I have a tape deck in my car which only gets used to read one of those dummy tapes that feeds from a 3.5mm headphone jack. I have no use for a CD player and would not like (nor can I afford) a new head unit. I was wondering if there is a reasonably strait-forward way to expose some sort of auxiliary input for hooking up an mp3 player?

  • I realize this question is pretty old, but just in case someone else will look for a solution - there exist cheaply priced (~$20) FM radios and MP3 media players w/o a CD in a deck form factor. For those who do not need the CD player, this is a nice solution, and should be better than an FM modulator, as the audio is amplified directly from the digital source. No need for modulation and demodulation (also FM radio quality does not come close to CD quality).
    – ysap
    Commented Jun 21, 2013 at 22:39

2 Answers 2


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):


Then you can plug your MP3 player into the modulator and the signal travels straight into the radio! The setup looks something like this:

FM Modulator Setup

  • Well, I'll be, this was an unexpected answer. I never knew that such a thing existed. Makes sense, old TV peripherals used RF modulators. Commented Mar 8, 2011 at 15:15
  • Some of the fancier ones actually provide USB connections and otherwise for stuff like steering wheel controls for an iPod. These simple ones are pretty cheap; much easier than dropping bank on a whole new stereo.
    – Cᴏʀʏ
    Commented Mar 8, 2011 at 15:26
  • I use one of these. A cheap one. Beware, they are rather susceptible to interference. I'd make sure you get one with enough power to drown out external radio sources on the frequncy you are using. Commented Mar 8, 2011 at 17:58

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.

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