AUX IN and Bluetooth for Every Car Casette Player!

by claudiopolis

29K5178

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

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.

53 Comments

Nnaheed 3 years ago

Hello claudiopolis.

Am running an original toyota cassette and cd player.i already dismantled my audio cassette and followed your instructions.but i cant find the datasheet on the net OD A12216.
I looked for the left and right output but i cant find them.its written at the back of my circuit.am confused.can you help me please.if possible we can email if u wish.am sending you some pics.2

Chris71Ka 3 years ago

Hello Claudiopolis,
thank you for your guide, I really love it!
I would like to ask you for your recommendation for my specific situation with the TA2068N chip in the Sony audio system PMC-107L. I think cutting the power source (no. 19) would not be a good idea since beside pre-amplification the chip is also needed for the selection of the input source. But will it also work without cutting the power supply? Will removing of the connector from the playback head be sufficient?
Thank you for your help!

danik.de77 3 years ago

Hello,
I can not find output pins of this chip.
Text on chip- dolby 9L A12194.
Can anyone help me:(

Bransonio 3 years ago

Hi Claudoiopolis,

Thanks for this interesting, clever guide. Couple of questions for you, one about your guide and one more generally about cassette head signal routing.

First, you describe how you augmented your custom aux input with a Bluetooth module, but I don't believe you mentioned a solution for setting the Bluetooth device into pairing mode. Most auxiliary Bluetooth devices I've encountered have a button that must be pressed in order to activate pairing mode to make a connection. Did you add a button that does this somewhere to the interior of your vehicle?

Second, I noticed on my cassette unit (in a 1999 Ford F-150 AM/FM, cassette stereo), there is a ribbon cable coming off of the cassette head containing five connections. Forgive me, as I may not be using totally accurate language for these components. Anyway, those five connections appear to run to solder points on a small board that are labeled FL, FR, RL, RR, and Ground. Having found no online documentation of this particular device, I am assuming that FL means "front-left," FR "front-right," RL "rear-left", and RR "rear-right." Do you think I am correct in this assumption? It seems strange to me that the signal would be split like this immediately from the head, considering it has a long way to go before reaching the car speakers.

Any insights you might have would be appreciated. Thank you.

claudiopolis 3 years ago

Hi,
My bluetooth module was already paired with all the devices I needed it to be, before installing. Even so, by pushing the tape door I can still access the pairing button as it's close enough to reach with my fingers. So no, no additional button.

Your setup is weird. But then again, I haven't opened many car head units. Does it have AutoReverse? Because it might add additional headaches because of that. Mine doesn't. Anyway, despite your head's output ribbon, you have to find the pre-amplifier chip. It's there, somewhere. Might be a double preamplifier, I don't know, as it has to serve two tape heads (autoreverse) That's where you add your input, the the chip's output. Google, magnifier lens, a keen eye, patience helps.
But if I'd have a F-150, I'd surely want a Android Auto compatible headunit.

Bransonio 3 years ago

Thank you for your detailed response. Good news: we found the outputs on the preamp and then traced them on the back of the board until we found good solder points. Interestingly, as we were deciding how to route the aux wiring through the bottom of the case, we discovered two holes in the bottom cover aligned perfectly above our agreed-upon solder points. Seems as if the designers anticipated this kind of use. Maybe it was for testing. Don’t know. Anyway, good news for us. We got the aux input to work and mounted the input cleanly in the dash. Going to attempt a Bluetooth module in my Ford Ranger next weekend.

Thank you for the excellent guide, it was a great help.

janeobanda 4 years ago

Hello. I have the same radio model (SEAT AURA) and I want to make AUX. Have you got pinout where can I solder the R,L,GND? Many people says that we must solder at the casette pre amp and cut of the pin nr. 9 which is a VCC power. How about simulate the working casette player? What is been displayed on the screen of radio?

FlorinN10 4 years ago

Hi . excellent instructions. I have a PIONEER KEH-P3600, a legacy from my father-in-law (resting in peace), which I would like to transform into an audio unit in his memory. but it's a lot different. I leave the pictures, and I can wait for opinion.

claudiopolis 4 years ago

Hi Florin. Yes ... it's different. Probably an aftermarket unit. With CD-changer control. Perhaps dual-headed, too. I wouldn;t try to convert it. Too complicated. Even if you trick the microswitches, the logic is still there as there are too many sound options on those buttons. Better stick with the car's default player (the cheaper ones work best for this instructable).

FlorinN10 4 years ago

multumesc. ai dreptate, prea complicat. as fi vrut sa profit de performantele audio ale lui, pe langa faptul ca acum multi ani, in tinerete, mi-a incantat calatoriile cu vechea mea Dacie. poate o sa il folosesc asa cum este , intr-un sistem de boxe.
multa sanatate si spor .

HencoS1 5 years ago

Hi claudiopolis. Thank you for the great guide. I did this to my Audi Symphony radio and I'm glad to say that is working( well sort of). I have a slight problem which I do not quite understand. I used a male-female AUX cable so that I can hide the cable somewhere out of sight. For some reason though if I skip or pause a song I need to plug out from the female end and reinsert untill I get a connection again. Any advice on fixing this problem?

claudiopolis 5 years ago

Does your player defaults to radio when that happens? What does the display show?

HencoS1 5 years ago

Nope. It still stays on tape mode. Attached I added a video of what it does.

I AUX cable I used was dirt cheap though and I don't know whether that might cause the problems. The left and right channel audio inside te aux was also incorrect.

claudiopolis 5 years ago

Video does not work. I think your problem is preamp-related. You still have it there, active. (And the tape player, too?) Your unit seems to have some background noise cutout feature. When you skip or pause, it thinks there's a gap like in between songs on a tape. So it mutes the output despite the new song starting. The reconnection causes a "pop" noise that makes it think a new song starts and resumes playback. Try removing the preamp chip. And browse your unit settings for any noise-cutout feature, it has to go. The ground is the same in the entire car.

HencoS1 5 years ago

Does not matter which device I use. Same problem with all of them. Though for some reason when playing anything from YouTube I do not get the same results. I can pause and play as long as it is withing about 2 sec, and I can skip through the videos and start playing something else without any issues. I tested with my standard music player and with Google Play music and it stop working immediatly when I pause or skip.

Regarding the comment on testing the AUX. As soon as I plug in to the 'radio' I can hear a popping sound, also when I touch the ends of the AUX. And the cable I use to plug in has never given me problems. And still doesn't when using it on other radios, so I can only think that the cheap AUX (which I plug into) is possibly the problem.

But thank you very much for the advice. I'll first replace the cable that is soldered to the radio an see whether that fixes the problem. If not I'll cut the power to the IC. And hopefully after that my problems will end. But the sound quality is amazing. Never thought it would be that good.

Highly appreciate all the effort and willingness to help.

claudiopolis 5 years ago

Have you tried other music source? A table, another phone? Same thing happens?

HencoS1 5 years ago

Danm wish the video worked. It shows exactly what happens. But the phone also 'looses' connection with the AUX if I can say it like that. When this problem occurs, I should then plug out from the female end and start the music on my phone again and give it a second or two until it realises there is an AUX cable plugged in and only after that I can plug back into the female end and the music wil start playing as it should.

claudiopolis 5 years ago

Two scenarios can happen in your case.
1. Weird cable. Change it, all the way to the car player. Use another. Take the player out of the dash and confirm with a multimeter that every pole on that jack goes to the right signal insertion point, without any interruptions. Ground can be tested by checking continuity between the stereo jack's ground and the car ground (metal door lock, for instance) or the car player's outer metal shell.If that's no happening, you're not using the right ground.
2. Take the preamp IC out. At least cut it's Vcc IN with a nail clipper so that it's not operating. If the problem persists, it's hidden in some noise reduction feature of your player. Put a switch on the line and live with it. Or, find the main amp inputs and solder there. It's up to you. Judging by the sound quality, I think it's worth the trouble, isn't it?
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