Ignition noise in stereo

[rgoodrich]

I have an 81 911 SC. I just had a sophisticated stereo/nav/phone system installed, and we can't get rid of the ignition noise. It comes on as soon as the switch is turned on, and worsens with rpm, despite the fact that the sound system is wired directly to the battery. When a battery not connected to the car is used, there is no noise. The stereo guys have tried filters, without success.
Anybody have any ideas or suggestions?

[rusnak]

change your grounds, or isolate the signal cables from the head unit away from the speaker cables. What kind of setup do you have?

[white99c2]

1.Verify that all levels are set properly.

2.With the system turned off, unplug the RCA inputs to the amplifier.

3.Start the vehicle and turn the system on. If the noise is gone go to step 8. If the noise is still present, it is coming from the amp or the speaker wiring. Continue.

4.Turn the system off and disconnect the speaker harness.

5.Start the engine and verify that no noise is present. In a few rare instances, I have actually heard speakers reproduce noise without being connected to an amplifier. This noise was being induced by power cables that were very close to the speaker wire. If you do have this type of noise, reroute the appropriate speaker lead and go to step 3.

6.With the speaker harness still disconnected, check to make sure there are no shorts between the speaker leads and the chassis of the vehicle. A shorted negative speaker lead will create a ground loop by establishing a second audio ground reference point. If you do have a short, trace the wire out and repair it then go to step 3.

7.With the RCA inputs and speaker harness still disconnected from the amplifier, use your VOM to measure from the shield of the RCA jacks on the amp to the chassis of the vehicle. This reading should not be a direct short (100 ohms or more is acceptable.) If this reading does indicate a direct short, you might have a defective amp and should contact the manufacturer for verification. (Note that there are a few "inexpensive" amps or boosters on the market that have their audio ground and electrical ground commoned internally. For units of this type, the information in this article will be of very little value.)

8.If you've made it here, you know that the amplifier and speaker wiring are okay.

9.Connect the accessories in front of the amp (crossovers, equalizers, etc.) one at a time and check for alternator whine. When each device is tested, there should be nothing plugged into the input of that device. In this way, we will work toward the source unit piece by piece. Be sure to turn the system power off before connecting or disconnecting any cables or accessories.

10.Repeat step 9 until all accessories have been tested.

11.If a particular accessory is causing noise, try disconnecting it's power ground wire. Go to step 9.

12.Now it's time to connect the source unit. Do that now and test for noise.

13.If noise is present, try unplugging the antenna. If the noise goes away, you will need to use an antenna isolator. This little gismo opens the shield wire of the coax to eliminate the ground loop caused by the ground at the antenna.

14.If you still have noise, try connecting the source unit's ground wire in another location,. preferably as close to the source unit as possible.

15.Does the noise vary in amplitude when you adjust the volume control? If it does, the problem is probably power line related and not a ground loop. If this is the case, run the source unit's B+ (yellow) wire directly to the positive terminal of the battery. If this doesn't do the trick, you will probably have to use a power line filter on the source unit's B+ (Yel) and Ignition (Red) wires.

and...

1.Make sure you are using resistor type spark plugs and resistor type plug wires.

2.Determine where the noise is coming from. If the noise is a popping sound that occurs 2 or 3 times a second, you probably have a loose or bad plug wire. First, make sure that all plug wires are seated properly. If this doesn't do the trick, you may have a bad plug wire. Usually this occurs due to a pinhole in the insulation of the wire. Whenever the plug wire is energized, an arc jumps through the pinhole to the chassis of the vehicle. Replace with silicone resistor plug wires.

3.If the noise is a buzzing sound, the problem is usually associated with the points, distributor, or coil. Try replacing the condenser on both the coil and points. Make sure all plug wires are seated properly in the distributor cap. Additionally, you might try adding a 2200 uF cap from the positive terminal on the coil to chassis ground.

4.Don't use the fuse block in the vehicle to derive power for the source unit. Run the Constant Hot B+ (memory) wire directly to the battery's positive terminal.

5.If you still have noise, it could be occurring because of induction. Try pulling the source unit out of the dash and check for noise. If the noise is eliminated, try rerouting any wiring harnesses that are close to the deck. If this is not possible, try using self adhesive metal shielding. This might just do the trick.

[nineball]

damn. nice post.

[Johnb911]

Ditttttttoooooooo
I have spent years in custom car audio.
Great trouble shoot.

[kodioneill]

Originally Posted by azrob226

1.Verify that all levels are set properly.

2.With the system turned off, unplug the RCA inputs to the amplifier.

3.Start the vehicle and turn the system on. If the noise is gone go to step 8. If the noise is still present, it is coming from the amp or the speaker wiring. Continue.

4.Turn the system off and disconnect the speaker harness.

5.Start the engine and verify that no noise is present. In a few rare instances, I have actually heard speakers reproduce noise without being connected to an amplifier. This noise was being induced by power cables that were very close to the speaker wire. If you do have this type of noise, reroute the appropriate speaker lead and go to step 3.

6.With the speaker harness still disconnected, check to make sure there are no shorts between the speaker leads and the chassis of the vehicle. A shorted negative speaker lead will create a ground loop by establishing a second audio ground reference point. If you do have a short, trace the wire out and repair it then go to step 3.

7.With the RCA inputs and speaker harness still disconnected from the amplifier, use your VOM to measure from the shield of the RCA jacks on the amp to the chassis of the vehicle. This reading should not be a direct short (100 ohms or more is acceptable.) If this reading does indicate a direct short, you might have a defective amp and should contact the manufacturer for verification. (Note that there are a few "inexpensive" amps or boosters on the market that have their audio ground and electrical ground commoned internally. For units of this type, the information in this article will be of very little value.)

8.If you've made it here, you know that the amplifier and speaker wiring are okay.

9.Connect the accessories in front of the amp (crossovers, equalizers, etc.) one at a time and check for alternator whine. When each device is tested, there should be nothing plugged into the input of that device. In this way, we will work toward the source unit piece by piece. Be sure to turn the system power off before connecting or disconnecting any cables or accessories.

10.Repeat step 9 until all accessories have been tested.

11.If a particular accessory is causing noise, try disconnecting it's power ground wire. Go to step 9.

12.Now it's time to connect the source unit. Do that now and test for noise.

13.If noise is present, try unplugging the antenna. If the noise goes away, you will need to use an antenna isolator. This little gismo opens the shield wire of the coax to eliminate the ground loop caused by the ground at the antenna.

14.If you still have noise, try connecting the source unit's ground wire in another location,. preferably as close to the source unit as possible.

15.Does the noise vary in amplitude when you adjust the volume control? If it does, the problem is probably power line related and not a ground loop. If this is the case, run the source unit's B+ (yellow) wire directly to the positive terminal of the battery. If this doesn't do the trick, you will probably have to use a power line filter on the source unit's B+ (Yel) and Ignition (Red) wires.

and...

1.Make sure you are using resistor type spark plugs and resistor type plug wires.

2.Determine where the noise is coming from. If the noise is a popping sound that occurs 2 or 3 times a second, you probably have a loose or bad plug wire. First, make sure that all plug wires are seated properly. If this doesn't do the trick, you may have a bad plug wire. Usually this occurs due to a pinhole in the insulation of the wire. Whenever the plug wire is energized, an arc jumps through the pinhole to the chassis of the vehicle. Replace with silicone resistor plug wires.

3.If the noise is a buzzing sound, the problem is usually associated with the points, distributor, or coil. Try replacing the condenser on both the coil and points. Make sure all plug wires are seated properly in the distributor cap. Additionally, you might try adding a 2200 uF cap from the positive terminal on the coil to chassis ground.

4.Don't use the fuse block in the vehicle to derive power for the source unit. Run the Constant Hot B+ (memory) wire directly to the battery's positive terminal.

5.If you still have noise, it could be occurring because of induction. Try pulling the source unit out of the dash and check for noise. If the noise is eliminated, try rerouting any wiring harnesses that are close to the deck. If this is not possible, try using self adhesive metal shielding. This might just do the trick.

WOW I want you to install my sound system. Nice post.

[rgoodrich]

Rob,
Thanks for the extensive explanation. I see that you are in Carefree. Do you do car audio professionally?
I live in Lake Havasu, and would gladly make a run over. you can e-mail me at rgoodrich40@msn.com.

[flatsixjunky]

Helo,

Great advice, this one goes to my subscribed folder.

Azrob226 thank you for taking the time to write it.

O-

[white99c2]

Make sure its not caused by some condition in the engine bay - the ignition wires or coil, are the plugs resistor type? Run the car in a dark garage for a minute, do you see anthing sparking near the distributor? My gut tells me it all stems from the way your new system is wired in the cabin. The stereo you removed wasn't whining or having boise issues was it? If not than it can't be the car its got to be the install.

Its easy to fix once you isolate what is wrong, it just takes time and you've got to keep starting the car up to listen to it as you move forward, first the head unit, the power lead - run it from the battery, the speaker leads, the antenna, the amp, the sub amp, than sub speakers.

I'm not an expert but I am the one my friends come for help, I've installed dozens of systems through the years and I've learned by doing. You can fix this in a couple of hours in a warm garage.

[rgoodrich]

Thanks, guys, for all the suggestions. I've ruled out anything with the install, and am starting to work on the engine. I already have new resistor plugs and wires. I have ordered the capacitor, and hope to try it this week. I'll let you know how it works out.
Robert

[nineball]

what exactly do you mean by capacitor? are you talking bout a part for the engine or one for audio purposes? if it is the latter cancel your order now. a capacitor will not help your system, it only adds another component that needs to be charged and will actually tax it harder.

a good read

Why you don't need a capacitor - Realm of Excursion

[rgoodrich]

nineball,
Thank you for the input. I read the article. Mostly over my head, but illuminating.

The capacitor is a 2200 microfardaI ordered 35v and 50v, just in case.for the engine, based on Rob's post above.
If the thing ever comes in (Christmas season and all that) I'll let you all know how it works out.

Robert

[rgoodrich]

No luck with the capacitor.
My mechanic disconnected my CDI box, and the noise that comes on with the key was gone. He thinks a Permatune or an MSD might solve the problem.
Any thoughts?Are we on to something, or are we just breaking the circut/

[juanbenae]

Originally Posted by rgoodrich

I have an 81 911 SC. I just had a sophisticated stereo/nav/phone system installed, and we can't get rid of the ignition noise. It comes on as soon as the switch is turned on, and worsens with rpm, despite the fact that the sound system is wired directly to the battery. When a battery not connected to the car is used, there is no noise. The stereo guys have tried filters, without success.
Anybody have any ideas or suggestions?

the stereo, the fancy nav, and anything else deemed "sophisticated" enough that it may, or might buzz should be turned off until you park. your motor makes good noise, problem solved.

just sayin.

[MrScott]

I used a ground loop isolator like this: PAC SNI-1 RCA Ground Loop Noise Isolator at Crutchfield.com to eliminate noise from an ipod charger/line-out device. Maybe that's what you meant when you said the shop already tried 'filters' ?

Someone with more experience might chime in, I've heard these things reduce dynamic range. I wasn't too concerned with audio quality, just functional sound for long trips.

[rgoodrich]

The problem with the noise is that it combines with driving slow, something I always try to avoid. The engine and the Fabspeed system do a great job of masking the irritating buzz with a pleasurable one! Unfortunately, I still get caught in traffic sometimes (boo). I have been referred to a high end shop in Sacramento that does a lot of 911 installs. Hopefully we can come up with an answer. I'll let you know how it goes.

81 911 SC
Robert

[dshepp806]

As Rusnak pointed out in post 2, these primary culprits for what you describe,..however that CDI box may be spraying stuff,..check any related grounding there, as well..

Some had asked if the removed equipment worked OK,..(before removal)....yes? Was the same ground points used for the installed gear (all having the same ground point, that is)

Best,
?

[dshepp806]

The filters can be of MANY varieties...some being simple circuits that would"round off" the sprectrum (addressing high frequency interference)....

However, a ground loop isolator works slightly differently......and isn't necc'l bandwidth limiting.

A buzz is not a whine ,..neither of these are "hums"...but can be in a car.

As MrScott suggested, this device may be the ticket.......what, exactly, did the previous shop use (these "filters)? Possibly it wasn't a ground loop eliminator style?

[dshepp806]

I would have to assume that many CDI guys have fully functional stereos with no artifact....or is it a inherent?

Just wondering....

[JFairman]

I have an old Mallory "super CD" for points ignition I bought in the mid seventies. Still works too.. I never installed it in a Porsche but used it in several BMW's and an old Ford.

It made the high pitched CD thyristor whine like the bosch CDI or an on camera flash unit and the annoying whine would come through when using the casette deck but not the radio. Instead the radio got the buzzing noise from the spark plugs or cap and wires.

Tried alot of things and could never get rid of the CDI whine that came through the speakers.
I finally got an MSD 6 ignition and they don't whine. Neither does the permatune for that matter... anyway the never ending old school Mallory CD whine went away with the non whining MSD 6.