I think the only step I have left is a filter that connects inline with the alternator, but I'm wondering if I missed something. The Crutchfield chart suggests I need a power filter, as do my own tests

Powering the amp from wall power via an extension cord from my house, but feeding though the same RCAs in the dash to the amp (with the amp turned on by shorting ignition sense to amp sense since the ISO connector isn't plugged into the unit) I get no noise. This as well as the Crutchfield tests absolves the amp; It also absolves the RCAs and the speaker wiring.

The Empeg is grounded only to the vehicle chassis at the same spot the amp is, with 6 gauge stranded copper. I also tried using one side of a jumper cable to ground the Empeg chassis directly to battery ground (as the only ground) with no effect, just to be sure.

An American International S10A power filter connected inline on the constant power and grounded does nothing for the noise. For the heck of it I also tried filtering ignition sense, again with no effect.

This implies one of:
-it's insufficient to take care of the noise
-the wiring on the sled itself is in some way hosing me, since the wall power test didn't use the sled wiring.

Is there something obvious short of alternator inline filtering I can try? Battery electrolyte levels are fine, and I've found nothing else which looks plausible.

Your first problem is assuming that the "power is dirty". Electricity isn't like a water supply that can get contaminated upstream.

What you're experiencing is most likely a variation on a ground loop, which has nothing to do with whether the power source is dirty or not. Playing the player with the A/C adapter has not absolved any component of responsibility, it simply confirmed you have a ground loop problem.

Have you looked through this FAQ entry and the documents linked therein? I see you've already hit Crutchfield, but there's some other resources there, too.

More details about the system, including details about the amp, and perhaps a wiring diagram, would be useful in helping diagnose the problem.

I'm considering writing a FAQ entry called "What exactly is a ground loop?". I'm wondering if it would be useful to anyone...

The FAQ entry was where I found the Crutchfield document. Your installdr links are stale and I meant to mail you about that.. Take out the /InstallDoctor/

For a ground loop to exist, something has to be multiply or poorly grounded, yes? Well, the first post should have covered that, but...

The amp is installed under the driver's seat and the ground is about a foot long; screwed into the chassis and yes, the paint is scraped. Attempting to replace this ground by grounding direct to the battery changed nothing.

The ground from the Empeg is 6 gauge and it's not grounded anywhere other than where the amp is. Nothing else is touching the chassis and removing it from the dash and letting it hang changes nothing.

For kicks, removing the tuner module also changes nothing, so it's not antenna noise:-)

That exhausts everything from the InstallDr links except EMI noise. EMI noise shouldn't change depending on how the Empeg is powered.

I don't see that there's much more I can do to remove the possibility of ground loops; Certainly nothing in those documents suggests anything other than ground loop isolators on the RCAs, which I suppose I could try, but the likelihood of the RCAs having a lower potential to ground than the 6 gauge wire grounding the Empeg to the same ground the amp has now seems a bit far-fetched.

Your installdr links are stale and I meant to mail you about that.. Take out the /InstallDoctor/

Crap. They changed the links AGAIN?

For a ground loop to exist, something has to be multiply or poorly grounded, yes?

Not necessarily. When you start talking about complex systems with multiple DC powered devices, you can get some very interesting cases of ground loops without necessarily needing a poor ground in the mix to make it happen.

It's all about potential to ground, and doesn't necessarily mean a bad ground.

Something as simple as having a different-gauge wire for the power feed and the ground line can cause it.

I see that I never mentioned that the particular noise I have is attuned to the engine; it gets loud when I rev, goes to a minimum when the car's idling.

Even taking out the /installdoctor/ part of it doesn't resolve the links for me. Crap!

> Something as simple as having a different-gauge wire for the power feed and the ground line can cause it.

Well, heck, the amp uses 6 gauge battery and ground wire; the empeg has a 6 gauge ground (now) and is connected to the power where the Chrysler radio was, but grounding it via the Chrysler radio ground (only) instead also changed nothing.

I see that I never mentioned that the particular noise I have is attuned to the engine; it gets loud when I rev, goes to a minimum when the car's idling.

This is standard behavior for most ground loops.

Something else to check is the wiring on the sled connector. Are there any loose wires there? Are there any blown fuses in the system anywhere?

You could also try running the power source directly to the battery instead of through the chrysler harness.

I get a match at http://www.installdr.com/TechDocs/999502.pdf as well at the obvious path to the other one

No blown fuses anywhere; Took care of all that fun just before this was installed when the turn signal switch failed and the steering column started smoking while I was in a remote area on a mountainside.

IIRC no loose sled wires, but I'd have to check again to say that with 100% certainty, which means another trip in the dash.

> You could also try running the power source directly to the battery instead of through the chrysler harness.

I'd like to avoid that if I can, but I suppose since I have the jumper cables it's not vastly hard to try.

> Your first problem is assuming that the "power is dirty". Electricity isn't like a water supply that can get contaminated upstream.

A friend with an EE background when asked to listen offered the same conclusion, and went on to say:

The thing is, "dirty power" is not a bad description.
The power is supposed to be ~12VDC.
It sounds like the power is actually 12VDC plus an AC component whose
frequency varies with engine speed. This could be tested with a meter
but that shouldn't be necessary.
If that is the case, then regardless of whether the AC component comes
from an electrical problem or RFI, a suitable capacitor (filter) should
eliminate it.

But it's easier to try the "power direct from battery" since I have all the stuff I need to do it in the car here at work with me, so...

Also, I wouldn't use jumper cables when trying this stuff, they weren't made for powering audio gear and might have some inherent resistance built in (not sure about that one). I'd use high-quality audio power cable from a fresh spool.

Does this EE have any experience in debugging car audio noise problems? There's some really specific things that happen in this situation that even an EE might not run into unless he's got lots of DC audio experience.

The real experts are the shops that do custom stereo installs with multiple amplifiers. They have to deal with this stuff all the time.

Can't do any worse than I'm doing now, and I can try it with what I have on hand. New wire requires going somewhere.

> Does this EE have any experience in debugging car audio noise problems? There's some really specific things that happen in this situation that even an EE might not run into unless he's got lots of DC audio experience.

Not car radio, but DC audio. Yay amateur radio:-)

> The real experts are the shops that do custom stereo installs with multiple amplifiers. They have to deal with this stuff all the time.

Well, perhaps letting Best Buy install it was a mistake then.

Well, perhaps letting Best Buy install it was a mistake then.

Oh, jeez, you should have told us that from the beginning. God, they probably cut wires off of the sled connector and everything. No wonder you're having problems...

> Oh, jeez, you should have told us that from the beginning. God, they probably cut wires off of the sled connector and everything. No wonder you're having problems...

No, I knew about that and was careful to point that out:-)

I've had the sled completely out of the car since the install, and it's fine.

the particular noise I have is attuned to the engine; it gets loud when I rev, goes to a minimum when the car's idling.


By that do you mean the frequency of the noise increases, or the volume of the noise increases?

tanstaafl.

recollection is frequency. i should go out and check given that i'm shipping my unit back for repairs tomorrow (the display has 2 vertical lines which are discolored)

>>the particular noise I have is attuned to the engine; it gets loud when I rev, goes to a minimum when the car's idling.

>By that do you mean the frequency of the noise increases, or the volume of the noise increases?

Now that the empeg is back from its journey home, and I've been away for a wedding 2 funerals and another trip, I can come back to this.

It's frequency.

At this point my list of things to try is power direct from battery (probably not today since it's raining) and ground loop isolators. Bearing in mind that I already tried a power filter, and feeding the externally-powered empeg through the same RCAs produces no odd noise, if that fails I'll be at a complete loss.

I never did try direct power from the battery, but for $15 I figured I'd try a ground loop isolator. That worked, so I spent the second $15 and now I have a completely happy empeg in my minivan.

Of course, in the meantime I got another (very used) car, so now I need to find another empeg and play this game again.

Next week I will receive the RF Modulator I ordered last night from Cruthfield to install in my Caravan. So that will make two Dodge Caravan's with an empeg.

I'm sure I will be posting with problems with my install. I went the modulator route because it's a company van and I want to leave the original audio equipment alone. I hope to be ordering what I want for my Nova the end of May or in June. I think I will have the only Nova with an empeg.

The factory radio in this was dying anyhow, so even if I wanted to leave it "factory" it would have required effort, but I can appreciate that you might want to do it. I suspect you're looking at a somewhat different class of problems as a result, though.

The second car is a Dodge Spirit, which amusing has a radio which is somewhat worse: when you play with the volume knob, the volume jumps all of the place, taking about 30 seconds to settle down, at which point your eardrums have already blown out:-)

In reply to:

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I suspect you're looking at a somewhat different class of problems as a result, though.

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I am afraid you are going to be right. I'll probably end up taking it and having it done professionally but Crutchfield assured me that I would be able to do it myself. Famous last words.

I doubt you could screw it up any more than the professional installers would

> I doubt you could screw it up any more than the professional installers would

At least in that case it's theoretically someone else's problem to fix.

I got a $40 - $50 quote today from an installer if I decide I can't do it. Nice to have a plan B ready.