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      10-04-2012, 06:40 PM   #1
taibanl
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Exclamation Audio Troubleshooting

My idea is this will be a master thread where folks can post troubleshooting (i.e. UNEXPECTED) questions here AFTER SEARCHING FIRST!. If you need a How-to, there are plenty of other threads, notably the Start Here Sticky..

I will try and put FAQs at the top of this post periodically.

So...I'll begin...

Last edited by taibanl; 10-04-2012 at 07:30 PM.
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      10-04-2012, 06:48 PM   #2
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Exclamation

Guys,

I've mentioned that I have an analog noise in my system. I recently narrowed it down and was wondering if anyone had any ideas.

Noise: "Buzz Sound"
Location: Front Left Tweeter
System: HiFi (recoded from Stereo)
Conditions: Only Occurs when:
Brake is depressed
MS-8 volume is up: Muting MS-8 completely eliminates the noise (thus JL Amps are not the culprit so it's either an INPUT to the MS-8, or generated by MS-8 (note, the MS-8 also produces a processor/digital noise which I can hear but its not as bad.

I thought this problem was new since my JL HD amp install but realized that I'd heard it before when the cruise control applied the brakes (at that time still had the stereo coding and the JL XD600/6). When i correlated it to the brakes today, I had an aha! moment.

Any help? 6spdcoupe? VP Electricity? Technic? ....?
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      10-05-2012, 12:17 PM   #3
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So what you're saying is, when the brake pedal is pressed OR when the C/C applies the brakes, and various things happen (most notably the brake lights come on), it affects your left channel?

I would start swapping L and R channels at various places in the signal chain and see when it moves and when it doesn't. I suspect you will find it to be some induced noise associated with the brake lights.
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      10-05-2012, 12:31 PM   #4
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Quote:
Originally Posted by taibanl View Post
Guys,

I've mentioned that I have an analog noise in my system. I recently narrowed it down and was wondering if anyone had any ideas.

Noise: "Buzz Sound"
Location: Front Left Tweeter
System: HiFi (recoded from Stereo)
Conditions: Only Occurs when:
Brake is depressed
MS-8 volume is up: Muting MS-8 completely eliminates the noise (thus JL Amps are not the culprit so it's either an INPUT to the MS-8, or generated by MS-8 (note, the MS-8 also produces a processor/digital noise which I can hear but its not as bad.

I thought this problem was new since my JL HD amp install but realized that I'd heard it before when the cruise control applied the brakes (at that time still had the stereo coding and the JL XD600/6). When i correlated it to the brakes today, I had an aha! moment.

Any help? 6spdcoupe? VP Electricity? Technic? ....?
The only way that I can see something like this happening is by the ground connection point being shared between the MS-8 and the tailights.

The "buzz" is the tailights lighting up and the audio picking it up via a weak ground.
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      10-05-2012, 01:41 PM   #5
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Quote:
Originally Posted by VP Electricity View Post
So what you're saying is, when the brake pedal is pressed OR when the C/C applies the brakes, and various things happen (most notably the brake lights come on), it affects your left channel?

I would start swapping L and R channels at various places in the signal chain and see when it moves and when it doesn't. I suspect you will find it to be some induced noise associated with the brake lights.
Correct (yes brake lights were already suspect but wanted to throw it out there before tearing things apart). The interesting thing is that this was present in my old configuration, which I completely removed and later reinstalled with the new amps.

It's louder now with more power but wiring to the new stack is completely new . It rarely bothered me before; but now, if I have no music playing before driving off and my foot is on the brake, it drives me nuts.



Quote:
Originally Posted by Technic View Post
The only way that I can see something like this happening is by the ground connection point being shared between the MS-8 and the tailights.

The "buzz" is the tailights lighting up and the audio picking it up via a weak ground.
I will pull the connector to the tail and check if it remains.

Thanks to both of you for your time and responses
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      10-05-2012, 02:36 PM   #6
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I would put "perhaps" in front of the last 4 words - "via a weak ground" - because if it is induced due to routing or locations, the ground connection you make may not affect it. That could be it, but it isn't necessarily it. Watch that driver's side grounding bracket - lotsa emi there.
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      10-05-2012, 05:07 PM   #7
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Ok...so as many questions as answers:

New info:

Engine On, Brakes Depressed (brakelight on) - Buzz
Engine On, Brakes Depressed (light disconnected) - No Buzz
Engine Off, Brakes Depressed (brakelight on) - No Buzz
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      10-05-2012, 05:09 PM   #8
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Ok...so as many questions as answers:

New info:

Engine On, Brakes Depressed (brakelight on) - Buzz
Engine On, Brakes Depressed (light disconnected) - No Buzz
Engine Off, Brakes Depressed (brakelight on) - No Buzz

So obviously there is direct A/B correlation with the lights...but for some reason only when the engine is on. Could it have anything to do with ABS?...what else is different when the engine is on.
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      01-23-2013, 09:42 PM   #9
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So update to this thread:

and these ones:
http://www.e90post.com/forums/showth...ighlight=noise
http://www.e90post.com/forums/showth...ighlight=noise
http://forums.macrumors.com/showthread.php?t=872009

I found this document...

Last edited by taibanl; 01-24-2013 at 05:35 PM.
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      01-24-2013, 05:29 PM   #10
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Ok so here it is....any thoughts?

Mine is a 7/10 build so I guess it wouldn't cover my case.
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      01-24-2013, 06:00 PM   #11
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Sorry I didn't see this thread until now. I will tell you that I had the exact same problem! I actually already posted about it, but it got buried in a thread.

My symptoms were:

- buzzing sound/static noise when brake pedal depressed
- engine noise/whine
- all through only ONE MS-8 channel (center)

It drove me crazy and I got to the point where I was going to tear everything out, everything! None of the traditional trouble-shooting steps for engine noise worked and the brake-light buzz gave me nightmares, literally.

I double, triple, quadruple checked all the wiring for the center channel, to make sure there was no interference being picked-up by the wires. I even ran new RCAs and speaker cables for the center OUTSIDE the car, and there was still noise!

It was actually just dumb luck that I found the source of the noise. It is not anything I had ever thought could possibly cause this problem, since it was just one channel and not all of them.

Here's a couple of pics to illustrate what was going on:




I originally ran the ground cables for the amps parallel to the RCA as shown in the picture. There was about 1/2" clearance, but the RCA plug (on the HD600/4 amp) for one of the underseat woofers (CH 3 or 4) picked-up the noise from the ground wire, then back-travelled into the processor, and then magically reappeared on CH 5 (center) output of the MS-8 and went through the RCA back to the other amp (HD900/5).

As soon as I unplugged the RCA cable from the HD600/4 nearest the ground cable, the noise stopped. So I just re-ran the power and ground wiring AWAY from any RCA plugs and voila, problem solved!

I hope this helps you but at least it shows that the cause of the noise is not always something logical!
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      04-28-2013, 05:05 PM   #12
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Painful to post update....

So I cut my technic harness (source to MS-8) (couldn't easily access the RCAs) and I have silent bliss...I've been assuming its an installation ground or alternatively a ground loop like kaigoss's...but its not...its coming from UPSTREAM of the MS-8...i.e. the headunit or that area....

Possibilities:
  • Power line for my BMW station for apple iphone?
  • Damaged ground or something else when I installed the bmw station for apple iphone? (requires repinning sections of the OEM vehicle harness).
  • Routed technic harness close to some other power/EMI source?
  • defective OEM head unit?
  • anyone other ideas?


Where do I start to test cost effectively? Anyone have an OEM hu I can borrow?

Maybe its time for my idrive upgrade.
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      05-08-2013, 10:43 AM   #13
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So have you tried plugging your iPhone directly into the MS-8, any noise?
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      05-08-2013, 03:49 PM   #14
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Quote:
Originally Posted by kaigoss69
So have you tried plugging your iPhone directly into the MS-8, any noise?
No but i will
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      11-05-2013, 06:44 AM   #15
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Hi, any update on this? Always interesting to know as I'm also struggling with noise issues (car will go back tomorrow to the shop for a fix hopefully).
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      11-05-2013, 08:34 AM   #16
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Unplug ALL RCA plugs at the amps EXCEPT for the one channel that is making noise. Still there?
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      11-05-2013, 09:06 PM   #17
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Update:

Two issues.

1) faulty head unit which probably ha a bad cap. Could hear things like the cd shuttle spin up through the speakers

2) technic harness replaced with twisted pair version which eliminated brake light noise pickup.
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      12-09-2013, 09:34 AM   #18
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any updates on this brake hiss?
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      12-09-2013, 06:46 PM   #19
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Brake his resolved when i switched to twisted pair
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