Ground loop isolators: Are they all created equal?

EndersShadow

So I recently noticed that when I listen to my music in my car I get a really high pitched whine.

No matter if the volume goes up or down the whine stays the same. If I kill the source it keeps up for a brief few seconds afterwards then goes away.

I know its coming from the amps and I believe its the dreaded ground loop issue.

So I was told to get a ground loop isolator for one set of RCA pre-puts on my Cd player.

My question is are they all created equal or are there some specific ones I should get, or stay away from.

Thanks in advance

Vital

From what i know they "take out" some of the frequencies (highs??) of the actuall music as well hence using them is basically a last resort. Keep in mind i'm no expert in "ground loop isolators" so i could be wrong but that's was i was told at one point.

btw since curing the problem is more important then "patching it up" this might be helpfull:

Route wires away from the car's electronics like the ECU...

Keep power wires away from signal wires.

Use one ground. not separate grounds.

Do not make an RCA "service loop" near any power wires.
[A service loop is a roll of wire..makes a very nice inductor for engine noise]

also check the receivers ground make sure its a great ground...sometimes factory stereo grounds dont work well with aftermarket receivers

Vital

btw why are you sure it's coming from the amp?
What brand/model?
Which wires do you use?
Did you try swapping an amp with a different one? (your spare, your friend's, "rental" from best buy lol?)

EndersShadow

Vital wrote: »

btw why are you sure it's coming from the amp?

Because its coming from the trunk and when I get my ears next to the amps its right there

Vital wrote: »

What brand/model?

Sundown 125.2
Sundown 1200D

Vital wrote: »

Which wires do you use?

2 sets of Memphis Audio RCA's

Vital wrote: »

Did you try swapping an amp with a different one? (your spare, your friend's, "rental" from best buy lol?)

Dont have any spares, no freinds with amps, and not even gonna try to install and then return one to BB lol....

I am gonna do a bit more detective work to see if its something I can fix by routing the cables differently in the rear of the car, but not sure....

Vital

If it is ground loop (which looks to be the case) it doesn't "come out of the amp". I mean some amps could be causing it but noise itself will not come OUT OF THEM... and Sundown is a really good brand, i doubt they couse that noise.

I'd assume it would be easy to get your head in the trunk and ask someone to press on a gas to def hear where that noise is coming from if it's possible to point it out to begin with.

Try moving wires around as far away form amps and power wires as possible while u're at it. That includes speaker wires too, not just RCAs.

Jstas

EndersShadow wrote: »

Because its coming from the trunk and when I get my ears next to the amps its right there

Uhhh...that's not a ground loop. Unless you're not describing it correctly. What it sounds like is probably a harmonic in a power circuit somewhere caused by a bad ground.

Bad grounds could be:
- damaged/cracked/broken interconnects (RCA cables)
- improperly ground amplifier power
- bad output jacks on your head unit
- bad input jacks on your amp
- bad output terminals
- bad chassis grounds inside the amp and/or head unit
- bad turn-on lead connection/terminal

There's probably other stuff but if all the amps are doing it, I'd check everything. Power/ground wires, interconnects, signal lead, even swap out the head unit if you can.

Ground Loop definition:

a ground loop usually refers to a current, generally unwanted, in a conductor connecting two points that are supposed to be at the same potential, often ground, but are actually at different potentials. Ground loops created by improperly designed or improperly installed equipment are a major cause of noise and interference in audio and video systems. They can also create an electric shock hazard, since ostensibly "grounded" parts of the equipment, which are often accessible to users, are not at ground potential.

A ground loop is not synonymous with a bad ground. For a ground loop to occur, both points have to be properly ground. You get the humming, like engine whine, when one ground point is not at the same potential. This usually happens with engine whine and sourced in the head unit. This is because your engine needs to be grounded to the chassis. Since the firewall is directly attached to the chassis, the engine ground strap is usually attached there. Guess what else gets attached to the firewall for a grounding point? A head unit. The potential problem occurs because the engine can actually increase the potential of the immediate area surrounding the grounding point on the firewall because of not only electrical activity in running the engine but a static electricity charge from the moving engine parts. Because of that, the ground point for the head unit has a higher potential than the ground for the power circuit on the head unit chassis. This causes feedback which manifests in an audible hum being amplified by the amplification circuits picking up the feedback through the amp or head unit chassis ground.

A ground loop isolator essentially does two things. Creates a break in the current path which eliminates the potential problem by presenting a balance potential to either end of the ground and provides line conditioning to prevent the feedback the causes the hum. They work provided that the problem is actually a ground loop and not a bad install job or broken equipment with bad grounds.

That same potential problem can cause an EM field to be picked up by a tape head in a cassette deck and then amplified by the amplifiers. Ground loop isolators typically won't fix that problem. But typically, this issue is caused by a bad ground on the engine ground strap, starting system ground, battery ground or ignition system ground. Fix those and the tape hum goes away. Not that tapes are really an issue anymore.

EndersShadow

Jstas wrote: »

Uhhh...that's not a ground loop. Unless you're not describing it correctly. What it sounds like is probably a harmonic in a power circuit somewhere caused by a bad ground.

Bad grounds could be:
- damaged/cracked/broken interconnects (RCA cables)
- improperly ground amplifier power
- bad output jacks on your head unit
- bad input jacks on your amp
- bad output terminals
- bad chassis grounds inside the amp and/or head unit
- bad turn-on lead connection/terminal

I will check that stuff but.....

Jstas wrote: »

Uhhh...that's not a ground loop. Unless you're not describing it correctly. There's probably other stuff but if all the amps are doing it, I'd check everything. Power/ground wires, interconnects, signal lead, even swap out the head unit if you can.

I dont think both amps are doing it, it however is hard to isolate since they are side by side which one is doing it.

I am thinking its due to EM in the RCA's and I plan to check their routing later this week when I have time. It requires me to take out my spare and some other stuff plus then rechecking all the wiring.

The noise is a constant high pitched whine that is the same volume regardless of what the volume is on the HU, and what source is being listened to.

It also seems to happen more when the car is super hot as in the morning its not as likely to happen (although I dont jam as hard on the way to work as I do on the way home )

Vital

here's another "data" that might be helpfull

http://www.termpro.com/articles/noise.html

EndersShadow

Vital wrote: »

here's another "data" that might be helpfull

http://www.termpro.com/articles/noise.html

Wierd thing is that it only does it in the afternoon when its hot. I jammed at full volume all the way into work and nothing.... Part of me is wondering if its not possibly something in the amp not working (like a fan if it has one)

Couple of those are what I plan to check out this weekend (mostly the power and signal wire one since I didnt install it....):

II. Don't introduce ground loops. Ground loops are created whenever an audio ground is established at more than one location. Theoretically, the only place the audio ground should be connected to the chassis ground is at the source unit. In my experience, I've found that in systems that have noise problems, a ground loop is the culprit nine times out of ten.

III. Never run signal wires alongside power cables. This is especially true in installations where high powered amplifiers are used. Large amplifiers are capable of drawing large currents. These currents vary with the musical demand of the program material as does the electromagnetic field surrounding the power cable. The more current that flows through the wire, the bigger this field becomes. If audio cables are located in close proximity to this fluctuating electromagnetic field, noise could be induced into the system.

jay27

There's some good advice here.

You don't happen to have a Pioneer head unit, by chance? If you do, a blown pico fuse could be your problem.

My experience with a ground loop isolator is that it used to caused incredible amounts of distortion at higher volumes for some reason. It sounded like my subs were preparing for lift off. So, I would look at how good your ground points are and improve them or move them elsewhere.

I read through a Zed Audio manual recently and they thought it was actually fine to have multiple ground points in the car.

I've never, in my experience had any noise from running rca's, speaker wire, etc., close to power cable. I've also had no noise running the cheapest rca cable Monoprice has to offer.

EndersShadow

So interestingly enough when I got home it was annoying the hell outta me....

So I disconnected both sets of RCA's from the input on the amps and the whining sound remained.

I switched RCA's on one of the amps and still got the same noise.....

I would assume this would make it something with the amps since it was still making the same noise even w/ the RCA's disconnected....

Jstas

EndersShadow wrote: »

So interestingly enough when I got home it was annoying the hell outta me....

So I disconnected both sets of RCA's from the input on the amps and the whining sound remained.

I switched RCA's on one of the amps and still got the same noise.....

I would assume this would make it something with the amps since it was still making the same noise even w/ the RCA's disconnected....

Most likely.

Check your ground points.

No seat frames, no hinge mounts. No paint. Best thing to do is drill a new hole and scrape the paint off around the hole. Then put a flat washer on the bolt, then a star washer slide the bolt in to the hole then a star washer a flat washer, your ground cable terminal end and the nut. Crank it down **** tight so the star washer bite in to the sheet metal.

Then, get a power distribution block with no fuses. Run all your amp grounds in to the block. Then take the ground cable installed in that hole you drilled and attach it to the big end of the distro block.

That is a solid ground.

The constant humming you are hearing is likely your fuel pump if you amps are located at the back of the vehicle somewhere in the trunk. The fuel pump is on in an electronic fuel injection system all the time when the ignition is on. So if you pulled your RCA's and still had the whine, it's not a signal source problem or your RCA's.

another problem it might be is how your amps are mounted. If you have the metal amp chassis screwed right to the car sheetmetal, that is causing a grounding problem because you now have a ground that is at potential and one that is not. If you have your amps mounted that way, unmount them, get a piece of wood or MDF and screw that down where your amps were. Then mount the amps to that wood/MDF. It will insulate and isolate your amps from the rest of the car. The only electrical contact your amps should have with the car is the ground point.

Vital

This is probably off topic but - is running a 0 gauge wire straight from battery's negative post into amp's ground a good idea? I've heard people saying it's the best way to ground your amps and i also heard it's the worst thing u can do... Really not sure on this but would def like to know the verdict.

OP - sorry if it's off topic but if answer is "yes, it is the best way to ground amps" you will get another option on grounding them