Disclaimer:
I was a
mechanic in a past life and have quite a lot of experience. While I think
this process is pretty easy, you need to read through the directions and
evaluate it yourself to decide whether or not you can do it. The details
presented here are believed to be correct but they are not not guaranteed
to be correct. I am not responsible for any damage that you may do to
your car or injury that happens to you as a result of following these
directions. Proceed at your own risk.
Since my requirement was to hard wire and use the line out, I had to come up with my own custom cable. I constructed it using over the counter parts. To do this, I needed to start with a car charger that had a dock connector and line out. There are three car adapters that I have heard of that offer a line out:
I had not heard of the SiK adapter until after my project was done but I would not have used it anyway. The reason is that it has two cables and would require another plug in connection for the audio circuit. Each plug connection slightly reduces sound quality (in theory - don't know if my golden ears could actually hear it, though). This is the same problem I had with the Monster. The Monster had one more problem, though. When plugged into the doc connector, the 3.5mm audio jack sticks out to the right (click link above and look at the close up pictures), making it awkward in a vehicle (at least left hand drive vehicles). I settled on the Belkin for three very important reasons:
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Single cable design
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Open box can be found on eBay for ~$10
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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:
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Unscrew the retainer (pictured below - it's the part at the far right and has two flat sides)
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The pin and fuse will then fall out out and the spring might too
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Next, pop off the little metal ring that is left with a small screw driver driver
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Now you can wiggle the first part of the gray plastic case out (top most plastic piece in the picture)
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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.
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Free the metal power and ground contacts. These are the spring metal pieces in about the center of the picture below.
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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.
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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.
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Throw everything away except the cable
By the way, the circuit 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).
Here's what you want to end up with. Referring to the picture below and going from top to bottom, here is the wiring pin out:
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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.
The following picture is 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:
http://www.marsport.demon.co.uk/smd/res.htm
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 Belkin pin outs above. When looking at the Radio Shack cable, remember your R's. Red = Right. Solder the yellow and green wires 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. 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 use heat shrink tubing or electrical tape to insulate the wires from each other. Solder the twisted cable shield from the Radio Shack cable together and also solder the shield from the Belkin harness together (top wire in the picture plus the two twisted wires at the right).
Here you can see the resistor connected to the white wire. Notice how I connected the first black ground wire to the other end. Also connect the outer shield (third of three ground wires - pictured below between the resistor and the red wire) to the other end of this ground wire. The outer shield and black wire go straight to ground. The white wire goes to ground via the resistor.
I chose this style of connector to tap into power and ground of my cars. 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 the complete harness. Notice how I doubled over the harness and wire tied them. I did this for strength (takes the load off of the tiny wires) because the wires in the Belkin harness 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 unstitched power source such as directly to the battery or where the circuit has no fuse. What is nice about tapping into a switched power source is that when the power is switched off, the iPod goes into a paused state.
This page was last updated on
April
23, 2004 10:50
AM
