View Full Version : Auxiliary input on a ’97 STS any suggestions?

12-10-06, 09:22 PM
I have the standard sound system that come with the ’97 STS and, as you all know, it has no CD player and auxiliary input. Well the CD part can be solved with the trunk mounted CD changer but still the auxiliary input problem remains. The options I got are Cassette adapter (boo), FM transmitter (boo) or FM Modulator (again boo!).
The only right way to do-it is to actually tap wires before the volume control (I did-it on simpler audio devices).
First I got a stupid question, if I remove the car stereo and connect it back (assuming is in the same state) will still work (I mean no security codes and other funny stuffs). Why I am asking this: I found somewhere the stereo removal instructions but with the following note: “Do not disconnect the wires!” (no explanation).
The second question: Has anybody done this or has the electronic diagram?

Appreciate any suggestion otherwise I will have to stick with a FMM100.


12-10-06, 09:27 PM
your car predated theft lock so youll have no issues unpluging it and pluging it back in so long as you clear the codes afterwards and before you ask how its been beaten to death do a search

no one has done this and unless you have some way of AMPING the sound signal it will sound worse than an fm modulator connecting it to your speakers..

if you have bose then your better off because the radio sends out a preamped signal which is amped by the 4 mini amps on each speaker, then you have to account for the fact how are you going to switch from one signal to another and block the non wanted sound source not to mention you need to find a way to remote power each of the 4 mini amps...

in english it will be a hack job to say the least, just upgrade and put an aftermarket set up in...

12-10-06, 10:23 PM
Thanks’ CadillacETC1997 for the unexpectedly prompt answer…waw!

So, I like the loooong and difficult solution. Maybe I was not clear enough, I am not planning to connect the signal to the speakers directly; I want to insert-it between the preamp and amp (before the volume control) because I want to have volume control from the HU.
I know is difficult because is a digital control, on a analogic device the project is pretty straight forward, just tap it on the potentiometer and you are good to go.

Is good to know that I have no security problem removing the HU (sometime is better to be less sophisticated) but on the other hand on a newer one you will not have this problem at all (the 98’s and up have the aux input in the glove compartment, dammit!).

Anyway, thanks’ man I learned something very useful!

12-10-06, 10:30 PM
98 and up do not have and aux in...
thats the 99-00 CDROM nav systems in sevilles and devilles that had that and Eldos NEVER had that....

if your looking for a simple rca input then why not just buy the adapter that plugs into the 12 disc changer plug and gives you a left and right audio....

there is NO way to run an between line source and control the volume via the hu
you need it to go IN to the hu then OUT to the speaks in order for the hu to control the volume
the hu does not act like a gain nob boosting the power of the amps, it acts more like a signal knob and boosts the sound signal volume before it goes to the amps...

and why not aftermarket?
its so much simpler and better sounding....

heres a pic of my car when i had my alpine hu in and then with my pioneer avic-n1 navi systems the sound quality improved 100 fold over the stock bose crap..
1st pic was with my gfs camera and 2nd with my cell phone so the quality kinda sucked

12-10-06, 10:38 PM
Aa, you asked how to remove the unwanted sound sources, is pretty easy, just use some switch female jack (just like the one in the picture). Sorry for the bad focus, I used my cell phone camera, but I think you got the idea.

12-10-06, 11:06 PM
Nice, touch with the LCD!

Ever since I bought the car I was thinking to go video, installing an actual computer (more likely an SBC) and a touch screen display to the car. I found one very nice idea on this forum (I said to myself “wow I am not the only one”). If I will find the time to start the “computer project” definitely I will write my own software (especially GPS, I have a lot of experience with this stuff). The drawbacks are: no more radio station display, the time required booting the computer, and I will still require an auxiliary input because I am keeping the HU board for the steer well controls and bell. Also I will loose the tape player (I know this are the 2000’s and I only use-it once in one year but still). Also, it will be extremely elaborated the software and electronics to control the radio (using the parallel port). Then again, you will have the DVD, the USB ports and GPS (Home made), mp3-s, rear view camera…

12-10-06, 11:32 PM
someone did a carputer in a CTS
you prob wanna contact them and follow up with them on how to do that
thats a whole nother realm from what i know lol

12-11-06, 12:15 AM
The RCA adapter connected to the CD Changer cable is excellent but it will eliminate the CD Changer option (not such a big deal considering that I don’t have one). Probably if I can not tap the wires this is the best solution.
Know a compatible one and a place to buy-it?

As for my idea, this is how I believe that the simplified - One wire block diagram of the standard HU should look like.
All I have to do is find the “red” spot.
Once again, a detailed HU schematic will really help a lot.

12-11-06, 12:20 AM
ebay has them all the time for like 100 bucks

12-11-06, 08:10 PM
I am :confused:

So you want a input after the hu and before the speakers? Just the plug I assume? How would you switch between the input and the hu? I would be worried about the quality of the input and the hu after the wiring is done.

I would say aftermarket but you were kinda clear on no...

12-16-06, 04:46 AM
Hi guys, I will try to be more specific…
Ok, so one more time, I need to insert a line level audio signal inside the HU BEFORE the volume control. Usually the signal level in that area is compatible with the line level (exactly what you would get from an iPod for example). By “usually” I understand all the audio devices (radios, tape and CD players) I ever opened.
I already posted above a diagram with how I believe the HU generic block diagram should lock like. The red spot in the diagram is the point where I am looking to connect my signal. The fact that the amplifiers are inside or outside the HU is just a minor detail; my signal will already be on line before the volume control (witch is upstream from the amplifier input). The sound quality is excellent (the best you can get) as long as the signal level is not to high (i.e. you don’t get signal from a high power amplifier). The signal switch part is the easiest thing in the whole project, like I said, just use a simple switch 3.5’’ female jack connector (check the “jack.jpg” diagram attached). The female jack is a simple mechanical device. When the male connector is off (1) the signal from “R in” and “L in” is directed towards “R out” and “L out”. Imagine that you insert this on the signal way (just before volume control) basically you would listen what ever is selected in the HU (radio, Tape or CD changer option). Inserting the male jack in (2) the signal from “R in” and “L in” is disconnected and the signal on “R out” and “L out” is the one coming from the male jack (i.e. your iPod).
Now, in an analog volume control based device the task is simple, you just insert the female jack connector on the potentiometer wires (see "diagram2.jpg").
In a digital volume control device, the connection points are not so obvious as in the analog version. A chip (usually having several other functions) does the actual volume control.
As my HU has a digital volume control, the task is not so simple WITHOUT A SCHEMATIC.
I would appreciate a schematic!


12-23-06, 11:36 PM
I just bought from e-bay a HU (apparently fully functional) witch I am planing to use for training just in case I fry/break something while working on my auxiliary input project.
Now I am ancient to receive-it (is on the way) so as soon as I have some results I will keep you inform.
Probably if all goes well I will end up with two HUs with a unique feature (one for me and the other one I will e-bay-it)…

01-15-07, 01:06 PM
OK guys, my HU I bought from ebay arrived a few days ago, and turned out to be from a 98 Catera (not 97 Seville as I would expected). I know they are not compatible but I hope that most of the sh*t inside is the same. The amplifier is a TDA7384A (4 x 35W QUAD BRIDGE) pretty common and straightforward to use (I got the diagram). The outputs (pins 7-9, 5-3, 17-19 and 21-23 in the order of channels) are going directly to the back connector (I did not note the actual pins on the connector). The inputs (pins 11, 12, 15, 14 again in the channel order) seems to come (passing to a 0.1 microF capacitor each) from a chip (AND THIS IS WHERE I NEED HELP). This chip I suspect to be the one that switch between the radio, tape player and CD Changer. The problem is that I CAN NOT FIND THE feacking thing on the Internet.
On the chip you can read:

I did not heave enough time and tools to draw the schematic from the board (as my meter is somewhere between Hong Kong and Canada) but from a visual inspection the outputs from the tape player and radio board seems to head towards this chip.
If someone out there has a diagram for this 200945 I would appreciate it.
And I keep you updated.

01-15-07, 01:50 PM
if you needed a 97 radio
i have my old one from my 97 eldorado ill sell you its just missing 2 of the knobs i gave them to my mom for her 96 deville...

04-30-07, 12:54 AM
Today we had a beautifully sunny day, so I worked on my auxiliary input project and IS WRKING! :thumbsup: (The sound is perfect and all I used was 7 - 20 AWG wires and one 3.5'' jack female connector w/o 2 sw.)
Now I have AUX input on my ’97 HU with no funny stuffs (like FM modulator/transmitter, cassette adapter or CD Changer-Aux. input)
For the moment is just a temporary set up (the connector is sticking on the upper left corner of the ashtray - see the picture), I still have to decide where to locate it (suggestions anybody?).
As you see in the schematics I inserted two NC switches before pins 7 and 13 sync. with the male connector insertion. This will mute the radio while the AUX signal is going to pins 17-18 (left) and 19-20 (right).
So far I have no HU volume control (other that MUTE when volume at minimum and ON at any other position).
I will have to use shielded cable between the AUX connector and the HU board (especially if I will locate it away and not on the front panel). Also I will try to relocate de AUX signal in such a way to take advantage of the HU volume control :stirpot: .
FOR THAT I NEED TO HAVE THE ZPLA744 DATA SHEET (I can not find it anywhere:rant2: ), if anybody has the diagram I will appreciate it :worship: (apparently is the same chip used in the ‘98 Catera HU’s).

One more time I will appreciate the ZPLA744 Data Sheet. :worship:

04-30-07, 11:48 AM
congrats i seriously tip my hat to you
if it was me i would of just bought the cd cable adapter which doesnt use FM modulation either.
ideas for the plug, ive seen people drill the hu for the plug, just make a small hole in the lower left or right and you should be fine

04-30-07, 08:24 PM
Actually on the upper left/right corners (on the same level with the EJECT/SIDE/REV-FF) buttons is the easiest way to do-it. On the other hand I am somehow attracted to the idea of having it located under the ashtray panel (I eliminate the wire dangling over the radio and climate control). Moreover I can manufacture/buy a 3.5’’ male/male connector that will hold the Ipod in like a pin. But I like the panel mount idea too, especially if I put a cell phone holder on the right side of the HU…
As for the CD-Changer cable … I still like to keep my option of adding a CD changer. The problem is that an OEM can only read CDA format, not very attractive idea in our Era, I am looking, more or less actively, for a CD changer with mp3 capabilities (something like a NeoCharger).

04-30-07, 09:08 PM
alot of companies make adapters which will plug in and allow you to control the changer through the factory hu

05-28-07, 03:09 AM
After analyzing every single audio processor chip diagram posted on ST site I finally found THE ONE. The actual ZPLA744 chip is TDA7342EQ2N. The chip has 3 inputs per channel (L/R) plus one mono (for the chime).
- Pin 5 = CD Changer R input
- Pin 6 = Cassette R input
- Pin 7 = Radio R input
- Pin 8 = Mono input (chime)
- Pin 11 = CD Changer L input
- Pin 12 = Cassette L input
- Pin 13 = Radio L input
The Mixer (controlled by I2C buss) selects the desired pair of pins and the signal is sent to:
- Pin 3 = Mixer R output
- Pin 16 = Mixer L output
The signal is feed back to the chip audio inputs:
- Pin 2 = Audio R in
- Pin 15 = Audio L in
And then the signal is processed based on I2C buss data (volume/mute) and:
- Pin 21 = Bass R in
- Pin 18 = Bass L in
- Pin 1 = Treble R
- Pin 32 = Treble L
As you can see in my previous post my inputs are on the bass input pins (this is why the auxiliary input volume is controlled by the bass knob). The volume control is done before the bass controls, so the volume knob has no effect over my auxiliary input (except for mute done on the outputs).
The pins of interest are 2 and 15, by disconnecting pins 3 and 16 from there and connecting my inputs (using 100 nF capacitors) I can “force” in the chip my own signal regardless of what is selected by the mixer.
Now, that everything is so clear having the diagram, all I need is time to do-it.

07-30-11, 03:17 PM
New poster here, Bringing this thread back from the dead. N* I have a Delco CD player I am trying to add an aux jack to. I have done this to older radios, by tracing the signal to the pre-amp. I am have having trouble with the new radio. Just wondering if you could lend a few suggestions.

08-03-11, 05:12 PM
What year/model car?
Is it BOSE?

09-22-11, 12:24 PM
I own a 99 Eldorado ETC and made a wiring harnes to plug into the factory allowing me to use an aftermarket HU. After some time...I decided to revert back to the factory HU and did so with ease. My question is this....my radio is or looks exactly as the one you have pictured here....it is a NON bose system....and i found a cd changer plug in the trunk. I was able to get a6 disc changer from a 2000 SLS but havent had any luck with it reading the discs (Err message altho everything seems to work)...whether they were placed with the label down or up..it didnt matter...my guess is that the changer operates on a different data system like the bose...am i correct? I recently purchased the ACDelco 16199553 12disc changer you had recommended on earlier posts...im hoping this will work....if im incorrect please point me to the correct way and Im researching your aux input mod. If you can help me with buying the input or where to locate the parts needed as well as some instructions to install ill appreciate it. I know it involves breaking the HU down and im skilled enough to do soldering(or comfortable enuff to). i can be reached at techn@usa.com and if needed i can give my cellphone # if contacted. After reading your posts and trying the aftermarket route...its gonna be better and easier to just leave it stock and modify what is there.....i also want to tie in an aftermarket amp in the rear & im thinking it will be as easy as tieng into the rear audio signal with a line adapter and running the audio to the amp with rca. Thanks and i read a lot of your postings. Honestly u seem to be the togo to guy when it comes to these cadillac issues!!!

09-25-11, 11:01 PM
All you need for a non-BOSE setup is a jack connector with switching action. Is like $2 at ANY electronics part supplier, just make sure it has switching action (i.e. is 3.5 jack stereo but had 5 pins not 3). Is still 2 channels (stereo) but 1 pin is GND, one is Left IN, another is left OUT (NC contact) and the same for the right channel.
This is one connector you can use (http://canada.newark.com/switchcraft/35rapc4bhn2/connector-phono-jack-3way/dp/96F9607).

As for the CD changer 6 or 12 disk works with the HU but only 12 disk was used in your car, the CD changer was designed for both BOSE and base sound systems the E&D data line between the HU and CD changer is the same.

09-26-11, 09:08 AM
Thanks for reply Ncaddy. Im having a problem with both changers coming up with an Err messsage. Both power up and cycle through the discs but when any one of the discs is called up...the error message is displayed and then it reverts to radio. Im at my wits end. Im just confused. Although I think I can do the aux modification if im careful...will u accept the work to do the mod if I look at it and decide its not in my realm of things? I can ship to you if need be....Ive read about use of a 8 pin but the 5 pin as u suggested i would suspect to be easier to deal with.....my eyes arent that great anymore. as noted in prior reply...i can be reached at the email listed. Thanks and hopefullly ill eventually figure this cd problem out......is there any module in between the radio and chnager that maybe i should look to see is in the car?

09-27-11, 07:50 AM
If the CD changer cycles to the disks but comes up with error then is unable to read the disks, so I am thinking the lens is dirty, or it has water damages and the pins on the banner cable going to the lens assembly are corroded. So open up the CD changer and disconnect all banner cables going to the CD module (one at a time) and inspect/clean the connectors. On this occasion, using a Q-tip, clean the lens, make sure the disk is spinning (that I had in a CD changer, it was not spinning the disks because of the banner cable connector).
The CD changers are easy to fix, just make sure you observe all the screws holding the top cover (including the ones on the section that sticks out in the back (and I believe there is one underneath too, so that sticking section in the back where the connector goes is removed first).
As for the AUX input, if you take care of shipping I can do it over one weekend free of charge obviously.

10-10-11, 10:42 AM
Got the 12 disk changer to work.....it may have been a combination of both. The 6 disc isnt reading but the 12 is now after i cleaned and checked the plug. As far as an aux input installed....im highly interested in having u install it...i'll pay to have it shipped to and from you of course. If u can contact me with shipping info i can try and send it this week. my contact email is techn@usa.com. Thanks and its definetly nice to be able to use my cd's again!