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So, this weekend I decided to buckle down and finally attempt to add my own auxiliary input to my car stereo, after weeks of telling myself that I wouldn't buy a new stereo under any circumstances. I ended up, after having much trouble with my first plan, soldering lines directly to the Amp IC inside of the head unit, and ran the lines out of the box. I took a 3.5mm cable broken out and soldered the right and left channels to the right and left line level ins on the Amp IC and then tested it. The audio works, however, the sound quality is awful. And I mean awful.

Here's what I'm confused about. I still have the FM Transmitter and CD player in the car and working, and when the auxiliary input isn't used the quality is fine, and actually exactly the same as before. So, I know that the problem here is something wrong with my input configuration, not the actual modification that took place.

For clarification, my setup involves an iPod Touch 3rd Generation outputting through the 3.5mm jack, going through a standard 3.5 cable split out to the left, right, and ground/shielding. The ground/shielding is not connected to anything, the left is connected to the left front and left rear while the right is connected to the right front and right rear on the Amp IC. I then have the stereo set to CD mode with a CD that has an 80 minute track of silence burned to it.

To additionally note, the sound goes out if the ground line broken out from the 3.5mm jack is ever connected to ground, whether through a ground connection on the board or to the head unit/car frame. If the ground line coming from the iPod is simply kept disconnected from anything in the car, sound plays at extremely low quality. This sound changes based on the position of the cable. Also, if I touch the screen on the iPod, static comes out of the speaker. I fully realized that this is a grounding issue, but I just don't know where to connect the ground, as the sound cuts out whenever the ground is connected.

Here are some sound clips to show what is going on right now with the system:

Passion Pit - Little Secrets: https://drive.google.com/file/d/0B5RwcGf405qYbGdzNC1JdExjWTg/edit?usp=sharing

Of Monsters and Men - Little Talks: https://drive.google.com/file/d/0B5RwcGf405qYTEtoWGNCZVhxUjQ/edit?usp=sharing
 

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I did a Firebird a couple of years back for a friend. That was pretty easy, all I had to do was tap into the CD outputs with a 3mm switch...that way when you plugged your iphone or mp3 player it would open the CD's signal (won't go through) and once you remove the 3mm plug the CD would play again like normal.

So that can be an idea if you can find out which wires (inside) are the CD's output signal and tap into those...that way the signal gets properly amplified.

Sounds like your missing a common ground on the 3mm plug (it should have three wires, Left/right/ground sleeve.)


PS: When the ground on ours broke it sounded exactly like the clip you uploaded "Of Monsters and Men - Little Talks"...the vocals where very low and the instrumental sounded like crap, hard to explain but sort of watery.
 

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PS: When the ground on ours broke it sounded exactly like the clip you uploaded "Of Monsters and Men - Little Talks"...the vocals where very low and the instrumental sounded like crap, hard to explain but sort of watery.
Yeah, that's exactly what's going on! Those clips were recorded with a disconnected ground. So, just for clarification, the L/R from the iPod were connected to the Amp IC inputs, but the ground coming out of the iPod was left disconnected.

So, what seems like is happening is the iPod is partially grounding itself simply though contact with other objects in the car (hence the change in sound when I touch the screen, hold the metal casing, etc.). The thing that I'm confused about is that when I connect the ground on the 3.5mm breakout to any of the available ground pins on the head unit or simply to the chassis, the audio completely cuts out. I can tell that it's still passing current though from my iPod, as when the volume on my iPod is turned up pretty loud you can hear the speakers crackle (I only did this once, and damn did it scare me, but it helps to know I guess...).

So I guess my question is why grounding it "properly" would be causing it to stop delivering any audio, but still deliver current.

Also, to respond to kustomkaraudio, the vehicle in question is a 2006 Kia Sedona.
 

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You need a ground....when it comes to signals you need a reference point, which is ground unless its a balance output then both signals would be AC except one would be 180 degrees out of phase (inverted) this is not the case here.

Does this help (pic below)? Search Kia's forums, they usually already have done this mod and may be able to help.



Might need an FM transmitter.
 

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You need a ground....when it comes to signals you need a reference point, which is ground unless its a balance output then both signals would be AC except one would be 180 degrees out of phase (inverted) this is not the case here.
Right, I know that much. Basically, I've noticed that if I don't give the iPod a hard ground, it gives the sound in the audio samples from my original post, this being because it grounds itself through noise and/or other objects in the car. But, when I give it a hard ground (to either the head unit or directly to the chassis), there is no audio but still delivered current. Have any of you ever seen this happen before?

Does this help (pic below)? Search Kia's forums, they usually already have done this mod and may be able to help.
And sorry, but unfortunately this doesn't help. It seems as though this is an installation diagram for models of the Sedona that have built in Aux capabilities, with this being for the surface mounted connections on the dash. Thanks though :)
 

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Not familiar with that vehicle, you might need a ground loop isolator like the one below. They are 13 bucks shipped....its basically something very simple, a couple of small transformers with caps (might not be included in this model) thats why you loose a bit of the signal output but you have control of that with the HU volume so not really a set back. I can't guarantee that this will fix the problem but its worth a shot.


Am not familiar with the song Passion Pit - Little Secrets, so I can't really tell if there is static or not. I even tried listening to a youtube original version to judge the difference but can't stand that kind of sound.
 
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