AUX IN and Bluetooth for Every Car Casette Player!


Introduction: AUX IN and Bluetooth for Every Car Casette Player!

About: I am a graphic designer with many hobbies. I love electronics, computers, LEDs and all things tech.

If you have an older car, with a cassette player in it, I KNOW you'd want it to be able to play the music from your phone. You might have even tried different ways to do that and neither one was perfect.

This one is. It's the best way to do it. I'm not bragging, I'm stating the facts. I hate to see a good amplifier (the car player is also an amplifier, a good one, too) rendered obsolete because people can't connect their phones to it.

But you need to know your way around with a soldering iron. If you do this right,, not only you'll get crystal-clear AUX IN sound (on any cassette player!) but you can also upgrade it to a Bluetooth-connected sound system! Read on and do it, it's worth it.

If you're afraid of ruining your car's tape player, buy a used one and work on that (just get its anti-theft code with it). They're cheap now and still put out around 40W of good quality sound. The sound settings will still work. You'll make yourself a cassette player that puts out solid sound from you phone using a cable or a Bluetooth connection.

Step 1: Car Cassette Players. If Only Those Had AUX IN ...

Well, they could have had it but back then phones as music sources weren't the norm at all, you know. So nobody thought about that. Maybe a few. But the norm was most of the old car cassette players had no AUX IN.

If you're like me, the owner of an old car that had a factory fitted cassette player you would long for a stereo input jack enabling you to play all that music you have in your phone. Or drool whenever you saw a phone streaming music over Bluetooth to the new car's sound systems. Yep, I've been there.

All sorts of AUX IN devices sold over the internet tricking some CD output of some car players but those were newer than mine so I didn't bothered with those. Besides, many users reported low quality playback using those devices.

So here's how I did it. I consider it the best way there is. I gathered this information from a lot of sites with different procedures. Zero noise, perfect digital quality, no volume degradation, on the contrary you get additional signal gain so your music is now loud and clear. But you have to be skillful with the soldering iron. And you have to have some understanding of what we're doing. Also, a multimeter is mandatory. So here goes.

Step 2: Here Goes Nothing ...

First of all, be aware of the PIN code of the car player. You have to have it. Because if you don't, the next time you put the player back into the dashboard it won't work without it. At all.

So, get the cassette player out of the car. Open it. It'll look like this, or similar. Take a photo using your phone. Carefully take the tape player part out. It's mostly mechanical stuff, with springs and levers. But it also has micro switches with wires. (and a reading head). Some are depressed and some are not when a tape is in so try the mechanism with a tape and see how the switches state change (also, take photos...). Make a note of it all.

Take it all out, (make photos of every step) you can cut the wires but label the pairs for each micro switch and the ones that power the small electric tape motor. Those switches tell the radio it has a tape and it changes the source from radio to tape. Then, cut the wires and solder a normal switch (the kind that stays pressed when push it and you have to push it again to release) to those wires in order to change the source just by pressing it. Great. Now we have a switch that tricks the player into playing a cassette that doesn't exist anymore. We'll take care of that soon.

For now try and find a place for your switch so that you can access it. I re-used the eject button for that and didn't ruined the car player's look. I advise you do the same.

Step 3: The Hunt for AUX IN Lines

It's a hunt, but an easy one. You already saw where the tape head ribbon (or wires) connects to the mainboard. It's a connector, visible here. Follow the traces from it and it will ALWAYS go to a preamplifier integrated circuit. This small IC (also visible here) amplifies the weak signal from the tape head to deliver a proper volume to the main amplifier.

Once you found that integrated chip, search Google for its datasheet. In that you'll see the stereo OUTPUTS of that chip (usually left out, right out and ground). Make a note of those. Those pins are the ones you'll use for the AUX input. Let me repeat, we need the stereo OUTPUTS, not INPUTS. Many people on the internet mistakenly used the stereo inputs, ending with horrible sound quality. So don't make that mistake.

In fact, once you find those OUTPUT pins, the best way is to de-solder the entire IC from the board. We don't need it anymore, there's no tape head to be amplified anymore. And the phone's stereo output is louder than its output anyway. So take it off and throw it away. Solder a stereo IN jack to those wires and place it in a hole somewhere on the player's faceplate. Or place as a very ugly wired connector dangling out of the cassette door. Your choice. I did it different, you'll see it soon.

You could leave the IC on the mainboard but you'll get noise. A lot. Because that IC still receives power from the player and it has internal noise, despite the lack of signal from the tape head.

The easiest way is to take a nail clipper and cut the power pins of the preamplifier IC, check the datasheet for that. Then, it'll be silence. I recommend this way, it's less work.

Step 4: Feast Your Ears

Now that you have a switch and a stereo input jack, it's time for a test. Place the player intro the dashboard, input the code if necessary and turn it on. Radio should be unchanged. Now press the switch. The player should indicate "TAPE". Connect you phone and play a song. If you did it right, pure digital sound will flow, making you wonder why did it take you so long to do this. You'll discover new life in those tired factory-fitted car speakers, believe me.

If you hear nothing, check the following - is the car player indicating "TAPE"? If not, you messed up the wires from the micro switches. If it does, and you still hear no sound with the phone connected, you messed up the stereo OUT pins of the preamplifier IC. Taking photos of the entire process is the only way to go back to the drawing board. In fact, this instructable is made out of my "backup" photos of the entire process.

As you see, I got creative in placing that switch and stereo connector. This is a SEAT car player I modified for my brother. Try to do the same, it's more work but everyone will think that car tape player had those factory-fitted.

If this is all you wanted, stop here and enjoy your connected phone music. Despite the required cable connection, it's simple to do and reliable. Make a photo of your achievement and let me know you made it.

But I wanted more. I wanted Bluetooth connection. The next step is for the brave ones.

Step 5: Bluetooth Car Music on a Budget

Bluetooth enabled car players are expensive. Or they come with an expensive car. It shouldn't be like that, but it is. Well, I wanted it cheap. So I found a good stereo Bluetooth receiver in one store. It must be a reputable brand, cheap Chinese stuff sounds horrible, believe me, I tried. So in my case, a Philips AEA2000/12 fit the bill. And the sound quality was great. It was powered by a small 9V power supply.

I opened it up to see it's actually using a 5V regulator (7805) that can easily take 12V but first I replaced the 10V rated capacitors around it with higher voltage ones. So now it works on 12V.

Remember the power wires from that electric motor? Measuring voltage on those lines with the player in TAPE mode revealed it was a 12V one. Good! Here's the power supply ready! And it turns on only when the player is put in TAPE mode (using the switch). Just perfect.

I soldered my stereo AUX IN wires from the earlier steps (with a multimeter I found better soldering points than those small IC pads) to the output of this Bluetooth receiver and powered it with the electric motor's wires (mind the polarities). I placed everything inside the player (we do have the space now). One quick pairing and the sound coming out of my car with me standing outside was all the rage of the evening. I measured about 25 meters range for my connection. I only need about 2-3m so I was extatic.

I can connect to it with any android/Windows/IOS phone and tablet. The sound is perfect. No hum, no static. It's way better than the FM stations I get on the radio side.

The last photo shows my brother's setup, he purchased a different Bluetooth receiver powered from USB 5V so I sacrificed a car power supply to power it from those electric motor wires. Insulate it well, you don't want it to touch anything in there.

My Bluetooth receiver uses Bluetooth 2.1 EDR standard, my brother's is 4.0 with auto connect. On mine, I have to manually connect each time (cumbersome, I know, but there are apps for that) but I got 25 meters range! His setup self connects to his phone but only has about 3-4 meters range. Bluetooth 4.0 has a shorter range but increased data speed. For music 2.1 is enough, but higher is always better. You can use any brand, but it has to be a good one. Test it before using it for this project.

That's about it. If you have questions, just ask, I'll try to answer them.

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31 Discussions

claudiopolis, I loved reading this ible! I decided to give it a go, but (always a but) my deck is older and spartan compared to yours. For reference, it's from a 1994 Jeep Cherokee. Chrysler Radio model P56007214 (made by Mitsubishi). I am posting a pic of the unit with tape removed. I can not find a preamp chip anywhere. I have located the AM receiver and tape motor chips, but that's it. I am not expecting you to know everything about all radios, although it would cool, however, just by the pic can you tell anything at all about where I should be looking?

Looking forward to your reply. Thank you.

P56007214 radio.png
8 replies

Thank you, sir! Actually, I am a member of that forum and have read that post many, many times. The problem is, my model of radio has a lot of bleed through when adding an aux to the pins that others use. Unless you know of a way to eliminate that extra noise?

Noise on cars' AUX comes usually comes from:

1. Unshielded/RF noise-generating alternator. That noise varies as you rev the engine. Only a car service can get rid of it. They need to change the alternator's filter capacitor

2. Dried capacitors inside your radio. Look for bulged or leaked ones, those need replacing. That noise is constant.

3. Ground loop noise. You need a ground loop filter between that AUX and your signal source (phone). Your car and your signal source handle grounds differently.

In your case, it may also be because your signal still goes thru the tape head preamp (every tape player has one, the tape head's signal is way too weak to feed a proper amplifier chip). Follow the traces from your tape head. It goes directly to that preamp chip. Always does. A multimeter set to continuity helps. That chip must be disabled as in my instructable and the AUX signal applied to its OUTPUTS.

Let me know how it goes.

It's not going that well. This unit seems to be configured entirely different from most others. New pics show a small board that is connected to the tape deck part of the radio. I had to go macro to see the markings. I highlighted the areas that look like to be relevant. I inset a macro of the only area that looks like a R, L, channel, but I don't know.

Your thoughts?


Yes, seems like a stereo out. Try feeding the three wire connector with your signal, bypassing this entire small board. Make sure the player believes it's playing a cassette.

Are there no markings at all on that supposedly preamp IC?

Correct, no markings at all on "preamp" chip. Not sure how to trick the tape. The ribbon to the head is damaged and does not work. I hoping that I could mod this with the tape workings removed. Possible?

I'm afraid I'm out of ideas. Unmarked preamp, tape assembly removed before figuring out how the player detects tape input ... it's a lost cause. Unless some electronics guru spends a day probing it and figuring all out, I don't see it a good candidate for this conversion. If you're keen on doing it, I'd start fresh with another used one. Or, a new aftermarket unit, depending on your budget..

Yeah, not easy doing this stuff remotely. Thanks for your time and efforts. I'll keep plugging along. I have all the parts, just need to figure out what's what.

Hi Caludiopolis, there are so many of us like SankarA2 that have these headunits or ones very similar. Would you be interested in following up on a this type of unit to update or improve the instructable? I would be willing to send you a unit if you're interested in showing us all!


1 reply

Hi there,

I know. There are a lot of types & brands of headunits in yesterday's car's. And a lot of people would like them upgraded. But this is a case by case scenario. My instructable would apply to owners of Skoda Fabia/ Seat Leon, it would also apply to any other brands, but, there are differences. The principle is always the same: trick the cassette player to believe it has a tape (by switches) and bypass (not feed) the head preamplifier with a direct stereo input.

The car manufacturers produced a lot of car models, and a lot of headunit options for each one. So a guide for ANY model would be a huge task, and database, and resources.

I started this instructable because I wanted to do it for myself, and, hearing the result in mine and my brother's car I figured it can help a lot of folks. And it did, and still does. Yours and SankarA2's headunits are complicated ones. Having autoreverse & other features, is making the task of tricking the logic board much more difficult. But not impossible.

Thank you for your offer but my time does not allow me to try other models just for a proof of concept. It is possible, that's for sure. Try to keep the cassette mechanism in place and put a dummy cassette, it should work. As long as you cut the head's output signal and feed your own (AFTER the preamplifier), the only thing you have to do is to put the dummy cassette (one with no tape) each time you play your music from the telephone or tablet. As a last resort find someone that's still repairing them, it would help you if you hit a dead end.

I hope it helps. A bit.

Hi Caludiopolis, Awesome work! I found a similar work in youtube but in a non-English language which I unfortunately couldn't understand. After reading your post, i was so excited to fix my car (2000 Jetta - premium iv a non-monsoon radio system by Calrion - PU-1666A). I followed your steps and was looking for preamp ic. I believe the attached pic is the correct IC - please confirm. The data sheet of this IC ( found from google says pin 1 and 24 are OUT A and OUT B - and 16 is GND. These pins are very tiny and so I wanted to solder them from the back of the board. On my search to find the correct pin, I noticed pin 1 and 24 are not connected to anywhere. I'm now confused if I'm looking at the correct correct IC. Please confirm. In your steps you mentioned, cut the wires from tape switches and connect to normal switch. I'm not sure if I really need this switch if tape is left inside but power cables are disconnected? If you say yes, then I would like to know what wires needs to be connected to this new switch. It's not clear enough in your description. Please explain. I wonder, if the power to the preamp is disconnected how would the AUX sound connected to output pin would be pushed to power amp? Your help would very much be appreciated.

7 replies

Hi. If those pins do not seem connected, they still might be. Their traces could run under the IC and escape to some via's on the other side of the board. Your preamp seem very complex given the task. If I were you I would start from the final amplifier. There are two input pins (Stereo L and R) on that amplifier that must go to this preamp. Use a multimeter or continuity tester from each pin on this preamp to each pin of that final amplifier IC. There are two channels (pins) you need to identify (The amplifier IC datasheet will tell you if it's right or left), the ground is common and can be taken from anywhere.

The switches are on the cassette mechanism and have wires to the mainboard. When a tape is inserted, some are opened, some are closed. You need to replicate the same thing with just one switch by connecting them to this switch (should have 6 pins with NO/NC states) so that when you switch it on, the board thinks it's having a tape inserted and switched the source. After that, the entire tape mechanism is not needed anymore, just this switch.

If you just leave a tape in it, you would have no radio until you eject it. Or, the preamp could jump on radio when it doesn't detect signal from the tape. Replacing the entire tape mechanism with one switch IS the best way to do it.

Any AUX signal connected to the output of the preamp IC would go to the power amp and get amplified. You don't need power to that preamp. You could unsolder it completely and just use those output traces.

Look, I did say you need to be skilled with electronics to do this conversion. The title "for every car casette player!" doesn't mean "by everyone".

Hi, Here I'm again. I had a little time last weekend and looked at the board closely. I figured out Stereo L and R locations and got them connected successfully.

I then took the wires out of cassette player. I bought 3 switches (4 pins, 5 pins, and 6 pins). Since my cassette player did not work before, I have no way of knowing how these switches work to mimic. There are two switches but both of them are completly covered not like yours. However, I inserted a cassette to see how they work. One of the switch has a lever which got moved when inserted. I assume, that switch is NO state and when cassette is inserted it connects. With that information, I took the wires of both the switches and played with 4 pin switch and 5 pin switch but nothing worked. The deck was saying Tape Error. I read your post again and noticed you have only one motor whereas mine has two motors (refer photos) which means I have 10 wires in total. My question is, what wires go to what pin? do the motor wire have to be connected with the switch as well? if so what pin and what state NO or NC? what are the wires need to be connected together and then with switch? I see in your switch you split the brown wire into two and connected the switch with the wires that were connected to motor. Got confused. I'm stuck now. It would be very helpful if you please explain what wires need to be connected? don't worry about switch state. I can play with them. But I need to know what wires need to be used and what needs to be tied together to the switch. Help me out again! Thanks!


Hi. That is one very complex tape player. Besides the two switches, you also seem to have a relay near switch A (yellow and orange wires). That relay does something. It's either establishing a contact or pulling a leaver. You need to know the voltage of that (try measuring the feeding wires) If it's zero, play with the switches until it changes to something. Or with the TAPE SIDE button on front.

That relay could be a third switch or a mechanical switch that pushes a leaver to change the rotation of the tape, I don't know. You need to see it in action. You need to replicate that action just by connecting or disconnecting wires, or by manually doing what it used to do, electrically.

You have two motors but the small one is not involved in the tape movement, rather in some tape ejecting movement. It's probably triggered by the TAPE/EJECT button on the front. You should be able to ignore it and its wires.

Rules to follow: Always measure voltage on the wires you plan to connect. If it's present, don't do it, a short circuit is never intended.
Electronics aside, go mechanical first. Insert a tape, see how it turned, how the entire mechanism worked, How it switched tape direction. How it ejects. I know yours is broken but it's all in leavers/springs/wheels to turn. Once you see what's happening, you'll be able to understand the switches.

The switches are NO or NC position depending on the tape. You need a tape in there to see that clearly. There's no playing in figuring their state, you need to know that right from the start, a tape and a multimeter is all you need.

About the wires color. I never split any wire. The voltage feeding wires (ex motor) are powered by the switches being NO/NC (tape inserted). I used them for my bluetooth receiver. They have no role in audio out.

That's it, I'm out of remote troubleshooting ideas. If all else fails, find a simpler tape player for your car. Used ones are very cheap these days. I'm not saying yours can't be used. But it's up to you and your skills.

I forgot one thing. The wires powering the motors can be totally disregarded. Insulate them and use only the switches wires to fool the player by replicating their NO/NC states.

You were right about a possible third switch. It did play a role when I try to connect wires with different combination. It showed Playing Tape A. But I couldn't get it showing every time with the same wire combination. It was frustrating to figure it out when the tape was broken. I tried my best and gave up. I went ahead with my Plan B which is to make use of CD player. It was simple and I got it working now with a DPDT push button. Thanks a lot for your help.


No problem. You're welcome.
Maybe not the best stereo car player to be converted. I would have scratched my head on that one, too. That auto-reverse thingy and double reading heads is way too complicated.

Hi, Thanks for your response. Though it seems bit complex, it's not super complex. Moreover the way you described in the original post seems pretty easy for anyone do it. I have a great passion in learning electric and electronics though i'm a mathematician and computer engineer. This is going to be my next project and I'll get it right. Your last line actually got me going now. Thanks again for your quick response and help.


11 months ago

Hi claudiopolis, great instructable, really informative. Like Coffeecat84+ I, too am working on a Ford 5000 RDS EON but have come across a noise/connection issue. Everything is identical to his pictures and the IC has been cut but I'm getting what sounds like a heartbeat when I connect my phone (Samsung Galaxy S7 Edge). I've tried the phone with other AUX devices and it works fine. All the cables I've tried are working with my phone, my daughters tablet and other AUX devices. My daughters tablet works perfectly with the AUX IN that I've fitted to the 5000 RDS. The really weird bit is that if I connect my phone to the socket remove the ground cable and then reconnect it the heartbeat sound disappears and it all works perfectly. Any insight or ideas would be greatly appreciated.