Adding AUX input to stock stereo (Tape/CD, no changer, no XM, no bose).

[TequilaWarrior]

I've had a Kicker ZR120 and (2) 10" CompVR subs in my Bravada for nearly 10 years. The amp has given me intermittent issues for years but I finally broke down and resoldered the daughterboard in it so the KickEQ card stops cutting out and shutting my amp down. Now it finally hits like it should. Cue my current problem.... no good music source. I got rid of all my CDs over the past several years (stupidly) and don't have any tapes. I've been using a tape adapter to hook a selection of MP3 players and phones. I even found a bluetooth tape adapter... a pretty slick piece of kit. It rocks, but I have to align it to the tape head every time I use it, it has a physical switch I have to turn on and off so it doesn't run the battery down, and it needs charged after 6 to 8 hours of use. I don't mind all these things when I've got a trip of any length.... but for quick trips to drop the kids off at school or to the grocery store, I don't even bother turning the stereo on. I live in radio hell... gospel, talk radio, and static are my only radio station choices... so I need a good solid music source. An additional complication is that even with aligning the tape adapters as best I can, regardless of which one I use or what settings I use the left side signal is always weak compared to the right.

So, I remembered that there have been many people who have added AUX ports to Delco head units over the years using various methods. It's infinitely easier to do so when you have a "band" or "source" button (which I don't have) because you can intercept the music signal coming in from an external source such as an XM tuner or CD Changer. I don't have that option. I found where people have successfully done so tapping into the signal wires INSIDE the head unit coming from the internal CD player. I figured the same must be possible for the internal tape player. I'm not a fan of altering how my head unit works with CDs in case I ever actually try to put one in it... but I'm totally down with altering the internal tape signal.

I've ordered a (4) pack of 5 pin Aux ports and will be picking up some CAT5e or CAT6 cable to do the wiring. What I could use some help with is if anyone knows WHICH wires inside the head unit I need to tap into to provide the audio signal. There are 2 pigtails that go to the internal tape player. I don't yet have photos but one pigtail has probably 9 or 10 wires and the other maybe 5 or 6. I'm 90% sure I need the 1st and 3rd pin (wire) of the 9 pin pigtail, but I don't know for sure. If anyone can clear it up, I would appreciate it. I've done extensive searches on multiple forums but I couldn't find anything that covers this specific scenario. Of course I could replace the head unit altogether and not worry about any of this, but I can't really justify pouring hundreds of dollars into a modern head unit for a vehicle that's 21 years old with 300,000+ miles on it. When I actually attempt the wiring and do the modifications I intend to take pictures and report results to hopefully contribute in some small way to this great site.

 

[TequilaWarrior]

SUCCESS!
I performed this mod in a little bit of a hurry so I didn't take the pictures I wanted, but I can report that what I wanted to accomplish worked beautifully.

After removing the head unit and popping off the metal shield covering the tape deck there are 2 plugs that go to the tape unit. One of those plugs has 7 pins(wires). The audio signal for left and right is on pins 5 and 7. I'm not sure which is left and which is right. For a ground just use the head unit's metal chassis.

For my audio jack, I ordered some 5 pin 3.5mm balanced sockets with switch.
These, actually: https://www.amazon.com/dp/B01FPRAT2Q/?tag=gmtnation-20

I also used some CAT3 multi-strand wire, but you can easily use cat5 or cat6. The cat3 I had contains solid copper conductors which actually made the soldering easier... my soldering skills are less than exemplary so I needed all the help I could get.

I cut about a foot of cat3, stripped the ends off the conductors on both ends and soldered a single conductor to each of the 5 pins on the jack. I kept the color pairs together so that left TO the socket and left FROM the socket are blue and blue/white and right TO the socket and right FROM the socket are orange and orange/white. The socket I ordered can be spliced into a low level audio path and will interrupt the existing signal when a jack is inserted into it. It's a pretty slick solution. The solid green conductor I soldered to the ground pin on the socket.

Once my socket had the cat3 conductors soldered to it, I used heat shrink to clean up the socket end then passed the other end through an opening in the side of the head unit's chassis. I then cut wires 5 and 7 of the 7 pin plug approximately halfway between the ends - to allow for some slack. I presumed (correctly) that pin 1 was the single black wire in the plug. Then I soldered each of the TO conductors to the corresponding conductor coming from the tape deck and each of the FROM conductors to the corresponding conductor coming from the control board. This was followed by applying heatshrink tubing to everything. The ground conductor was stripped and wrapped around one of the tape deck chassis mounting screws. I then reassembled the head unit and installed it.

For the time being I have the "pigtail" with my new socket just sticking out of the top of the dash for testing purposes and until I find a good mounting location. My original intent was to mount the socket in the faceplate of the head unit, but my head unit's faceplate has a circuit board from edge to edge leaving no voids to mount the socket. I then contemplated drilling a hole in one of the trim panels and mounting the socket there, but the trim panels are thicker than the panel mount on these sockets... so I need to find a thinner location to mount it, or just secure the darn thing and call it done.

Operation couldn't be easier... When this mod is done to the CD player you have to have a CD in unless you want to mount a switch to kill the CD unit after it spins up.... which I wanted to avoid altogether. When modding the tape unit in this fashion, you simply need a tape in the deck... since I have multiple faulty tape deck adapters, I removed all the electronic components for one leaving just the tape path and capstan gearing - basically it will mimic a valid tape but produce no sound whatsoever.

So, insert decapitated tape adapter, insert 3.5mm jack and hit play and voila.... some of the purest audio I've ever heard come out of this set up. There is no hiss, hum, or flutter that occasionally occurs when listening to a "tape" (or adapter). The audio is as clean and pure as you can get from an external source - in my case I'm using an old Galaxy S10 with the sim card removed. I've loaded 30+ gigabytes of MP3s on it and some random music player from the Google Play Store. Why the S10? Because it's one of the last "feature phones" that actually has a headphone plug on it... and I had one laying around. I also have a few bluetooth to 3.5mm dongles available in case I want to just use my current Galaxy S22 Ultra or if anyone else wants to bluetooth to the stereo.

What's more amazing... now that I'm sending CLEAN audio to my Kicker amp and subs... it hits harder than ever... Pushing it while using an adapter I would pop fuses left and right and the amp would overheat constantly. After installing this mod the amp barely gets warm.... and I moved up a fuse size to 35 amps from 30... (only after reading that it's common to need to with this amp and that it's stable to almost 50 amps).

This was only possible utilizing bits and pieces from these two links:
Specifically information regarding which wires to tap into inside the head unit came from here:

How to hack an AUX input into a Delco tape deck for $10

I’ve searched high and low for this information, and I couldn’t find it online. After I figured it out myself, I thought I should share. A recent annoyance with our cars has been the la…

notesfrommosquitohill.com

And the pin out/wiring for the socket came from here (post 5 to be exact):

How you can add an aux input/mp3 player without an adapter - LS1TECH - Camaro and Firebird Forum Discussion

Wiring, Stereo & Electronics - How you can add an aux input/mp3 player without an adapter - I've finally decided to switch my 98 Camaro CD unit out for an aftermarket HU, and now I'd like to move it into my Grand Am. Since I don't have to worry about killing it now, I've decided to take it part...

ls1tech.com

So... why the hell would I mod the stock head unit in a 21 year old vehicle with 300,000 ish miles on it?
Years ago I added my kicker subs using one of the Pacific Audio Components adapters designed for this application (the add-an-amp unit to give me RCA). From day one, I struggled to get good, clean audio when not listening to the radio (which I despise) and not listening to a CD (which I no longer own any of). I used tape adapters over the years, but they wear out and recently I had to "fiddle" with them to get them seated correctly in the tape deck... the audio was never quite right though. I even found a bluetooth tape adapter - a really slick little gizmo whose biggest drawback was that it's rechargeable and runs for about 6 hours of playtime. It too needed to be "fiddled" with to get it to seat correctly in the tape deck. As a small bonus, because the socket I used is the "switching" kind, if I unplug the 3.5mm jack, the tape deck reverts to factory behavior entirely. Now that I've done this mod.... the audio is amazing. To be fair, I replaced(also years ago) all my stock speakers with Kicker DS6.5s.... They essentially dropped right in with no cutting or fab work needed (~maybe~ self-tappers). So that's 4 Kicker DS6.5s being driven by the STOCK head unit and 2 Kicker CompVR10s driven by a (very) old school Kicker ZR120 at 2 Ohms... roughly 480 watts of class A/B power. I'm not going to set any records... but the sound is amazing.... and my neighbors are very annoyed.

If I pull the head unit again to sort out the mounting of the socket, I'll pop it open and take pictures of the wiring and post them in this thread... but all instructions to do this are above and in the links. I have some experience with wiring and soldering and the like, but never had the confidence to attempt this until my frustration pushed me to it.