The test setup of my new install has a ground loop; the same ground loop as my first install because they both use the same components. The old install was done at a shop, so they put "filters" on the RCAs to cure it (and hurt my sound quality?). But the new install is my job, so I'd like to fix it properly.

The setup is: empeg and Alpine deck, switched with MPSS-4 relay, all connected to the car's wiring harness to use its internal amp and speakers. That's three ground wires and three+ power wires connected to each lead from the car's harness. Problem? And for now, they're only twisted together with caps. Another problem?

The loop occurs when the empeg is docked, powered on or in standby. The noise can be heard when the empeg or Alpine is playing. The noise adds static to the radio, crushing some frequencies (88.3).

The problem seems to be from empeg RCA to relay RCA. Even after reading the FAQ and its links, I can't imagine why this is or how to fix it correctly. FAQ asks for heavy-gauge cable, but the empeg harness (and Alpine harness) uses wimpy cables and there's not much I can do about it. I don't understand the other FAQ terminology (potential, "filter power feeds", etc).

To diagnose, I connected the empeg "directly" to the car's wiring harness, bypassing the relay. All I did was move its four RCAs to the harness and directly connect emepg's amp sense line to the car (instead of through the relay). I left the Alpine and relay power and ground connected. The ground loop was eliminated in this test, even with all the other components connected and receiving power (but with no audio connection).

I hope this doesn't require a ground line run off the battery since each component works while individually connected to the car's harness. It's just that pesky relay which causes the loop. Maybe Crutchfield can help. Any ideas? Thanks.

My pesky ground loop was reduced by heavier wiring to the battery.
It went away completely when I finally grounded the sled to the car chassis.

On your 'test' install (I'm picturing components and wires all over the floor of the car) use some alligator clips to ground various components and see if anything helps.

I'm not an electrical expert, but good luck!

Robotic: Thanks, I will try grounding different parts to the chasis of the car. I have trouble finding an unpainted spot, but I'll dig.

Tony: No relay leaves me with only 1 headunit. I really like having the Alpine for radio/CD.

I wonder if the relay has poor wiring. I've already added Sony XA-39 II to my eBay search notification list, hoping I'll find that supposedly better relay.

Or maybe the car's wiring harness ground wire is too thin to handle three components. But it has no problem when I put the empeg RCAs direct to the wiring harness with all three components still powered and grounded.

The only difference between the Alpine (no noise) and the empeg (causing the noise) is: The Alpine's switched 12V line is wired to the relay and the empeg's is wired to the car. Worse, the empeg's switched line is wired along with its constant line to the car's constant line because the car has NO switched line. I'm going to tap into the cigarette lighter somehow for this.

But why should it cause radio static? When I had this problem in the Volvo, there was empeg "processor" noise and alternator whine, but the radio worked ok I think. Maybe because I'm using an antenna adapter?

I'm guessing that the only reason you're using a relay instead of going aux-in to the Alpine, is because the Alpine doesn't have an aux-in?

Just for ha-ha's... Try having the alpine go aux-in to the empeg. See if that gets rid of the ground loop, therefore letting you have both stereos without the relay.

I'm confused why eliminating the relay leaves you with only one stereo.

I will try that, and the laundry list of other things I've compiled from searching the BBS.

The Alpine could run as Aux in to the empeg, but then it wouldn't function when the empeg was out. The relay allows me to leave the empeg at home and just use radio/CD when I'm going somewhere that I can't bring the empeg in with me (movie, restaurant, less trusted part of town, etc).

Also, the relay lets me use the volume and audio controls of each device independantly. Not a huge deal, but it's nice.

Thanks for all the tips. I'll try everything, then eventually just get the isolators.

Actually. I was saying what he thought I was saying. I meant it, though, just as an experiment or as a temporary solution.

The only reason I can imagine he needs the relay (for his stated purposes) is because his alpine doesn't have an aux-in.

If the alpine's got an aux-in, then of course use it, and everything is taken care of, no relay needed. I'm sure he doesn't have that option or he would have done it that way from the beginning.

Which headunit was it? I looked at some previous posts and if it is the CDM-7874R (is that right?) you can buy a 'M-Bus V-Link' RCA Adapter cable KCM-122B to give you AUX-in on that.

It does mean buying that cable though.

I used to have a similar set up. The empeg ran in to my Alpine's AUX in.

Some info here:
1998 Isuzu Trooper with empeg and XM

sein: Thanks for the info. No problem buying cables; whatever will make it work.

The problem seems to be the ground wire I'm using is not strong enough (thick enough?) to do the job. Two head units and relay using the stock headunit ground wire.

To test, I'm tempted to run a jumper cable from the netagive terminal of the battery and clamp it to the ground wire of the three components. Do you think that will fry my audio components?

The jumper cable should be the most powerful ground wire ever. If it fixes the ground loop, then I just need to run a stronger ground to a bolt on the chasis (I've no idea how I'll work both the nut and bolt end) or have a negative line run from the battery (in which case, I might as well have a better power line run also).

And I was hoping this would be easy...

I also have 2 head units in my Miata, but i have the Empeg feeding into the AUX input on the Clarion and then the Clarion feeding the amps. The only downside to this is that i cannot use the equalizer on the Empeg when the Clarion is th source...but i can live with that

having said all that...and i am sure i have bored our members to tears with...i have chronic igintion noise on my system which i have managed to reduce it to happen when i have some hi-drain accessories on (headlights-A/C-read defogger)....

so what i did was to buy a high powered amp so that i could keep the gains fairly low and thus lower my noise floor...

HOWEVER...the amp, at 200 wpc, was a bit too powerful for my speakers (Infinity reference components) and melted the mid-drivers...soooo...i replaced them with a pair of kicker components...and i melted those too (true story...honest!)

soooo i am now upgrading to a set of speakers with a higher power handling capacity with the goal of FINALLY having my dream system...being one that is quiet and pleasurable to listen to

i dont know what car u have but this car of mine is PLAGUED!!!!!

good luck!

Ed

i hear that.....i had the gains set at approx 10 o'clock....way down from max....and the burning smell was pretty pungent along with the fog of smoke eminating from the grills

i am thinking that i have to put some high pass filter in the line as it was only the mid-ranges that fried and not the tweeters

edsmiata, I've seen your many threads while searching the BBS for grounding issues. It's sad to see that you're plauged. I have no idea how to help, unfortunately.

I do think I've cured my ground loop. Accidentally, of course. While testing the two decks sitting on my car seat, I placed the empeg on top of the Alpine and the sound stopped. Yup, when the sled (or docked Rio) touched the Alpine, the ground loop stopped.

So, I bought the wire, o-ring, and M4 screw (though I thought it needed an M3) to make a grounding point for the empeg sled. Haven't soldered it together yet, but maybe this weekend.

Wikipedia is darn dangerous like that. I went to look up "soldering iron" and found a featured article about an astronomical organization redefining the term "planet" which may include three more in our solar system. Of course, I had to read about all three (which I'd seen mentioned in previous Wikipedia sidetracks like this). This lead me to reading about the 40 year old Deep Space Network with led me to Mars Spirit and Opportunity, which led me to their photo gallery. Two and a half hours later, I still hadn't learned anything about tinning the tip of a soldering iron.