My 2005 Legacy iPod input hack -- no blank CD required!

No matter what set-up I tried, or how much I tried to convince myself that it was "good enough", I wasn't happy about using an FM modulator to listen to my iPod in my 2005 Legacy.

 

As FM set-ups go, the last version I attempted was fairly nice: a direct-wired FM modulator and a Belkin iPod adapter wired up inside the dash, with the iPod cable coming up through a slot in the back of the dashboard cubby, and a little switch just inside the cubby door for turning on the FM modulator. The sound quality was certainly better than I got from a wireless FM transmitter, but still not satisfactory.

 

I'd read about the CD-changer based solution -- a solution which was even more tempting to consider now that someone's making a convenient $35 kit -- but the idea of having to play a blank CD, and of putting up with brief dropouts in sound whenever the blank CD ran out and repeated, really bugged me.

 

My thought was this: If you can tap into where the CD signal goes into the head unit, why not tap into where the AM/FM tuner goes in instead? If you could do that, all you'd need to do is turn on the radio in order to have the head unit's amplifier up and running.

 

Of course, unlike the CD changer solution, just letting signals mix together wouldn't work -- you wouldn't want a radio station or radio noise mixed in with your iPod's output, and there's no radio equivalent to playing a blank CD. The tuner's signal would have to be completely severed when you wanted to use your auxiliary input.

 

To cut a long story short, I disassembled my factory head unit, got it wired up to run on my "test bench" (a.k.a. dining table), and tracked down where the left and right channel signals came out of the tuner -- as was no surprise, these signals could be found on couple of solder points directly underneath the shielded metal box into which the antenna wire disappears. Counting from the back of the radio forward, these are pins 5 (left) and 6 (right). (For the curious, pin 4 appears to be a monophonic signal which, in this Subaru system, doesn't get used.)

 

http://www.shetline.com/subaru/subaru_aux_mod.jpg

 

http://www.shetline.com/subaru/subaru_aux_mod_close.jpg

 

The red x-es mark where two traces have to be cut to break the audio connection to the radio. Danger, Will Robinson! This obviously voids your warranty, as does the rest of what I shall describe. Proceed only at your own risk.

 

I could have been more diligent about taking pictures along the way, but at least no one has to look at my less-than-picture-perfect soldering and my inelegant use of duct tape. I also could have taken better notes on the disassembly and reassembly process, but for anyone with the adventurous spirit and warranty-defying bravado required to apply this aux input hack, I would hope what follows is sufficient:

 

1) Remove the sound system/climate control head unit from your dashboard. (You can find other threads in these forums outlining that procedure.)

 

2) Almost completely disassemble the head unit. There are lots of different screws of different sizes and types, so be careful to keep track of what you're doing so that you can reassemble everything correctly.

 

I didn't remove the vertically mounted circuit boards from the front control panel, nor did I do anything with the CD changer beyond getting it out of the way, but I did detach the front panel and take the rest of the radio box apart down to having the main PC board completely free. That degree of disassembly might not be absolutely necessary, but I think it made my work easier.

 

3) If possible, set yourself up so you can test your work along the way. I had a 12V power supply and a pair of speakers hooked up to the rear audio connector using alligator-clip test leads. With the main board propped up on top of a couple of books, I slid the front panel in place as needed to test the head unit. Without the support I used to match the height of the main board to the height of the two connectors on the front panel, I think it would been far too easy to slip up and snap one side and/or the other of those connectors right off their circuit boards.

 

Both BAT and ACC have to be connected to +12V for the head unit to operate. For reference, here are the pin-outs for the rear panel audio connector:

 

http://www.shetline.com/subaru/subaru_audio_connector.png

 

4) Cut the traces as marked in the picture above, which shows the underside of the main PC board. This cutting, and the soldering that follows, must be done in a very small, tight space, so magnification and good lighting are highly recommended.

 

5) Solder wires as leads to the four solder points indicated above. I used an eight-conductor strip of ribbon cable, with every other conductor being connected as a ground lead. The big solder pad in the upper right of the close-up shot provides a convenient place to get a ground connection.

 

6) Loop these wires around the front of the circuit board. At least with the ribbon cable I used, there was adequate clearance to run these wires around the front edge of the board after the front panel was re-attached.

 

7) From this point on, one could do a number of things. My quick-and-dirty solution was to use a 12V DPDT relay (which is a little bigger, just over an inch in length in the longest dimension, than the current online spec sheet indicates) for signal switching.

 

http://www.shetline.com/subaru/subaru_aux_in_schematic.png

 

Inside the unit, I mounted the relay on a small pre-drilled circuit board and used a bit of duct tape to gather the wires together and to prevent any exposed leads from shorting with the rest of the head unit. The relay and the wiring fit comfortably in empty space that was available between the top side of the main PC board and the bottom of the CD changer.

 

I brought RCA phono leads out of the back of the unit as shown below, and used the same switch to control the aux input that I'd already installed before to turn my FM modulator on and off.

 

http://www.shetline.com/subaru/subaru_aux_in_back_view.jpg

 

(My antenna lead looks different than usual for an '05 Legacy because I'd previously modified it to have a standard Motorola antenna connector.)

 

Here's what it all looks like all put back together and in use:

 

http://www.shetline.com/subaru/subaru_ipod_in_use.jpg

 

http://www.shetline.com/subaru/subaru_ipod_in_use_close.jpg

 

 

I am SOOOO much happier with the sound of my system now than I was before -- it's a night and day difference to me. And while I won't knock the CD changer solution -- it's far less intrusive and risky to do -- I'm glad that I won't have to mess around with playing a blank CD just to play my iPod.

 

This set-up works almost identically to the way things had worked before for using the wired FM modulator, with the main difference (besides vastly better sound) being that it doesn't matter at all what station the radio is tuned to, or even if it's AM or FM. I just turn on the radio, flip the switch in the cubby hole to the ON position, and let my iPod play away.

 

Three caveats:

 

1) I ended up adding in an isolation transformer between the new aux inputs and my Belkin iPod adapter to get rid of some ground loop noise. Even without the transformer the sound quality was much improved, but the isolation transformer really helped clean up the noise floor, and at least to my ears had little effect on sound quality.

 

2) The relay switch kicking in and out can create a loud thump on your speakers. A design using a solid state audio switch, rather than a primitive relay, would probably eliminate this issue. Grounding resistors on the new aux inputs (not sure what resistance would be best offhand) might also help. One can simply turn off the radio before flipping the switch or before turning off your car to avoid the thump.

 

3) If you're using the built-in Subaru CD player, you may need to turn off the aux input switch, otherwise the head unit will gladly play both sound sources blended together at the same time. Apparently the design of the head unit relies on shutting down the radio or muting its outputs rather than disconnecting the inputs from the radio.

Verrrrry Interesting.

Very nicely done... I have none of the required balls or experience to start this project myself - but I was always skeptical of using a blank cd. I'm currently suffering through an fm-modulator install, and when I have enough emergency money to replace the radio I'll most likely try what you've done here.

 

If you ever take your radio apart again, it'd be great to see your solders (good, bad or ugly - wooeee wooeee wooo, wah wah wah).

 

thanks for the post

I've never understood why something similar to this couldn't be done with the other mods. Why isn't it possible to include a switch to cut out the input sound on the plug and play mod that Jazzymt made? I still think that you get the occasional 2-second cut out though if it switches cds. Not sure. But regardless, I think we're getting closer to a more realistic plug'n'play solution that i'd be very interested in.

(good, bad or ugly - wooeee wooeee wooo, wah wah wah)

 

 

That took me a sec to grasp, but now I'm laughing my ass off. Didn't think that could be done phonetically.

Very neat, but since I limit my soldering to a pistol-grip 1500 watt soldering gun, I should probably not try this...

 

Nice work.

This is almost exactly what I did. Tha main difference is that I didn't cut the traces on the PCB - I used a solder sucker to remove as much solder as possible from the tuner pins and then levered them out of their holes. I think I could put them back if a warranty issue came up.

 

I also used an isolation transformer to get rid of ground loop hum, and I also get the thump when switching the relay (though not bad enough to need to switch the radio off). I was going to play around with adding a shunt diode and/or more sheilding to reduce the thump but decided it wasn't bad enough to worry about.

 

I mounted the switch and RCA jacks inside the center console instead of the top cubby.

 

Unfortunately, this method is only for people who are comfortable with delicate soldering and who don't mind potentially voiding their head unit's warranty. I don't see a way to make this solution "plug and play" - the other two solutions on this forum are better in that regard.

What do you want to bet that some of those "missing components" on that board lead to other inputs, like tape/dat/sat/etc which we don't get..

What do you want to bet that some of those "missing components" on that board lead to other inputs, like tape/dat/sat/etc which we don't get..

From what I saw, this doesn't seem too likely.

 

The audio circuitry in the '05 head unit doesn't appear to include any actual audio switching capability. It appears that the tuner outputs and the CD outputs simply merge through a passive network -- much like the passive network used in the CD changer-based iPod mod -- and the only reason you don't end up listening to mixed audio sources is that playing a CD shuts off the tuner, and using the tuner pauses or turns off the CD.

 

Any decent design for handling a wide variety of inputs would need some active signal switching capability which isn't there.

It would be interesting to directly compare the OEM MP3 unit found in the high-end Outbacks with our stock ones and see if there's another spot to tap. Nice work with that method, though.

Th3Franz ... yeah, I always wonder too, but seeing as I've already shelled out over 600 clams for my VDC headunit ... I don't want to do any experimenting on it!

went ahead and move this to the walkthrough forums, nice writeup!

If this is not the right place to post this, delete this topic.

 

I might be interested in doing this for people, but didn't know what people would be willing to pay for it.

 

This is how it would work.

 

1.) I modify my radio similar to the way it is listed above except that I would modify the 4th position (aka Sat button) on the CD/AM/FM button to be the switching button.

2.) Pay me the agreed upon amount ship me yours. After receiving yours, I send you the modified one.

3.) Get the modified one back and enjoy!

Nice work! I can see several variations on this theme. (personally, I am happy with the blank CD trick).

 

Mods, this should be moved to interior/audio with all the other line-in solutions.

 

Craig

1.) I modify my radio similar to the way it is listed above except that I would modify the 4th position (aka Sat button) on the CD/AM/FM button to be the switching button.

Does this actually do anything from the HU's perspective (i.e. says SAT and mutes other inputs), or are you just pirating the button position?

I would just be hijacking the button to use for mine...it would still say FM/AM but would bypass that audio for this instead...

So you don't have a radio anymore?

So you don't have a radio anymore?

My radio works just fine.

 

If I turn off the switch I installed (you can see the switch in one of my pictures, in the lower right corner of the dashboard cubby -- I've also diagrammed this switch schematically as well) I get the radio, if I turn on the switch, I get my iPod. In the off position, the relay re-completes the original connections which are broken by cutting the marked traces.

 

Further, having the radio running would be the default condition if I removed the connection for the external switch.

Again, I ask, is there any reason this concept couldn't be incorporated in Jazzymt's ribbon cable plug'n'play set up? Would it not generally work the same way? Or would it only work with the CD player?

 

Thoughts? Anyone?

Jazzy's only works on the CD because it uses the Ribbon Cable. He could do what I did and have it switch the audio between the CD and the "iPod/RCA" input and you wouldn't have to use a silent CD, but you would still get skipping at the end of a CD when it repeats or changes CDs, but not between tracks.

Is the tuner in/out trace located before or after audio amplification, in simple when you connect your ipod, do you still have control of the volume knob on your stereo to control the line out level of your ipod?

It's before the pre-amp and amp stages... you can treat it as a line-level input. The volume and tone controls on the Suburu head unit function as you'd expect to control the sound of your iPod.

 

Now, whether or not your iPod's volume control has any effect depends on how you hook up your iPod. If you simply used the headphone output from your iPod, the iPod's own volume control would also, additionally affect playback volume.

 

In my case, I'm using a Belkin iPod adapter, one that plugs into the iPod's dock connector. The adapter powers and recharges the iPod, and has its own audio output with its own volume control, independent from the iPod's own volume setting.

 

What I did was adjust the Belkin volume control so that the volume of music from my iPod was approximately the same as the volume from an FM radio station, while keeping the Subaru volume control in the same position and switching back and forth from FM to iPod. Once that adjustment was done, I put a small piece of duct tape over the Belkin volume control, and hid the whole adapter inside my dashboard, and then, from that point on, iPod volume is controlled solely using the volume control on the Subaru head unit.

Very neat, but since I limit my soldering to a pistol-grip 1500 watt soldering gun, I should probably not try this...

 

Nice work.

 

what, no ColdHeat???

I am going to run a PC using Win XP MCE 2005. It is easier to control volume when you have a knob than it is software based. Now, with this connection, you said you can be on either FM or AM and the audio be the same as AUX in right? Now you also mentioned some groundloop problems, what isolation transformer did u use?

 

As for the switch to change from FM to Cd without iPod Line leak, i think there should be a trace point on that board that goes active low/high when AM or FM is chosen, you could possible use that to automatically drive the switch.

Now you also mentioned some groundloop problems, what isolation transformer did u use?

It's one I'd bought at Radio Shack years ago for an in-house ground loop problem between two stereos. I think there's a comparable model still available. It's a little bulky compared to some isolation transformers I've seen for car use, but there's a fair amount of room in the cavity behind the head unit for using the larger form factor.