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Old 26th October 2005, 06:35 AM   #1
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Angry Engine noise (tried almost everything) please help!

Aight yall. Heres my prob. I've got a 91 Silverado and I have BAD engine noise on my subs and my tweeters. I have an Audiobahn A8000T amp hooked up to my subs and an Audiobahn A6004T 4 channel amp on 4 tweeters. I regrounded all my grounds in new places and was SURE to make a solid connection. I also purchased some Rockford Fosgate dual twist signal cables for both amps. I thought for sure this would eliminate the engine noise. But its still there. Before I start the truck up, everything is chrystal clear. When I start the truck the subs rumble really low and the tweeters make a high pich buzz noise. Ive tried messing with all my settings and nothing changes it. Adjusting the level only makes it louder or softer. What can I get to eliminate this engine noise or what can I do? I've got my power wire that runs from my battery, through the firewall, down the passengers side of my truck back to my amps. The wire is 4GA from the battery to a splitter in the truck and then the wires split to two 8GA wires. One of those runs directly to my A6004T amp and the other runs to an Audiobahn capacitor and my A8000T amp. Each ground is in a separate place on the frame of the truck and are 8 GA wires. My signal cables are only 6.6ft and run from my CD player down the middle of the truck to the amps. The CD player is a Pioneer DEH-P9600MP and is only 6 months old. I may also point out that before I had the A6004T amp, I had a Sony 4 channel amp and there was LITTLE engine noise. None on the subs. Now that I put in this new amp, Its gotten way worse. All help is appreciated.


This is what I've done to try and diagnose the problem:
-Unhooked the signal cables from amp (noise stops)
-Unhooked signal cables from headunit (noise stops)
So now I KNOW my signal cables aren't picking up the noise and my amps are fine because the noise stops when no signal cables are connected
-Tried all steps found at http://www.crutchfieldadvisor.com/IS...int=1&page=all
- I have not yet purchased a noise suppressor because I wanted other opinions. Acording to what crutchfield says, I need a noise suppressor to hook up to my power wires of my head unit (power line noise suppressor). Will this help? I've read a few bad things about Pioneer head units having bad engine noise problems (not very happy about that) through the pre amp outputs... If i KNEW the suppressor would help i would buy one because i really like my CD player.

What are your opinions?
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Old 26th October 2005, 09:04 AM   #2
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Many times, when installing a new amp, people allow the RCA shield to come in contact with a live power wire. If this happens, it generally burns a shield ground trace in the head unit. To check for an open shield, set your ohm meter to ohms or diode check, unplug all RCA cables from the head unit and check for continuity from the case of the head unit to the output shield. It should should read ~0 ohms (~0 volts on diode check). If it reads as open, the shield ground is likely burned. A temporary grounding of the shield to the case of the radio can confirm that this is indeed your problem. If the noise goes away with the temporarily grounded shield, the head unit needs to be repaired.
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Old 26th October 2005, 09:31 AM   #3
dhaen is offline dhaen  Europe
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You may have ground loop problems. These can be fixed by fitting audio isolation transformers in the signal leads. Have a look here for more details.
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Old 26th October 2005, 03:52 PM   #4
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you can put a large computer cap right on the alternator positive and ground. this will reduce any noise coming from the charging system. This is probably not the problem, but change your amps. audiobahn invests a large amount of money on the outside of their amps, not on the inside.
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Old 26th October 2005, 06:44 PM   #5
sdoom is offline sdoom  Germany
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Hi


usually noise that changes frequency with engine RPMs is a GND-loop problem, but it it is sometimes generated by input impedance of the amps , that might be the reason why the noise is louder with the audiobahn amp than with the old amp. I would try to get rid of the noise without using the in line transformers, I would use those transformers only if all other possibilites fail.


One thing that really affect GND is your big capacitor. Make sure that the cap is not connected to the carīs chassis . (BTW: the cap is not doing what it is supposed to when connected to the carīs chassis or when the wires running to the cap are longer than 10 inches) . Place the capacitor as near as possible to the amp that drives the woofer and connect the cap-wires directly to the power-terminals of your subwoofer-amp.

As "boxcustom" mentioned audiobahn is not a high-end product. I assume itīs closer to a korean standard amplifier. Those units usually use a very small wire to "shield" or better said ground the amplifier chassis (this wire is inside the amplifier) . Sometimes this causes problems, when the amplifiers are mounted where the amplifier mounting screws are directly touching the carīs chassis. Try to unmount the amplifers and make sure that the ampolifierīs case are completely isolated from the car chassis. If that eliminates the noise you can use a piece of wood , screw down the wood to the car and mount the amp on the wooden surface.


Depending on your amplifiers inside it could also be another problem. Some manufacturers connect the music-signal GND (meaning the RCA-shilding) to chassis GND (e.g. older Philips car amplifiers). If so your car stereo (=head unit) may have really problems and also might already be damaged like "Perry Babin" mentioned.


Also sometimes the noise goes away when a big GND-wire is attached to the amplifierīs housing. You should also consider running complete new power-wires to your car stereo.
Another thing you can try is to use a different GND- point for your amplifiers. You should connect both amplifier GND-wires to one point at your car chassis. Usually good points are the buckle-screws as those usually go into the carīs frame.


As you see, there a lot of things you can test. I would suggest you first try to get the system noise free with only one amplifier installed.



Steph
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Old 26th October 2005, 07:54 PM   #6
TO-3 is offline TO-3  Peru
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Default Re: Engine noise (tried almost everything) please help!

Quote:
Originally posted by wally91chevrole
Aight yall. Heres my prob. I've got a 91 Silverado and I have BAD engine noise on my subs and my tweeters. I have an Audiobahn A8000T amp hooked up to my subs and an Audiobahn A6004T 4 channel amp on 4 tweeters. I regrounded all my grounds in new places and was SURE to make a solid connection. I also purchased some Rockford Fosgate dual twist signal cables for both amps. I thought for sure this would eliminate the engine noise. But its still there. Before I start the truck up, everything is chrystal clear. When I start the truck the subs rumble really low and the tweeters make a high pich buzz noise. Ive tried messing with all my settings and nothing changes it. Adjusting the level only makes it louder or softer. What can I get to eliminate this engine noise or what can I do? I've got my power wire that runs from my battery, through the firewall, down the passengers side of my truck back to my amps. The wire is 4GA from the battery to a splitter in the truck and then the wires split to two 8GA wires. One of those runs directly to my A6004T amp and the other runs to an Audiobahn capacitor and my A8000T amp. Each ground is in a separate place on the frame of the truck and are 8 GA wires. My signal cables are only 6.6ft and run from my CD player down the middle of the truck to the amps. The CD player is a Pioneer DEH-P9600MP and is only 6 months old. I may also point out that before I had the A6004T amp, I had a Sony 4 channel amp and there was LITTLE engine noise. None on the subs. Now that I put in this new amp, Its gotten way worse. All help is appreciated.


This is what I've done to try and diagnose the problem:
-Unhooked the signal cables from amp (noise stops)
-Unhooked signal cables from headunit (noise stops)
So now I KNOW my signal cables aren't picking up the noise and my amps are fine because the noise stops when no signal cables are connected
-Tried all steps found at http://www.crutchfieldadvisor.com/IS...int=1&page=all
- I have not yet purchased a noise suppressor because I wanted other opinions. Acording to what crutchfield says, I need a noise suppressor to hook up to my power wires of my head unit (power line noise suppressor). Will this help? I've read a few bad things about Pioneer head units having bad engine noise problems (not very happy about that) through the pre amp outputs... If i KNEW the suppressor would help i would buy one because i really like my CD player.

What are your opinions?
I had that problem before with my Saturn. I did a lot of different things to get the noise to go away. I found out that the chassis, of my car, was spotwelded which increased the chassis ground to the amplifier systems' ground resistance. I ended up running a ground wire from the battery to the chassis ground point. This made the noise go away.

I am not a big fan of isolation transforms as they mask your underlying problem and add frequency distortion.

Another thing you might try, is increasing the size of the alternator-to-chassis ground. Most OEMs are too small for larger systems.
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Old 27th October 2005, 04:45 AM   #7
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best still.use a big inductor in series with the power line which enter the system.connect one end of inductor to the wire from battery and other end to amp system i/p power lines

i had same prob,ditto same in my car.all silent and great at car engine off but buzz(like small crackers phat phat phat phat sound) came in when engine runnin.

its called engine whine(someone in forum told).i used an inductor from smps of an old pc.also used 100nf caps at points where power just enters the amp system and the noise was all gone.
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Old 27th October 2005, 04:49 AM   #8
TO-3 is offline TO-3  Peru
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Default Re: Re: Engine noise (tried almost everything) please help!

Quote:
Originally posted by TO-3
...
Another thing you might try, is increasing the size of the alternator-to-chassis ground wire. Most OEMs are too small for larger systems.


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Old 27th October 2005, 02:27 PM   #9
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isolate the ground you are using for your amplifier to the main ground by a diode. Anode at your amp's ground.
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Old 28th October 2005, 05:13 AM   #10
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TO-3 is correct. Your amp is actually drawing power from the ground conductor of the RCA's not the power ground wires.
Current flows along the path of least resistance, and steel is an awful conductor compared to copper...even lots of steel. Run 4awg power wires(+ and -) directly to the battery terminals, then
throw all those noisesuppressorwhatchamacallits away.
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