A full response would be a big file (including photos) and I thought it better to take WDK up on the offer to post it on a web site. But, since you asked here it is with out photos.
The following outlines how to replace the stock CD player (or short plug if a stock CD player is not installed) with an input for an external audio device such as an MP3 player. Information for this project was obtained from the rec.autos.makers.mazda.miata newsgroup as well as
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The solution is to simply replace the stock CD player with a normally closed
1/8" stereo phono jack (see photo at right and wiring diagram below) connected to a 13 pin DIN plug. When nothing is plugged into the phono jack, it acts just like the short plug that is used when the CD player is not installed (i.e., the output signals are returned to the head unit by the closed contacts in the phono jack and the radio and cassette play normally). Plugging a 1/8" phono plug into the jack disconnects the output signals from the head unit and connects the signals from the phono plug to the input to the head unit.
You should be able to find a 1/8" Normally Closed Stereo Phono Jack at any electronics parts store (e.g., Radio Shack part number 274-246). However, the 13 pin DIN plug is harder to find. One source is
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(part number CP-1013-ND). The phono jack and DIN plug should be connected using shielded cabling. If you can't find 5 conductor shielded cable you can cut the ends off of a 5 pin male DIN to 5 pin male DIN cable (e.g., part number
42-2151 from Radio Shack). The length of the cable needed depends on where you plan on mounting the phono jack.
The cable is constructed by connecting the left and right input and output pins of the DIN plug to the respective connections on the phono jack. For the parts listed above, the pins are connected as listed below:
Head Unit Signal DIN pin # Phono Jack Connection
Left Output 1 3
Left Input 2 2
Right Output 3 4
Right Input 4 5
Signal Ground 5 1
The connections on both the phono jack and DIN plug are small so you will need to be careful and use good soldering technique (e.g., tin the connections and wire ends before final soldering). You will also need to cover the ground wire to ensure that it does not short any of the connections.
If you have not already done so, you can correct the common power-on problem of the stock head unit by connecting pin numbers 5 and 11 with a resistor as suggested by David Thompson as at
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The final question is where to install the phono jack. Some obvious choices include either of the glove boxes. These are attractive locations since the player or other input device can be left out of sight. Also, a power connection (using pin #7 of the DIN plug) could also be installed in either of these locations. Another option is to install the phono jack in the little punch out on the passenger side of the transmission tunnel that covers the mounting bolts for the center console. This is out of the way and allows the MP3 player to be mounted on the dash or in the storage bin under the head unit.
Parts:
a.. 1/8" Stereo Phono Jack (RadioShack part number 274-246) = $2.99 b.. 13 pin DIN plug (Digi-Key part number CP-1013-ND) = $1.65 plus shipping c.. 5 conductor shielded audio cable (I cut the ends off of a 5 pin male DIN to 5 pin male DIN cable from RadioShack, part number 42-2151 = $5.99 Total Cost is about $15 including shipping of DIN plug.
Gus (91 BRG)