noise in sound system
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=100912
Printed Date: April 28, 2024 at 2:09 AM
Topic: noise in sound system
Posted By: ice32
Subject: noise in sound system
Date Posted: January 08, 2008 at 1:22 AM
Hey all,
Lets start by letting you know what system I've got:
Pioneer DEH-P7950UB (headunit)
200w Fusion splits in the front
200w Fusion 3-way speakers in the back
1000w ebay amp (khormoah) or something of the sort,(powering the speakers) (2x 30amp fuses)
1200w max boss sub
300w max boss audio amp (powering sub) (2x 15amp fuses)
8ga to a disto block then both 8ga to each amp
8ga ground cable
Stock speaker wiring
90amp alternator
all installed in a Mitsubishi lancer ce
Atm when i turn my ignition on and listen to music, its fine no excess noise, once i start my car theres a faint whine(i guess you could call it)which is in tune with the engine's rpm, e.g when you rev up it gets louder.
It has gotten a bit worse since i replaced my 220w pioneer 3-way front speakers with the splits. I've tried earthing the RCA leads due to the pioneer HU problem, that just made the noise worse, I've unplugged the HU all together so its just amp and speakers and the whine is still there with just those 2.
my alternator has three suppressors on it, and that hasnt reduced it any, the only other things i can think of are a ground loop, alternator isn't big enough or the flee market amp is on its way out.
I plan to upgrade the big 3 in a month or so when money prohibits to see if that might fix the problem.
I've put up with this noise for a few months now doing small things now and then to try and eliminate it, but I've had little to no success
So does anyone out there have a possible suggestion as to what could be causing this noise?
any help would be great, thanks
Regards Chris
P.S please let me no if you need any more info to help.
Replies:
Posted By: ice32
Date Posted: January 09, 2008 at 5:34 AM
bump, anyone able to help?
Posted By: i am an idiot
Date Posted: January 09, 2008 at 6:20 AM
Have you tried turning the gains down on the amps?
Posted By: ice32
Date Posted: January 09, 2008 at 7:23 AM
nope, I'll try that tomorrow, thx for the suggestion
Posted By: greenbroncoguy
Date Posted: January 09, 2008 at 8:55 AM
Maybe try measuring the retun resistance of the grounds for the amps - anything < 1ohm will be ok. Anything more and you could have problems. Sounds like ground troubles to me...
Posted By: advanced_audio
Date Posted: January 09, 2008 at 9:25 AM
Agreed being all swap meet brands there probably is a bad ground in there somewhere and your picking it up in your amplifiers because there cheap and have poor filtering. Not trying to diss on your setup or anything because everyone starts some where just throwing out suggestion on what i have seen that could possibly cause this noise but surely do what green said and measure the resistance. There's a thread on how to do it.
Posted By: advanced_audio
Date Posted: January 09, 2008 at 9:28 PM
Does the whine change with the rpms of the engine at all?
Posted By: ice32
Date Posted: January 09, 2008 at 9:39 PM
yeh, it does, its really noticeable just before gear changes (guessing coz thats at the highest rpm)
Posted By: tedmond
Date Posted: January 09, 2008 at 9:56 PM
try this. every pioneer deck i had alwasy gave me this issue. The rca connections, make sure the outer part is not exposes as it picks up noise. My friend has the same issue and what he did was ground the outer spart of the RCA right to ground by a wire, solder and a bold. No problem after he did that.
Posted By: ice32
Date Posted: January 10, 2008 at 12:18 AM
turning the gains down got rid of it, but i might make sure the rca leads aren't exposed either, thanks
Posted By: greenbroncoguy
Date Posted: January 10, 2008 at 9:31 AM
ice32] wrote:
urning the gains down got rid of it, but i might make sure the rca leads aren't exposed either, thanks
Turning your gains down to get rid of system noise is a bandaid in this case - you have a ground problem that neds to be fixed. If it were me I would set my gains to match the input signal/desired listening volume, then try and diagnose the ground problem.
Posted By: i am an idiot
Date Posted: January 10, 2008 at 8:28 PM
And all this time I have been using the gain control to get rid of noise. Silly me.
Posted By: greenbroncoguy
Date Posted: January 10, 2008 at 9:44 PM
i am an idiot wrote:
And all this time I have been using the gain control to get rid of noise. Silly me.
Why would you mis-adjust your system to get rid of alternator whine that can be fixed correctly? If oyu had something like a hiss problem from a processor or line driver, then maybe playing with the gains would be a viable option, but if you have system induced noise from an installation issue, then IMHO fix the issue and set your gians where they are supposed to be...
Posted By: ice32
Date Posted: January 11, 2008 at 3:34 PM
greenbroncoguy wrote:
ice32] wrote:
urning the gains down got rid of it, but i might make sure the rca leads aren't exposed either, thanks
Turning your gains down to get rid of system noise is a bandaid in this case - you have a ground problem that neds to be fixed.
If it were me I would set my gains to match the input signal/desired listening volume, then try and diagnose the ground problem.
ok, so you've steped up and told me that i have a problem that needs to be fixed. well yeh thats why im asking for "help" to solve that problem, not for people to say yeh you have a problem, so your help would be appreciated.
I tested my ground resistances on both amps and the HU, all measured 0.07.
Anywhere else i should look for a bad ground?
Posted By: greenbroncoguy
Date Posted: January 11, 2008 at 4:15 PM
^^^ I wasn't trying to be rude, I just gave my opinion on the other method that was given. I didn't see in any of your responses where you said you had the equipment grounded - are all the amps grounded in the same spot? I realize they probably aren't grounded where the H/U is, but I usually try to ground all my equipment in the same place in the trunk to avoid ground loops...
Posted By: ice32
Date Posted: January 12, 2008 at 5:12 AM
speaker amp is grounded under the passenger seat bolt to the chassis, sub amp is grounded in the "trunk" as you Americans call it, more commonly known as the "boot" here in aussie.
Posted By: greenbroncoguy
Date Posted: January 12, 2008 at 8:34 AM
ice32] wrote:
peaker amp is grounded under the passenger seat bolt to the chassis, sub amp is grounded in the "trunk" as you Americans call it, more commonly known as the "boot" here in aussie.
Yeah - seatbelt bolt is usually NOT considered a proper ground for anything; especially audio equipment. They usually only have a nut on the bottom that is welded to the chassis with a spot weld - two if you're lucky. I would suggest finding another grounding point for that amp inside the cabin to begin with.
Posted By: tedmond
Date Posted: January 12, 2008 at 11:11 AM
find a spot clear of gas lines or electrical, take some 150 gritt sand paper or a dremel, clean the area about 1.5 inches then use a self tapping screw and a star washer. now you have a very good ground. testing with a DMM to see resistance less than 1 is best.
Posted By: ice32
Date Posted: January 12, 2008 at 8:59 PM
well its more to the point grounded where the bolt hole goes down, i filed back the paint about a cm each side of the hole put a ring terminal on the end of the ground lead put a washer over the ring terminal and just use the bolt to pull it down tight.
i also found out its grounded through the amp legs as well where i mounted it to the car with self tappers
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