What you need is an FM modulator -- a device that you install between your car antenna and the stereo. A device like this (I'm not recommending this particular device, just using it as an example):
http://www.amazon.com/Scosche-Audio-FM-Modulator-Universal/dp/B0007THIDQ
Then you can plug your MP3 player into the modulator and the signal travels straight into the radio! The setup looks something like this:
audio - Wire a headphone jack into a head unit - Motor Vehicle Maintenance & Repair Stack Exchange
How can I take 4 ohm output from a car radio and adapt it to a headphone jack?
Need some guidance on adding an aux jack 3.5 mm to old car stereo.
Connect speaker wire to a 3.5mm jack?
What you need is an FM modulator -- a device that you install between your car antenna and the stereo. A device like this (I'm not recommending this particular device, just using it as an example):
http://www.amazon.com/Scosche-Audio-FM-Modulator-Universal/dp/B0007THIDQ
Then you can plug your MP3 player into the modulator and the signal travels straight into the radio! The setup looks something like this:
I had an old pioneer super tuner 3 and I thought about doing the same thing you were talking about in the original post, so that's what I did. I popped the case open, tracked down the connectors for the head to the pcb, and it was pretty much a no-brainer as to which wires to use. You have ground, then you have power for the right and power for the left, so I soldered leads onto the pins that I thought were right and soldered the other end to a headphone jack and voila. The only problem that needs worked out is that I rigged the mechanism to think there was a tape in there and it's stuck on fast forward, but the audio still comes through. The bass is a bit nasty. I'm not sure if it's picking up noise from the motor spinning.
Hi,
I want to make a DIY boombox with an old Acura radio from 1995.
Front of Radio
Back of Radio
Sticker on Radio
Wiring Harness
Basically, I want to have small speakers in the enclosure, but loud sound isn't a priority. Mainly, I want to be able to use headphones with it as if it's a desktop tape deck and occasionally use speakers if wanted and I can always just upgrade those later. For those, I know I can get away with any old 4 ohm speakers. What's tricky for me is the conversion from straight 4 ohm output intended for car speakers to a headphone output. When in speaker mode, I want the volume knob on the deck to be the only thing controlling volume. But when headphones are plugged in and a switch is flipped, I want the output to go to the headphone jack, but also be lowered enough so I don't blast my ears.
I don't know much about voltages, mW, or any of the terms, just that you should generally match the ohms for speakers, and the consumer side of line-in/out, mic in, headphones, etc, but nothing in depth. I want to know how I can get the 4 ohm speaker signal down to a manageable headphone output; even if it means putting a secondary volume knob just for the headphones, I'm okay with it.
If it helps as a reference, when using my actual tape deck with my headphones, these are the specs for the headphone output of the tape deck.
I know with lots of advances in sound technology over the last 25+ years there's probably a semi to super easy solution to this problem; I've seen those tiny amplifiers on circuit boards you can use on tiny PCs or other small devices, so maybe a reverse of that, an attenuator? I searched for some, but they all seem to have a 3.5mm in and 3.5mm out. I don't know if the signal from the head unit is compatible level/voltage/mW/dB-wise or whatever. Whatever the item happens to be, I plan on using spade connectors for the output switch wiring to the speakers and whatever is needed for the headphone jack.
TL;DR: Need to convert 4 ohm speaker wire signal to headphone jack at corresponding volume level while being able to bypass and go straight to speakers if desired
Thanks!