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:
Once you have the Belkin connector, do the following:
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:
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:
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
23, 2004 10:50