DIY: (Almost) free AUX-in for Symphony or Concert

[Mad Cow]

This is a very simple and cheap way to add an AUX-in to basically any head unit that uses an external CD changer, I've done it to my old Concert and now my Symphony. All you need is a 3.5mm jack, a bit of wire, and a blank CD. The basic principle behind this is you inject your audio stream through the CD changer pins at the head unit's connector, the need for the blank CD will be explained further in. There's many ways you can do this, but since I prefer not to splice into factory wiring I took the rear plate off my head unit and soldered wires directly to the connector pins on the back of the PCB like so: (the text refers to the pins directly to the left)


Then I drilled a hole in the plate for my 3.5mm jack, there's a perfect spot by the male spade connector, it's even indented so you know where to drill. The finished product from the inside:


And outside:


Now this is where the blank CD comes in. The head unit won't accept audio through the CD changer pins unless the changer tells it that it's playing something. Again there's many ways to go about this, but the simplest and fastest is to just burn a CD full of silence and toss it into the changer. If it's the only CD in the changer it'll automatically play it on repeat and the audio won't ever cut out even for a split second. To do this I used Audacity. Install and open it, go to Generate --> Silence and set it to either 74 or 80 minutes depending on your CD, if you're not sure just use 74, the extra 6 minutes really won't make any difference. Then go to File --> Export, save it as a .wav file and burn that file as an audio CD using your favourite disc writing program.

Now just pop that into your changer and find a way to route your new male-male 3.5mm cable, I ran it down by the passenger footwell since mine is 6 feet long, with a shorter cable you might have to get more creative.

All in all this project cost me less than $2.00 and took about half an hour, sure beats paying $30 or more for an external box that does basically the same thing. This same method can be used for almost any stock head unit, I did it to my E36 before, but used the tape player audio input and a gutted tape. With my Concert it was basically the same deal, but I couldn't find the room to mount a 3.5mm jack so I ran a wire out through the backplate and used an inline jack.

EDIT: The location I chose for my jack isn't the best place to put it, after fully installing the head unit I noticed that the plug could hit the HVAC ducting which only sticks out in that one corner. I'm just going to use a right-angle adapter, but for future reference you'd probably be better off finding another spot for it.

[gtr3nos1]

This is awesome

[audi-medic]

This is great! I've been trying to do a cheap AUX "mod" and this is def good info thanks!

[Tree.]

very nice, been looking for a way to incorporate an AUX input

[paulorama]

Dude. Yes. Thank You.

[ianwpb]

Question - I'm pretty sure I didn't see the answer in your post but I may have missed it.

Essentially you're just splicing in an Auxiliary Cable, instead of cutting the Left and Right and splicing the Ground to the CD changer harness. Does this mean that you can still listen to CD's?

I did mine the other way, where you cut the wires so I have no Audio input from the CD changer, therefore I can't listen to CD's. Not a big deal, but sometimes it's such a short trip or I'm just too lazy to connect my phone to the Aux cable.

[Mad Cow]

Question - I'm pretty sure I didn't see the answer in your post but I may have missed it.

Essentially you're just splicing in an Auxiliary Cable, instead of cutting the Left and Right and splicing the Ground to the CD changer harness. Does this mean that you can still listen to CD's?

I did mine the other way, where you cut the wires so I have no Audio input from the CD changer, therefore I can't listen to CD's. Not a big deal, but sometimes it's such a short trip or I'm just too lazy to connect my phone to the Aux cable.

Exactly, the wires from the changer still go to the head unit so the changer still works. I've only used it a couple of times and I really don't need it, but I'm just not a fan of cutting/splicing factory wiring unless it's absolutely necessary.

[B72011]

Could you show us the real close up pics? Makes perfect sense, but I'd love to see some close up pics. Also, will this work on the Symphony II unit ? thanks

[biketsai]

Very nice! Ill put this in the DIY section

[melomandn]

This is awesome

[Mad Cow]

Could you show us the real close up pics? Makes perfect sense, but I'd love to see some close up pics. Also, will this work on the Symphony II unit ? thanks

My soldering job was terrible, no need to show that to the world. It's all pretty simple, just attach the new wires to the little cones of solder on the back of the PCB. I can't see why it wouldn't work for the II, it'll be more difficult to find a place for the jack though because the backplate is so much smaller.

[burgurboy]

this is awesome. perfect timing too. I just ordered stereo removal tools like an hour before i saw this thread.

Again there's many ways to go about this

Here's MY problem...

Someone removed the cd changer from my car. The cables are there, just no CD changer. Any idea wether or not I can short any wires to fool the Head Unit into thinking the CD changer is playing? Maybe put a low-impedance/value resistor between two of the connections? Although I'm sure there is a lot of circuitry within the CD changer itself, I would think there is only a simple signal wire telling the cd player to power on.

[paulorama]

Got it workin today! Thanks

[ianwpb]

Exactly, the wires from the changer still go to the head unit so the changer still works. I've only used it a couple of times and I really don't need it, but I'm just not a fan of cutting/splicing factory wiring unless it's absolutely necessary.

Great thanks.. I'm going to take apart the radio from my Wife's Jeep liberty. I'll see if I can piggy back off the tape deck input. Good stuff man.

[Mad Cow]

this is awesome. perfect timing too. I just ordered stereo removal tools like an hour before i saw this thread.



Here's MY problem...

Someone removed the cd changer from my car. The cables are there, just no CD changer. Any idea wether or not I can short any wires to fool the Head Unit into thinking the CD changer is playing? Maybe put a low-impedance/value resistor between two of the connections? Although I'm sure there is a lot of circuitry within the CD changer itself, I would think there is only a simple signal wire telling the cd player to power on.

Unfortunately it's not that easy, the CD changer uses a serial communication protocol so there's likely some sort of challenge-response thing going on to enable audio. I want to get rid of the changer requirement at some point too, my plan is to find the chip that controls this behaviour and hopefully short out 2 pins or something to force it to let audio through. I have a broken Symphony sitting in front of me, so I'm going to tear it down and try to find something useful.

[burgurboy]

Dang! Those Germans.... I was hoping it looked for a simple 12v signal.

Hmmm.... In the mean time, I guess I'll shoot for the tape deck. Does the tape deck output the same voltage as as the other inputs? I dont want to too powerful of an input going in and blowing a preamp.

Thanks

[Mad Cow]

Dang! Those Germans.... I was hoping it looked for a simple 12v signal.

Hmmm.... In the mean time, I guess I'll shoot for the tape deck. Does the tape deck output the same voltage as as the other inputs? I dont want to too powerful of an input going in and blowing a preamp.

Thanks

No clue, you'd have to look up datasheets and such. I can't see why it wouldn't work though, I've done it in an E36 this way and it was fine.

[RDA990]

Here's MY problem...

Someone removed the cd changer from my car. The cables are there, just no CD changer. Any idea wether or not I can short any wires to fool the Head Unit into thinking the CD changer is playing? Maybe put a low-impedance/value resistor between two of the connections? Although I'm sure there is a lot of circuitry within the CD changer itself, I would think there is only a simple signal wire telling the cd player to power on.

Unfortunately it's not that easy, the CD changer uses a serial communication protocol so there's likely some sort of challenge-response thing going on to enable audio. I want to get rid of the changer requirement at some point too, my plan is to find the chip that controls this behaviour and hopefully short out 2 pins or something to force it to let audio through. I have a broken Symphony sitting in front of me, so I'm going to tear it down and try to find something useful.

Any update on this? I have a Symphony II without a CD changer, but all the wiring and everything. The only thing preventing the Aux input from working is the Radio not communicating with the CD changer. There has to be a way to "fool" the head unit so it "sees" the CD changer and enable the Aux input. The closest I've gotten to solving this is noticing there are only 2 "data/power" cables that go from head unit to CD changer. One of those I'm sure is power, and the other the communicator that hopefully just get a voltage to show that the CD changer is connected. Many aftermarket Aux input devices have figured it out, they use the same exact ports but have found a way to electronically enable the CDC/External CD/Aux in function.

[fR3ZNO]

Any update on this? I have a Symphony II without a CD changer, but all the wiring and everything. The only thing preventing the Aux input from working is the Radio not communicating with the CD changer. There has to be a way to "fool" the head unit so it "sees" the CD changer and enable the Aux input. The closest I've gotten to solving this is noticing there are only 2 "data/power" cables that go from head unit to CD changer. One of those I'm sure is power, and the other the communicator that hopefully just get a voltage to show that the CD changer is connected. Many aftermarket Aux input devices have figured it out, they use the same exact ports but have found a way to electronically enable the CDC/External CD/Aux in function.

Thread revival!

I'm in a similar situation. I'd like to do this mod, but as I understand it, you need to have a CD changer installed, which I don't have.

I do have an aftermarket device that replaces the CDC and allows you to plug in your iPhone/iPod via a 30 pin connection. A few months ago, this unit crapped the bed after about two years of use which is disappointing. The customer service for the company is non existent (managed to get a hold of someone via chat on their support page and they'll "repair" it for damn near the cost of a new one on amazon). So lately, I've just been using CDs which is a pain.

I would love to know if there is a way to run this AUX cable from the head unit without using a factory CD changer installed.

[FearDaFish]

Hey guys, sorry to revive this thread but I'm having trouble finding the information I need about this. I have a 99 audi a4 with concert radio, and external CD changer, and cannot find the pins that are listed here in the picture. Is the "PCB" that he shows the head unit? I took a part mine and it doesn't look anything like this. Is this for the concert 2 maybe? Any help would be appreciated!

[Mad Cow]

This is for the Symphony I, but the exact same process applies to both Concerts and Symphonys. That PCB is on the inside of the back cover, there's about half a dozen screw holding it on. It's right on the other side of the 4 main connectors, you can't miss it.

[FearDaFish]

On the inside of the back cover of the head unit? I apologize if that this is a dumb question.

[fR3ZNO]

Found this thread again looking for an aux cable for my B5.5 Passat. I came across this on eBay: Clicky Click

From what I can tell it does the same thing as what OP did, without soldering on the PCB in the radio? I'm not sure.

[crazexr7]

Found this thread again looking for an aux cable for my B5.5 Passat. I came across this on eBay: Clicky Click

From what I can tell it does the same thing as what OP did, without soldering on the PCB in the radio? I'm not sure.

Nice find. I imagine this completely bypasses the CD changer.

[fR3ZNO]

Nice find. I imagine this completely bypasses the CD changer.

Thanks. That is what I am thinking as well.

[bhusted]

Nice find. I imagine this completely bypasses the CD changer.

I'm not sure if this is possible. There is a digital handshake that occurs between the CD changer and the headunit before any music is played. This is why the OP used a CD with recorded "silence". I've been working on an Arduino project to simulate the CD changer, but haven't had time to work on it lately.

[fR3ZNO]

I'm not sure if this is possible. There is a digital handshake that occurs between the CD changer and the headunit before any music is played. This is why the OP used a CD with recorded "silence". I've been working on an Arduino project to simulate the CD changer, but haven't had time to work on it lately.

Yeah, after doing a bit of thinking/research I would have to agree. Although the eBay ad states fitment with a B5 Passat (and a VW Polo?), I asked the seller and he said that it only fits 05-12 Passats, which doesn't make sense since the plugs for the radio are completely different. I am taking the information from the eBay seller with a grain of salt.

For this to work, I am thinking that I would need to pull pins 13 through 17 out of the blue plug and transfer it to the aux cable plug (top row, right side of below pic). However, this would still require a CD changer with a CD that has "silence" burned to it.



Although this may not be what I was hoping to accomplish, this approach allows someone to avoid opening their radio and soldering wires, if they aren't comfortable with that. I feel that swapping pins over to a different plug would be a little easier for some.

Also, for my Passat, the trunk CD changer plug is the same as a MKIV Jetta/Golf, and is different from the Audi. This may not help you guys, but I have been able to find a few CD changers from Jettas at my local Pick n Pull for about $30 which makes this mod still relatively cheap compared to buying an aux/iPod kit that costs roughly $160

Audi CD changer plug:


VW CD changer plug:


I would be interested to see what you come up with for simulating the CD changer via Arduino. I would imagine it can't be terrribly difficult considering that is essentially how the aftermarket iPod inputs operate.

Check this out, it is for an A8, but I believe they have the same CD changer.
clicky click

If you'd like I could try taking mine apart, and seeing what's inside. It is fairly light and can't be that complex. This is what I have:

[RDA990]

I have tried one of those eBay aux cables that connect to the back. The only thing it does is add the actual aux cable, like others have said you still need to fool the head unit into thinking it has a CD changer to be able to switch on the aux input.

[fR3ZNO]

I have tried one of those eBay aux cables that connect to the back. The only thing it does is add the actual aux cable, like others have said you still need to fool the head unit into thinking it has a CD changer to be able to switch on the aux input.

Ahh. I see. This is what I was thinking too. I figured at the least I could swap the necessary pins over for the CD changer.

[FearDaFish]

Awesome find! Doing it this way works well, however I am having an issue with bass. It seems it doesn't hit as hard as lets say listening with headphones, or listening to the same song on a CD. Could this be an issue with the connection made by the soldered wires? I used stranded wire and not solid wire, if that would make a difference. Maybe because of that the connection isnt solid enough?Anyone know?

[Mad Cow]

Awesome find! Doing it this way works well, however I am having an issue with bass. It seems it doesn't hit as hard as lets say listening with headphones, or listening to the same song on a CD. Could this be an issue with the connection made by the soldered wires? I used stranded wire and not solid wire, if that would make a difference. Maybe because of that the connection isnt solid enough?Anyone know?

From my experience the stock HU expects a (relatively) high voltage input from the CD changer, not many phones or mp3 players can drive it well enough. I've only ever had one phone (Nexus S) that worked as well as with a regular aux input, everything else ended up being really quiet and sounding weak in general. I ended up wiring up this preamp to it later, made a night and day difference. I did modify it a bit but it worked fine out of the box, just wasn't ideal.

[crazexr7]

Untitled by Josh Randall's Photo Dump, on Flickr

Added bluetooth instead of the aux input. Works awesome, only thing is it's a little quiet. I assume the amp madcow linked would help with this but not entirely sure where I would even wire it without making the center console even more cramped from my singledin to doubledin conversion.

[scottyboyx845]

For those of us without a CD changer in the trunk: Would it be possible to tap into the L,R & GND for the single CD player in the head unit(instead of the CD changer)? That way you'd be able to play a blank CD in the dash with the same effect.

[crazexr7]

For those of us without a CD changer in the trunk: Would it be possible to tap into the L,R & GND for the single CD player in the head unit(instead of the CD changer)? That way you'd be able to play a blank CD in the dash with the same effect.

It's def possible but you may have to do something similar to what this guy did. I watched this the other night, it's bluetooth, but the same can be done with aux or whatever.

[scottyboyx845]

It's def possible but you may have to do something similar to what this guy did. I watched this the other night, it's bluetooth, but the same can be done with aux or whatever.

^That's definitely an elegant solution. I'd be hesitant to try mapping out the chip pins myself.

I had some time to do some research and found this.

http://www.instructables.com/id/Audi...heap-AUX-Port/

I bet with a simple 3PDT switch you could retain the functionality of the CD player while adding an AUX.

I'll follow up when I get around to trying this.

[crazyazz]

I am trying to find out the Left and right inputs for the tape player on the audi concert plus. If anyone had any info I would appreciate it.