Homemade iPod Cable Construction

I used the Belkin Auto Kit for iPod for three very important reasons:
  • Single cable design

  • Open box can be found on eBay for ~$10

  • You can chop off the amplifier portion and have a good starting point for your harness

Once you have the Belkin connector, do the following:

  • Unscrew the retainer (pictured below - it's the part at the far right and has two flat sides)

  • The pin and fuse will then fall out out and the spring might too

  • Next, pop off the little metal ring that is left with a small screw driver driver

  • Now you can wiggle the first part of the gray plastic case out (top most plastic piece in the picture)

  • Now you can pop out the bottom gray plastic piece with wire harness and amplifier circuit board from the white plastic bulb. Grasp the plastic bulb in one hand and push up slightly on the gray plastic with the other hand. It should pop free and pull out.

  • Free the metal power and ground contacts. These are the spring metal pieces in about the center of the picture below.

  • There is a little part of the lower gray housing that acts as a retainer clip to hold the circuit board in place. Hold this back with a small screw driver and wiggle the circuit board free.

  • Once you have the parts wiggled free, you can snip the wires. Snip them as close to the circuit board as possible to maintain the length. You will be left with the harness still poking through the lower gray plastic housing. Since you can't slide the harness back through, you need to snip away the gray housing with a pair of side cutters until the cable is free.

  • Throw everything away except the cable

(By the way, the circuit board is nothing more than a cheap line level amplifier. Nothing is done to the power signal ,it's "pass-through" according to Belkin tech support.)

This is how it will look once you have taken everything apart:

And here's what you should have left over after cutting off the circuit board:

Referring to the picture above and going from top to bottom, here is the wiring breakdown:

  • Thin Black wire:
    This is one of three ground wires. It is the same type of a wire as the white, red, green and yellow wires.

  • Red wire:
    This is power, +12VDC. I called Belkin tech support and they said that power is just pass-through (the front line support guy was good enough to check with engineering with little pressure from me). In other words, the voltage can actually be anywhere between 11 volts (if you have a bad battery and the car isn't running) and 14.5 volts (car running). The iPod can apparently handle this variance, perhaps by way of a Zener diode; only Apple knows. Anyway, just to be sure, I verified this with my handy Fluke meter. It is indeed pass-through voltage from the car.

  • White wire:
    Connect this to one end of a 1/4 watt 1 mega-ohm resistor and connect the other end of the resistor to ground. You can pick up a package of these resistors at Radio Shack for about $1. Part number is 271-1356. The other end of the resistor is the second of the three ground wires. I didn't experiment much and do not know what purpose the white wire with resistor to ground actually serves. I may experiment with this later or call Belkin. Anyway, I'll update this page with the results.

  • Medium Thickness Black wire:
    This is actually the shielding around the green and yellow wires, which are in a separate cable within the main cable. Anyway, this is the common audio ground. Connect it to the negative audio signal but not actually to the ground circuit. In other words, do NOT connect this to the other three ground wires.

  • Green wire:
    Left audio signal

  • Yellow wire:
    Right audio signal

  • Thick Black wire:
    This is actually the braided shield for the main cable that is just twisted together and inside some heat shrink. This is the third of three ground wires.

This picture is a close-up of the 1 mega-ohm resistor that is on the Belkin circuit board. It is the little black thing at the bottom labeled "01E." It is an SMD style resistor and the code for it can be looked up here.

Just to be sure, I carefully de-soldered it and measured the resistance using the Fluke meter. It is exactly 1 mega-ohm, which matches what the code translates to. Measuring the resistance while still in the circuit will give a false reading.

Make your audio connections

I used a Radio Shack 3 foot Y adapter audio cable, part number 42-2550. Refer to the wiring breakdown above. When looking at the Radio Shack cable, remember your R's. Red = Right. Solder the yellow and green wires from the Belkin cable to the corresponding inner cores on the radio shack cable. Gather all of the shielding and twist it together. DO NOT LET THE SHIELDING COME INTO CONTACT WITH THE AUDIO SIGNAL AT THE CORE. Gather each twisted cable shield from both sides of the the Radio Shack cable and twist them together (to make one wire). Then solder the shield from the Belkin cable to the 2 RCA ground wires you just twisted together (top wire in the picture plus the two twisted wires at the right).

If the tiny wires inside your RCA cables look exactly like the ones pictured on the right, you can skip this blue paragraph: (Depending on the brand of RCA cables you choose, there might be 2 seperate tiny wires inside each RCA cable. Just remember that the red one is always the right audio channel [positive], and the black ones will always be the audio ground [negative]. If this is the wiring set up in your RCA cables, connect the right [red] & left [other color] to the corresponding wires in your Belkin cable. Then wrap the 2 black wires from your RCA cables together [to make one wire] and connect them to the sheild from the Belkin cable [top wire in the picture plus the two black ground wires from your RCA cables].

The wires are thin and can be hard to see. This can be tedious for some so please have patience. Though not pictured, be sure to ALWAYS use heat shrink tubing or electrical tape to insulate the wires from each other after each connection you make.

Here you can see the bottom end of the resistor connected to the white wire.
Notice how I connected the first black ground (thin) wire to the other end (the top end, but not the very top) of the resistor (It doesnt matter which side you choose to be the "top" or "bottom").
Also connect the outer shield (third of three ground wires - the fat one pictured below between the resistor and the red wire) to the top end of the resistor, but ABOVE where the thin black wire is already conntected. Then you will have to attach a new wire (not pictured) to the very top end of the resistor. This will be your main ground wire. The outer shield and black wire go straight to your main ground wire. The white wire goes to the main ground via the resistor.

The remaining red wire will be your main power wire. You'll have to attach a new wire to the end of this wire to extend it. I suggest that you add an inline fuse between the thin red Belkin wire & your new extended wire.

I chose this style of connector to tap into power and ground of my cars, but you can choose any connector style that is easiest for you based on your type of car. When sliding the light blue portion into the darker blue portion, be sure that the little "tongue" slides in correctly. It's easy to push it out of the way and have NO connection even though you pushed them together properly.

Here is my complete harness. Notice how I doubled over the harness and wire tied them. I did this for strength to take the load off of the tiny wires in the Belkin harness that are very thin and can break easily.

Since I tapped into the audio accessory wiring harnesses in the cars, which are already fused circuits, I did not add another fuse. You can perform this optional step if you'd like. You SHOULD DEFINITELY DO IT if you wire the iPod directly to an unswitched power source such as directly to the battery or where the circuit has no fuse. I suggest tapping into a "switched" power source (meaning one where power is cut when the car is turned off) because when the power is switched off, the iPod goes into a paused state.