I have just recently installed my amp to my 6X9's and I hear an audiable humming, I grounded the amp to the chassis, but in a previous forum it says ground the rca cable to the amp? if that is so how do I do that?
Replies (8)
swez on 05/22/2006 22:14:39
The humming is usually a poor ground connection at HU, amp or both. We need a bare metal ground for both HU and amp grounds.
The 2nd common cause of noise, is setting the gain on amp too high. This amplifies audio and noise.
The last one is a bad RCA cable or loose amp jacks (grounds) in the PB board. If either is present, hum is often the result.
QUOTE: "but in a previous forum it says ground the rca cable to the amp? If that is so, how do I do that? "
I have no idea what that means.
In one sense, the RCA cable(s) have 2 wires. One is a center wire with insulation and a 2nd braided wire is weaved around the center one. That, is the ground return for audio signals from the Source Unit, to the amplifier. It also helps reject outside noise problems.
Other than that, the amp needs a separate power supply ground, as does the HU. Aftermarket HU's need a dedicated ground to body, (Floor pan and/or firewall) as does the amp. (Floor pan)
Swez
Victor on 05/23/2006 00:04:08
take the HU out from the dash leaving all connections intact..
start the car, put on the HU play some music at low volume, roll up ur windows .
take a small wire, identify 2 parts of the RCA jack, the inner protuding pin and the outer part , now attach one end of that small wire to the outer part of the RCA out and th eother end to the HU chassis.
If the noise goes, fix that wire permanently and it solves ur problem..
I have had this problem in many cases, after going thru all the grounding and wiring of hu and amps, it finnaly comes down to the grounding of the RCA's.. Also make it a practice to ground the HU chassis to the Car...
Victor...
swez on 05/23/2006 06:45:31
Ahhhh, this makes a bit more sense now... the HU RCA's are not making full contact with the HU chassis ground and therefore, one gets hum problems. (inadequate grounding)
I still don't see the need for this type of supplementary grounding technique. It's a bandaid fix and not solving the real issue at hand... well grounded signal lines from HU to amps.
I can see this working on HU wires that are not well fitted to HU due to space constraints or wires that are being flexed to a point where poor fitting RCA grounds are an issue.
Victor, say more about this patch/fix method.
Swez
ttocs on 05/23/2006 10:38:25
I think it has more to do with the installation in most of the cases I see, not to insult the installer. I had a bad case last week on a truck I was working on. I tried a new set of rca's ran down the opposit side of the vehicle from the power wires, didn't help at all. Tried grounding the rca's, and ran power and ground to the amp so the deck would get power in the same place as the amp and nothing worked. Tried grounding the rca as mentioned above, still didn't go away. Tried a ground loop isolator forwards and backwards while grounding the brown wire on it, still nothing.
I popped the hood in desperation and followed the amps power wire from the battery to the fuse mounted really nicely right above a MDS(multiple spark discharch) ignition advance...... The pwr wire ran along side the ignition wires into the firewall. I pointed it out to the owner/manager and he said he knew about it, but the owner didn't want it moved. I tried running the power wire a few different ways but I couldn't make it even slightly better. We sent it out with a frown and instructions to move the msd box as there was nothing I/we could do.
try all the things I mentioned in my ramblings. I have only seen a couple of cars in 10+ yrs that I couldn't fix in some way, but there are some that have extremly noisy ignition systems that ya just can't do much with but I wouldn't think a saab would be on that list.
How did you do your signal? If you tapped the rear speakers with a loc you are probably getting the signal after it goes through the factory amp. I beleive it is in the bottom of the dash in the center, but it has been a while since I did one.
Zach1989 on 05/23/2006 13:01:05
I have installed an aftermarket sony xplod and wired the ground into the harness, the rca cables seem to be on there quite well, I am going to try to ground the HU to a point I found earlier to see if that fixes it. If not I'll keep trying to fix it the right way.
Zach1989 on 05/23/2006 17:08:28
hey guys thanks for your help I grounded the HU to a spot on the firewall there and reground the amp a little better and the humming totally stop. Now I know for the next install, I didn't do too bad for it being the first time and doing it myself.
swez on 05/24/2006 08:20:32
There ya go... that fixes about 95% of this type of problem.
Swez
ttocs on 05/25/2006 00:27:44
I remember some friends and I used to laugh as every time we had a question for a local shop they would always say to check the ground. Now I find myself saying the same thing as it can fix sooo man things, probably only second to a technical tap.......
Replies (8)
swez on 05/22/2006 22:14:39
The humming is usually a poor ground connection at HU, amp or both. We need a bare metal ground for both HU and amp grounds.
The 2nd common cause of noise, is setting the gain on amp too high. This amplifies audio and noise.
The last one is a bad RCA cable or loose amp jacks (grounds) in the PB board. If either is present, hum is often the result.
QUOTE: "but in a previous forum it says ground the rca cable to the amp? If that is so, how do I do that? "
I have no idea what that means.
In one sense, the RCA cable(s) have 2 wires. One is a center wire with insulation and a 2nd braided wire is weaved around the center one. That, is the ground return for audio signals from the Source Unit, to the amplifier. It also helps reject outside noise problems.
Other than that, the amp needs a separate power supply ground, as does the HU. Aftermarket HU's need a dedicated ground to body, (Floor pan and/or firewall) as does the amp. (Floor pan)
Swez
Victor on 05/23/2006 00:04:08
take the HU out from the dash leaving all connections intact..
start the car, put on the HU play some music at low volume, roll up ur windows .
take a small wire, identify 2 parts of the RCA jack, the inner protuding pin and the outer part , now attach one end of that small wire to the outer part of the RCA out and th eother end to the HU chassis.
If the noise goes, fix that wire permanently and it solves ur problem..
I have had this problem in many cases, after going thru all the grounding and wiring of hu and amps, it finnaly comes down to the grounding of the RCA's.. Also make it a practice to ground the HU chassis to the Car...
Victor...
swez on 05/23/2006 06:45:31
Ahhhh, this makes a bit more sense now... the HU RCA's are not making full contact with the HU chassis ground and therefore, one gets hum problems. (inadequate grounding)
I still don't see the need for this type of supplementary grounding technique. It's a bandaid fix and not solving the real issue at hand... well grounded signal lines from HU to amps.
I can see this working on HU wires that are not well fitted to HU due to space constraints or wires that are being flexed to a point where poor fitting RCA grounds are an issue.
Victor, say more about this patch/fix method.
Swez
ttocs on 05/23/2006 10:38:25
I think it has more to do with the installation in most of the cases I see, not to insult the installer. I had a bad case last week on a truck I was working on. I tried a new set of rca's ran down the opposit side of the vehicle from the power wires, didn't help at all. Tried grounding the rca's, and ran power and ground to the amp so the deck would get power in the same place as the amp and nothing worked. Tried grounding the rca as mentioned above, still didn't go away. Tried a ground loop isolator forwards and backwards while grounding the brown wire on it, still nothing.
I popped the hood in desperation and followed the amps power wire from the battery to the fuse mounted really nicely right above a MDS(multiple spark discharch) ignition advance...... The pwr wire ran along side the ignition wires into the firewall. I pointed it out to the owner/manager and he said he knew about it, but the owner didn't want it moved. I tried running the power wire a few different ways but I couldn't make it even slightly better. We sent it out with a frown and instructions to move the msd box as there was nothing I/we could do.
try all the things I mentioned in my ramblings. I have only seen a couple of cars in 10+ yrs that I couldn't fix in some way, but there are some that have extremly noisy ignition systems that ya just can't do much with but I wouldn't think a saab would be on that list.
How did you do your signal? If you tapped the rear speakers with a loc you are probably getting the signal after it goes through the factory amp. I beleive it is in the bottom of the dash in the center, but it has been a while since I did one.
Zach1989 on 05/23/2006 13:01:05
I have installed an aftermarket sony xplod and wired the ground into the harness, the rca cables seem to be on there quite well, I am going to try to ground the HU to a point I found earlier to see if that fixes it. If not I'll keep trying to fix it the right way.
Zach1989 on 05/23/2006 17:08:28
hey guys thanks for your help I grounded the HU to a spot on the firewall there and reground the amp a little better and the humming totally stop. Now I know for the next install, I didn't do too bad for it being the first time and doing it myself.
swez on 05/24/2006 08:20:32
There ya go... that fixes about 95% of this type of problem.
Swez
ttocs on 05/25/2006 00:27:44
I remember some friends and I used to laugh as every time we had a question for a local shop they would always say to check the ground. Now I find myself saying the same thing as it can fix sooo man things, probably only second to a technical tap.......
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