Hi,
I'm pretty new when it comes to car audio installs, but I was just wondering if anyone could help me...
I've just rewired and and updated my car audio wiring, used better quality cable/proper guage wire/changed some of the wire runs to try and get rid of the small amount of alternator whine I was having. It seems to have worked as the speakers sound fine, but instead I'm left with a strange noise which sounds like an electrical hum of a household AC adapter, coming from under the back seat where my power and earth distribution boxes are. The funny thing is that it is still there when the two amps and HU are switched off, and it isn't coming through the speakers.
Could anyone help please? Thanks!
Gav
Replies (11)
swez on 08/4/2005 09:33:07
1. Try re-grounding the amp block to a bare metal preped surface
2. Also, make sure the HU ground is also grounded to floor pan or firewall. Also a bare metal connection
3. Check the amp gain settings... if too sensitive, (below 2 volts) this will amplify music and noise too
4. Power & ground cables are well separated fro RCA audio lines as run through the vehicle. (0.5 meters or more apart)
Good luck and welcome to CK!
Swez
supagav on 08/4/2005 17:59:13
Thanks for the reply, any help is much appreciated!
I've already tried the ground connections, as I sanded a small area down before i secured the connection to the distribution box, but I'll give the others a try and see how I get on. Just a few quick questions...
1. I'm currently using the factory fitted HU wiring loom that came with the car, where do I connect the ground lead?
2. What is the firewall?
3. How do I check if the amp settings are below 2 volts?
Sorry if these are a bit basic, and thanks again!
Gav
swez on 08/4/2005 18:52:49
Good, at least the amps are grounded well.
1a. Factory wiring loom often has a ground that is daisy chained to other dash componets too. (lamps, gages ect.) Best not to use that one as it has too many loads on it already. Best to go right to the floor pan.
2a. Fire wall is a metal partitian between engine compartment and passenger compartment. Protects passengers from engine fires and crash damage. If you have a rear mounted engine vehicle, the fire wall is located at the back of the passenger compartment, opposing the engine compartment.
3a. Most (all) amps have a gain sensitivity adjustments. They control how much voltage will be allowed into the amp from HU RCA's. Usually, the sensitivity range is between 0.5 to 4.0 volts. Midpoint on the adjustment is ~2 volts. If we set sensitivity too low, (below 1 volt) we amplify music signals along with any engine noise that may be riding on the power lines or RCA's.
Note: If we set the gain sensitivity too low (say... 1.0 volts) the amp will deliver full rated power at 1.0 volts. If HU is putting out 2 volts (typical) or more, the amp will attempt to take the higher voltage and multiply it to its limits. This causes the amp to clip signals, (high distortion values) which are very hard on speakers.
See DIY sections for additional Info:
http://www.clubknowledge.com/Car_Audio_FAQ/?t20
http://www.clubknowledge.com/Car_Audio_FAQ/?t3
Hope that helps,
Swez
supagav on 08/5/2005 01:16:59
Thanks very much, I'll let you know how i get on!
Gav
ttocs on 08/5/2005 09:51:37
wait, your getting noise from under the back seat, by the distrobution blocks? Where is the equipment in relation?
swez on 08/5/2005 10:51:06
Do any amps have fans in them? If yes, pull them out and have a close look when they are in operation. Also note if amp lights are on, even when system seems to be shut off.
Something is strange here. It may not be related to audio system if the humming/buzzing is there with amps off. Could be a relay, fuel pump or some car component causing this as well.
Hint: When tracking down spurious noises, use a 6-8mm dia hose (~1 meter long) line as a noise probe. Insert one end of the tube into ear, other end as a probe for noise. Basically, a poor mans' stethoscope idea here. That can help isolate the source of this noise, then deal with it as needed.
Keep us posted OK?
Swez
PS Thanks ttocs, I overlooked part of his presenting issues and you caught it. Good catch Mang!
Swez
supagav on 08/5/2005 11:00:43
The amps are in the trunk, and the distribution boxes are under the back seat, about a 1/2 a metre in front. I was getting some alternator whine, but after I upgraded the wiring and re-positioned the RCA cable runs it has seemed to have pretty much gone (touch wood!) The noise now sounds more like an power adaptor buzz, its not very loud, but comes on with the engine. The strange thing is it is still there even when the HU and amps are off and unplugged, even when the RCA leads are unplugged as well...
I'm going to try and re-ground the HU to the floor pan, so fingers crossed, but any ideas are much appreciated!
Thanks,
Gav
supagav on 08/5/2005 20:43:49
Thats great guys thanks, will try that! I think your right though, it probably isn't the audio gear. The amps don't have fans and all the lights are off when the system is off. (you can tell because they've both got a lighted viewing window on the top of each unit). I made a long drive today across the UK and the system was sounding great, much better now I've popped in a new set of component speakers, so I think it could be the car.
I'll investigate further and let you know, though the noise is quite faint and may disappear when I put all the interior trim and seats back in the car.
Take care,
Gav
ttocs on 08/6/2005 09:28:30
your gas tank is normaly located under the seat, the fuel pump is normally located in the tank. You might be hearing that....... I can hear mine when I first turn on the key, but not after.......
supagav on 08/6/2005 17:38:23
Yeah it could be that, I think I was just getting so frustrated with trying to rid the car of alt whine that I began hearing noises all over the place! Gav
swez on 08/6/2005 18:13:51
The quieter your ride becomes, (noise dampening) the more oddball noises will begin to surface from other parts of the car. It's like washing the car, only to note the windshield is dirty, the seats needs cleaning and the interior needs a good scrub too. Never ends huh?
Cheers,
Swez
I'm pretty new when it comes to car audio installs, but I was just wondering if anyone could help me...
I've just rewired and and updated my car audio wiring, used better quality cable/proper guage wire/changed some of the wire runs to try and get rid of the small amount of alternator whine I was having. It seems to have worked as the speakers sound fine, but instead I'm left with a strange noise which sounds like an electrical hum of a household AC adapter, coming from under the back seat where my power and earth distribution boxes are. The funny thing is that it is still there when the two amps and HU are switched off, and it isn't coming through the speakers.
Could anyone help please? Thanks!
Gav
Replies (11)
swez on 08/4/2005 09:33:07
1. Try re-grounding the amp block to a bare metal preped surface
2. Also, make sure the HU ground is also grounded to floor pan or firewall. Also a bare metal connection
3. Check the amp gain settings... if too sensitive, (below 2 volts) this will amplify music and noise too
4. Power & ground cables are well separated fro RCA audio lines as run through the vehicle. (0.5 meters or more apart)
Good luck and welcome to CK!
Swez
supagav on 08/4/2005 17:59:13
Thanks for the reply, any help is much appreciated!
I've already tried the ground connections, as I sanded a small area down before i secured the connection to the distribution box, but I'll give the others a try and see how I get on. Just a few quick questions...
1. I'm currently using the factory fitted HU wiring loom that came with the car, where do I connect the ground lead?
2. What is the firewall?
3. How do I check if the amp settings are below 2 volts?
Sorry if these are a bit basic, and thanks again!
Gav
swez on 08/4/2005 18:52:49
Good, at least the amps are grounded well.
1a. Factory wiring loom often has a ground that is daisy chained to other dash componets too. (lamps, gages ect.) Best not to use that one as it has too many loads on it already. Best to go right to the floor pan.
2a. Fire wall is a metal partitian between engine compartment and passenger compartment. Protects passengers from engine fires and crash damage. If you have a rear mounted engine vehicle, the fire wall is located at the back of the passenger compartment, opposing the engine compartment.
3a. Most (all) amps have a gain sensitivity adjustments. They control how much voltage will be allowed into the amp from HU RCA's. Usually, the sensitivity range is between 0.5 to 4.0 volts. Midpoint on the adjustment is ~2 volts. If we set sensitivity too low, (below 1 volt) we amplify music signals along with any engine noise that may be riding on the power lines or RCA's.
Note: If we set the gain sensitivity too low (say... 1.0 volts) the amp will deliver full rated power at 1.0 volts. If HU is putting out 2 volts (typical) or more, the amp will attempt to take the higher voltage and multiply it to its limits. This causes the amp to clip signals, (high distortion values) which are very hard on speakers.
See DIY sections for additional Info:
http://www.clubknowledge.com/Car_Audio_FAQ/?t20
http://www.clubknowledge.com/Car_Audio_FAQ/?t3
Hope that helps,
Swez
supagav on 08/5/2005 01:16:59
Thanks very much, I'll let you know how i get on!
Gav
ttocs on 08/5/2005 09:51:37
wait, your getting noise from under the back seat, by the distrobution blocks? Where is the equipment in relation?
swez on 08/5/2005 10:51:06
Do any amps have fans in them? If yes, pull them out and have a close look when they are in operation. Also note if amp lights are on, even when system seems to be shut off.
Something is strange here. It may not be related to audio system if the humming/buzzing is there with amps off. Could be a relay, fuel pump or some car component causing this as well.
Hint: When tracking down spurious noises, use a 6-8mm dia hose (~1 meter long) line as a noise probe. Insert one end of the tube into ear, other end as a probe for noise. Basically, a poor mans' stethoscope idea here. That can help isolate the source of this noise, then deal with it as needed.
Keep us posted OK?
Swez
PS Thanks ttocs, I overlooked part of his presenting issues and you caught it. Good catch Mang!
Swez
supagav on 08/5/2005 11:00:43
The amps are in the trunk, and the distribution boxes are under the back seat, about a 1/2 a metre in front. I was getting some alternator whine, but after I upgraded the wiring and re-positioned the RCA cable runs it has seemed to have pretty much gone (touch wood!) The noise now sounds more like an power adaptor buzz, its not very loud, but comes on with the engine. The strange thing is it is still there even when the HU and amps are off and unplugged, even when the RCA leads are unplugged as well...
I'm going to try and re-ground the HU to the floor pan, so fingers crossed, but any ideas are much appreciated!
Thanks,
Gav
supagav on 08/5/2005 20:43:49
Thats great guys thanks, will try that! I think your right though, it probably isn't the audio gear. The amps don't have fans and all the lights are off when the system is off. (you can tell because they've both got a lighted viewing window on the top of each unit). I made a long drive today across the UK and the system was sounding great, much better now I've popped in a new set of component speakers, so I think it could be the car.
I'll investigate further and let you know, though the noise is quite faint and may disappear when I put all the interior trim and seats back in the car.
Take care,
Gav
ttocs on 08/6/2005 09:28:30
your gas tank is normaly located under the seat, the fuel pump is normally located in the tank. You might be hearing that....... I can hear mine when I first turn on the key, but not after.......
supagav on 08/6/2005 17:38:23
Yeah it could be that, I think I was just getting so frustrated with trying to rid the car of alt whine that I began hearing noises all over the place! Gav
swez on 08/6/2005 18:13:51
The quieter your ride becomes, (noise dampening) the more oddball noises will begin to surface from other parts of the car. It's like washing the car, only to note the windshield is dirty, the seats needs cleaning and the interior needs a good scrub too. Never ends huh?
Cheers,
Swez
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