Auxiliary audio input for Saab 9-3 head unit.

Disclaimer: This article describes how I modified my head unit. I cannot take any responsibility for anything you do - it is your choice if you want to give it a go. There is risk associated with this sort of thing - ESD strikes could damage your unit. Proper ESD precautions should be followed, failing that grounding yourself before starting might help (I didn't do either, but in theory you should).

Introduction

This project basically disconnects the audio signals from the head unit's internal CD player, and connects in audio signals from an auxiliary device instead. I've not seen this done with the internal player (using a CD changer's signals has been around for a while, as has using the telephone input) so thought I'd post instructions on this blog. Note that unlike other solutions, NO tracks need to be cut on the head unit's PCB, and the modifications are fully reversible.

In this simplest configuration the internal CD player can't be used after the mod, but if you have your entire CD collection available in your MP3 player, do you need it ? To enable the audio paths there must be CD in the player - see later.

You will need:

• Insulating tape
• About 20cm of stereo audio cable (ie. shielded twin core)
• Stereo jack plug
• Stereo extension cable
• Pair of standard DIN removal tools (to extract head unit)

Procedure

I would strongly recommend reading all the way through these instructions, so you know exactly what's involved !

1. Remove the head unit from your 9-3 and dicsconnect all the cables (connectors are keyed, so you don't have to remember which one's which).

2. Remove the bottom metal panel by unscrewing the single screw (see picture) and carefully prising panel off unit.

3. You should now see something like this:

The flexy connector from the onboard CD is indicated, and you can see my auxiliary audio cable attached.

4. CD signal names are marked on the PCB, but only the last few are of interest for this project:

……
AGND
DOUT
L-CH
R-CH
5V
CD-G
GND
GND
8V
8V

5. Now for the tricky part. You need to unsolder the left and right audio wires (L-CH and R-CH). A fine tipped soldering iron is the best for this, and a solder sucker or solder braid can be used to remove excess solder. An alternative may be to cut the two wires before they reach the PCB.

6. Fold the wires back and secure with insulating tape or similar (see picture below - you might want to download it and zoom in).

7. Connect your audio jack to one end of the audio cable. The tip and ring correspond to left and right respectively. Here is a drawing:
(Note that the cord grip is also the ground connection for the cable). You may need to buzz out the connections with a multimeter, but usually they are quite obvious.

8. Prepare the other end of the cable by stripping about an inch of the main insulation back to expose the ground shield. Gently twist the ground shield from both left and right wires together. Strip a few millimetres of insulation from the signal wires (usually white and red). Tin the end of the ground shield and signal wires with solder.

9. There are testpoints on the PCB for the left and right CD channels. They are marked but to be completely sure you can use a multimeter to check back to the flexy connector (the two pads where you unsoldered the wires from). Solder the two signal wires to the relevant testpoints (tip is left, ring is right - see drawing above) - see picture in step 6 above.

9a. An alternative would be to solder to the pads that you unsoldered the wires from in step 5.

10. Solder the ground shield to a suitable analogue ground point. There is actually a 'through-hole' point just to the right of the testpoints which is nice and strong (see picture in step 6).

11. You might want to provide some strain relief to your new cable - I put on a bit of insulating tape just to hold it while I put the panel back on. The wire is actually held quite nicely as it comes out of the back of the unit by the panel.

This is the finished article:

Now you can test the implementation:

1. Connect your extension cable to your new aux in cable, and connect up all the cables to the head unit. Partially refit the unit back into its slot, with the extension lead sticking out of the front. Be a little bit careful not to touch the new jack plug too much, in case you zap it with static.

2. Insert the jack into your iPod (or MP3 player) headphone socket.

3. Power up the unit and make sure the radio still works ! Insert a CD (any CD with playable tracks).

4. Turn on your iPod. 'Play' the CD on the head unit. Make sure your iPod is playing.

You should now hear audio coming through your in-car system ! You may have to turn the volume up on the iPod to full, and maybe a bit on the head unit too.

[I measured the audio levels out of my iPod with an oscillosope - the maximum voltage is about 2.7V peak-to-peak. The head unit's CD levels are about 3V peak-to-peak]

Next steps

Slide the head unit out again, and route the extension lead somewhere sensible. You can remove the passenger side panel (on UK cars at least) to facilitate this. I routed my cable through to the little cubby hole under the ash tray (there is a hole already, so no drilling required !), but you could route it through to the armrest box, or an iPod holder.

For a more professional and robust iPod solution, I bought some dock connectors. You can get them here: http://home.swipnet.se/ridax/connector.htm Note that the pitch of the connections is quite small - you'd better have a microscope ! The pinout for the connectors is available here: http://ipodlinux.org/Dock_connector

To maximise playback time I generated a CD with 74 minutes of silence. Note there is a brief pause at the end of the CD as it tracks back to the beginning to play it again (or so it thinks !).


Longer term steps
1. Add some resistors so that the CD and aux in signals can be safely combined, so the CD player can be used as well.
2. Incorporate a charger into the iPod connection (relatively straightforward).
3. Hack the SID unit's bus to display track information (don't hold your breath !) - if anyone knows of someone getting anything onto the display, please let me know !

Please feel free to ask me any questions - I'll update this blog with any information that's missing (if anyone reads it that is). Probably best to post to Saabscene, or PM me from there. Related post is: http://www.saabscene.com/saabforum/showflat.php/Cat/0/Number/31603619/an/0/page/1#31603619

Good luck !