[monster]

Couple of questions, for all of you out there who know their stereos.

1. I'm currently just using the stock h/u, which is a Jensen MP7610. It has an AUX input, RCA female, to which I've connected a male-RCA-to-1/8"-stereo-jack cable.

My iPod car charger has a line-out jack in the dock connector (at the bottom), and that's where I plug the headphone jack from my AUX. Sounds good. If I plug the car charger into one of the power points, though, I get a whine. Other forums I've checked indicate that this is ground loop interference, for which I need a ground loop isolator.

Question -- is there a way to get rid of the whine without a ground loop isolator? I've seen references to grounding the 12V power point, but I'm not sure to what. FYI, I plug the charger in the power point behind the center console, the one facing the back seat.

2. I have an old Eclipse E5509CDC 8-disc CD-changer and was wondering if it's compatible with the Jensen MP7610. I know the MP7610 has a separate input for a CD changer, but I don't know how to find out which CD changers it's compatible with. Does anybody know?

Thanks in advance for any info. :thumbsup:

 

[Pinchy]

Hi Monster, hopefully I can help you out.

Ground loops are very tricky things to work with. A ground loop occurs when two devices (for example your iPod and your MP7610) are grounded to different locations, grounded using different guages of wiring, or using different lengths of ground wire for each. There are other ways that it can happen, but these would be the most likely causes.

The simplest way to fix this problem is to cut two low guage wires (pretty much anything 10 guage or lower) to the same length. Take each of these wires, and connect them to the same place on the frame of the vehicle so they are grounded in the same spot. Next remove the existing ground wires from both devices (in this case, your head unit and the cigarette lighter adapter for your iPod). Replace both grounds with the low-guage wires you made and connected to the frame earlier. Now both devices will have the same resistance level in their ground wire, and should eliminate the ground loop buzz. This is what the reference to grounding to the 12V will be - they are telling you to ground both items to a common 12V ground in the vehicle instead of the seperate places they are currently grounded to. Each device on a different fuse is likely grounded seperately - just like your head unit and the cigarette lighter will be.

The second way is to use a ground loop isolator, like you've seen. It essentially performs the same task, in that it provides the same resistance level to each device connected to it for ground. The first method is preferable because it will provide a lower resistance to ground for each device, but it's also a lot more work to install.

There are other ways to do it, but these will be the two easiest and most productive way to fix it.

One thing to note is that sometimes it's not just a ground loop at fault. If the sound of the buzz changes when the engine is running at higher or lower RPMs, it's more likely a result of induction (think of an antenna). A wire in your system in this case is most likely running parallel (side by side or wrapped together) with a 12V line. Any wire carrying an electric load will "broadcast" a field of electromagnetic (EM for short) interference around it, and when a low-voltage wire (like your speaker wires, antenna wires, etc) runs closely and parallel to it, the low-voltage wire acts like an antenna receiving the EM from the power wire - giving you a hum that will change with the speed of the engine's RPMs. These ones are usually pretty easy to fix - buy a good wiring kit and replace the crappy factory wiring, especially to the speakers. You gain two things with this - ability to use bigger amps/speakers, and better sound - you really can't go wrong.

As for the Eclipse CD changer, you can call Jensen's tech support line at 1-800-323-4815 and they will give you a list of compatible changers.

Hope this helps,

Devin

 

[monster]

muchos gracias

Devin --

Thanks much, my man -- that was very helpful. Sounds like the ground loop isolator might be the easier way to go, so I'll start looking around for one. Any suggestions on what to look for, or is a standard Radio Shack isolator good enough to do the trick?

On the first, more involved method: are there any "side effects" to grounding the head unit and the charger in the same place?

It's also possible that it is the induction thing you mentioned, as I do run the h/u-jack cable right next to the charger cable, so it's cleaner. Not sure though if the whine goes up when I rev -- I'll give it a listen later. If so, can I fix this by changing the wire that goes from the h/u to the jack with a better quality cable, say, a shielded cable? Or is there a way I can shield the current cable, I have, maybe wrap it in something?

Again, thanks a heap.