Radio Amplifier noise - HELP!

[rahlstrom]

I have a replacement Alpine amplifier installed in my 2003 Boxster S and I have the dreaded radio hum. I already have directional/shielded RCA cables installed and an in line noise filter. I am running the cables through the firewall on the driver side which then requires the cables to go by the battery. That, I'm guessing, is the issue. Is there a place to bring the wires through the passenger compartment on the passenger side? Any other ideas on how to fix besides putting the amp behind the seat?

Radio: Pioneer AVIC D3

Amp: Alpine PDX-5

Speakers: Stock - front, rear, door.

[Ross1]

I have a replacement Alpine amplifier installed in my 2003 Boxster S and I have the dreaded radio hum. I already have directional/shielded RCA cables installed and an in line noise filter. I am running the cables through the firewall on the driver side which then requires the cables to go by the battery. That, I'm guessing, is the issue. Is there a place to bring the wires through the passenger compartment on the passenger side? Any other ideas on how to fix besides putting the amp behind the seat?

Radio: Pioneer AVIC D3

Amp: Alpine PDX-5

Speakers: Stock - front, rear, door.

Running the cables past your battery is not the problem! It sounds like you have a ground loop! The first thing that I would do is make sure your amp and your head unit are grounded to the chassis. I would also connect the positive of the amp directly to the battery. The less that you use the stock wiring, the better off you will be. You shouldn't need the in-line noise filter if you have done it right! Try that out and let us know if it fixes the problem! If not, let us know how you have it wired and we'll figure it out!

[heyjae]

I have a replacement Alpine amplifier installed in my 2003 Boxster S and I have the dreaded radio hum. I already have directional/shielded RCA cables installed and an in line noise filter. I am running the cables through the firewall on the driver side which then requires the cables to go by the battery. That, I'm guessing, is the issue. Is there a place to bring the wires through the passenger compartment on the passenger side? Any other ideas on how to fix besides putting the amp behind the seat?

Radio: Pioneer AVIC D3

Amp: Alpine PDX-5

Speakers: Stock - front, rear, door.

Porsche's inherently have a lot of noise and having the cables near the battery probably isn't the problem. I'm not familiar with the Pioneer AVIC D3, but you will need as high a voltage output from the source/radio to the amp as possible. Hopefully the radio is capable of outputting at least 4 volts. Then adjust the output. Start with the lowest sensitivity on the amp. Then set the volume of the Pioneer at about 80% maximum, then adjust the amp sensitivity upward until it is about as loud as you will listen to the stereo. Setting the radio output as high as possible masks the interference. I hope that helps.

[rahlstrom]

Another thing to note is that after I installed the AVIC I initially used the head amp to power the front and rear speakers and had no noise. It was when the Alpine amp was added that the noise began so it seems like it's related more to the amplifier than the head. The Amp power does go directly to the battery and the ground also goes directly to the battery. Would it be better to use the chassis over the battery for grounding?

[Ross1]

Another thing to note is that after I installed the AVIC I initially used the head amp to power the front and rear speakers and had no noise. It was when the Alpine amp was added that the noise began so it seems like it's related more to the amplifier than the head. The Amp power does go directly to the battery and the ground also goes directly to the battery. Would it be better to use the chassis over the battery for grounding?

Ground looping is caused by your amp and head unit having different grounds than your audio signal. You are probably using the stock wiring with your AVIC and so when it was connected to the stock amp they had common grounding. Grounding your amp to the chassis instead of the battery should eliminate the loop!

Edited May 15, 2008 by Ross1

[rahlstrom]

Ground looping is caused by your amp and head unit having different grounds than your audio signal. You are probably using the stock wiring with your AVIC and so when it was connected to the stock amp they had common grounding. Grounding your amp to the chassis instead of the battery should eliminate the loop!

It worked! A combination of moving the amp ground to the chassis and careful routing of the RCA cables out the back of the head unit did the trick. The RCA cables were wound up near the back of the head unit and must have also been picking up signal noise.

Thanks for all the help!!!

I plan on posting a DIY on the AVIC D3/Alpine PDX-5 install shortly so others can benefit from all the great support I've received from this forum.

[juniinc]

prolly wasn't the RCA's especially when they are shielded, proper ground did the trick!

[chitowndad]

Ok, so I also installed the Avic D3 and had the hum sound initially. I fixed my problem as follows. The mute and parking brake wires can be group grounded but they need to be grounded to a good source. For me, I ran a common ground wire back to where the factory amp was located and the bracket that the amp bracket slid onto was the best source for me. Here's any easy way to find the best ground. Turn the unit on throw in a music DVD and then touch the ground wire to a few sources (with the engine running) when the whine goes away you've found a good ground. Don't ground these wires to the black radio ground which is what I originally did and had my whine issue. Make sense?

Drop me a private email if you want to chat over email, etc.

The only remaining issue that I currently have is a pop sound when I turn off the radio. I installed a really large amp.

-Steve

[chitowndad]

Sorry, I didn't read that you had already solved the issue... Any ideas why my amp goes POP when I turn it off and remove the keys? My amp is wired to the + on the battery and the - to the thick brown wire off the amp harness which goes back to the frame.

-Steve

Ok, so I also installed the Avic D3 and had the hum sound initially. I fixed my problem as follows. The mute and parking brake wires can be group grounded but they need to be grounded to a good source. For me, I ran a common ground wire back to where the factory amp was located and the bracket that the amp bracket slid onto was the best source for me. Here's any easy way to find the best ground. Turn the unit on throw in a music DVD and then touch the ground wire to a few sources (with the engine running) when the whine goes away you've found a good ground. Don't ground these wires to the black radio ground which is what I originally did and had my whine issue. Make sense?

Drop me a private email if you want to chat over email, etc.

The only remaining issue that I currently have is a pop sound when I turn off the radio. I installed a really large amp.

-Steve

[rahlstrom]

Sorry, I didn't read that you had already solved the issue... Any ideas why my amp goes POP when I turn it off and remove the keys? My amp is wired to the + on the battery and the - to the thick brown wire off the amp harness which goes back to the frame.

Sounds like some type of power spike. Have you tried an inline power conditioner of some kind. Who makes the amp?

[Ross1]

Ok, so I also installed the Avic D3 and had the hum sound initially. I fixed my problem as follows. The mute and parking brake wires can be group grounded but they need to be grounded to a good source. For me, I ran a common ground wire back to where the factory amp was located and the bracket that the amp bracket slid onto was the best source for me. Here's any easy way to find the best ground. Turn the unit on throw in a music DVD and then touch the ground wire to a few sources (with the engine running) when the whine goes away you've found a good ground. Don't ground these wires to the black radio ground which is what I originally did and had my whine issue. Make sense?

Drop me a private email if you want to chat over email, etc.

The only remaining issue that I currently have is a pop sound when I turn off the radio. I installed a really large amp.

-Steve

The pop sound is caused by your amp still being turned on when the radio goes off! You need to find the AMP ON/OFF wire on the AVIC D3 and connect it to the ON/OFF connection to your amp.

[rahlstrom]

Ok, so I also installed the Avic D3 and had the hum sound initially. I fixed my problem as follows. The mute and parking brake wires can be group grounded but they need to be grounded to a good source. For me, I ran a common ground wire back to where the factory amp was located and the bracket that the amp bracket slid onto was the best source for me. Here's any easy way to find the best ground. Turn the unit on throw in a music DVD and then touch the ground wire to a few sources (with the engine running) when the whine goes away you've found a good ground. Don't ground these wires to the black radio ground which is what I originally did and had my whine issue. Make sense?

Drop me a private email if you want to chat over email, etc.

The only remaining issue that I currently have is a pop sound when I turn off the radio. I installed a really large amp.

-Steve

The pop sound is caused by your amp still being turned on when the radio goes off! You need to find the AMP ON/OFF wire on the AVIC D3 and connect it to the ON/OFF connection to your amp.

Ah yes, you need to connect the "remote" wire from the AVIC D3 to your amp to control power on/off. There is a remote wire available in the factory harness. For my year/radio configuration it's the white/red wire on pin 4 on the yellow radio connector and pin 1 on the amplifier connector. See the attached for the full factory wiring diagram for my 2003 with the MOST bus.

[Daryl80]

Hi All,

I'm sure I wrote this in another post, but I can't find it. Anyway, rahlstrom, are you saying that your RCA's were all jammed in the back behind the HU, and that you were able to carefully route the RCA's to the HU.

My only question is how did you do that. I just see no way of avoiding the battery, given where the hole in the firewall is located. Which path did you take?

Ross1 and Chitowndad, ground looping makes sense, and using the same ground, the chassis, also makes good sense too. I can ground the amp to the body, where the battery connects to the metal, but how about the HU?

I originally used the factory brown wire, and you're right, got that hum. But where else is there a clean piece of chassis metal inside the cabin? I didnt have the factory amp, so and advice on where I should ground the HU to the chassis and how I should run the wire would be greatly appreciated.

Thanks

[Ross1]

Hi All,

I'm sure I wrote this in another post, but I can't find it. Anyway, rahlstrom, are you saying that your RCA's were all jammed in the back behind the HU, and that you were able to carefully route the RCA's to the HU.

My only question is how did you do that. I just see no way of avoiding the battery, given where the hole in the firewall is located. Which path did you take?

Ross1 and Chitowndad, ground looping makes sense, and using the same ground, the chassis, also makes good sense too. I can ground the amp to the body, where the battery connects to the metal, but how about the HU?

I originally used the factory brown wire, and you're right, got that hum. But where else is there a clean piece of chassis metal inside the cabin? I didnt have the factory amp, so and advice on where I should ground the HU to the chassis and how I should run the wire would be greatly appreciated.

Thanks

Ground your amp to the chassis and just use the stock wiring ground for your HU! That worked for rahlstrom!

[rahlstrom]

Hi All,

I'm sure I wrote this in another post, but I can't find it. Anyway, rahlstrom, are you saying that your RCA's were all jammed in the back behind the HU, and that you were able to carefully route the RCA's to the HU.

My only question is how did you do that. I just see no way of avoiding the battery, given where the hole in the firewall is located. Which path did you take?

Ross1 and Chitowndad, ground looping makes sense, and using the same ground, the chassis, also makes good sense too. I can ground the amp to the body, where the battery connects to the metal, but how about the HU?

I originally used the factory brown wire, and you're right, got that hum. But where else is there a clean piece of chassis metal inside the cabin? I didnt have the factory amp, so and advice on where I should ground the HU to the chassis and how I should run the wire would be greatly appreciated.

Thanks

Ground your amp to the chassis and just use the stock wiring ground for your HU! That worked for rahlstrom!

Yes, the radio ground in the factory harness goes directly to the chassis. The cable type/routings did make a difference (directional, shielded). If you coil the extra RCA cable length directly behind the head unit it will generate noise. Keep the length behind the radio relatively short and handle the excess elsewhere. Also the cables were routed through the driver's side of the firewall rather than going behind the battery and going through the passenger side opening.

[juniinc]

All of U should get a Ground Loop Isolator.