Ground loop Squeal

[JoshMcMadMac]

I know a decent amount about this problem, but I don't want to spend any more time in the cold than necessary fixing this problem. First of all, my setup. I have a panasonic headunit, but that shouldn't matter. I am running a 4 channel, 600w amp as well as a 2 channel, 1200w amp. Those ratings are peak at 2ohm, and I run at 4ohm, so I am actually running at half those values. I also have a 1F cap. I am running 4gauge to the cap, and one 4 gauge ground. The cap and both amps are sent into a distribution block with 8 guage to the common 4gauge ground. I am pretty sure this is the cause of my problem.

I am getting a "squeal" that I believe is caused by the common ground. I had the 4 channel removed, and then the squeal went away. When it went back in, it came back. I cant tell if the problem still exists with just the cap and 2channel amp, since that amp runs the subs, and that high a pitch is out of range.

So, what is the best approach to fixing this? Should I give each component it's own ground, or should running bigger wire into the block fix it? Or what if I remove the cap from the block and leave the amps?

[Desert Stallion]

I would run short length individual ground wires for your components. This usually solves most problems. Also make sure that your speaker wires and RCA's aren't running near the power wires, as that can cause a 'squeal'.

[cason1]

Is it an all the time squeal or does it flux with rpms. I put an amp in my dad's old 00 grand marquis and it had a squeal with rpm's from power off the fuel pump.

[SQ_LSC]

Is this a problem that just started or was there an equipment change? I doubt that a larger wire would help so hold off on that one. Disconnect the cap for your testing. Try re-grounding the 4-channell amp seperatly and see what happens.

[JoshMcMadMac]

quote:Originally posted by cason1:
Is it an all the time squeal or does it flux with rpms. I put an amp in my dad's old 00 grand marquis and it had a squeal with rpm's from power off the fuel pump.

Actually, I think is is RPM. The higher the RPM, the higher the pitch.

[Aaron C]

I've got the exact same problem, it is a 'whine' that matches the engine revs. I dont have a cap but I do have 1 amp for speakers and 1 for subs. I have the wires running on the passenger side of my car just under the carpet. I bet its near a power wire or something but I dont know how I could remedy this, I dont want to go crazy trying to re-route the wires, it doesnt even seem possible. Any ideas?

[Desert Stallion]

Yeah, what I posted before. :D

Actually running wires isn't a big deal. My power wires run down the driver's side along existing wire bundles, and the audio/speaker wires run down the passenger side.

Also I would make sure that your power supply wires are hooked up to the battery either directly or through a block like Josh's.

But I think that short, individual ground wires help in a lot of cases. Good grounds, chasis grounds not some flimsy piece of trim that's sorta attached and sorta not.

Also try twisting your audio wires if you can.

[Capt. Zilog]

Also, make sure the amps are not touching the car body and grounding through there. That will give you a potential difference (a voltage) between the two grounds, which is beyond bad.

[JoshMcMadMac]

SQ - The problem is from going from stock to aftermarket. That is the only change I have made. When I pulled the amp (it died) I ran the speakers off of the stock speaker lines and the squeal was gone. The power line is on the Driver side, and the rest are on the passanger side. As I recall there are NOT any other lines the run down there other than for the antenna, but I do not have that antenna connected anyway. And I do intend to remove the cap for trouble shooting.

D - I've got a very "clean" wiring setup. The end is connected through a dual-out battery terminal, and all the ends of the wires are tined (sp?). And re-routing will only end up with RCA's running over the 4 gauge. Even if it is something giving off power now (which I really trult doubt) it would get worse with that! :rolleyes:

Capt. - Good point. That is not my problem, however. Hopefully it can help Aaron, but my amps are screwed directly onto the speaker box. No unintentional ground is occuring.

Thanks for the thoughts guys, keep throwing them at me!

[SQ_LSC]

First thing is to isolate the amp from the HU and rca wiring. Pull the rca's from the amp. take a short rca and plug both ends into the inputs of the amp which will short across them. This will not hurt anything so don't worry. After you jump them out turn the system on and check for whine. If it's still there you know it's not in the HU or RCA wiring. If it is still there next try simply turning down the gains on the amp. Post back with your results from this simple test.

[JoshMcMadMac]

This is what I have figured out. I isolated the 4-channel amp with just the 4-gauge in and out. The squeal remained. I was going to run RCA in from my MP3 player, but stumbled across the problem before getting around to it.

Without getting into the details of the problem, I have an intermittent ABS issue. Under certain circumstances the yellow "Check ABS" light will turn on. When that light is on, the ABS becomes inactive and is disabled by the vehicle. I had the ABS issue this weekend, and sure enough, when the ABS stopped working, the squeal practically disappeared! So, my conclusion is that the either the ABS computer or the wiring running to it is the source of this squeal. Granted, there is a FAINT squeal left after the ABS disengages, but it is inaudible unless you strain to hear it. I am inclined to believe that the ABS wiring is the problem, not the computer itself. I have the box with the amps mounted on it fitted directly behind the back seat. However, when swapping out the amp the box was shifted to the back end of the trunk, and there was no noticable change in the problem.

Regardless, it looks like I am in the market for noise suppresors. :rolleyes: Hopefully this will do the trick, but let me know if you have any other suggestions on fixing the problem. Maybe if I get some free time I will put some shielding around the ABS computer and see if it makes any difference. Thanks again for all your help!

[JoshMcMadMac]

I went on www.etronics.com (http://www.etronics.com) and found noise suppressors here (http://www.etronics.com/listproducts.asp?store=&catid=336). There are six different ones available, but two different types. One type appears to be power wire connected:
http://images.etronics.com/products/ns12.jpg


and the other RCA connected:
http://images.etronics.com/products/ns20.jpg

I have no idea what the dfference is or what the best one is for my application. I am running a 4 channel amp, 75watt per channel at 4 ohm RMS. Thanks!

[SQ_LSC]

If you shorted out the RCA's for your testing like mentioned above then you can eliminate the rca noise adapter as an option. Honestly, most those supressors are crap. Some are isolation taransformers which take 12v in and put out 12v changing the impedance slightly in the process. Others like the rca one's merely lift the ground from the rca. Notice the low amp ratings? There's not much suitable for amps being used for driving subs. Do another test before spending any money. Wrap a piece of wire around the outer ring of the rca's and ground it. See if that makes a difference. Sometimes the outer ring is not connected to ground internally and causes problems. Leave your rca's from the HU disconnected during the test.

[JoshMcMadMac]

Thanks SQ, I will get on that soon (or later :rolleyes: ) and hopefully get this figured out. If a noise suppressor won't work, what other option do I have? And I mean feasible options, not "rip the stereo out and start over." :rolleyes:

[Capt. Zilog]

I just read the fuel pump causes some problems. Remember it IS right there.

Also, I have this annoying crap sometimes too. Sometimes no, sometimes yes, but it's not based on RPM like yours. I would recommend not using a sound supressor. Every thing I read says they are junk.

Here's a thing you could try, although it would take mucho work. Put the sound system on a different 12V power stream (different alt, batt and you'd have to run ground cables front to back). That way you won't have any contact with ground noise from the car. Of course, it's a pain in the ass to even set that up. If it gets too annoying though, it is an option.

[pepsi2185]

That panasonic head unit probably does not exactly block those noises as it is. The install is very touchy when your headunit does not have noise supressors. Those boxes that hang from the old kenwood raiods made a huge difference. That squal (alternator whine) is from high power wires running next to your RCA's. What kind of RCA's did you use. The dual twist rockford RCA's make a difference they cost more but they are worth it. Run your RCA's as far as possible from the power wire (opposite side of the vehicle) this is why. Look into something like aluminum tape. Your way past starting over so try getting aluminum tape and tape the entire length of the rca's this shields them from magnetic or impedence interference. As SQ LSC says those suppressors are useless. They are bandaids. Cheap inductors and capacitors and they dont fix anything. If you have a friend with a sound system run RCAs from his. If the RCA's are not picking up the feedback its is the grounding of the amps and or location, but it sounds like an RCA problem. The headunit is probably picking it up in the first place. If the ABS caused a difference, that panasonic head unit (not offense) in my own experience doesnt exactly cancel out noise. Try that MP3 player trick and see how it goes. And finally you will hear not alternator whine from the subs cause of the low pass filter, but turn it off and see if they whine a bit.

Best of luck, sorry for the long post.

Big Joe

[SQ_LSC]

quote:Originally posted by pepsi2185:
Look into something like aluminum tape. Your way past starting over so try getting aluminum tape and tape the entire length of the rca's this shields them from magnetic or impedence interference.

Sorry I don't agree with this as a cure. Wrapping wires with aluminum foil will generally create a large antennae picking up even more noise.

[pepsi2185]

It doesnt have to be aluminum, its that silver factory shielding material the automakers use to block out interference with their signal leads.

[JoshMcMadMac]

I just ran the MP3 player through it, no squeal. That leaves wiring to the amp, and the head unit. When I get some other wires scrounged up to test the connection at the headunit, I will. SQ, can you run me through whatever tests you think are applicable? I didn't follow some of the ones you have already posted so well. :rolleyes: Whatever you feel is most applicable would be great!

[SQ_LSC]

Sorry, Josh. Sometimes it's hard to explain in text. The first thing I do when troubleshooting whine is check the level of the gains on the amplifier. Many times a whine can be eliminated by just turning those down.

After that, It's time to start breaking the system into sections to track it down. Wheather I'm troubleshooting a 2-piece system or a 10 piece system, I usually start in the middle.

First you'd pull the RCA's from the amp. You'd still have your speakers hooked up to the amp with no input. I usually shunt the inputs on the amp also. This is shorting the inputs together with a jumper wire. Basically plugging in your left channel input to your right channel input. This prevents airborn noise from entering. Then You'd power up the amp. If the whine would be gone, You'd know the problem lies ahead of the amp. If not, the problem is from the amp back. You don't need to use another source for whine testing like your mp3 player. If the amp has a problem, It doesn't matter if your sending music through it or not. It will whine.

You determined the problem is not in the amp so now you have to determine if the rca's are culprit, or the HU. If you ran the MP3 player through the rca's and it was ok, then those are probably ok. There's a ton of things that can be checked here, but you want to do the least painful one's first. Do you have resistor type spark plugs in? If your plugs and wires are not up to par, they can leak alot of interference from the coil. First thing I would do after checking the plugs and wires is pull the HU out of the dash and not disconnect anything. Just turn it back on and check for whine. Sometimes the proximity of the HU to the electronics is a problem. If the whine dissapers, you can probably shield the HU and stick it back in. If it's still there, It's time to check wiring.

Do a visual and make sure you have tight grounds to metal that's not rubber mounted. Do you know what type of RCA's you have? If there shielded one's, Are they grounded at both ends? I've found that the directional cables (the one's with arrows) don't work well in a vehicle. Those cables only have the shield connected to ground at one end. If your cables have a shield, It should be connected at both ends.

Sometimes your HU might not have the RCA's outer ring connected to ground internally and this could cause problems also. I have a 20' piece of crap wire with aligator clips on both ends, I use for grounding purposes. This is where I would brake it out. I connect one end to the battery's negative post and throw it through the window so I have a direct ground to the battery. I'll disconnect the radio's ground and substitute that one. If there's no change, I'll take another short piece of wire and jump from the ground wires to the HU's case. Test it again. If still there, I usually put the main ground back together and use the aligator to grab the rca's and retest. Then I'd grab the rca's in the back with the grounded clip and retest.

All those tests can be done in about 10min. without really having to rip anything apart and grounding is the number one culprit to be testing. Have you tried any of these?

[JoshMcMadMac]

Well, just figured I would let you know that I fixed the problem. I turned down the gain on the 4-channel amp, and with that the squeal toned down a lot. It still did not go away, though. I found a local electronics store (which is not an easy task in this area) and bought a noise eliminator that plugs into one of the the RCA lines. Noise is gone. It cost me $25, which is a lot more than going online, but I figure that supporting a local shop is a good thing. And the nice lady let me go into the parking lot and try it before I bought it! Try even returning something bought online. :rolleyes: So, the problem was interference between the two RCA lines that run the full-range speakers. I figured that out awhile ago though, by swapping the RCA's around between different channels. Problem solved. Thanks again for all our help, guys.

[pepsi2185]

sweet dude, glad to hear it, now go cruise the he%% out it

[RJ Sclafani]

Haha, that is funny how you fixed it. As I was reading the post, I was thinking RCA's, and it turned out to be. I always use Monster Cable. Not sure if it makes a difference, but I've never once had a problem with anything they have ever made.

[Capt. Zilog]

Wait a sec... So one of the RCA's was interfering with the other? Like a pair of RCA wires? That seems wierd. Tell me I'm wrong.

[JoshMcMadMac]

quote:Originally posted by Capt. Zilog:
Wait a sec... So one of the RCA's was interfering with the other? Like a pair of RCA wires? That seems wierd. Tell me I'm wrong.

Best I can figure. I could plug one set in, and then the other set in and remove the first set, and no noise. Noise was only with both RCA's plugged in.

[RJ Sclafani]

Were they two different brands of RCA's?

[JoshMcMadMac]

quote:Originally posted by RJ Sclafani:
Were they two different brands of RCA's?

Nope.

[Capt. Zilog]

So was it two pairs of wiring (like four actual tips) or was it just two wires?

If it was just two wires and not two pairs, then you bought crap wires man. RCA's are supposed to be co-ax, which should negate any interference they produce. Destructive waveforms. Anyhow, it's good that you solved it. smile.gif

[JoshMcMadMac]

It was most definately two pairs of wires, or four tips as you described it. They are not "cheap" but are by no means award winning, noise filtering, 2 gauge, $20 per foot RCA's either.