So they tell me its a ground loop....

[kingsxman 10+ year member]

I had install shop install my Alpine 3331 eq and a Profile 4 channel amp for fronts and rears. Buzzing occuring after install in my system. Fronts and rears. I also can hear a slight pop in the system when I apply my brake. Beeping coming through system when I reverse (car has beeper for backup). Only when one of the 2 RCA's is plugged in. Doesnt matter which one.

Originally they told me Profile amp was cause of buzzing so I replaced amp with another Profile (AP1040). Buzzing still there.... Brought back to shop. They pull apart and say its still the amp. Only thing to fix it is to only use 1 set of outs from EQ and Y them so they can plug into both sides of 4 channel amp. Buzzing gone...but I lose front/rear fading.

Head unit and EQ are grounded together up front to some ground. (not sure what). I asked that they run cable from front to rear to test to see if both amp and HU/EQ were grounded at same point if it would go away. They claim they did this but it didnt work. (not sure if I buy it. To me...this should have worked).

Can someone explain how this grounding issue might be occuring? I do not like losing the ability to fade Fronts and Rears. Also, can anyone explain how 2 amps supposedly could be causing the issue? Are Profiles more prone to this than others?

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[iceteebone 5,000+ posts]

try some new rca cables. make sure your ground wire on your profile amp is short and it's a good clean ground. try ground your headunit and EQ direct to the battery.

 

[kingsxman 10+ year member]

They have run new RCA's. (I know...becuase i was charged for them..and they didnt help!). Ground on amp is short and is well connected. The ground on the HU and eq runs to somewhere just under drivers side left food. I talked to installer about why he didnt use ground wire where factory radio was and he said that when he gets 2 componenets he needs a better ground...so he runs them to..." ". (I forget where he said they were grounded to).

Running them directly to the batter might be an option... My suggestion to them was to run ground from HU/EQ back to same ground spot that battery is grounded to. That should elminate any ground loops. They "say" they did that...but who knows for sure.

I'm in Minnesota where its now about 20 degrees out. My garage isnt heated so any work I do I want to only do once.

 

[knukonceptz 10+ year member]

When you disconnect the RCA's is this at the amps? You have to do this in a process of elimination otherwise, your just going to be more confused.

If you unplug the RCA's at the amp, is the noise gone?

No Noise -Plug back in, its not the amp (amps will amplify what is inputted into them...strange concept....lol if noise is coming from HU/RCA its getting amplified)go to next step

Noise Present - You elimianted the HU and RCA's its the amp or ground

With the amp plugged in, Unplug the RCA's at the HU, noise gone?

No Noise - Now all that is left is HU/EQ, bypass the EQ and see which is bringing in the noise.

Noise Present - Noise is being absorbed by the cables, you eliminated the amp, now all you added was RCA cables = bad cable

The best option is to run 10 or 12 gauge speaker wire from the HU power/ground to the rear and connect power and ground of the HU to the same location as the amps. I say speaker wire because it is 2 conductor and easy to run one wire then two. Factory harnesses can often be noisey from ignition wires and such. Common power/ground points greatly ruduce your chances of noise

 

[kingsxman 10+ year member]

Yes.

Whats weird is I can unplug either set of RCA's and the noise goes away. It doesnt matter which set.. Same way with plugging them back in. I can take them all out...but as soon as the 2nd set gets plugged in..(actually...the 1st connection of the 2nd set) the noise comes back.

I have not tried that. I'm assuming (bad..I know) that the shop tried this.



THis is what I recommended they do. Once again...they "said" the did that.

Has anyone ever heard of an issue like this with a certain brand of amps?

 

[knukonceptz 10+ year member]

Amps do not make noise, they just amplify it. I am sure under rare cases if an amp is bad, it will make noise. However if the amp has no input signal (ie no RCA input) and the noise is gone, it cant be the amp making the hum/buzz etc

If you unplug at the HU and the noise is gone, it is coming from the ground of the HU or EQ. check in the back to see if they ran any new wires or head back to the shop and ask him to show you this wire. After all you did pay for the work, they could at least show you where it is...... or isnt.

Forgot to mention - since you already replaced the amp once for noise, do you think two amps are going to be bad? Very unlikely two different amps result in the exact same problem

 

[maylar 10+ year member]

Classic ground loop symptoms. The HU and amp grounds are at slightly different potentials. The RCA cables connect the grounds together by nature of their shield wire. Each RCA you plug in reduces the resistance and at some point the RCA ground path is lower than the wire ground path and noise happens. That's been my experience, anyway. Maybe it's the phases of Jupiter's moons. At any rate, I feel your pain... my system does the same thing.

Yes, some amps are more sensitive to this than others. Some HU's too. Amps with well designed input circuits where the RCA jack is isolated from chassis ground are more immune to ground loops. My USX 4065 and Pioneer HU combo does exactly what you describe.

Solutions vary. Relocating the HU ground often does it. In my case it doesn't matter because the HU chassis is grounded to the metal dash and the ground wire don't do ****. Using "directional" RCA cables (with the internal shield disconnected from one end) worked for me. Last resort is ground loop isolator thingies on the rear channel RCA's.

Good luck. Noise sux.

 

[kingsxman 10+ year member]

My sentiments exactly. Hence my question as to whether or not Profile might be more prone to this than others. I mean, they're not exactly the most expensive amps out there...so there must be some corners cut. Maybe they ARE more prone to noise.



Yep, that certainly made sense to me...but they claim to have done it. Good info on the directional RCA cables. It actually is working ok right now with the Y cables. I lost fading..but I went to the back and adjusted the gains for my rear speakers so the level is about where I want it with the front. It IS quiet now....which is a plus.

I might try bridging the 4 channel amp to get more power to my fronts and eventaully add another amp for the rears. We'll see if that adds or reduces the issues.

 

[Shyne151 10+ year member]

Sounds liek a shitty shop if they can't fix a **** groundloop.

 

[kingsxman 10+ year member]

Shitty shop? Well, all I can sayt is I was disappointed to get charged for it...I'll tell you that. It is quiet now...but of course I lost my ability to fade. So...technically its fixed. Just not neccesarily to my satisfaction.

 

[Prowler573 5,000+ posts]

Shitty shop? Well, all I can sayt is I was disappointed to get charged for it...I'll tell you that. It is quiet now...but of course I lost my ability to fade. So...technically its fixed. Just not neccesarily to my satisfaction.

In my mind, this qualifies as not being fixed. They didn't 'fix' anything - they essentially put a band-aid on it rather than addressing the actual source of the noise. To me a ground loop isolator is the same thing...a band-aid, not a solution. Have the RCAs ever been disconnected from the HU while it was powered on? I have a sneaking suspicion that you're experiencing the infamous Pioneer ground trace issue. It looks like you've eliminated most other possibilities. Is there another HU that you could use for testing purposes temporarily to see if another HU cures these (I'm sure) rather maddening problems you're having?

 

[knukonceptz 10+ year member]

doh, did not even notice it was a Pioneer.

 

[kingsxman 10+ year member]

OK, this is the 2nd time I've heard of the infamous "Pioneer ground trace" issue.

STeve at Profile mentined this right away when I talked to him about needing a replacment amp becuase the shop said this one was bad.

I can solder very well... Is it an easy fix on the HU?

 

[TL-Focal25 10+ year member]

I have the same EXACT problem as you kingsxman and I have panasonic CQ-C8400U deck with 2 MA audio (High Current) series and a 3 farads cap. Problem still occurs even with Rockford Twisted Cable.

Well I can tell you that relocating the ground wire from your head unit is not gonna solve the problem. Because I connected it straight to the battery terminal.

Here's a list of things that we should try:

1. The best option is to run 10 or 12 gauge speaker wire from the HU power/ground to the rear and connect power and ground of the HU to the same location as the amps. I say speaker wire because it is 2 conductor and easy to run one wire then two. Factory harnesses can often be noisey from ignition wires and such. Common power/ground points greatly reduce your chances of noise

2. Make sure the RCA cables is not on the same side as the power cable.

anymore inputs are welcomed.

here's something you might want to read about

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

 

[TL-Focal25 10+ year member]

oh by the way, could u tell me if your rca cables is on the same side as your power cable? I assume the shop u went to have a lil bit of intelligent and wire it on opposite side. Obviously i didn't think about that, I'm don't want to re-run the wire if it still causing the sound. //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

Yup. the noise came from the Power line with the RCA. So kingxman, you should check for that. Mine is completely quiet now. Thanks everyone!