stereo help!!!!!
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Joined: Feb 2007
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From: Buhl Minnesota
Car Audio Noise Troubleshooting
One of the most frustrating aspects of car audio is noise in the system. Unlike home audio systems, car audio systems have many sources of noise to deal with. Here's a few of the most common noises found in car stereo and how to fix or avoid them.
Alternator Whine
Alternator whine is the granddaddy of car stereo noise. The most common and the most annoying. Alternator whine will be heard as a high pitched whine that will rise and fall with the engine speed. Most of the time this is caused by a poorly chosen ground for a piece of equipment. It is usually cured by grounding the equipment directly to bare metal on the chassis rather than an available factory ground bolt as is often used to save time. You'll also need to make sure your charging system is in top condition and that your connections between the battery and components are secure as well as the integrity of the factory ground strap, an often overlooked component. You might also consider switching your RCA cables to a twisted pair model. Twisted pair cables will usually be less prone to noise than their coaxial counterparts.
Accessory Pop
Accessory pop is associated with one particular electrical event in the vehicle. This can be switching on your turn signal, headlights, brakes, windshield wipers or even the rear window defrost. These high current drawing accessories are causing a voltage spike that is traveling into your car audio equipment with the result being heard as a sharp pop. Adding a small bi-polar capacitor (0.47 uF) between the accessory's power wire and ground will often absorb these surges. You may need to place the capacitor on the load or the power side of the switch (maybe both). See the diagram below to see how this is done. Note that the diagram is slightly different if the accessory has a relay in the circuit.
Accessory Pop Absorption Circuit
Body Rattle
I'm sure everyone has heard a car booming down the street with the body panels shaking and rattling with every bass note. This is an extreme case of body rattle. Less noticeable examples are interior panels that are worn and may slap together when a bump is hit. Door noise is less common and is usually more of a problem on the less expensive cars. Large and luxury cars are usually built with thicker metal and more sound absorption materials and are less prone to body rattle. Body rattle can be solved as easily as tightening the bolts and screws that hold the panels together or may require a full array of noise dampeners.
Noise Dampeners
Noise dampeners can be any material that is used to reduced body panel noise. The thick padding underneath the factory carpeting is a type of noise dampener. Various clays and putties are also used to act as an absorber between two body panels. The most commonly available product in the automotive aftermarket is the viscoelastic sheets and spray on materials. The most well known brand of sheeting material is Dynamat, a product of Dynamic Control. Other well known manufacturers are Stinger (Road Kill), Scosche (Accumat) , Rockford Fosgate (Dead Skin) and B-Quiet which makes a product called Brown Bread. Dynamat has the most extensive product line as this is their specialty. B-Quiet also specializes in sound deadening and though their line is not as varied their prices tend to be less expensive. Sheets tend to work well and are relatively easy to apply. If you have a rattling license plate than adding a layer of sound deadener behind the plate will definitely help. Rattling trunk lids may be caused by a loose trunk latch or a worn weather seal. Have this checked out by a qualified body repair person. Liquid spray on deadeners are popular for the interior door panels but are a little messier to apply. These are best left to the professionals or the adventurous DIYer. Keep in mind that sound deadeners tend to be heavy so if vehicle performance is important to you make sure you keep the weight down by using sound deadeners sparingly or by going with a lighter weight deadener sheet or spray on material.
Application of sound deadening sheets
(Image courtesy of Dynamic Control) Application of sound deadening spray
(Image courtesy of Dynamic Control)
Band Aids
Noise suppressors are not a solution in my opinion. Instead of fixing the cause of the problem a noise suppressor will try to cover it up in a "band aid" approach. This is a poor attempt to fix the problem and doesn't always work. It costs extra money and the noise filter drops the voltage going to the component as well. This is especially important with amplifiers as their power output is usually dependent on the input voltage. Less input voltage, less output power. I feel strongly that a shop owes you a noise free installation without charging you extra for the work. If they can't figure it out then that's their problem. You shouldn't have to pay for their inexperience. Get it in writing that they will give you a noise free guarantee with no extra charges. Have them sign it and you keep the original.
Proper Grounding
Most non-equipment related problems in car audio are the result of poorly chosen ground points. Always check the integrity of every connection including the battery, head unit, amplifiers and signal processors. Any part of the audio system can bring noise into the system. In general your connections need to be secure (grounds should be to the chassis), the charging system should be in top condition and all factory connections (battery posts, ground strap, alternator connections) should be secure. You may need to increase the size of your factory ground if you install a very large stereo system. It should also be noted that the negative battery post is usually a terrible place to ground car audio equipment. All of the ripple (noise) from the alternator and other items in the vehicle travel to this point. If you choose it as a ground point then you are inviting all of these elements into your sound system.
One of the most frustrating aspects of car audio is noise in the system. Unlike home audio systems, car audio systems have many sources of noise to deal with. Here's a few of the most common noises found in car stereo and how to fix or avoid them.
Alternator Whine
Alternator whine is the granddaddy of car stereo noise. The most common and the most annoying. Alternator whine will be heard as a high pitched whine that will rise and fall with the engine speed. Most of the time this is caused by a poorly chosen ground for a piece of equipment. It is usually cured by grounding the equipment directly to bare metal on the chassis rather than an available factory ground bolt as is often used to save time. You'll also need to make sure your charging system is in top condition and that your connections between the battery and components are secure as well as the integrity of the factory ground strap, an often overlooked component. You might also consider switching your RCA cables to a twisted pair model. Twisted pair cables will usually be less prone to noise than their coaxial counterparts.
Accessory Pop
Accessory pop is associated with one particular electrical event in the vehicle. This can be switching on your turn signal, headlights, brakes, windshield wipers or even the rear window defrost. These high current drawing accessories are causing a voltage spike that is traveling into your car audio equipment with the result being heard as a sharp pop. Adding a small bi-polar capacitor (0.47 uF) between the accessory's power wire and ground will often absorb these surges. You may need to place the capacitor on the load or the power side of the switch (maybe both). See the diagram below to see how this is done. Note that the diagram is slightly different if the accessory has a relay in the circuit.
Accessory Pop Absorption Circuit
Body Rattle
I'm sure everyone has heard a car booming down the street with the body panels shaking and rattling with every bass note. This is an extreme case of body rattle. Less noticeable examples are interior panels that are worn and may slap together when a bump is hit. Door noise is less common and is usually more of a problem on the less expensive cars. Large and luxury cars are usually built with thicker metal and more sound absorption materials and are less prone to body rattle. Body rattle can be solved as easily as tightening the bolts and screws that hold the panels together or may require a full array of noise dampeners.
Noise Dampeners
Noise dampeners can be any material that is used to reduced body panel noise. The thick padding underneath the factory carpeting is a type of noise dampener. Various clays and putties are also used to act as an absorber between two body panels. The most commonly available product in the automotive aftermarket is the viscoelastic sheets and spray on materials. The most well known brand of sheeting material is Dynamat, a product of Dynamic Control. Other well known manufacturers are Stinger (Road Kill), Scosche (Accumat) , Rockford Fosgate (Dead Skin) and B-Quiet which makes a product called Brown Bread. Dynamat has the most extensive product line as this is their specialty. B-Quiet also specializes in sound deadening and though their line is not as varied their prices tend to be less expensive. Sheets tend to work well and are relatively easy to apply. If you have a rattling license plate than adding a layer of sound deadener behind the plate will definitely help. Rattling trunk lids may be caused by a loose trunk latch or a worn weather seal. Have this checked out by a qualified body repair person. Liquid spray on deadeners are popular for the interior door panels but are a little messier to apply. These are best left to the professionals or the adventurous DIYer. Keep in mind that sound deadeners tend to be heavy so if vehicle performance is important to you make sure you keep the weight down by using sound deadeners sparingly or by going with a lighter weight deadener sheet or spray on material.
Application of sound deadening sheets
(Image courtesy of Dynamic Control) Application of sound deadening spray
(Image courtesy of Dynamic Control)
Band Aids
Noise suppressors are not a solution in my opinion. Instead of fixing the cause of the problem a noise suppressor will try to cover it up in a "band aid" approach. This is a poor attempt to fix the problem and doesn't always work. It costs extra money and the noise filter drops the voltage going to the component as well. This is especially important with amplifiers as their power output is usually dependent on the input voltage. Less input voltage, less output power. I feel strongly that a shop owes you a noise free installation without charging you extra for the work. If they can't figure it out then that's their problem. You shouldn't have to pay for their inexperience. Get it in writing that they will give you a noise free guarantee with no extra charges. Have them sign it and you keep the original.
Proper Grounding
Most non-equipment related problems in car audio are the result of poorly chosen ground points. Always check the integrity of every connection including the battery, head unit, amplifiers and signal processors. Any part of the audio system can bring noise into the system. In general your connections need to be secure (grounds should be to the chassis), the charging system should be in top condition and all factory connections (battery posts, ground strap, alternator connections) should be secure. You may need to increase the size of your factory ground if you install a very large stereo system. It should also be noted that the negative battery post is usually a terrible place to ground car audio equipment. All of the ripple (noise) from the alternator and other items in the vehicle travel to this point. If you choose it as a ground point then you are inviting all of these elements into your sound system.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Originally Posted by Some
Do this ... .
Originally Posted by Others
Don't do that.
It seems to me the battery is a good place for both power & gnds. esp. in a C3 w/ AMP in center compartment & battery beside it. Both the power & grounds have to get back to the battery.
There is a way to find out. Test results C3. Power directly from battery to both stereo HU & Amp.
Amp gnd. to "waterfall" & stereo HU gnd. to battery. Way too much whine!
Stereo HU gnd. to under console & Amp gnd. to battery. Way too much whine!
Stereo HU gnd. to under console & Amp gnd. to "waterfall". Very good.
Stereo HU gnd. & Amp gnd. to battery. Very good.
So evidently there are at least 2 ways to do it, not including the no. of possible gnd. points nor is it implied the test body gnd. points are best. The frame is normally considered best in that method.
Currently: Power directly from battery to both stereo HU & Amp.
Stereo HU gnd. & Amp gnd. to battery.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Some good info.
Originally Posted by knewblewkorvette
Chances is that it is a grounding problem. One way to troubleshoot this is to unplug the RCAs going to the amp. (always unplug/plug-in) RCAs with the power off to the stereo). Turn the stereo back on, if the noise is gone ,you have a hum coming done the RCAs. I don't think is the case though and you will still have the hum.
If you do still have the hum, relocate the ground AND to run an extra ground to the chassis from the negitive to the car's chassis. The best way to fix the problem is to run the ground of the amp to the negitive of the battery. Be sure and use the same guage wire as you did for the power wire. You will have ZERO noise like I do
If you do still have the hum, relocate the ground AND to run an extra ground to the chassis from the negitive to the car's chassis. The best way to fix the problem is to run the ground of the amp to the negitive of the battery. Be sure and use the same guage wire as you did for the power wire. You will have ZERO noise like I do
Originally Posted by bogus
I run my power down the same side as the battery. You don't want the power crossing the car, because it can pick up noise that way.
Another thing, check the RCAs themselves. If the metal ends are touching, you can pick up a hum.
Finally, check the "gain" setting on the amp. If it's too high, then the amp will pick up and amplify noise.
Another thing, check the RCAs themselves. If the metal ends are touching, you can pick up a hum.
Finally, check the "gain" setting on the amp. If it's too high, then the amp will pick up and amplify noise.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Back up for Al vettfixr (& conveniently Ganey) 
Originally Posted by Calm Screamer2
First, let me qualify myself...sometime we can be misguided on these issues. I'm currently an electrical engineer...I design government receivers/transmitters/antennas. I've installed many car stereos in my younger days (used to work at a high-brow audio outfit in Nashville Tenn (Nicholson's Stereo (sp?)).
Where the noise is coming from is pretty much a who-cares thing. We know where it’s coming from…the engine!
The first and easiest solution that should be attempted is, as stated above, install a three wire “noise suppression” filter in line with the power to the offending unit(s). If you have multiple units such as external amplifiers, equalizers, head unit, etc., then you may have to install a filter on every unit. Note that the head unit will have two power leads (RED and Yellow) both of which may need filtering. Make sure you add the filter between the fuse and audio unit.
If that doesn’t work…The next easiest solution is replacing the low level audio cables that run from the head unit to an external audio unit (if applicable, If not, move to the next step). This is rarely the cause of a noise problems, but it is possible if the ground internal to the cable is broken…and it’s relatively easier to do than the following last-resort procedure as stated below.
If this doesn’t fix the problem, or does not reduce the noise level enough, then you have a lot more work involved. The key to removing “engine noise” is proper wiring, especially, but not limited to the power lines. The power lines are usually the vehicle for transmitting noise to the audio system…as stated above, sometimes it can be a defective low-level audio patch cord (the RCA cables running from the head unit to the amplifier or other accessory unit).
The best way to wire car audio power lines is:
1) Remove all previously installed noise suppressing filters.
2) Install one very large (alt least 10awg) multi-strand ground wire directly from the battery to each audio unit. If you have one amplifier and one head unit, then you need two ground wires, one to each unit. Do not daisy-chain ground wires. Try to route the wires away from other wires. Note that with the way I’m detailing this procedure, experience tells me that wire routing is not the primary cause for engine noise. Sometimes keeping the wires away from others isn’t possible, but we have to make an effort. If at the end of this procedure, you still experience a small amount of engine noise, then properly installed noise-suppressing filters (as described above) will absolutely eliminate the problem.
3) Make every attempt to isolate external amplifiers or other accessory units from any ground connection other than the main ground wire (Don’t mount them directly to the frame).
4) Install one power lead directly from the battery to each audio unit (through fuses of course). Note that external amplifiers require larger wire due to larger current draw…consult the audio unit manual for proper wire size. If you’re not sure…make it big.
5) Did I mention one very large ground wire directly from the battery to each audio unit?
6) Make sure all connections are tight and the battery terminals are clean!
7) If the noise is still present at this point, install a noise filter on the RED power line of the head unit. If everything was done correctly, there should be no noise. If there’s still noise (this is a very rare case) it should be significantly reduced. Finish filtering the rest of the power lines with filters one at a time making sure the ground lead of all the filters is connected only to the main ground lead for the particular audio unit being filtered.
8) Did I mention one very large ground wire directly from the battery to each audio unit?
Where the noise is coming from is pretty much a who-cares thing. We know where it’s coming from…the engine!
The first and easiest solution that should be attempted is, as stated above, install a three wire “noise suppression” filter in line with the power to the offending unit(s). If you have multiple units such as external amplifiers, equalizers, head unit, etc., then you may have to install a filter on every unit. Note that the head unit will have two power leads (RED and Yellow) both of which may need filtering. Make sure you add the filter between the fuse and audio unit.
If that doesn’t work…The next easiest solution is replacing the low level audio cables that run from the head unit to an external audio unit (if applicable, If not, move to the next step). This is rarely the cause of a noise problems, but it is possible if the ground internal to the cable is broken…and it’s relatively easier to do than the following last-resort procedure as stated below.
If this doesn’t fix the problem, or does not reduce the noise level enough, then you have a lot more work involved. The key to removing “engine noise” is proper wiring, especially, but not limited to the power lines. The power lines are usually the vehicle for transmitting noise to the audio system…as stated above, sometimes it can be a defective low-level audio patch cord (the RCA cables running from the head unit to the amplifier or other accessory unit).
The best way to wire car audio power lines is:
1) Remove all previously installed noise suppressing filters.
2) Install one very large (alt least 10awg) multi-strand ground wire directly from the battery to each audio unit. If you have one amplifier and one head unit, then you need two ground wires, one to each unit. Do not daisy-chain ground wires. Try to route the wires away from other wires. Note that with the way I’m detailing this procedure, experience tells me that wire routing is not the primary cause for engine noise. Sometimes keeping the wires away from others isn’t possible, but we have to make an effort. If at the end of this procedure, you still experience a small amount of engine noise, then properly installed noise-suppressing filters (as described above) will absolutely eliminate the problem.
3) Make every attempt to isolate external amplifiers or other accessory units from any ground connection other than the main ground wire (Don’t mount them directly to the frame).
4) Install one power lead directly from the battery to each audio unit (through fuses of course). Note that external amplifiers require larger wire due to larger current draw…consult the audio unit manual for proper wire size. If you’re not sure…make it big.
5) Did I mention one very large ground wire directly from the battery to each audio unit?
6) Make sure all connections are tight and the battery terminals are clean!
7) If the noise is still present at this point, install a noise filter on the RED power line of the head unit. If everything was done correctly, there should be no noise. If there’s still noise (this is a very rare case) it should be significantly reduced. Finish filtering the rest of the power lines with filters one at a time making sure the ground lead of all the filters is connected only to the main ground lead for the particular audio unit being filtered.
8) Did I mention one very large ground wire directly from the battery to each audio unit?
Last edited by Ganey; Apr 23, 2007 at 09:31 AM.
Le Mans Master
Joined: Jul 1999
Posts: 9,206
Likes: 17
From: Sewell NJ
Ganeys always got my back on a good stereo topic. 
First let me say this. I've been installing aftermarket stereos in my cars since the days of Lear Jet eight tracks and reverb units so I've been around the block a few times. I'll also state that the corvette, at least mine, is probably the noisiest car electronically that I've ever gotten gray hairs over. I'm on my third head unit and second set of amplifiers and I've come to a conclusion. The quality of the head unit, and it's noise resistance, has everything to do with how quiet your system is. Why do I say this?
My first aftermarket head unit was a Custom Auto Sound and it was a complete and utter POS. When I first turned it on it sounded like I had tuned in to a siren being broadcoast. Well, I put a bunch of filters on it and lived with it until I could upgrade.
My next unit was a Blaupunkt which I thought was a pretty good step up. It still had alternator whine but not as bad as the previous unit. I ended up putting filters on the alternator and all the power leads that ran to the head unit and dual amplifier and it got pretty quiet. I ran this for quite a while until my most recent upgrade.
My most recent upgrade is an Alpine head unit with a California Profile 4 channel amp. When I installed this set up I pulled out all the wiring for the old system and rewired everything without any of the filters. I turned the unit on expecting to hear the usual alternator whine and assorted ignition pops and was met with total silence. Yep, nothing, zip, nada!!!! I don't know what Alpine does to achieve this but I can tell you it works.
So my recommendations are to make sure when you install the system you have good, correctly sized power leads and grounds for all your components. Once you have that done, and don't be surprised if your system is noisy, put a filter anywhere noise can come from until the system is quiet. You can use the noise filter I posted or you can go on Summit's website and get filters from MSD or other companies. Now, with the advent of computer controlled engines and data aquisition electronics, there are a number of manufacturers making good filters.
PS
I once had a problem with a Toyota I owned that had an intermittent whine that affected my CB radio (no comment please ). It used to drive me crazy because it wouldn't happen all the time. One day I happened to put the key in the ignition and turned it to on without starting the car. In that quiet moment I heard the electric fuel pump pumping up to pressure and then shutting off and heard the whine through the radio at the same time. I realized that every time the pump had to come on to bring the fuel system up to pressure the whine was present. I put a grounding capacitor on the fuel pump and the problem went away.
So when I say put a filter on all your components I mean not only the components in your stereo system but also all those places where a motor can generate noise, and there can be a lot of them. Good luck.
Thanks Ganey.
First let me say this. I've been installing aftermarket stereos in my cars since the days of Lear Jet eight tracks and reverb units so I've been around the block a few times. I'll also state that the corvette, at least mine, is probably the noisiest car electronically that I've ever gotten gray hairs over. I'm on my third head unit and second set of amplifiers and I've come to a conclusion. The quality of the head unit, and it's noise resistance, has everything to do with how quiet your system is. Why do I say this?
My first aftermarket head unit was a Custom Auto Sound and it was a complete and utter POS. When I first turned it on it sounded like I had tuned in to a siren being broadcoast. Well, I put a bunch of filters on it and lived with it until I could upgrade.
My next unit was a Blaupunkt which I thought was a pretty good step up. It still had alternator whine but not as bad as the previous unit. I ended up putting filters on the alternator and all the power leads that ran to the head unit and dual amplifier and it got pretty quiet. I ran this for quite a while until my most recent upgrade.
My most recent upgrade is an Alpine head unit with a California Profile 4 channel amp. When I installed this set up I pulled out all the wiring for the old system and rewired everything without any of the filters. I turned the unit on expecting to hear the usual alternator whine and assorted ignition pops and was met with total silence. Yep, nothing, zip, nada!!!! I don't know what Alpine does to achieve this but I can tell you it works.
So my recommendations are to make sure when you install the system you have good, correctly sized power leads and grounds for all your components. Once you have that done, and don't be surprised if your system is noisy, put a filter anywhere noise can come from until the system is quiet. You can use the noise filter I posted or you can go on Summit's website and get filters from MSD or other companies. Now, with the advent of computer controlled engines and data aquisition electronics, there are a number of manufacturers making good filters.
PS
I once had a problem with a Toyota I owned that had an intermittent whine that affected my CB radio (no comment please
). It used to drive me crazy because it wouldn't happen all the time. One day I happened to put the key in the ignition and turned it to on without starting the car. In that quiet moment I heard the electric fuel pump pumping up to pressure and then shutting off and heard the whine through the radio at the same time. I realized that every time the pump had to come on to bring the fuel system up to pressure the whine was present. I put a grounding capacitor on the fuel pump and the problem went away.So when I say put a filter on all your components I mean not only the components in your stereo system but also all those places where a motor can generate noise, and there can be a lot of them. Good luck.
Thanks Ganey.
Racer
Joined: Jul 2006
Posts: 499
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From: Colebrook Connecticut
Drifting
Joined: Aug 2005
Posts: 1,430
Likes: 8
From: Hamilton NJ
Ground Loop
Lot's of great suggestions here...
I had a whining problem that was not corrected by adding an in-line noise suppressor on the main power line to the head unit. I have not tried adding a filter to the alternator because I was led to believe it also won't work...save your money.
The ground for my KHE-100 head unit (POS aftermarket, direct fit in bezel) is attached to the front of the tunnel, freshly scraped to bare metal. Power is the main red wire from the harness, with an accessory start wire from the HU attached directly to the + terminal on the battery.
Two line outs from the HU feed through twisted pair RCA's to the a 2-channel amp in the rear. The amp is also grounded to a freshly scraped spot on the rear of the tunnel near the waterfall.
Big2Bird mentioned you have a ground loop. In effect, the two grounds, connected to the same tunnel, are interfering. A reasonable band-aid is to install a ground loop isolator between the HU outputs and the amplifier inputs (~$20 at a stereo install shop)... it cured my whining problem, not perfect but tolerable. I still get some noise with the cassette deck, no problem with CD/iPod jack or radio. And it was BAD before this.
For example:
http://www.crutchfield.com/S-NnkNO1A....asp?I=127SNI1
When I upgrade to a better unit in the future I will surely by an Alpine and hopefully have no issues with a clean install.
I had a whining problem that was not corrected by adding an in-line noise suppressor on the main power line to the head unit. I have not tried adding a filter to the alternator because I was led to believe it also won't work...save your money.
The ground for my KHE-100 head unit (POS aftermarket, direct fit in bezel) is attached to the front of the tunnel, freshly scraped to bare metal. Power is the main red wire from the harness, with an accessory start wire from the HU attached directly to the + terminal on the battery.
Two line outs from the HU feed through twisted pair RCA's to the a 2-channel amp in the rear. The amp is also grounded to a freshly scraped spot on the rear of the tunnel near the waterfall.
Big2Bird mentioned you have a ground loop. In effect, the two grounds, connected to the same tunnel, are interfering. A reasonable band-aid is to install a ground loop isolator between the HU outputs and the amplifier inputs (~$20 at a stereo install shop)... it cured my whining problem, not perfect but tolerable. I still get some noise with the cassette deck, no problem with CD/iPod jack or radio. And it was BAD before this.
For example:
http://www.crutchfield.com/S-NnkNO1A....asp?I=127SNI1
When I upgrade to a better unit in the future I will surely by an Alpine and hopefully have no issues with a clean install.
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Thread Starter
Advanced
Joined: Feb 2007
Posts: 62
Likes: 0
From: Buhl Minnesota
Lot's of great suggestions here...
I had a whining problem that was not corrected by adding an in-line noise suppressor on the main power line to the head unit. I have not tried adding a filter to the alternator because I was led to believe it also won't work...save your money.
The ground for my KHE-100 head unit (POS aftermarket, direct fit in bezel) is attached to the front of the tunnel, freshly scraped to bare metal. Power is the main red wire from the harness, with an accessory start wire from the HU attached directly to the + terminal on the battery.
Two line outs from the HU feed through twisted pair RCA's to the a 2-channel amp in the rear. The amp is also grounded to a freshly scraped spot on the rear of the tunnel near the waterfall.
Big2Bird mentioned you have a ground loop. In effect, the two grounds, connected to the same tunnel, are interfering. A reasonable band-aid is to install a ground loop isolator between the HU outputs and the amplifier inputs (~$20 at a stereo install shop)... it cured my whining problem, not perfect but tolerable. I still get some noise with the cassette deck, no problem with CD/iPod jack or radio. And it was BAD before this.
For example:
http://www.crutchfield.com/S-NnkNO1A....asp?I=127SNI1
When I upgrade to a better unit in the future I will surely by an Alpine and hopefully have no issues with a clean install.
I had a whining problem that was not corrected by adding an in-line noise suppressor on the main power line to the head unit. I have not tried adding a filter to the alternator because I was led to believe it also won't work...save your money.
The ground for my KHE-100 head unit (POS aftermarket, direct fit in bezel) is attached to the front of the tunnel, freshly scraped to bare metal. Power is the main red wire from the harness, with an accessory start wire from the HU attached directly to the + terminal on the battery.
Two line outs from the HU feed through twisted pair RCA's to the a 2-channel amp in the rear. The amp is also grounded to a freshly scraped spot on the rear of the tunnel near the waterfall.
Big2Bird mentioned you have a ground loop. In effect, the two grounds, connected to the same tunnel, are interfering. A reasonable band-aid is to install a ground loop isolator between the HU outputs and the amplifier inputs (~$20 at a stereo install shop)... it cured my whining problem, not perfect but tolerable. I still get some noise with the cassette deck, no problem with CD/iPod jack or radio. And it was BAD before this.
For example:
http://www.crutchfield.com/S-NnkNO1A....asp?I=127SNI1
When I upgrade to a better unit in the future I will surely by an Alpine and hopefully have no issues with a clean install.