the RCA input adapter purely for the sub (connected to the sub pre-out on the HU)
2. Replace the 4 Bose speakers and run them off a proper aftermarket amp (using the RCA input adapter purely for the sub (connected to the sub pre-out on the HU)
3. Try a good quality ground loop isolator between the RCA output from the HU and the adapter going to the Audi/Bose loom.
4. Remove the grounding transistors on the RCA output of the HU
5. Splice in capacitors on the RCA leads as detailed in the link posted earlier.

 

[Nuri]

Hi Andy,

I really appreciate the time you have spent on this with me. I was on here for a few hours last night reading a lot of posts about this. Kind of figured that the remedies would be as described.

Can you explain how the inline capacitor on the RCA (as described in the linked post) actually works. I like to try and understand things as opposed to just accepting them. I also struggled to find anywhere on the net last night that had the same rated caps that are used in the linked post. Any suggestions?

I will give a ground loop isolator a try too. No harm in giving it a go but going by the previous posts, its probably not going to do much. Can you recommend any good makes of isolator to try. The obvious is autoleads, but i'm sure there is better?

If i decided to replace speakers, either off the HU or with a new amp, how would you re-wire the door speakers in the front. Would you piggy back the old wire going from the boot or would you route new wires through the door harness. Any tips on new wiring, if thats the solution.

Again, thanks so much for your time on this. Its really appreciated. Sure you have better things to do!!

Nuri

 

[timps]

Your pop is caused by “DC offset”.
DC current is discharged from the Bose amp to the speaker causing a pop, the inline capacitor stops this DC current being discharged to the speaker.

You should be able to source the capacitors from http://rswww.com/

An alternative way round is to use DC offset protection between the amp and speaker.
http://www.velleman.be/ot/en/product/view/?id=9237

or make your own
http://sound.westhost.com/project33.htm
http://www.headwize.com/ubb/showpage.php?fnum=3&tid=5866

 

[AndyMac]

The Alpine uses a grounding transistor on the RCA output whwnever it does anything electrically noisy, this effectively mutes the signal going to the amp so that it doesn't amplify any clicks when you change CD tracks or turn the volume to zero.
Unfortunately the Bose amp uses an array of capacitors to filter any such noises as the Matsushita HU doesn't use the grounding transistor method. So when the Alpine grounds the RCA it's also grounding the capacitor array in the Bose amp causing the capacitor array to discharge immediately which causes the pop.
Putting a capacitor inline with the RCA feed to the amp prevents the grounding effect ever reaching the Bose amp.

With new speakers I'd pick up the feeds at the Bose amp, no point reinventing the wheel by rewiring them. It's always good practice to rewire with good quality cable, but to be honest over that distance the difference will not be discernable.

 

[Nuri]

You guys are awesome!!!

Andy, now that i actually understand whats going on i can get my head round the issue!!! Bring on the weekend. I will give it a go.

Timps, thanks for the links.I shall have a look and get ordering. Are the ratings of the caps dependant on the HU being used or is it to do with the amps? The point i am trying to get to is, will i have to experiment to find the right rated cap for my HU or will the rating in the linked post suit the Bose amps? Hope thats clear.

Thanks a lot boys.

ps: do you organise meets on this forum? Would be cool to put a face to the names and see some other like minded s3 appreciators.

 

[AndyMac]

The system in the link was a Bose system, so the ratings should be spot on.

 

[Nuri]

Hi Guys,

I had a go at making the RCA leads with capacitors in line last night, and i am extremely happy with the results!!

As described there is still a slight pop when you turn the system off and a when skipping tracks, but it is more than bareable considering the improvement in volume control.

When i was using the speaker outputs of the headunit, i could only get to volume 5 before it was too loud. At that level though the signal to the sub and amp was so small that you could not hear it!!

This is definately the best solution for this problem.

If anyone works out how to reduce the popping sound on turn off that would be good but not the end of the world.

Thanks very much for all your help Andy and Timps.

Nuri

 

[timps]

If anyone works out how to reduce the popping sound on turn off that would be good but not the end of the world.

The DC offset protection circuit between the amp and speaker in the links I posted above will get rid of that.

They sense DC voltage on the speaker line and break the circuit before it reaches the speaker.

 

[bberglund]

I am having the same problem with the popping and would like to try and install the Inline DC-Protection's behind each speaker. Per the above conversation, I went to this link: http://www.velleman.be/ot/en/product/view/?id=9237

Not sure how much these little things are or how hard they are to order, but can you (or anyone) send me a picture of how this would look after it is installed and set up in the speaker cabinet?

I have a 1997, Audi A4 that I just bought and it's still sporting a casette player... time to upgrade! I'll be using an Alpine CDA-9883.

Thanks,

Brandon