In my car I have an Alpine 9813 head unit playing 2 MB Quartz 6x9s, 2 MB Quartz 6.5" components , and a JL 12w6 through 2 Audiofonics amps. I did the install myself and it played perfectly until the last few months it developed this buzzing sound in the speakers. The buzz doesnt go up or down with the volume but it is only present when the car is running and does change pitch/volume with different electrical loads on my battery(i.e. loudest when the alternator kicks on and changes when i turn on my lights, changes with my turn signal flashing, etc...). I tried pulling various rca's from my amps to see if it is coming from a single input and it seems to be equally coming from each one. The car is a 63 chevy nova with a small block equipped qith computer fuel injection and an MSD ignition box. The battery is mounted in the trunk so the power cable is only 2-3 feet from battery to amps. The battery cable runs to the starter under the car and the rca's are run under my door sill plate(but on the same side as the battery cable). WHERE IS THAT DAMN BUZZ COMING FROM? Any help would be awesome.
Replies (8)
uochronos on 02/25/2004 02:28:50
well first rcas being close to battery well pic up sounds. i would think this is most likely suspect since its only present when car is on i personaly cant think of anything else because its got to be picking up alternator sounds since its only when the vehicle is on. someone else might have another idea but from my knowledge this seems like the most logical cause
swez on 02/25/2004 02:35:55
Nice ride bud... I remeber those mucles cars of the 60's!
Try redoing the whole audio grounding chain... HU & amps. These need to be bare metal body pan or similar.
Also, what are the gain settings on your noisy amp? That HU may be a 2 or 4 volt RCA output level. Your amp gains should match HU output or noise can enter the system.
Finally, have you added any new electrical devices since the install of your audio gear? If yes, what and where?
Swez
rspt on 02/25/2004 03:20:48
I put in ths MSD ignition and computerized fuel injection in since the audio. The msd is under the hood and the computer is mounted under the dash above the glove box(about 10-12 inches from the HU). Oh yeah, i also changed my alternator to a fancy chrome one. I have my old one that i have been planning on putting back in to see what happens. One other thing ... does anyone happen to know how to measure the output of an alternator(in AMPS) with a quality automotive digital multimeter. I know it works, i just want to know the rating cause it is too weak.
swez on 02/25/2004 03:37:34
Any good autoparts store can run a power check on your ALT & BAT output and general health. Most will do it for free in the parking lot or garage. Should only take a few minutes to tell you output. The output is lowest at idle and will climb steadily above 1500 RPM.
If you have a good multimeter with high current probe, this needs to be connected in series between ALT & BAT pos feed lines. Some of the newer meters have inductive field loops and you can measure current output w/o removing the ALT/BAT feed line.
Did this noise start after any new devices were added? If yes, need to figure out which item may be causing this noise. Some RF noise is always possible with High Performance ignition or FI systems. You may need to do a process of elimination diagnostics here to find out what device is causing your noise problems and then RF filter that device.
Swez
rspt on 02/25/2004 03:45:09
Thanks for the quick replies SWEZ. The weird thing is thatit is slowyl but persistantly getting worse and worse. I am thinking it could be the alternator. The ignition is a long ways from the stereo and if the key is on the computer is on even if the engine isnt running. In this condition the stereo sounds fine. I also need to redo my grounds as well. I have also been suffering from a minor"Pop" when i turn on the radio each time and it has been getting worse as well.
swez on 02/25/2004 04:10:57
Start with the easy stuff... reground the system. These older cars used to use a common ground speaker return system Only 1 wire from radio to speaker and ground was to body. I assume you rewired for a 2 speaker wire (isolated ground) system.
That ALT may be going south on you as well. There are diode packs in the casing. Some HO units pull the rectifier bridge out and mount them outside the case for better cooling and higher heat capacity. These models can cause noise too, but noise will show up when installed... not later.
The fact you haved little or no noise when engine is off, leads me to suspect grounding or that ALT. If you are handy, can rebuild that chrome ALT yourself. Brushes, clean the stator/communtator, new diode bridge and even a new voltage regulator if needed. The parts are cheap and easy to get at most good auto parts stores. Is this a high output ALT? (120A. or higher?)
If you do elect to rebuild it, just make sure you "clock" everything as is now. ID marks on the casing will give you that reference point for a good reinstall.
Swez
rspt on 02/25/2004 04:20:52
I did a basic rebuild on this alternator last summer. i do wonder about the condition of the case cause i know how some of the cheeper chrome parts are built .... cheesey. This isnt a very high output model but i definately need one to handle the electronics i have on this sweet ol' b****h. Were yousaying that the higher output types will definately/probably/or might cause some speaker noise?
swez on 02/25/2004 04:53:20
Not specifically... Quality HO ALTs are Primo in performance, power and price. Stinger and Ohio Generator come to mind as possible choices. All depends on how much current your amps and other gear draw.
Assuming you have a small block 350 cid Chevy engine here? You may be able to find a 140A. GM ALT at most good autoparts stores for under $200.00. A different pully may be needed and maybe some modified mounting hardware too. The newer GM ALTs use a 5 or 6 groove serpintine pully stock. If you have the older style single pully and V-belt off the crank pully, a different pully shieve is needed.
The Stinger and OG models produce >200A., but they are very pricey! They are high quality, built to your specs... but $350 - 500 beans.
May not need that much power though, depending on your amplifier power draw and add ons.
Hey, it's almost 5:00 AM here and I am lights out after this post. Catch you in the mid AM.
Swez out
Replies (8)
uochronos on 02/25/2004 02:28:50
well first rcas being close to battery well pic up sounds. i would think this is most likely suspect since its only present when car is on i personaly cant think of anything else because its got to be picking up alternator sounds since its only when the vehicle is on. someone else might have another idea but from my knowledge this seems like the most logical cause
swez on 02/25/2004 02:35:55
Nice ride bud... I remeber those mucles cars of the 60's!
Try redoing the whole audio grounding chain... HU & amps. These need to be bare metal body pan or similar.
Also, what are the gain settings on your noisy amp? That HU may be a 2 or 4 volt RCA output level. Your amp gains should match HU output or noise can enter the system.
Finally, have you added any new electrical devices since the install of your audio gear? If yes, what and where?
Swez
rspt on 02/25/2004 03:20:48
I put in ths MSD ignition and computerized fuel injection in since the audio. The msd is under the hood and the computer is mounted under the dash above the glove box(about 10-12 inches from the HU). Oh yeah, i also changed my alternator to a fancy chrome one. I have my old one that i have been planning on putting back in to see what happens. One other thing ... does anyone happen to know how to measure the output of an alternator(in AMPS) with a quality automotive digital multimeter. I know it works, i just want to know the rating cause it is too weak.
swez on 02/25/2004 03:37:34
Any good autoparts store can run a power check on your ALT & BAT output and general health. Most will do it for free in the parking lot or garage. Should only take a few minutes to tell you output. The output is lowest at idle and will climb steadily above 1500 RPM.
If you have a good multimeter with high current probe, this needs to be connected in series between ALT & BAT pos feed lines. Some of the newer meters have inductive field loops and you can measure current output w/o removing the ALT/BAT feed line.
Did this noise start after any new devices were added? If yes, need to figure out which item may be causing this noise. Some RF noise is always possible with High Performance ignition or FI systems. You may need to do a process of elimination diagnostics here to find out what device is causing your noise problems and then RF filter that device.
Swez
rspt on 02/25/2004 03:45:09
Thanks for the quick replies SWEZ. The weird thing is thatit is slowyl but persistantly getting worse and worse. I am thinking it could be the alternator. The ignition is a long ways from the stereo and if the key is on the computer is on even if the engine isnt running. In this condition the stereo sounds fine. I also need to redo my grounds as well. I have also been suffering from a minor"Pop" when i turn on the radio each time and it has been getting worse as well.
swez on 02/25/2004 04:10:57
Start with the easy stuff... reground the system. These older cars used to use a common ground speaker return system Only 1 wire from radio to speaker and ground was to body. I assume you rewired for a 2 speaker wire (isolated ground) system.
That ALT may be going south on you as well. There are diode packs in the casing. Some HO units pull the rectifier bridge out and mount them outside the case for better cooling and higher heat capacity. These models can cause noise too, but noise will show up when installed... not later.
The fact you haved little or no noise when engine is off, leads me to suspect grounding or that ALT. If you are handy, can rebuild that chrome ALT yourself. Brushes, clean the stator/communtator, new diode bridge and even a new voltage regulator if needed. The parts are cheap and easy to get at most good auto parts stores. Is this a high output ALT? (120A. or higher?)
If you do elect to rebuild it, just make sure you "clock" everything as is now. ID marks on the casing will give you that reference point for a good reinstall.
Swez
rspt on 02/25/2004 04:20:52
I did a basic rebuild on this alternator last summer. i do wonder about the condition of the case cause i know how some of the cheeper chrome parts are built .... cheesey. This isnt a very high output model but i definately need one to handle the electronics i have on this sweet ol' b****h. Were yousaying that the higher output types will definately/probably/or might cause some speaker noise?
swez on 02/25/2004 04:53:20
Not specifically... Quality HO ALTs are Primo in performance, power and price. Stinger and Ohio Generator come to mind as possible choices. All depends on how much current your amps and other gear draw.
Assuming you have a small block 350 cid Chevy engine here? You may be able to find a 140A. GM ALT at most good autoparts stores for under $200.00. A different pully may be needed and maybe some modified mounting hardware too. The newer GM ALTs use a 5 or 6 groove serpintine pully stock. If you have the older style single pully and V-belt off the crank pully, a different pully shieve is needed.
The Stinger and OG models produce >200A., but they are very pricey! They are high quality, built to your specs... but $350 - 500 beans.
May not need that much power though, depending on your amplifier power draw and add ons.
Hey, it's almost 5:00 AM here and I am lights out after this post. Catch you in the mid AM.
Swez out
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