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#285165 - 05/08/2006 12:25 Eliminating ground loop, again
FireFox31
pooh-bah

Registered: 19/09/2002
Posts: 2491
Loc: East Coast, USA
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.
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FireFox31
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#285166 - 05/08/2006 14:12 Re: Eliminating ground loop, again [Re: FireFox31]
Robotic
pooh-bah

Registered: 06/04/2005
Posts: 2026
Loc: Seattle transplant
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!
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#285167 - 05/08/2006 15:02 Re: Eliminating ground loop, again [Re: FireFox31]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31164
Loc: Seattle, WA
Quote:
bypassing the relay. ... The ground loop was eliminated


Ahem.
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Tony Fabris

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#285168 - 05/08/2006 22:34 Re: Eliminating ground loop, again [Re: Robotic]
FireFox31
pooh-bah

Registered: 19/09/2002
Posts: 2491
Loc: East Coast, USA
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?
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FireFox31
110gig MKIIa (30+80), Eutronix lights, 32 meg stacked RAM, Filener orange gel lens, Greenlights Lit Buttons green set

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#285169 - 06/08/2006 03:00 Re: Eliminating ground loop, again [Re: FireFox31]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31164
Loc: Seattle, WA
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.
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#285170 - 07/08/2006 01:57 Re: Eliminating ground loop, again [Re: tfabris]
FireFox31
pooh-bah

Registered: 19/09/2002
Posts: 2491
Loc: East Coast, USA
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.
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FireFox31
110gig MKIIa (30+80), Eutronix lights, 32 meg stacked RAM, Filener orange gel lens, Greenlights Lit Buttons green set

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#285171 - 07/08/2006 06:21 Re: Eliminating ground loop, again [Re: FireFox31]
sein
old hand

Registered: 07/01/2005
Posts: 889
Loc: Sector ZZ9pZa
Quote:
The Alpine could run as Aux in to the empeg, but then it wouldn't function when the empeg was out.

Tony was saying put the Empeg as Aux on the Alpine. If your Alpine has an Aux connector of course.
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#285172 - 07/08/2006 07:26 Re: Eliminating ground loop, again [Re: sein]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31164
Loc: Seattle, WA
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.
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Tony Fabris

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#285173 - 07/08/2006 08:49 Re: Eliminating ground loop, again [Re: tfabris]
sein
old hand

Registered: 07/01/2005
Posts: 889
Loc: Sector ZZ9pZa
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.
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#285174 - 07/08/2006 12:06 Re: Eliminating ground loop, again [Re: sein]
robricc
carpal tunnel

Registered: 30/10/2000
Posts: 4909
Loc: Orange County, NY USA
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
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#285175 - 08/08/2006 13:02 Re: Eliminating ground loop, again [Re: sein]
FireFox31
pooh-bah

Registered: 19/09/2002
Posts: 2491
Loc: East Coast, USA
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...
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FireFox31
110gig MKIIa (30+80), Eutronix lights, 32 meg stacked RAM, Filener orange gel lens, Greenlights Lit Buttons green set

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#285176 - 10/08/2006 16:48 Re: Eliminating ground loop, again [Re: FireFox31]
Robotic
pooh-bah

Registered: 06/04/2005
Posts: 2026
Loc: Seattle transplant
Quote:
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?

Nope.
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10101466 (2x60GB, Eutronix/GreenLights Blue) (Stolen!)

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#285177 - 16/08/2006 16:08 Re: Eliminating ground loop, again [Re: FireFox31]
edsmiata
addict

Registered: 18/08/2002
Posts: 544
Loc: New Jersey
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
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#285178 - 16/08/2006 23:04 Re: Eliminating ground loop, again [Re: edsmiata]
tanstaafl.
carpal tunnel

Registered: 08/07/1999
Posts: 5377
Loc: Ajijic, Mexico
Quote:
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!)


This does not seem reasonable.

There is no such thing as an amplifier "...too powerful for my speakers...". There is only playing the music louder than your speakers can handle. You could have a 50,000 watt amplifier, and it would not load the speakers any more than a 50 watt amplifier would at the same volume level. The only difference is that the gain on the big amplifier would be set much lower than on the small amplifier, but the sound level would be the same in either case.

If you are blowing speakers, it is because you are trying to get more noise out of the speakers than they can provide. You are actually more likely to damage speakers (especially in this instance) with a low power amplifier than you are with a high power amplifier, because in order to get the volume level you apparently are trying to reach, you will have to crank the gain up so high on the small amplifier that you will get clipping and distortion -- and that is what kills speakers.

Yes, you can kill a speaker with a high-powered amplifier, but it is not because the amplifier is too powerful. It is because you are using that power to play the speakers louder than they are designed to play. A speaker's rated power capacity is just a measure of how much power the speaker will draw at the maximum decibel level it is capable of playing. As long as you don't try to play the speakers louder than they can physically play, the size of the amplifier is irrelevant.

tanstaafl.
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#285179 - 17/08/2006 11:57 Re: Eliminating ground loop, again [Re: tanstaafl.]
edsmiata
addict

Registered: 18/08/2002
Posts: 544
Loc: New Jersey
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
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#285180 - 19/08/2006 15:02 Re: Eliminating ground loop, again [Re: edsmiata]
FireFox31
pooh-bah

Registered: 19/09/2002
Posts: 2491
Loc: East Coast, USA
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.
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FireFox31
110gig MKIIa (30+80), Eutronix lights, 32 meg stacked RAM, Filener orange gel lens, Greenlights Lit Buttons green set

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#285181 - 19/08/2006 16:03 Re: Eliminating ground loop, again [Re: FireFox31]
Robotic
pooh-bah

Registered: 06/04/2005
Posts: 2026
Loc: Seattle transplant
Quote:
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.

Hooray! Congratulations!
Marie Curie would be proud.

(Holy smokes! I only used Wikipedia to check the spelling of her name and stumbled upon the story of a fascinating and incredible woman! The wiki article doesn't even mention the traditionally familiar story of her 'accidental' discovery.)
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#285182 - 20/08/2006 11:52 Re: Eliminating ground loop, again [Re: Robotic]
FireFox31
pooh-bah

Registered: 19/09/2002
Posts: 2491
Loc: East Coast, USA
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.
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FireFox31
110gig MKIIa (30+80), Eutronix lights, 32 meg stacked RAM, Filener orange gel lens, Greenlights Lit Buttons green set

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