Saprissa

05-10-2005, 07:46 PM #95
05-10-2005, 09:08 PM #96
05-10-2005, 10:12 PM #97
05-10-2005, 10:17 PM #98
05-11-2005, 06:38 AM #99
05-11-2005, 06:41 AM #100
05-11-2005, 10:13 AM #101
05-11-2005, 10:22 AM #102
05-11-2005, 12:18 PM #103
Today, 07:00 AM #104
I just started noticing this humming whine when I turn up the volume really loud, and the car is moving over 80 mph. It is annoying !
inFiniTE LooP,
Can you tell me more about the GROUND LOOP ISOLATOR ? Where do you get it ? how do you install ? ????

Perhaps Scorchie or Steve (MBenzNL) could also provide any suggestions, as to the grounding of COMAND units, in order to prevent AUX input electrical humming.

Carlos

Saprissa@aol.com

JohnCL

I get wicked noise over my aux when using my XM radio, but when the Dell DJ is connected it is very quiet. I think that I may go back to FM transmission for my XM. I personally don't feel that it is the COMAND in my case.

steph280

Ground loop isolator can be purchased at radio shack or electronic shops. It's basically an inline filter between your source wires to eliminate ground loop. Ground loop occurs when there are impedance between different ground points in the car. For example, if your headunit is grounted to the front of the car chasis while the amp is grounded to the back of the chasis, the front to back chasis conductivity might not be "pure" thus causing difference in grounding impedance, resulting in the humming effect.

ctC230K

thanks Saprissa!! I was going to do this but you saved me a lot of work.

inFiniTE LooP

just took this from the other thread:

ctC230K

got a link to it? or the item number? thanks

ctC230K

Update: I've figured out where the noise is coming from. The cigarette lighter in the front console. I pulled up my aux cable and unplugged the stereo plug extension cable that ran from the MB aux cable to the Sirius and the sound was gone. Then I plugged it back in and the sound came back. First I thought it was the headphone jack extension cable because i had it coiled up and thrown under the seat but that wasn't it. I unplugged the Sirius cigarette lighter adapter and the sound was gone. Then I could plug it into the rear cigarette lighter socket and there was no hum! How come only the front cigarette lighter hums?? What should I do? Rewire it to the rear cigarette lighter? That would suck. Would this ground loop isolator help me?

inFiniTE LooP

interesting, it could be that there is a bigger difference in resistance between your front cig. lighter and rear one thereby only having the front one having this effect. if this is the case, then the ground loop isolator will fix your problem. if it doesn't fix your problem, then simply return the product and say it didn't work, they're cheap anyway, only about $16

ctC230K

thanks. i'm gonna see if i can get one today. i also want a 24" gold plated headphone jack to headphone jack cable, maybe monster cable makes one. that should cut down on some of the crap coming in through that line.

jello2594

um, gold headphone jacks will make absolutely NO difference with alternator whine or ground loops. Think about it. Your audio signal will go through some beefy cable, then into a jack, where the connection isn't soldered, its just a friction hold... then it goes into tiny unshielded wires behind the glovebox and into the radio, where its surrounded by all different voltages and impedences, and probably some magnetic fields.. and in the radio, its just lines on a circuit board..

I never understood this whole giant gold cable mumbo-jumbo...its never been proven to have any positive effect on sound quality.

ToonArmy

That definitely sounds like a ground loop problem. I have a very similar one in my R230 SL. Playing my iPOD thorugh the AUX input is fine, but plugging in the iPOD power into the cig lighter causes an almighty hum. I haven't tried a ground loop isolator yet, I just don't charge the iPOD while playing, and leave it charging when I'm not in the car if necessary.

Hmm. Wonder if the COMAND inputs and lighter plugs are on different grounding circuits, and if so why. I know I've got two batteries, but I thought everything except the starter was on one circuit.

jello2594

OK, I had the same problem with my aux input. When I played sound through my ipod, it was fine.. until I plugged it into the cigarette lighter, then the alternator whine took over, obviously a ground loop. I have since installed a Sirius receiver into this aux input, which needs a constant power source, since it isn't battery powered. The way I got rid of the whine is a bit more complicated, but it's the best solution, I think. I didn't get my power from the lighter at all.. I tapped into the power at the Bose amplifier in the trunk, and ran a regular 16guage speaker cable from the amp's positive and negative power leads to the power of the Sirius. No noise at all, now.

steph280

Hum from cigarette lighter is a good indication of ground loop. Just go to your local car stereo shop or radio shack and get a ground loop isolator (GLI) and connect it in between the AUX jack and your IPOD. You might need some adaptor for the right jack since most GLI comes with dual RCA plugs.

Here's the one from RatShack:
http://www.radioshack.com/product.as...t%5Fid=270-054

jello2594

This thing is just a bandaid to the problem, if it works at all...

steph280

bandaid or not, it is commonly used by stereo shops for installs. Some even put them in regardless if they have hums.

Some go to the extreme of installing a heavy duty ground wire across the car so all audio equipment have the same ground point. Being as complicated MB's already are, I would shy away from such mods.

cc4469

Hi,
your problems should only exist while using the cigarette lighter for power supply of external audio equipment, which is connected to the Aux-In-Jack in the glovebox.
The problem can be solved by deleting the connection between shield and ground of the harness A 203 540 61 07 (the Aux-In-Harness).
With a stock Comand system, there is the Aux-In-jack in the glovebox. The wiring to the Aux-In-jack has a connection shield<->ground (connection between mesh network and brown wire) near the jack. If you CAREFULLY remove the isolation about 1" from the jack, about 1/2" wide, you will find the shield (mesh network). If you ALSO CAREFULLY cut this shield around the wires and remove it completely, afterwards use adhesive tape for the isolation, your problem is solved.
If you can wait until December 2005 or January 2006, you can get a new wiring harness (successor for the A 203 540 61 07) at your local MB dealer.

ctC230K

Update #2: Thanks guys, I bought a ground loop isolator from Radio Shack this weekend ($15) solved all my humming problems. Also it actually replaces the headphone jack to headphone jack cable i was using and it is gold plated too! lol i'm not sure if that helps buy why not. now i just need to figure out where to hide it, it's the size of a D battery and looks funny hanging between my Sirius and Aux Cable Harness.

Now my next problem- I turn the radio up as loud as it goes and sometimes I still want it to go louder. Maybe the Sirius doesn't put out enough volume but I think the problem is the head unit limiting what it sends to the stock speakers so I don't blow them.
No one wants to touch my audio system because it's all fiber optics and they claim they can kill the whole system if they short out one cable by accident and it's too much of a liability.

inFiniTE LooP

does your Sirius have it's own internal volume setting, may wanna check the manual for it as most sattelite radio units have some kind of internal volume setting of their own

ctC230K

yes, it has a volume button on the side, i made sure it's turned all the way up. if i turn the volume on the stereo up to about 90% and have the bass and treble on their max settings, going past 90% only makes the mid tones louder, the bass and treble stay at a 90% max level. i think that happens because the speakers are maxed out and only the mid tones can be increased, has anyone else noticed that?

jello2594

Is this the Bose system? Have you tried disconnecting that Bose microphone by the rearview mirror, if so?

ctC230K

nope it's the basic, not bose, not command stereo.

Saprissa

Good info ! Thanks !
I'll try the $15 ground loop isolator first, and then get the new MB wiring harness when it comes out.

Carlos

Saprissa@aol.com

spanky

Do you by any chance have the part number of the filter? I tried searching for it online and was unable to.

Thx!

Tishers

Here are a few;

http://mcm.newark.com/NewarkWebComme...SKU=60-405&N=0

http://www.radioshack.com/product/index.jsp?productId=2062214&cp

http://www.audioxpress.com/reviews/media/AE600HA.pdf

spanky

Thanks for the info!