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Car stereo Modding

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Menticol

Active Member
Hello!!

It's a very old idea, but I want to add a Line In to my OEM car stereo (for iPod, or anything with 3.5mm jack). I have done it before with multiple Boom box models. Please, I have some questions

My first method for boom boxes, not used anymore: Wiring the iPod directly to amplifier IC input: I think is not a good practice, but anyhow it worked. I guess the stronger iPod signal masked the other. Is this dangerous for the amplifier or associated circuits?

(Now I use a switch to select between the radio module output and the iPod, is more decent)

Now, with the car stereo, I tried to bypass the cassete deck sensors, and intercept the signal coming from the tape head. Worked perfectly, but randomly a very strong interference is heard. I have read about impedance mismatch, but I cannot find any 1:1 transformer. As far as my knowedge goes, I use a resistor to keep the signal soft to avoid overdriving the preamplifier. But why did the thing sometimes work, at randon times, random volumes, and even without resistor?

Thank you!
 
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Probably cause you're just randomly trying to feed in a signal on something you don't understand =) How about finding the pin outs for the connector on your car stereo? even older cars tend to have an aux/cd input
 
Probably cause you're just randomly trying to feed in a signal on something you don't understand =) How about finding the pin outs for the connector on your car stereo? even older cars tend to have an aux/cd input

No Sceadwian, it have not any auxiliary inputs, and I cannot find the CD changer interface pinout either :confused:.

Haha well, I'm not an expert, but I understand a bit. What do you think about supressing the LA3161 deck preamplifier, and put the signal on what used to be its outputs?


Thanks Mike! I though about the cassete - iPod interface, but this deck has a lot of noise. Disconnecting the motor reduces the noise a bit, but a scratch is heard even at low volume. The stereo is connected to 12V battery, so is not AC interference.

Disconnecting the tape head also mutes my iPod signal, I'm not sure why.

I have forgot to mention, is not really my car stereo, instead is a old Pioneer keh-p5000 I have found lying around. I wanna recycle it for my experiments so adding a iPod interface would be a good way to take advantage of the amplifier inside.
 
So scope the CD players pins yourself. Use an old set of headphones you don't care about, tie one line of either the left or right earphone to ground and the other via a few uF capacitor and start touching pins while the CD player is playing until you get audio on the headphones, you'll hear a loud pop and might blow one of the headphones if you touch the main 12 volt line but that's why you use a pair of junk headphones for, you have 2 in case you blow the coil on one. You'll find at least two pins that have audio on them, one should be left the other right. Pretty simple, and a whole lot easier and safer than trying to tap the preamp.
 
So scope the CD players pins yourself. Use an old set of headphones you don't care about, tie one line of either the left or right earphone to ground and the other via a few uF capacitor and start touching pins while the CD player is playing until you get audio on the headphones, you'll hear a loud pop and might blow one of the headphones if you touch the main 12 volt line but that's why you use a pair of junk headphones for, you have 2 in case you blow the coil on one. You'll find at least two pins that have audio on them, one should be left the other right. Pretty simple, and a whole lot easier and safer than trying to tap the preamp.

Thank you by the tip Sceandwian!! unfortunetly the stereo doesn't have CD player, just the interface to connect a trunk-installed 6 CD changer. I'll use your method on a next stereo. The only hope for the actual one is reusing the tape deck. Do you think tapping the deck's preamplifier outputs with the iPod is enough to mask the signal (maybe it is, but could the stereo be harmed?) or must the preamp be removed completely?
 
So scope the CD players pins yourself. Use an old set of headphones you don't care about, tie one line of either the left or right earphone to ground and the other via a few uF capacitor and start touching pins while the CD player is playing until you get audio on the headphones, you'll hear a loud pop and might blow one of the headphones if you touch the main 12 volt line but that's why you use a pair of junk headphones for, you have 2 in case you blow the coil on one. You'll find at least two pins that have audio on them, one should be left the other right. Pretty simple, and a whole lot easier and safer than trying to tap the preamp.

I haven't actually done this, but it seems to me like you could save your headphones by first checking the pins with a multimeter to identify and mark the power supply lines. Is there something about doing this which makes it a bad idea?

I'd still use junk headphones. I sometimes take an extra cup of coffee in the morning and then I have the shakes for the rest of the day. :)


Torben
 
I sometimes take an extra cup of coffee in the morning and then I have the shakes for the rest of the day. :)
Torben

Damn, and I thought I'm the only person that gets that, a second cup stuffs up my day, I shake so much I can barely hold a pen.
Caffeine intolerant?
 
Damn, and I thought I'm the only person that gets that, a second cup stuffs up my day, I shake so much I can barely hold a pen.
Caffeine intolerant?

Maybe. Mostly I think it's because on those days I tend to replace food with coffee. Bad, bad idea.


Torben
 
For awhile I use to drink those cans of Starbucks expresso drink. Had to give that up when I started my first chem lab. It was to hard to pour things into the test tubes :)
 
I've come to replace coffee with rooibos tea.
It really helps, it can even make you see that it's time to buy a new car stereo.
 
I just use an RF modulator on mine - saves messing about.

Quality isn't bad - the modulator only cost me £10 delivered as well (around $20usd)
 
Menticol, don't give up yet, if it has a hookup for a CD changer then part of that hookup is going to be the audio lines, you may be able to use them still. Can you take a photo or make a crude drawing, or at least describe the connector, and what brand and model number your stereo is?
 
I DID IT! Thank you so much Sceadwian, Torben and Mike! Sound is clear as water, no matter volume settings. Solved all interference problems too. Using 3 ohm and 8 ohm speakers, is fine.

The stereo is a old Pioneer KEH-P5000

Using my iPod (ok actually it's a generic mp3 not an iPod, I don't like Apple products) as input signal

So here is the recipe, I'll upload the pictures and detailed procedure on my site soon

1. Get a cup of Colombian cofee (Baileys works too)

2. Take your 3.5 m.m. stereo plug and use its leads as "input signal"

3. Inspect the deck module wiring. Find the switches (or sensors) that detect the presence of a tape, and defeat them. In my case, was only NC and a NO switches.

4. Follow the wiring from the tape head to PCB, and then preamplifier. (for newbies: put the IC's code on google, you must find a xxxx 2 channel preamplifier)

5. According to datasheet, find the OUT pins and one GND. In my case, it as 3, 5 and 6

6. Inject the "IN" signal from the 3.5 m.m. plug on the preamplifier's OUT pins.

NOTE:

At least on my stereo model, defeating the decks sensors put the stereo on TAPE mode, so Tuner and other functions will be disabled. Attach a good-looking switch on the stereo, to select between defeating the sensors (and activate TAPE mode) or use stereo normaly.
 
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Congrats there.

Never thought coffee would help, but hey most software developers run on it.
 
Never thought coffee would help, but hey most software developers run on it.
I thought they just ran on bits of this and bits of that...:)
 
I thought they just ran on bits of this and bits of that...:)

A programmer is simply a device for turning coffee into software. (Although I believe that originally the saying was "a mathematician is a device for turning coffee into theorems".)

@Menticol: Nice work! I look forward to seeing the pictures. I must admit I didn't really help though--I was just asking questions. :)


Torben
 
It's something like that, just had a cup of coffee, so I better write some software quickly before I go and peee it all out.:D

Questions are good, because if the mind it's directed to listens, it gets the whole thought process in gear.
Questions changes minds, questions convinces otherwise and questions challenges set boundaries.

I like em.

When I was still teaching high school programming, if a scholar did something wrong, I would just place a well positioned question at them.
They then had to solve the dilemma based on the hint within my question and the question itself. I was hoping that would help them to think.
Unfortunately, a lot of kids did not want this kind of help. But some really improved using this technique.
I always said, if you do not learn a lot at school, it's not the end of the world, just as long as you learn how to think.
Then the world lies open before, pity then, very few people agreed with me on that.
In any case here I am going on again, and my brain self is very out of shape.
 
Haha yes, I remember when I was a kid, asking questions was equal to more boring homework and later beign hit by the bigger schoolmates. I think the interest (and questions) of students also depends of the teachers: they can make a boring topic extremely interesting, or bury the class in despair.

@ Torben: Here's my blog! Sadly is not in english, google translation makes meaningless phrases when working ES -> EN. I hope you have some spanish speaking friend, to understand the other works. At least it's plenty of pictures! :)

My idea is adding new functions to old equipment, or recycling old equipment to make diferent new one. Some people call this modding or hacking, I hate these words actually.

**broken link removed**
 
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Menticol, that's a rather good idea, also helps to save the planet.

You could always call it refurbishing. Adds a bit of class to what you're doing.

good luck further
 
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