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Help with Car Audio Noise? (ground/noise/wiring questions)

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Expand view Topic review: Help with Car Audio Noise? (ground/noise/wiring questions)

by lotas » Thu Jan 06, 2005 9:13 pm

71buickfreak wrote:yeah, sounds like a bad set of pre out. you can always use a y-adapter or rca-pass-throughs on the amps to combine the outputs and listen as normal.
except i think both might be bad...:-/

now i have to get my alarm - 700$
and a new headunit prolly 300-400$

holy hell....

by 71buickfreak » Thu Jan 06, 2005 6:17 pm

yeah, sounds like a bad set of pre out. you can always use a y-adapter or rca-pass-throughs on the amps to combine the outputs and listen as normal.

by lotas » Thu Jan 06, 2005 5:17 pm

Scarrell wrote:dang you are havin alot crappy luck man :sad:
yeah i know i keep thinking about just selling everything and going back to stock :-/


its a pioneer deh5500...two sets of rca preouts...i had the sub unplugged (cause the subs ground/rcas are very noisy i found out) and the speakers play extremely quietly. in one rca preout they barely even play...then in the other they play so quietly that i have the volume at about 35 for comfortable listening (when normally it would be 18 or so)

i have no idea...maybe the rca preouts are bad now and arent giving any voltage to the amp and thats causing the speakers to not play loud? thats my hypothesis.


EDIT: by the way i just wanted to clear up that its not a setting on the HU thats making them play quietly, not a filter or anything.

by 71buickfreak » Thu Jan 06, 2005 6:56 am

Try swapping the rcas from the subs to the mids and highs amp. you might have fried part of the pre out section. what kind of HU do you have? It is really starting to sound like you have a problematic HU and the HU ground isn't very good. it shouldn't have popped or sparked or done anything, unless the HU ground sucked and it grounded through the RCA's.

by Scarrell » Wed Jan 05, 2005 11:44 pm

dang you are havin alot crappy luck man :sad:

by lotas » Wed Jan 05, 2005 11:20 pm

hey thanks. today i unplugged one of the rcas behind the HU while the whine was going...and it touched metal on the HU body and the speakers made a loud pop and now they arent playing loud...how could that have blown them? and it was the RCAs for the sub amp that i was testing.

by 71buickfreak » Tue Jan 04, 2005 10:18 pm

ok, lets get started. First off, we need to seperate the 2 problems. engine noise is one, static is another. the two will probably end up being seperate problems, but may have the same origin.

First, you need to isolate the offending component(s).
First things to check:
Alt Whine
Are your amps grounded to the same spot? they need to be, that can cause a ground loop, ie alt. whine.

pull the rcas from the amp, individually. is the whine still there? if so, it is not in the signal path and is in the amp, probably bad ground or bad amp component.

Still there?
now reattach the rca's. pull them from the head unit. still there? you either ran across some OE wires, drove a screw through one, or have poopy cables. go buy some good ones.
If its gone, the problem will most likely be in the HU. Does the HU amp send a whine through to a speaker? is it staticy?you may have a bad HU. or it could be a bad HU ground.

More things to check. if you still can't isolate the problem, or if it is in the amp, try grounding a wire to the outside ring of the RCA plug. sometimes this connection breaks and will cause a GL. can happen at the deck or the amp. Not all cases will be solved by this method, but most will.Also, be sure to upgrade your grounds under the hood. I ran a 4ga from the engine block to the frame, the batt to the frame (same loc as the motor ground) and then in the back from the frame to a bolt used to secure the chassis ground for my dist block. so it is basically the best ground possible. if that don't fix it, let me know, we'll have to get out the noise sniffer (yes it's real, basically a tape head and an amplified speaker. pretty cool to use looking for noise. sniff sniff) :s_thumbup

by lotas » Tue Jan 04, 2005 9:40 pm

Mithrandir wrote:no because they arent carrying the signal i believe
er im sorry, what question are you referring to?

by Mithrandir » Tue Jan 04, 2005 9:12 pm

no because they arent carrying the signal i believe

Help with Car Audio Noise? (ground/noise/wiring questions)

by lotas » Tue Jan 04, 2005 9:06 pm

Hey folks, I’ve been putting up with this annoying noise in my car audio system for ages. I’ve almost gotten used to it, but it’s pretty embarrassing whenever someone else is in the car. I get all kinds of questions, and a friend even joked, “Dude, your car is being contacted by aliens!” 😆

So, here’s the deal—I’ve done the basics. Both grounds are on bare metal, sanded down, solid connections, the whole nine yards. I haven’t checked the head unit (HU) ground yet, but that’s next on my list for tomorrow.

A few questions have been bugging me, and if anyone’s got some insight, I’d really appreciate it!

1.) Power and RCA cables—everyone says don’t run them together.
I get it, they can cause noise if they’re too close. But what about running the power wire alongside the speaker wire? Could that be causing engine noise or static, or is that safe?

2.) Grounding the HU yourself—some forums say to ground it directly to the chassis.
But wouldn't that wire end up longer than the usual 36 inches? Is that actually okay? And what gauge wire should I be using, minimum?

3.) Different sources of noise?
Is engine noise vs. static caused by totally separate issues? Like, could a bad ground cause static while a pinched RCA cable causes engine noise? Or could both noises be coming from the same problem?

4.) Crossover placement—I’ve heard people say not to mount them in the doors.
Apparently, it’s similar to running power wires alongside RCA cables, because doors have tons of power wiring (windows, locks, mirrors). Is mounting crossovers in the doors really that big of a risk for interference?

5.) Ground points—sanding isn’t always enough?
Both of my ground points are sanded down well, so could my issue be with the spade terminals? Do I need to sand those too? And what about the bolts I’m using—could they be part of the problem?

6.) Ground resistance—is it worth measuring?
Has anyone here actually measured the resistance of their ground points with a multimeter to make sure they’re close together or under 0.3 ohms? Is that really a thing or just overkill?

Thanks a ton if you made it this far and have any tips to share! This noise is seriously driving me nuts. I don’t know if any of you have had to go without a stereo for too long because of little issues like this, but listening to my phone’s ringtones as my “music” is getting old fast. Here’s hoping I can finally get to the bottom of it! 🍻

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