The typo on the BMW diagram should read 0.22 uF....greencap or similar would be fine but needs to be marked 224, not 223 as shown in your photos.
The value is likely not critical and values up to 1 uF would be fine.
I expect you are losing low bass by using 223 caps.
The noise is due to earth loop between the the cig plug supply and head unit.
Run the iPod on batteries or use an audio coupling/ground isolator transformer as available at car audio shops fitted between the iPod and the BMW network.
You are likely able to delete the BMW network and use the transformer only.
Eric.
The value is likely not critical and values up to 1 uF would be fine.
I expect you are losing low bass by using 223 caps.
The noise is due to earth loop between the the cig plug supply and head unit.
Run the iPod on batteries or use an audio coupling/ground isolator transformer as available at car audio shops fitted between the iPod and the BMW network.
You are likely able to delete the BMW network and use the transformer only.
Eric.
I'll-be-damned. Looks like I need a ground isolator. The system is perfect on batteries. I have a bunch of rca filter set ups but no ground isolators for the power wire. I'll have to set up some RCA's on the line to run the rca ground loop filter. I have a PAC model in storage from when I owned car audio stores.
My low end seems useable, no real issue. The factory HK system doesn't really drop super low into the 40's anyway so perhaps it's helping more than hurting by rolling off unwanted subsonic notes.
My low end seems useable, no real issue. The factory HK system doesn't really drop super low into the 40's anyway so perhaps it's helping more than hurting by rolling off unwanted subsonic notes.
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I found an old stinger noise filter and opened it to convert it to wires from rca, also to go from 4 wire to 3 wire by connecting the ground on each side of the transformer since this is a common ground setup we are working with.
I'm installing it now. I'll report back soon.
see the two centers jumped together on the sides to make common ground.
I'm installing it now. I'll report back soon.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
see the two centers jumped together on the sides to make common ground.
An externally hosted image should be here but it was not working when we last tested it.
Another option instead adding transformers in the audio path would be a DC-DC converter power supply which wouldn't have one iota of impact on the audio - except to eliminate the noise. My previously described pseudo differential input would work as well but for simplicity the DC-DC converter wins.
Welcome to the world of eliminating ground loops.
G²
Adding the transformers and removing the caps has made everything perfect. 
I had no loss of low end with the caps, but I did have an attenuation of maybe 10db. Now it is wide open and full range. I never had a turn on pop since I built this from the diagram to being with, so I don't know if I eliminated a possible one with the isolator or not. I can only tell you it performs flawlessly.
Ten years go I owned 3 car audio stores, and 16 years ago was when I got my feet wet as a shade tree. Electronics repair and modifying only came within the last several year as a hobby so my ground loop experience previous was with components in the external sense, not building a back door into the unit like we have here. It's a new world, but a beautiful one at the moment because it al works
Thanks a bunch as always Perry, and to all that helped.
I had no loss of low end with the caps, but I did have an attenuation of maybe 10db. Now it is wide open and full range. I never had a turn on pop since I built this from the diagram to being with, so I don't know if I eliminated a possible one with the isolator or not. I can only tell you it performs flawlessly. Ten years go I owned 3 car audio stores, and 16 years ago was when I got my feet wet as a shade tree. Electronics repair and modifying only came within the last several year as a hobby so my ground loop experience previous was with components in the external sense, not building a back door into the unit like we have here. It's a new world, but a beautiful one at the moment because it al works
Thanks a bunch as always Perry, and to all that helped.
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