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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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Discussion Starter #1
This should work on late nineties NON Bose HU’s…

Open you stereo and look on the motherboard for a TQFP32 chip with the following print ZPLA774 and a ST logo on it. If you got it keep reading.

This chip is the audio processor of your HU. The actual part number is TDA7342EQ2N, here is the diagram.
How it works:
The chip has two stereo inputs per channel plus one mono input and one quasi-differential input. The sound signal coming from the radio, CD changer and tape player is selected based on the input from the “SOURCE” button (this is the mixer module of the chip). The selected signal is directed in the volume control module and bass/treble adjustments. Then the signal is sent out to the 4 outputs (2 x rear/front). All adjustments are done based on the control signal received from the HU processor (on I2C communication bus).
Enough with science, now what do you need:
Tools:
- Soldering Iron and Soldering Wire;
- Ohm meter;
- Flat head screwdriver;
- Knife;
- Sockets/Ratchet/Extension;
- Long nose pliers;
- Steady hand;
Parts:
- 3.5’’ - 3 conductors female jack connector with two normally closed switches connected to the contacts themselves (i.e. should have 5 pins not 3);
- Low signal shielded wires (like the one from your headphones or RCA cables, preferable 4-wire cable with braided shield).

Steps:
1. Remove your stereo from the dashboard (procedure varies from model to model);
2. Remove the upper stereo panel cover;
3. Remove the tape player mechanism by removing the 3 screws and the two connectors;
4. Locate the audio processor: a TQFP32 format chip (i.e. square with 8 pins on each side), about ¼ of an inch big, usually covered in silicon with the ST logo and ZPLA744 print. On Seville HU’s is located in the front/left side of the board and on Catera in the middle.
5. Clear the silicon covering the chip and the surrounding area (use a knife and be very careful);
6. Locate the pin pairs 2, 3 and 15, 16 (use the pins description page 6 in the diagram). If between the pin pairs is a capacitor (100 nF on Seville HU’s) then disconnect the line between pin 3 and capacitor (same with pin 16) by scratching it with the knife. Be very careful this is a very delicate operation. Use the meter to make sure that you have no more continuity between the capacitors and the corresponding pins (3 and 16). On Catera, just scratch the circuit-connecting pin 15 and 16. Pin 2 and 3 connection is under the chip, so in this case desolder one of the pins (be very careful not to bend the pins, they break very easily).
7. Locate a ground connection close to the audio processor (using the meter) and now solder the braided shield on the ground (if you have more wires connect all the grounds together). Then connect one wire to pin 3, one wire to pin 16 (direct connection) and the other two wires on pins 2 and 15 (on Seville connect the wires before the capacitors: serial connection and not directly on pin 2 and 15).
8. Use the meter to identify the pins for left and right channel on the 3.5’’ jack female connector. Usually the outer most pins are the outputs and the inner pins are the inputs (ground is the one in the middle). Connect wire from pin 3 to the Right channel input pin of the connector. Connect the wire from pin 16 to the Left channel input pin of the connector. Connect the wire coming from pin 2 (on Seville from the capacitor connected on pin 2) to the connector’s right output pin and the one from pin 15 to the connector’s left output pin.
9. Test with the meter for continuity. When no male connector is inserted in the female connector, you should have continuity between the wires for the left and right channel. When a male connector is inserted you should have no continuity between but wires coming from the female connector outputs should have continuity with the corresponding channel core wire from the input cable. On Catera due to the fact that you have no capacitor in serial connection with pins 2 and 15, you might have the input signal level to high (resulting in distortions). In this case you have to insert 2 100nF capacitor in serial connection on the core wires from your input cable (one for each channel). Seville already has the capacitors so the signal level is perfect (no need to add the capacitors).
10. Is your choice where to place the input connector (stereo fascia, glove compartment, etc.). I will not insist on this aspect.
11. Follow step 1 to 5 (in reverse order) to put everything back and ENJOY.

Follow the diagram, is much more comprehensive than 100 pages of tutorial.

When you insert a male connector (let’s say coming from the Ipod) the mixer output signal is interrupted and you will hear on the speakers the signal from your Ipod. You have full control over the volume, bass and treble (including the steering will controls). The quality is the best you can get as good as the one of the CD changer adapters only that you will keep the option of having a CD changer.

Warning! :thehand: If you don’t have experience with electronic devices this is NOT a job for you.
 

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1995 Sedan Deville Spring Edition
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268 Posts
Wow,

Nice write up and pics. I admire your ingenuity, as I have been know to do mods like this from time to time. I modified the IPC in my 95 Deville to add steering wheel controls (not factory offered until 1996) and it was a major project. Obviously, this isn't for everyone (it does require some skill and a certain comfort level to do) but this kind of project can be rewarding for the satisfaction of doing something so useful without spending a ton of money on adaptors, aftermarket heads and amps, etc.

KDirk
 

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'97 Seville STS
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162 Posts
Holy crap N*Caddy that is freakin' awesome! You mofo's are getting savvy out here. I'm probably going to try your suggestion.

How did you figure out the pin numbers for the ICs, like the TDA7342EQ2N for example?

I wish I would have known about this forum earlier. (I'm here now because of trouble w/ my shocks). Previously I did some mods on my radio, and I had to figure out that the TDA7342EQ2N was the audio processor and then discover pins and various signal properties by trial and error with a broken O-scope and DMM. (I took a look at the pdf for the TDA7342EQ2N, and it verified some of what I determined empirically -- that's a relief).

I don't think I could have ever "discovered" how the aux inputs work though. That is nifty.

(My mod was to tap into the pre-amp output prior to the power amplifier ICs, and use the signal for an A/D with S/PDIF optical output (TOSLINK); below is a link to a write-up w/pics: http://www.rockfordfosgate.com/forum/topic.asp?TOPIC_ID=28139)
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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6,405 Posts
Discussion Starter #4
Hello Wachuku,
The audio processor is pretty easy to spot by examining the board. You will locate the final stage amplifier, the radio board, the tape (witch is the most obvious), the controller and then you will see that the sound tract goes towards the TDA7342EQ2N. The easiest way is by following the sound signal from the tape board. Then by simple logic you will pretty much figure out the pin layout (outputs are the easiest one). I will say that the pin layout I figure-it out about 80% before finding the chip schematic. These devices are pretty well designed and easy to “read”.

Oh yea, I see what you did, pretty nice!
 

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95 Fleetwood Brougham / 01 DTS / 11 CTS Lux / 11 DTS Platinum
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7,085 Posts
Very nice. Can we do such a thing on a 2000 + Bose with NAV?
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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6,405 Posts
Discussion Starter #6
UPS… I just discovered an error on my diagram (“Aux imput.jpg”), please note the channels are swapped (left with right). The text description is correct just the drawing is wrong. So I posted the CORRECT diagram one more time (including file name spelling).
Aux input.JPG
As for 1998 and up I wish I would have a diagram or some high quality pictures with the stereo’s PCB so I can figure out what’s going on. I know that some come with an AUX input jack in the glove compartment or something (not sure witch one maybe somebody will enlight me here:hmm:).
On mine I placed the input jack in the ashtray below the cigarette lighter. I also placed an LED next to the jack witch is changing color when the jack is in from red (on - while stereo is on) to a bluish green (somehow matching the dashboard display color). I obtained the color by combining green and blue and having a control over the intensity of each color (you will see in the pictures some two round trimmers). It has nothing to do with the Aux input functionality is just a gismo.
Jack Mount.JPG
This weekend I replaced all the light bulbs from the stereo, climate control module and doors with cold white LED’s. I will try to describe all in a thread it’s awesome (but is an over 12 h job!).
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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Discussion Starter #7
Just in case you stumble upon this thread and you have a BOSE sound system, a hard wired auxiliary input mood is easier since you don’t need to open the HU. I have described here in this thread the way you can get it working for BOSE. Is good for all ‘96 and up (<’04) BOSE equipped vehicles.
You don’t sacrifice anything (i.e. the CD changer stays) and the quality is as good as the input you provide.
Probably when the time will allow me I will unify both in one thread.
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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6,405 Posts
Discussion Starter #9
Where are you located?
If near Toronto just drop the HU one Friday afternoon and you got it until Sunday, for free just pay me the parts (~$5) or I will tell you what connector you need and where to get it for. Or you can ship the HU and as long as you pay shipping both ways + ~$5 for the connector you will get it after one weekend.
But if you are confident with the soldering gun I can assist you via PM or e-mails, is not a big deal.
What king of stereo you have BOSE or base?
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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6,405 Posts
Discussion Starter #11
Uhh, Florida is nice and beautiful, maybe one of the best places to live in the world but unfortunately is also far from me (thus shipping will cost you an arm and a leg).
Find a friend that is proficient with a soldering gun and I can help you two to have it done. Again what kind of sound system you got BOSE or base? If is BOSE you don’t have to open the HU, is just a mater of making a harness using a set of Wal-Mart connectors (the harness does involves soldering though).
 

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Deville
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50 Posts
I dont have the bose.. I have the regular one... Funny thing, everywhere online it says I have 5.25" speakers in the door... But It has Factory Seperates... I have a tweeter mounted 2 inches abover the speaker is that normal?
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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Discussion Starter #15
NOOOOOOOOOO!
That's not it!
You need a PCB mountable 3.5 mm jack with 5 pins (or more).
This is the EXAT 3.5 mm female jack connector w/switch you need. This will provide the minimum audio switching requirements.
Click on the picture for the actual link

The side with the pins is considered the bottom side. So left picture is bottom view (pins) and the view from right is top view. Then the front of the connector is the side where you insert the male connector (the one with that ring). Let’s concentrate on the left view. You see 5 pins in this configuration:
_____________
|..A……………….|
|…………….….B.|
|………………C...|
|..D……………….|
|…………………...|
|…….…E…..…….|
|___.........___|
......|____|

Just try to match the pins on the left picture with the letters by rotating the connector ring-down (ignore the dots, is just a trick to position the letters on the line because the text editor can not accept TAB or SPACE characters).
On my diagram above:
E – is COM (or Audio -);
A – is LEFT channel IN;
D – is LEFT channel OUT;
B – is RIGHT channel OUT;
C – is RIGHT channel IN;

This is only available for this particular connector, the pin layout can be different from connector to connector (but generally from my experience the outside most pins are the outputs). Bellow is a picture of the 3.5 mm male jack stereo connector (the one that you will insert in the female connector).
This is the same connector as the one from your Ipod headphones for example. Now observe the small metal tab springs in the right view and think how they move when the male connector is inserted and you will understand why I said what is A, B etc.
So in the male connector picture you will notice the actual connector has 3 sections separated by 2 black rings. The tip of the connector is the left channel (+), the middle section is the right channel (+) and the other section (larger, towards the jacket) is the common (-). Every time I am referring to LEFT or RIGHT and is about audio I am referring to the channel (i.e. the channel that you hear in that side speaker) so is not the left or right side of the connector (just to be clear on this).
F - LEFT audio (+) - tip of the connector
G – RIGHT audio (+) – Middle section
H – COM audio (-) the larger section near the jacket


Here is how the female jack connector works:
If no male connector inserted then A is connected to D and B is connected to C.
Inserting the male connector in the female connector A will be disconnected from D and F will be connected to D, and B will be disconnected from C and G will be connected to B.
Here is a simple diagram:

Male connector OUT:
Left channel:
A connected to D while F is not connected
Right channel:
B connected to C while G is not connected
COM:
E not connected to H

Male connector in:
Left channel:
F connected to D while A is not connected
Right channel:
B connected to G while C is not connected
COM:
E connected to H

Based on the above due the math and see what is connected to what in terms of female jack pins and sound processor chip. Also notice the outputs from the female jack connector for the sound processor chip are inputs and the other way around (again do not confuse, always output goes to input and input goes to output, you can connect 2 or more inputs together to one output but never the other way around).
As for the audio processor inputs (pin 2 for Right channel and pin 15 for Left channel) notice the connection goes in serial with a capacitor. Also now I notice another error on my last drawing: swap the left channel input and output at the female jack connector.
When you open the radio you will notice the SMD capacitors connected between the pin 1 and 2 and pin 15 and 16. You need to break the connection (using a needle or a very small flat head screwdriver - the kind you will use to repair a wristwatch) between capacitor and pin 16 and between the other capacitor and pin 3. Then solder the wires one on the capacitor side and the other on the pin side (for each channel).

Here are other examples of female jack connector that will work for you:



Click on the picture for the actual link
Notice the 5 pins!

Personally I would recommend you the last one. You can also see the specification sheet (very, very easy to understand).

If you need one that also turns on an LED or something on the radio display (like I did in this radio bellow turning on WX when an aux audio device connected) then you will need one with 3 more pins (i.e. 8 pins). The 3 pins are just for a switch that will control your display (or what ever function) is not electrically connected with any of the audio pins but it is linked mechanically so will switch in the same time with the audio switches.


If you need to hack the display chip so it will display something that you want like "A IN" (when the aux connector is inserted) I can supply any information you need (is just very laborious work for that) this is why I only modified to show WX (only one bit). But everything is possible providing you have time. Also you can use mini relay to do the switch (if you want a fancier solution, since here why not a time delayed and just go nuts with your imagination). But seriously to have some LED on or a letter on your base display (BOSE is a lot more work because the display is made of pixel like segments but same idea) is not such a big deal.
Above is the OFICIAL pin layout for the audio processor (is not done by me is the manufacturer). Click on the image to see the chip’s specifications.
This should only concern you if you have base sound system. If you have BOSE (non-NAV) then read up to picture and after that follow my link to the BOSE setup. You will see that the in/out of the chip are replaced by HU outputs and RIM inputs. Is relatively a simpler setup can be done with an extension harness.
OK, enough electronics for now. This should be detailed enough to be able to do the aux input. If you truly understood the above and you are good with a soldering station then good luck. If not please DO NOT attempt!

Also I have to mention I only tried on ‘96-’97 Seville/Eldorado with the HU pictured above (NON BOSE). I did not tried the BOSE solution but I know it should work based on the system diagram (same assumption I had for the one I tried).
This is also possible for ’95 and older base stereos (I have seen it done) but I don’t know the details (although I believe is the same audio processor since pre ’95 BOSE rims are using the same idea chip).
 

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09 silverado CC,SRX (N*), 07 Silverado crew 4X4, 2000 Impala
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Hey N* Caddy I'm so happy to see this post, I NEED to do this to my SRX to hook in my SIRIUS, and oh yea 19 year old son want's Ipod to function. Now the Sirius has built in FM transmitter but much prefer the jack.
I have the 6 CD changer with BOSE, how hard what do I need to do?
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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Discussion Starter #17
Hey Jake,

I am not very familiar with SRX (unless is SRX with navigation). But if you have a RIM then is the same setup, maybe not compatible, but the same setup as BOSE Sevilles/Eldorados. In witch case follow my BOSE thread for how to make the adapter harness. I don’t know the pins on a SRX but as long as you know which is audio left/right/COM you are all set.
Another idea (simpler) is to connect the jack connector on the CD changer harness (if the changer is remote) and you will have AUX input while on CD Changer mode (the CD changer will work but once you insert the AUX jack instead of hearing the CD changer you hear the aux signal). The CD changer has Audio Let, Right and COM wires, shield wire, 12V supply, 0V and the data wire. You insert the connector on the audio wires.
So in terms of solutions you can either tap on the audio signal wires between the HU and RIM (and you can listen to aux device instead of HU – i.e. anything but CD changer) or tap on the CD changer audio wires and you can listen to aux device while on CD changer mode). Off course once the aux jack is unplugged you will go back to listening the HU or CD changer signal. All these with full volume, Bass, Treble, Balance and Fade controls (including steering wheel).
But as mentioned I am not familiar with the SRX setup, I have good reasons to believe is similar with Seville in which case is as described above.
 

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Deville
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Instead of doing all this hard soldering why not just use the wires that go to the tape deck? The input has to go to the tape deck does it not? The tape deck has 8 wires on one connector and 14 on another...

 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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Discussion Starter #20 (Edited)
I took the liberty of using your picture as a didactic material, hope you don’t mind.
Yeah sure you can use it I can even tell you the pins (see the picture bellow).

Pins 2, 6 and 8 are GND
Pin 5 is LEFT TAPE AUDIO OUT (+)
Pin 7 is RIGHT TAPE AUDIO OUT (+)

As you can see in the schematic LH tape channel goes to LH INPUT 1 on the sound processor (PIN 13 – via a capacitor) and RH tape channel goes to RH INPUT 1 on the sound processor (PIN 7 – via a capacitor).

But think about it, if you insert your AUX INPUT connector on this lines (see the red lines on my diagram) as follows (consider the notations I used above):

PIN E (COM) connected to either of the GND pins (2, 6, 8)
PIN A (Left CH IN) connected to pin 5
PIN D (Left CH OUT) connected to PIN 13 (INL1) of the audio processor (via the capacitor)
PIN C (Right CH IN) connected to pin 7
PIN B (Right CH OUT) connected to PIN 7 (INR1) of the audio processor (via the capacitor).

The AUX in will ONLY work while ON TAPE! If you like it like that, I mean no problem is easyer, just insert the connector on the banner cables (keep in mind this time B goes to 7, and C connects on the piece of wire coming from the tape module, while D goes to 5 and A goes to the piece of cable coming from the tape) think about it!
What the %$$%%$ I am sure you don’t understand so here is another diagram:


Just note A and B use to be one wire same as D and A (see circled yellow).

But if you want to have AUX IN no matter what is the radio on to (RADIO/TAPE/CD) then you have to use pins 2 and 3 (Right channel) and 15 and 16 (Left channel).
Looking at your radio board, locate the audio processor chip (see in your picture is surrounded by a light green circle). The audio processor pins are matching EXACTLY the diagram in the left of the picture. If you carefully check your PCB you can see the tract going from pin 15 to pin 16, but you can not see the one from 2 to 3 because is under the chip (as shown in the pictures – thick black line).
Here is the CORECT diagram:

In order to cut the tract between pins 2 and 3 you need to take the chip off. Is pretty complicated job and you might end up breaking some pins or damaging the PCB (this is for the professionals with proper tools). So your best option is to de-solder one of the pins and lift it slightly off the plate (make sure you don’t break-it) this way the contact between pins 2 and 3 is interrupted. Needles to day you need an EXTRA small soldering tip (something like a thick needle) and the wires to use are no thicker than the ones in that tape banner cable.
This EXACT layout pictured above is ONLY valid for the ‘98 and up radios, the ’96 – ’97 (non-THEFTLOCK) radios have a different plate layout (see the blurry picture bellow).
These radios have the SAME chip but the tract between pins 2 and 3 is not under the chip (so is easier to modify). But these radios have a capacitor between the pins 2 & 3 (right channel capacitor) and 15 & 16. Connect as shown on the diagrams from page 1 (capacitors on the inputs pin 2 and pin 15).

To hack the display (OPTIONAL) here is a prelim diagram so you can get an idea:

WARNING! The above connections (to the auxiliary female connector) are only as an EXAMPLE. Chances are the pins are different between manufacturers (see some of the variations in my previous posts). You have to figure out yourself witch pin is what (whit an Ohmmeter). I explained in one of the threads, should you not be able to figure out let me know I can help (but you need an Ohmmeter).
 
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