ground loops. ug.

I have a ton of alternator whine in my system. If I remove the alt belt there is no noise, if I remove the field wire from the alt there is no noise. and needless to say, without the engine running there is no noise.

what I've done so far is to use one power lead and one ground lead, both with inline filters, direct to the battery for the empeg and the amp. If I remove the RCA inputs to the amp there is no noise.

I tried adding a ground line to the empeg sled, tried grounding and isolating the amp case.

odd thing is that from time to time, while driving, the noise will fade away for a short spell and return. this may be that the alternator is failing, but that is a long shot.

the car has a new battery, a new voltage regulator (both changed to cure problem).

a scope test shows a normal alternator pattern.

I'm stumped.
can a ground loop be 'seen' (voltage drop, scope pattern.....)?

i read through the FAQ, checked the crutchfield help site.
odd thing is that as i turn the gain down on the amp, the noise gets worse.

Greetings!

odd thing is that as i turn the gain down on the amp, the noise gets worse

Definately a ground loop. And, from the sound of the above, it sounds like it is running through your signal lines (did you turn up the empeg to compensate for the lower amp?). You can try filters in your signal path, or reconnect / check your grounds at both the empeg and the amp.

odd thing is that as i turn the gain down on the amp, the noise gets worse.

That's odd, it should be the opposite.

Have you tried playing some other line-level device through the amp? Perhaps the amp itself is the problem. What is the make and model of the amplifier?

just tried another amp. no change.
is it possible that the problem is in the empeg unit (riocar)?
how would I know if it is?
even with the car off i get some 'drive noise'. is this normal?

Have you carefully checked all wiring and connections, especially the wires going into the back of the sled harness? Have you tugged on all connections (both your connections and the ones on the sled) to make sure there's nothing loose?

Refresh my memory: Is this problem with a brand new installation of the player, or did it work fine for a while and then the noise suddenly appeared? What was installed in the car prior to having the empeg player installed in the car?

not a new problem. player has about 3 hours total use so far.
a battery operated mp3 player was hooked to the amp before. problem did not exist then. but that's little help.
can't get to the back of the sled very easy, but a glance some time ago seemed to check out.

the power and ground are overkill, large leads direct to battery (both power leads together, always on).

with the engine on, and the empeg on pause, the noise gets louder with each RCA jack I remove from the amp, loudest with just one plugged in, then nothing with them all out. tested a few amps at this point. all the same.

ug

can't get to the back of the sled very easy, but a glance some time ago seemed to check out.

When diagnosing ground loops, never assume that a given connection is good, just because it's in a hard-to-inspect location. Everything must be checked out. You have to be completely methodical.

One thing you could try is unplugging all 4 RCAs and, with the empleg playing, touch the tip of one (or some) against the empeg casing. If this introduces noise then the test should prove to you it's not the empeg creating the noise. Unfortunately, the opposite effect (no noise) doesn't necessarily prove the empeg itself is at fault.

Also, have you checked for other unwanted earths in your wiring eg. speaker cables? I expect you've already done this; try running the empeg on the seat to rule out any accidental earthing taking place when it's installed in the dash.

you're right. into the dash i go.
I'm told that there are inline RCA filters, but I'll guess this is a poor methode of masking the problem. any comments?

I'm told that there are inline RCA filters, but I'll guess this is a poor methode of masking the problem. any comments?

These filters are supposed to break the ground loop between the amp and the head unit, if that's what you've got. However, they tend to reduce the frequency response of the sound traveling through them. The ones at Radio Shack are reported to have bad frequency response specs, and there is supposedly a different kind which have OK specs, I don't remember whether the part number of the "good" one ever got repeated to me and put in the FAQ...

One of the noise-troubleshooting documents linked from the FAQ has an interesting perspective: These filters cost money. Whereas locating and fixing your ground loop problem (assuming it is a ground loop) is free. The filters would just be an expensive band-aid on an existing problem that would never get solved.

I was helping another empeg owner (Russmeister) this weekend with trying to get rid of the alternator whine in his system. We double and triple checked all wiring, regrounded all the amps, the sled, the player, etc...with no dice. Also tried adding a ground loop isolator...still no dice.

Finally we fixed the problem. We ended up taking the amp apart and soldering a ground wire from the ground on the circuit board to the ground on the RCA inputs in the amp. After doing that, it worked like a charm!

Don't know if that'll help in your situation, but it's something else to try.

You say that the noise gets louder as you remove RCA connections until you remove the last one, whereafter the noise is elliminated ? Sounds to me like you are pulling current through your RCA connections. Do a couple of checks: Grab a multimeter and with your RCA's disconnected and the system turned on, measure the voltage between 1:your negative battery post and the RCA shield on the Empeg and 2: your negative battery post and the RCA input shield on the amplifier. If your Empeg has a voltage difference between shield and ground (battery), you need to check all your ground connections and your docking connector. If that's all good, then you could have an internal ground problem (warranty/contact support ?). If there is a voltage difference on the amplifier side of the system, the same checks hold true for the amplifier. The third alternative (maybe temporarely) would be to disconnect the shield connections at the amplifier end of your RCA patch cords, leaving just the signal connections (center pin) hooked up. Your line level signal return path will then be forced through your main power connections, elliminating a ground loop, but not solving that one of your pieces is still hunting for a better grab of the negative battery terminal !!
Good Luck

Lars

wow heavy.
if I understand this then the outer contact of each
RCA jack needs to have a perfect ground? can I just tie in to the open wires at the back of the sled?
at this point every wire in use is new. all gounds and power leads are right to the battery.

What happens if you take a short piece of wire and hold it between the amplifier's ground terminal and its RCA shield while the system is playing and the car is running ?

I just re-read your original post. Do you have a noise filter installed between the amplifier's ground terminal and the negative battery post ? If so, remove it and any other filter installed in your system on the ground side. The system needs a solid connection to ground (meaning: proper gauge of copper wire and nothing else) before any more experimentation is done.

thank you all for the input and help so far.
I do have a filter on the ground line, and will remove it.
one thing i don't understand is if the issue is the poor ground to the RCA, why would the engine running (alt working) make any difference?
seems like a killer set of RCA patch cables would have a ground lead hanging out from one end. just a thought.

one thing i don't understand is if the issue is the poor ground to the RCA, why would the engine running (alt working) make any difference?

Explained here.

Quote:

"When this happens, your stereo's audio output circuity suddenly becomes part of your car's electrical system. Every single thing in your car that interacts with the electrical system will be amplified by your stereo. The alternator, the spark plugs, the air conditioner, the headlights, the brake lights, the car's emissions-control computer, the stereo's electronics, the electric motor that spins the CD in your CD player (or spins the hard disk in your MP3 player), everything. All of these things will suddenly cause non-musical noise to come out of your speakers."

makes me wish i lived in a perfect world.
I like bunnies.

Heh, wasn't sure if anyone else thought that was as funny as I did.

I am having a similar problem. My current setup does not include an external amplifier, though. It has the empeg running through the AUX in on my CD receiver.

Recently I was having a voltage problem with the empeg, and so I wired the constant power (yellow) line directly to the battery with an inline fuse. Before I had done that, there was still some noise in the system, but it was not audible unless I paused playback on the empeg and turned the volume up on my CD receiver higher than I would ever go.

But now that the empeg is wired directly to the battery, the noise becomes audible at a lower volume on the CD receiver. The CD receiver's AUX in is on the front panel. If i disconnect it, the noise vanishes. Also, when the engine is running, this noise does change pitch with the engine's rev or even the empeg's drives spinning. With the engine off, the noise remains, and still changes pitch with the empeg's drives spinning.

So, knowing that the noise is coming from the empeg, what would be the most likely cause?

• The direct constant power (yellow) line to the battery?
• The sled is not grounded well enough?
• Or something else entirely?
  

How are the power and ground connections hooked up in your system currently ?

How are the power and ground connections hooked up in your system currently ?

Are you asking me, or the guy that started this thread?

i think he means you. we can share the the thread (:

I am asking Justin.

Lars.

Alright.

As of yesterday, this is my current setup:
98 Honda Civic EX Coupe
empeg in dash:
- yellow (constant) line put directly to the battery (in-line fuse used, of course).
- red (switched or ignition) line is wired to the Honda harness, sharing it with the red line from the CD receiver.
- black (ground) is wired to a part of the frame (bare metal) of the dashboard, just behind the glovebox.
- white (headlight sense) line is wired to the orange/white line (headlight sense) from the Honda harness.
- green & blue wires not used, covered by electrical tape.

CD receiver mounted behind shifter, in space originally meant for Honda CD changer. It's connections (constant, switched, ground, and speakers) are all connected to the wires from the Honda harness.

I recently discovered that there is a bit of noise that belongs solely to the CD receiver. But it only becomes audible in AUX mode, with nothing playing, and the volume up way beyond the highest level I can stand.

My major concern is that since the time I have wired the empeg's constant (yellow) line to the battery, much more noise is noticeable with the empeg running. I still have to pause playback to hear it (I can also hear it during "quiet" parts of a song), but it becomes audible at a much lower volume level than the CD receiver's own tiny bit of noise. This noise, coming from the empeg, changes pitch both with the engine and with the empeg's drives spinning up. Also, the noise does not disappear or become quieter when the engine is off.

P.S. - You asked.

It may be that your ground is not grounded properly. Some dash interior metal parts don't end up touching the rest of the chassis. ISTR that Hondas were particularly bad about that, but ICBW. Regardless, try running a temporary piece of wire from your ground to other possible grounding points and see if the noise goes away.

It may be that your ground is not grounded properly...

I had thought of that... and I will try it again if I can find another possible grounding point, but...

The empeg used to get its connections via a T-Harness made especially for Hondas (in order to keep the keyless entry which is housed inside the factory radio). I have sacrificed keyless entry (never used it anyway) in order to have my empeg. When using the T-Harness, the empeg and the CD receiver were grounded on the same ground line (going through the standard Honda wiring harness), but at different points on the line. This minimized noise greatly. However, when they were grounded to the same point on the line, I experienced noise similar to what I have now.

I am quite sure that I have to find a better ground for the empeg, and possibly its docking sled. But with its recent behavior after giving it a direct line to the battery, I also feel the noise may have something to do with that new connection. Is there some way to minimize or kill noise that might be coming down the power line?

I notice you're doing the power and ground runs for the two components (empeg and amp-- the CD receiver IS the amp) two different ways. Something as simple as different wire gauges or even different wire lengths for the two runs can cause a ground loop.

You might want to re-do all power and ground wiring for both units, using heavier gauge wire, where the gauge is the same for all runs on all components. And make sure they're both grounded to the same point, and both getting their constant power from the same point.

grounded to the same point, and both getting their constant power from the same point

As I mentioned, when the empeg and the CD receiver were grounded to the same point (on the same line), I had more noise than when they were grounded to different points (on the same line).

Constant power cannot come from exactly the same point in my case, unless I want to run the CD receiver's constant power line directly to the battery as well. The direct line to the battery is the solution to a voltage dropoff I was having when the empeg and CD receiver were on the same constant power line (using the aforementioned T-Harness).

But yes, the grounding is two different ways at this point. The empeg's ground is connected to a bolt on the frame of the dashboard, whereas the CD receiver's ground is connected to the normal ground wire from the original Honda wiring harness.

And as for wire gauge, I believe the empeg is all 18AWG? My CD receiver is 16AWG all-around. And the direct line to the battery for the empeg's constant line is 12AWG with an in-line fuse near the battery.

I would start by following Tony's advice. Bring another #12 black (ground) in from the battery, like you did for the +12v. You can in all likelyhood share the two #12's between your two headunits and just hook them up together right behind the units in the dash. Ensure that you have good connections throughout ie; if you are using lugs at the ends of your wire to the battery, solder them, etc. There are several other things to pursue, but let's start with the basics first. Keep us posted regarding your findings.

Tony: Do you know how much current is consumed by the Empeg on the switched ignition wire ? Or for that matter, all of its "sense" inputs ? I would think almost nothing, but I may be very wrong...

I would start by following Tony's advice.

I plan to. Running both units' constant and ground lines to the battery sounds like a good start. But if I'm right and I'm getting noise from the constant power line to the battery, how would I take care of that?

You're getting noise because you are connecting two headunits (via the RCA's) that are not at the same electrical potential. Therefore current is flowing through the RCA connections. That's what we're going to eliminate by process of elimination....... did that sound weird to you too ??

just commenting in case it is helpful...

lastdan: im not sure if youve already passed this hurdle but, have you eliminated the empeg as the source of the sound? ie, just wanted to suggest running the RCA cables from the empeg, off to a portable stereo or home stereo, and see if the whine is picked up there (ive done this to troubleshoot my own unit, parked in garage and run RCAs to my room to listen to the output) it will at least tell you if the loop is coming from the empeg, or elsewhere (amp wiring)...?

justin: if youre not getting alternator whine (or other electrical interference) then i dont think it is a ground loop issue? just my first thought - going on wild goose chases ripping up ones dash is no fun, as i know

if youre not getting alternator whine

If you reread my posts you will see that I already mentioned that I do have alternator whine. The noise changes pitch with the engine's rev. But, the noise doesn't disappear when the engine is off.

much like my problem. but the alt noise may be caused by the same problem that makes it noisy when it's not running (I'll live with that, if i can)

please let me know if you all get a little 'drive' noise, even if it;s no biggie. boot up is most noticable.

Fuel pump noise? Probably RF radiated? Needs a suppression capacitor?

please let me know if you all get a little 'drive' noise

I already mentioned that I have this problem, too. And it's just as noticeable as the "alternator whine."

Edit: It looks like I've hijacked your thread... I apologize.

Fuel pump noise? Probably RF radiated? Needs a suppression capacitor?

One suggestion from someone I know was that it's possible that my high output alternator is causing noise on the constant power line of the empeg. The direct line to the battery passes within 18 inches of the alternator; possibly even closer. I tend to overestimate measurements.

I never heard the term suppression capacitor. But someone suggested a power line noise filter, if it is determined that the noise is coming down the empeg's constant power line.

The ones at Radio Shack are reported to have bad frequency response specs,......
Any idea what the specs are? Is it primarily bad in the upper or lower spectrum?
I have, I think, the inline RCA fground noise filters you're talking about with the big black pill shaped filter in the middle. I use this on the powered sub.

Alternators are supposed to be shielded, since they would otherwise fail RF tests. Unless the casing of the alternator is not earthed, this should not be an issue.

Alternators generate noise if the regulator is damaged. If you ran the engine without the battery or a load connected, you could have damaged the alternator.

It is more likely your battery is going high impedance, and if it is being force charged by a "hot" alternator, then the fluid levels may be low. Check and top up with distilled watter, or have the electrolyte checked at the garage.

A suppresiion capacitor is a high voltage foil capacitor used to short circuit noisy devices such as ignition (breaker type), wiper motors, AC motors, etc. They are common at spares shops.

A power line noise filter is likely to be an in-line coil filter, installed in line with your main power feed to either the empeg or your amp. The empeg already has one built into the harness.

You are just a wealth of information. After taking all of that into consideration, this is all I can say:

I doubt it is the fault of either the alternator or the battery, as both are brand new; recently installed and tested by my mechanic, whom I trust.

I'm not sure what to think about a supression capacitor, as I've never seen or heard of it before new and so don't know how it's used. And as for the power line noise filter, is it possible that there is so much noise that the empeg's isn't enough?

But anyway, I've decided to put this on hold. The noise isn't audbile until high volume levels, and I find that cleaner sound is important to me. So I will not turn it up very loud if the sound gets too dirty. So this problem will wait until I put in my amplifier, which should be soon. Hopefully.

Thanks everyone for help and suggestions. I will keep this thread in My Favorites so that I can use it later in order to nail down the ground loop when I do the amp install.