OverLOAD

Several possibilities:
1. your audio input level is too low or high. Try adjusting the level of your source device to find the ideal level

2. you've got a ground loop causing interference. If you can run the device on battery power only (car-not-running) and the noise goes away, that's the problem. A ground loop isolator will fix that, but may be expensive, and/or hard to find. Radio Shack will usually carry them

3. you've somehow messed up the wiring and connected a signal to the gound and a ground to the signal. Recheck your wiring to make sure that your wires are going to the right places. This would likely sound like there was just something wrong with the setup.

Check it out, maybe it'll be ok. Also, try using a different audio source device (like a portable cd-player) to see if it works with that any better..

Regards,

OverLOAD

ectomort

I got tired of waiting, and didn't want to rely on the cassette module, so I opened up the headunit itself and patched in to the CD output channels. (Kudos to OverLOAD, l8r and others for their valuable information.)

It wasn't too risky or hard (some simple soldering), it doesn't require any additional modules, cost about $10 (for the minijack extension.) The technique will work for either the Bose or base head units.

The result: seemless integration and perfect sound from my iPod. Next, I plan to figure out how to pass the steering wheel controls to the iPod's wired remote input.

I'll post more info on what I did if anyone is interested.

MrWigggles

Please post the info.

As an electrical engineer who does a lot of circuit design and testing, I would recommend that just trying to inject a signal into a signal stream isn't the best of ideas.

Sometimes it will work fine other times you might damage something or get poor results; it really depends on your MP3 player and its output impedance. The iPod is probably robust enough in design to not cause any problems but other MP3 players might not like the forced mixing connection.

Please show us what you did. (detailed shots of the ciruit board would be nice with part numbers. I'll try to make some comments on them.

Thanks in advance.

-Mr. Wigggles

OverLOAD

That reason, in particular is why the tape module hack doesn't sound as clean as it could. If you connect into the expansion connector, you might be able to get a better signal, but it's the same thing, the module has to be completely disabled from it's original function, and doesn't work the way it used to.

Ectomort, It sounds like you've got decent results, but I'll bet if you disconnected the audio outputs (cut the CD audio source traces) at the point before you tapped in, you'd get even better sound, at the expense of loosing a functional CD module, then you could play any CD, and the source wouldn't mux into the stream

It could be dangerous to the head unit if you pumped up the volume too much though.. be careful.

Still working on a Plug and Play solution which integrates with the radio.... and getting closer.....

OverLOAD

ectomort

Here's a description of how I patched an auxiliary line-in to the head unit. I have the Bose head unit, but I'd be surprised if this approach doesn't work for the base unit, too.

Follow the standard instructions (posted elsewhere on this forum) to remove the audio assembly from the car and separate it from the control-trim panel.

This picture shows the audio assembly from below (the lower module is empty.)



Turn the unit over. Detach and remove the upper module (CD/MP3/CD6 player) from the assembly.



Remove CD module front plate (thing with the black felt dust guard) according to the instructions printed on the top of the CD module.
To expose the head unit circuit board:[list=1]
[*]remove 2 3mm short phillips screws from front of unit
[*]remove 2 5mm screws from bottom of unit
[*]remove 2 5mm screws from rear of unit (back plate will come off now)[/list=1]

Gently pry off the head unit cover plate to expose circuit board and remove the right (on the left in the photo) side plate to expose CD-head unit PC board.



On the left side (not visible in this picture) is a little board which connects signals from the CD module connector to the head unit's main board.

I'm sorry the next picture isn't clearer, but it shows a closeup of the head unit from the left side, the green board connects the CD module connector to the main head unit circuit board. (You can see a portion of the pink sticker in this photo that also appears in other images I've posted.)

I've added a diagram which shows the various lines (labeled as they were printed on the board.) I've marked the locations where I patched in in green. There are no electronic components on the board, so it's relatively safe to solder there without risk or heat-damage to components on the head unit itself.



I purchased a stereo minijack extension cord and snipped off one end, leaving the male plug end to connect to the line out from my iPod. Then, I threaded the cord through the hole in the frame near the pink tape. (It's important to use this location, so that the cord is not crimped when the audio assembly is re-installed in the car.)

Next, I prepared the end of the cord, stripped and tinned the wires, and used the continuity test function on my digital multimeter to identify the left and right channel and ground wires. (On a stereo mini-jack, the tip is left channel, middle is right, and the base is the ground.) Then I soldered the cord as shown above and used the continuity tester to verify a good connection between the male end of the mini-jack and the corresponding lines going into the main circuit board. It's a shame the picture of the final solder job didn't turn out.

I then reassembled everything. Here's a picture of the nearly complete assembly showing the patch cord.



And here is the iPod in the car. I use a Monster Ultra-Low Profile Charger for iPod™ with Dock Connection (http://www.monstercable.com/computer...r.asp?pin=2132) which gets power from the accessory outlet and attaches to the iPod's docking port. It provides line level output which the patch cord plugs into. There's no risk of blowing to the head unit with the signal, since the iPod's volume control doesn't affect the line output. The adaptor includes a voltage inverter, so there isn't any noise from ground looping. I get perfect sound.

The patch signal source merges with the CD player source, and the head unit won't accept input from the CD player unless it's playing a CD, I've burned an audio CD which contains nothing but silence (I call it 4'33" extended remix, a tribute to John Cage.) When that CD plays, the iPod effectively owns the audio channel. The CD player auto repeats, so every 80 min or so I have to tolerate a 2 second dropout while CD cycles. Since my iPod has over 7200 songs on it, I won't often need to pop in a normal audio CD, but as long as I turn of the iPod, there's no problem.

ectomort

I'm a software engineer with a bit of EE background. I didn't check on the input impedances, but since I'm dealing with a line level signal from the Monster adapter, and the results sound so good, I doubt there's any problem w/ my set up.

ectomort

As I posted above, the signal is line level (from the iPod's dock connector.) Should I plug into the iPod's headphone jack, I would have to be concerned with pumping too much signal through.

I use a "silent" cd to ensure only iPod is supplying audio.

I remain appreciative of your efforts to bring a custom module to market, since there are obviously many folks who won't want to open up their HU and tap it like I did. I just ran out of patience and decided to experiment a little.

yanksfan_98

FWIW:
A more significant consequence of this method is that you are now exposing your head unit to static electricity. Usually inputs like this would be properly ESD protected.

Admittedly, I don't know how the car would handle this, since the car isn't grounded anyway. And not that I have ever seen anything damaged by ESD, but i sure have been zapped while I was wearing a wool sweater.

speedmaster

First of all, congratulations for an ingenious and easy to be done solution albeit costly...

How is your sound quality? I've just installed my deck one day before you passed this instructions and I'm somewhat unahppy with the flat sound I'm getting from my IPOD. I have the same setup in my wife's Stratus and the sound is much better... I've even exchanged the whole setup IPOD+tape adapter (one each time and then both altogether) and the result didn't change. The Mazda tape head has far less treble than the one in the Stratus

I hope it is due to the head quality and that bypassing it will give better results. On the flip side if the whole circuit is built taking into consideration that the frequency response of the tape head is limited than it won't make any difference...

Would you let me know what do you think comparing the sound with a tape adapter and the direct connection you cleverly designed and implemented.

Thanks.....

OverLOAD

You can get near-CD quality sound, if you want to sacrifice ever using the tape module to play tapes again. It's not really that difficult, (if you've done some soldering before) but you have to completely disconnect the audio sources from the factory RX-8 connector, and feed your audio source directly into the HU. IT's possible to overload the circuit and blow the HU tho, so it's pretty risky.

I'm thinking about doing a small write-up next time I take my tape module out so that I can explain the process better. It's really very similar to what ectomort has done with his CD module.

Regards,

OverLOAD

spicedham

Well, I tried doing the CD Hack, and I think i messed up my HU pretty bad. I followed Ectomort's instructions, put everything back together, and then put the HU back in my 3. I tested out the hack but I was only getting audio out of my right channel from my iPod, however, the rest of the stereo was working fine. So I removed the head unit again, took it apart, and tried re-soldering the ground and left channels. I put the HU back in my car, but the unit was dead - no power, nothing lightning up. So I took the HU out again, took it apart, and removed the soldering. Put it back together, and put it back in my car. Now the HU powers up when I turn on my car, the front panel lights work, and the stereo makes the beeping noises when I use try to use the steering wheel controls, but other than that, the HU is still not working. None of the modes (radio, cd) work and the display, though backlit, remains blank (no Hello! message). Any suggestions, or am I going to have to bite the bullet and buy a new HU?

P.S.
I tried this hack because I had a long road trip coming up and couldn't wait for Overload's AUX IN module, which I still plan on installing when it becomes available

volboyjerry

Overload,

Thanks for this great information.

Even though the Icelink should be available in 3-4 months, I'm still going to do this mod today. UPS should be delivering the cassette module as I write.

I can no longer stand the FM option. This will hold me over.

RAM

If you do the hack, can you install the original trim piece so there is no cassette opening? Will it fit as a totally "invisible" install?

volboyjerry

Interesting question.

I suspect you would have to put a dummy tape in the player, then you might be able to install the trim piece.

I'll check it out and let you know.

RAM

Thanks. I figured I would have to install the dummy tape before I "enclosed" the deck. I think it would look better that way and you can buy the cassette module for about $50 less if you don't buy the trim piece.